Synergistic effect of hydrogen bonds and π-π interactions of B(C6F5)3·H2O/amides complex: Application in photoredox catalysis

Shi-Jun Wang; Long Wang; Xiang-Ying Tang

doi:10.1016/j.isci.2023.106528

. 2023 Mar 30;26(4):106528. doi: 10.1016/j.isci.2023.106528

Synergistic effect of hydrogen bonds and π-π interactions of B(C₆F₅)₃·H₂O/amides complex: Application in photoredox catalysis

Shi-Jun Wang ¹, Long Wang ¹, Xiang-Ying Tang ^1,^2,^∗

PMCID: PMC10148046 PMID: 37128550

Summary

B(C₆F₅)₃·H₂O has been long recognized as a common Brønsted acid. The lack of X-ray crystal structure of B(C₆F₅)₃·H₂O with other substrates has greatly limited the development of a new catalytic mode. In this work, a complex of B(C₆F₅)₃·H₂O and amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one with hydrogen bonds and π-π interactions is characterized by X-ray diffraction. Such noncovalent interactions in solution also exist, as verified by NMR, UV-Vis absorption, and fluorescence emission measurements. Moreover, the mixture of amide 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one and B(C₆F₅)₃·H₂O, instead of other tested Brønsted acids, shows a tailing absorption band in the visible light region (400–450 nm). Based on the photoactive properties of the complex, a photoredox catalysis is developed to construct α-aminoamides under mild conditions.

Subject areas: Organic reaction, Physical organic chemistry, Chemical phenomena

Graphical abstract

Highlights

•
Aerobic oxidation under visible light conditions
•
No need for an external photocatalyst
•
Hydrogen bonds and π-π interactions between B(C₆F₅)₃·H₂O and amides were identified

Organic reaction; Physical organic chemistry; Chemical phenomena

Introduction

Tris(pentafluorophenyl)borane, B(C₆F₅)₃, as a main group Lewis acid, has been deeply investigated during the last decade.¹^,²^,³^,⁴^,⁵^,⁶^,⁷^,⁸ Besides, with the discovery of crystal structure of B(C₆F₅)₃ with various molecules,⁹^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸ the catalytic mode of B(C₆F₅)₃ was further revealed.¹⁹^,²⁰^,²¹^,²²^,²³^,²⁴^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹On the other hand, owing to the moisture sensitivity of B(C₆F₅)₃, it is likely that the Brønsted acid B(C₆F₅)₃·H₂O acts as the real catalyst.³²^,³³ Although, there are some reports indicating that this effect can be attenuated in frustrated Lewis pairs (FLP) chemistry,³⁴^,³⁵^,³⁶^,³⁷ the strict anhydrous conditions are still necessary in most B(C₆F₅)₃ catalyzed transformations.

B(C₆F₅)₃·H₂O is a strong Brønsted acid³⁸^,³⁹^,⁴⁰ and the strength is similar to that of HCl in acetonitrile.³⁸ It has been reported that B(C₆F₅)₃·H₂O shows superior activity than other Brønsted acids in some transformations.⁴¹^,⁴²^,⁴³^,⁴⁴^,⁴⁵ However, it is difficult to identify the real catalytic species under moist conditions, because Lewis acid and water-mediated pathways are competitive.³⁴^,³⁵^,³⁶^,³⁷^,⁴¹^,⁴²^,⁴³^,⁴⁴^,⁴⁵^,⁴⁶^,⁴⁷ In the water-tolerant FLP-catalyzed hydrogenation, for instance, ethers could competitively replace water to coordinate with B(C₆F₅)₃ (Figure 1A).³⁴^,³⁵^,³⁶^,³⁷ Meanwhile, B(C₆F₅)₃·H₂O are mainly considered as a hydrogen bond donor. For instance, in the B(C₆F₅)₃·H₂O catalyzed ring opening reactions of epoxides,⁴⁶^,⁴⁷ hydrogen bond interactions between B(C₆F₅)₃·H₂O and epoxides/alcohols are revealed by microkinetic modeling and density functional theory calculations (Figure 1B).⁴⁴ Even though existing studies could account for the hydrogen bond interactions, other noncovalent interactions are barely considered. Thus, the direct and intuitive evidences such as X-ray single crystal diffraction are highly desirable.

Competitive boron Lewis acid, water-and alcohol-mediated pathways

A myriad of X-ray structures of four-coordinated complex via anhydrous B(C₆F₅)₃ were reported.⁹^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷^,¹⁸ In contrast, there have been very limited reports involving X-ray structures of B(C₆F₅)₃·H₂O with other molecules,³⁸^,³⁹^,⁴⁰ resulting in difficulties understanding the difference between B(C₆F₅)₃·H₂O and other Brønsted acids. Herein, we wish to report an interesting X-ray crystal structure (C1) of B(C₆F₅)₃·H₂O and 2-phenyl-3,4-dihydroisoquinolin-1(2H)-one (1aa), forming through intermolecular hydrogen bonds and π-π interactions. Meanwhile, the mixture of B(C₆F₅)₃·H₂O and 1aa in tetrahydrofuran (THF) solution showed reinforcement both in UV-Vis absorption and fluorescence emission. On the basic of these observations, a photoredox oxidation reaction was developed using the combination of B(C₆F₅)₃·H₂O and 1aa as the photocatalyst.

Results and discussion

Identify noncovalent interactions between B(C₆F₅)₃·H₂O and amide 1aa

The crystals of C1 suitable for X-ray crystal structure analysis were obtained by slowly solvent evaporation of the solution of 1aa and B(C₆F₅)₃·H₂O (1:1) in dichloromethane (Figure 2). The B-O bond lengths in C1 are 1.5692(19) and 1.5557(19) Å, slightly shorter than that in aqua complexes of B(C₆F₅)₃.³⁸^,³⁹^,⁴⁰ Correspondingly, the C=O bond lengths are elongated to be 1.2579(19) and 1.2622(19), respectively.⁴⁸^,⁴⁹

X-ray crystal structure of C1 (B(C₆F₅)₃·H₂O + **1aa**)

F atoms and part of the hydrogen atoms are omitted for clarity. Selected bond distances (Å): B1–O1 1.5692(19), B2–O3 1.5557(19), C1–O2 1.2579(19), C2–O4 1.2622(19). CCDC (2207426).

As can be seen from Figure 3, there are two π-π interactions between –C₆F₅ of B(C₆F₅)₃ and phenyl moiety of 1aa. The twist angles of aromatic rings are 21.21(14) and 1.32(16) degree respectively. Besides, the distances between centroids are in the range of 3.30–3.80 Å.⁵⁰

π-π interactions

Hydrogen atoms are omitted for clarity. Selected distances (Å) and angles (deg): plane centroid of C1–C6 to plane centroid of C7–C12 3.8065(10), plane centroid of C1–C6 to plane C7–C12 3.4126(16), plane to plane twist angle 21.21(14); plane centroid of C13–C18 to plane centroid of C19–C24 3.5511(10), plane centroid of C13–C18 to plane C19-C24 3.3748(12), plane to plane twist angle 1.32(16).

There are four oxygen atoms and four hydrogen atoms, forming an eight-membered ring in the conformation of boat-chair via hydrogen bond possessing the lowest transannular strain and energy (Figure 4).⁵¹^,⁵² The O … O distances in O–H … O hydrogen bond system range is 2.5627(15)−2.7583(15) Å, relatively shorter than the reported intermolecular O … O distances (2.70–3.00 Å),⁵³^,⁵⁴ suggesting the existence of stronger hydrogen bonds in crystal C1.

Structure analysis of eight-membered rings of hydrogen bond

Selected bond distances (Å): O1-H1 0.89(3), O1–H2 0.86(3), O3–H3 0.86(3), O3–H4 0.90 (3), O4 … H1 1.69(3), O2 … H2 1.97(3), O2 … H3 1.71(3), O4 … H4 1.83(3), O1 … O2 2.7583(15), O2 … O3 2.5627(15), O3 … O4 2.6578(15), O1 … O4 2.5659(15).

Encouraged by the above discoveries in C1, we considered that similar interactions might exist in solution. Compound 1aa showed a¹H NMR resonance at 8.15 ppm in CDCl₃ (Figure 5A, black curve). With the addition of B(C₆F₅)₃·H₂O (1.0 equiv), the resonance shifted to 8.07 ppm (Figure 5A, blue curve), indicating the formation of π-π interactions in solution.⁵⁵^,⁵⁶ The ¹⁹F NMR of B(C₆F₅)₃·H₂O also changed on the addition of 1aa. The original peaks of B(C₆F₅)₃·H₂O were observed at −135.2, −155.7 and −163.0 ppm (Figure 5B, black curve).⁴¹ Upon addition of 1aa (1.0 equiv), the characteristic peaks changed to −134.7, −157.7 and −164.0 ppm, respectively (Figure 5B, blue curve). According to previous reports,³⁶^,³⁷^,³⁸^,⁴¹^,⁴² intermolecular hydrogen bonds should exist between 1aa and B(C₆F₅)₃·H₂O in solution.

NMR experiments

0.05 mmol **1aa** was dissolved in 0.6 mL deuterated chloroform (CDCl₃).

(A) **1aa** (black); **1aa**/B(C₆F₅)₃·H₂O (1:1) (blue).

(B) B(C₆F₅)₃·H₂O (black); **1aa**/B(C₆F₅)₃·H₂O (1:1) (blue).

In tetrahydrofuran solution, 1aa as well as the mixture of 1aa and p-toluenesulfonic acid (TsOH), show no absorption in visible light region, respectively (Figure 6A, black and blue curves). Similarly, using other Brønsted acids instead of TsOH as hydrogen bond donors, such as phenylboronic acid, cyclohexanecarboxylic acid, and methanesulfonic acid, the corresponding mixtures also show no absorption in the visible light region (see supplmental information for detail, Figure S4). However, the mixture of 1aa and B(C₆F₅)₃·H₂O exhibits a tailing band from 400 to 450 nm (Figure 6A, red curve).

UV-Vis absorption and fluorescence emission measurements

(A) **1aa** in THF (10⁻³ M, black); **1aa** and B(C₆F₅)₃·H₂O (1:1) in THF (10⁻³ M, red); **1aa** and p-toluenesulfonic acid (TsOH) (1:1) in THF (10⁻³ M, blue).

(B) Fluorescence emission spectra of C1, excitation wavelength, 330 nm.

(C) Fluorescence emission spectra of **1aa** in THF (10⁻⁴ M), B(C₆F₅)₃·H₂O were added to the solution of **1aa**, excitation wavelength, 330 nm.

(D) Emission intensity, 387 nm and 402 nm.

The fluorescence emission measurements of C1 and 1aa/B(C₆F₅)₃·H₂O were attempted. The solid fluorescence emission spectrum of C1 showed three peaks at 381 nm, 390 nm, and 401 nm (Figure 6B). Similar emission peaks were observed in solution. There were two fluorescent peaks at 387 nm and 402 nm, which are enhanced in terms of the emission intensity by increasing the B(C₆F₅)₃·H₂O fraction (Figure 6C). When the ratio of B(C₆F₅)₃·H₂O/1aa is 1.5:1, the emission intensity was comparable at 387 nm and 402 nm. With the addition of B(C₆F₅)₃·H₂O, the emission intensity at 402 nm gradually became stronger than the emission intensity at 387 nm, indicating that the rotation of aromatic rings was more restricted because of increased π-π interactions.⁵⁵^,⁵⁶ In comparison to B(C₆F₅)₃·H₂O/1aa (5:1) and 1aa, the fluorescence emission intensities at 387 nm and 402 nm were enhanced by 23% and 38%, respectively (Figure 6D).

To further explore the properties of mixture of B(C₆F₅)₃·H₂O and 1aa, electron paramagnetic resonance (EPR) measurements were conducted. As can be seen in Figure 7, directly subjecting the THF solution of 1aa, B(C₆F₅)₃·H₂O and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) to EPR, a weak radical signal was detected (Figure 7A). A strong signal appeared when the above solution was irradiated by blue light for 2 min (Figure 7B). As the irradiation time was extended to 5 min, further enhancement was observed (Figure 7C). According to previous reports, DMPO-O₂^- species is formed (α_N = 13.1 G, α_H = 9.1 G), indicating that the mixture of B(C₆F₅)₃·H₂O and 1aa can activate molecular oxygen probably through energy transfer on visible light irradiation.⁵⁷^,⁵⁸^,⁵⁹^,⁶⁰

EPR measurements

0.05 mmol scale, **1aa**/DMPO/B(C₆F₅)₃·H₂O (1:1:1) in THF (1 mL) under air.

(A) in the dark.

(B) irradiated by blue LEDs for 2 min.

(C) irradiated by blue LEDs for 5 min.

These observations of the complex of B(C₆F₅)₃·H₂O and 1aa inspired us to further exploit its catalytic potential in photoredox catalysis. Therefore, the reaction of N-phenyl-tetrahydroisoquinoline (1a) and 4-isocyano-1,1′-biphenyl (2a) was investigated. As expected, the reaction gave corresponding product 3aa in 58% yield in THF using 10 mol % of B(C₆F₅)₃·H₂O/1aa as photocatalyst (Figure 8A). Besides, in the absence of isocyanide, 1a could be converted to 1aa in 30% yield catalyzed by B(C₆F₅)₃·H₂O, with 61% 1a recovered (Figure 8B). Thus, when 1a and 2a were treated by B(C₆F₅)₃·H₂O, the desired product 3aa could still be obtained in 51% yield (Figure 8C). Meanwhile, only trace amount of 3aa was formed in the dark (Figure 8C).

Catalytic properties of B(C₆F₅)₃·H₂O and **1aa**

(A) C1 Catalysis Experiment: 1a (0.15 mmol), 2a (0.1 mmol).

(B) generate **1aa** via 1a direct oxidation, 1a (0.1 mmol).

(C) 1a was found to generate to **1aa**, subsequently combined with B(C₆F₅)₃·H₂O to catalyze the reaction. 1a (0.15 mmol), 2a (0.1 mmol).

In addition, the UV-Vis absorption measurements of reaction mixture showed a tailing band from 400 to 450 nm (Figure 9A), similar to the absorption curve of B(C₆F₅)₃·H₂O/1aa (Figure 6A). The mixture of 1a and B(C₆F₅)₃·H₂O in THF showed no absorption in visible light region (Figure 9B), different from the result that an Electron Donor-Acceptor (EDA) complex was formed between 1a and anhydrous B(C₆F₅)₃.⁶¹ EPR measurement of the reaction mixture with DMPO showed similar signals (Figure 9D) as those of the mixture of 1a/DMPO/B(C₆F₅)₃·H₂O (Figure 9C), further confirming that the combination of B(C₆F₅)₃·H₂O and 1aa (in situ formed from 1a) acts the photocatalyst of the reaction.

UV-Vis absorption spectra and EPR measurements

(A) 1a, 2a and B(C₆F₅)₃·H₂O (1:1:1) in THF (10⁻³ M) irradiated by blue LEDs for 2 h.

(B) 1a in THF (10⁻³ M, blue); 1a and B(C₆F₅)₃·H₂O (1:1) in THF (10⁻³ M, red).

(C) 0.1 mmol 1a/DMPO and B(C₆F₅)₃·H₂O (0.01 mmol) THF (1 mL) irradiated by blue LEDs for 30 s.

(D) 0.1 mmol 1a/2a/DMPO (1:1:1) and B(C₆F₅)₃·H₂O (0.01 mmol) in THF (1 mL), irradiated by blue LEDs for 30 s.

Substrate Scope

Under the optimized reaction conditions (See supplmental information), the generality of the reaction was tested by variation of different tetrahydroisoquinolines (Figure 10). All reactions proceeded smoothly to give corresponding products 3 in moderate to good yields. 3aa was obtained in 62% isolated yield in gram scale. Substrate with a β-naphthyl group was compatible with the reaction conditions, and the desired product 3ba could be obtained in 83% yields. For tetrahydroisoquinoline with a hydrogen bond acceptor CN group, the reaction furnished product 3ca in 57% yield. For substrate bearing a Cl atom on the N-aryl ring, the reaction delivered 3da in 34% yield. Substrates having electron-donating methoxy substituent were also suitable for this transformation, giving 3ea and 3fa in 66% and 37% yields, respectively. For substrates with a para- and meta-Me on the N-aryl ring, corresponding products 3ga and 3ha were isolated in moderate yields. When substrates had two methoxy groups on the benzene ring (R¹), the reaction could still perform smoothly to give 3ia in 52% yields. To our delight, bupivacaine analogue 3ja could be obtained in 32% yield from N-Ph piperidine, and the reaction of N-Ph proline also provided corresponding product 3ka in 39% yield.

Next, a variety of isocyanides were examined and the results are presented in Figure 11. For isocyanide bearing a methoxy group on the benzene ring, the reaction produced the desired product 3 ab in 86% yield. The reactions of electron-deficient aromatic isocyanides provided the corresponding amides 3ac-3ag in moderate yields. 2-biphenylyl isocyanide led to amide product 3ah in 77% yield. Similarly, for other 2-biarylyl substituted isocyanides, products 3ai-3ak were obtained in moderate to good yields (73%–84%). Aliphatic isocyanides were also suitable for this transformation and gave the desired products 3 aL-3ar in 56–90% yields. Notably, ester tethered isocyanide furnished the target product 3as in 92% yield.

Substrate scope of Isocyanide

Reaction conditions: 1a (0.1 mmol), 2 (0.15 mmol), B(C₆F₅)₃·H₂O (10 mol %). a, Reaction time: 14 h.

Mechanistic studies

Light on/off experiments were conducted to investigate the effect of light. The mixture of 1a, 2b and B(C₆F₅)₃·H₂O in THF/H₂O was stirred for 2 h, alternating between 10-min periods of blue LED irradiation and 30 min in the dark. It was noted that the reaction proceeded smoothly on light irradiation, but the consumption of the isocyanide 2b immediately stalled without light, indicating that continuous light irradiation is essential for the reaction. (Figure 12).

Light on/off experiment

1a (0.15 mmol), 2b (0.1 mmol), B(C₆F₅)₃·H₂O (0.01 mmol), THF/H₂O 10:1, the conversion of 2b was monitored by GC.

The reaction mixture was monitored by ¹⁹F NMR after completion of the reaction. As shown in Figure 13, the resonance shifts appeared at −135.7, −160.7 and −165.2 ppm, suggesting that B(C₆F₅)₃·H₂O is remained after the reaction.⁶² Moreover, potassium iodide-starch test showed discoloration, implying that oxidizing substances were formed in the reaction. Subsequently, H₂O₂ was observed by a reported method using Ti(SO₄)₂ as the chromogenic agent, the characteristic peak was monitored at 405 nm (see supplmental information for detail).⁶³

¹⁹F NMR measurement after completion of the reaction

Plausible reaction mechanism

Based on the aforementioned results and reported photoredox aerobic oxidations,⁶⁴^,⁶⁵^,⁶⁶ a plausible mechanism is proposed (Figure 14). Initially, amide is formed via autoxidation of 1.⁶⁷ Then, the photocatalyst species PC is formed via hydrogen bond and π-π interactions between B(C₆F₅)₃·H₂O and amide. In addition, for 1j and 1k, N-phenyl group of the corresponding amides might take part in the π-π interactions. Next, singlet oxygen (¹O₂) is generated via energy transfer (EnT) by excited PC∗. Subsequent oxidation of compounds 1 by¹O₂ gives imine cation intermediate, together with the formation of H₂O₂ as a byproduct. Finally, the multiple component reaction occurs between imine cation, isocyanide and H₂O delivers the final products 3.

Conclusion

In summary, the crystal structure of B(C₆F₅)₃·H₂O and amide 1aa was obtained, from which hydrogen bond and π-π interactions are observed. This crystal was composed of six molecules with an eight-membered ring via hydrogen bonds. The boat-chair conformation of the eight-membered ring possesses the lowest energy and the hydrogen bond strength is stronger than normal ones reported in the literature.⁵⁰^,⁵¹^,⁵² Moreover, similar noncovalent interactions were also observed in solution as confirmed by NMR measurements, UV-Vis absorption and fluorescence emission spectra. The π-π interactions demonstrate the specific characteristics of B(C₆F₅)₃·H₂O among other Brønsted acids. Based on the synergistic effect of hydrogen bonds and π-π interactions in B(C₆F₅)₃·H₂O/amides complex, a photoredox catalysis under visible light is developed using the complex as the photocatalyst.

Limitations of the study

The reaction works well with N-aryl tetrahydroisoquinolines; for N-alkyl substituted tetrahydroisoquinolines, very low yields were obtained.

STAR★Methods

Key resources table

REAGENT or RESOURCE	SOURCE	IDENTIFIER
Chemicals, peptides, and recombinant proteins

1,2,3,4-Tetrahydro-2-isoquinoline	Meryer	CAS: 91-21-4
1,2,3,4-tetrahydro-6,7-dimethoxy-isoquinolin	Meryer	CAS: 1745-07-9
4-Aminobiphenyl	Meryer	CAS: 92-67-1
4-Chlorobromobenzene	Energy Chemical	CAS: 106-39-8
4-Bromobenzonitrile	Energy Chemical	CAS: 623-00-7
2-Bromoanisole	Energy Chemical	CAS: 578-57-4
4-Bromoanisole	Adamas	CAS: 104-92-7
3-Bromoanisole	Adamas	CAS: 2398-37-0
4-Bromotoluene	Adamas	CAS: 106-38-7
3-Bromotoluene	Adamas	CAS: 591-17-3
4-Bromoaniline	Adamas	CAS: 106-40-1
4-Iodoaniline	Adamas	CAS: 540-37-4
p-Anisidine	Adamas	CAS: 104-94-9
4-Aminobenzonitrile	Adamas	CAS: 873-74-5
4-Nitroaniline	Adamas	CAS: 100-01-6
2-Aminobiphenyl	Adamas	CAS: 90-41-5
4′-Methyl-Bpphenyl-2-ylamine	Adamas	CAS: 1204-43-9
4′-Methoxy-Bpphenyl-2-ylamine	Adamas	CAS: 38089-03-1

Deposited data

Complex of B(C₆F₅)₃^.H₂O and amide 1aa.	CCDC	CCDC-2207426

Other

Silica gel (200-300 mesh)	Huanghai	https://www.aladdin-e.com/
AVIII 400 MHz	Bruker	https://www.bruker.com

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Resource availability

Lead contact

Further information and requests for resources should be directed to and will be fulfilled by the lead contact, Xiang-Ying Tang (xtang@hust.edu.cn).

Materials availability

All materials generated in this study are available within the article and the supplemental information or from the lead contact upon reasonable request.

Method details

General information

The nuclear magnetic resonance spectra were recorded on the Bruker Avance III 400 MHz with tetramethylsilane (TMS) as an internal standard. High resolution mass spectra were recorded using analyses by BrukerDaltonics SolariX 7.0T. Organic solvents used were dried by standard methods when necessary. Commercially obtained reagents were used without further purification. Flash column chromatography was performed using 300-400 mesh silica gel. For thin-layer chromatography (TLC), silica gel plates (Huanghai GF254) were used. EPR (electron paramagnetic resonance) spectra were recorded by Bruker EMXmicro-6/1 instrument. X-Ray diffraction were collected by XtaLAB PRO MM007HF Cu (Rigaku, Japan). UV-vis spectra were obtained on a UV-2600 (Shimadzu). Fluorescence spectroscopic studies were performed with a RF-5301PC (Shimadzu). All heat sources are oil bath. All light sources are 3 W blue LED bands and the wavelength of peak is 427 nm. The distance from the light source to the container is 3-5 cm.

General procedure

Synthesis of substrate isoquinolines

A mixture of Pd₂(dba)₃ (3 mol%) and ligand (2-Dicyclohexylphosphino-2',6'-dimethoxybiphenyl) (8 mol%) were placed into an oven dried reaction tube. Subsequently, the reaction tube was degassed with N₂ for three times. Then, dry toluene, bromoarene (1.0 equiv.), 1,2,3,4-tetrahydroisoquinoline (1.2 equiv.) and ^tBuONa (1.4 equiv.) were sequentially added under nitrogen protection. Then the reaction mixture was heated to 100 °C for 12 h. After completion, the resulting reaction mixture was slowly cooled to room temperature, quenched by brine and extracted with ethylacetate. The organic layer was dried overNa₂SO₄ and concentrated under reduced pressure. The crude product was purified by column chromatography on silica gel. In addition, 1a-1h are known compound.

Synthesis of isocayanides

A mixture of HCOOH (2.0 equiv) and (CH₃CO)₂O (2.0 equiv.) were stirred at 55 °C for 2 h. Before aniline (1.0 equiv.) was added the reaction mixture was cooled down at 0 °C, then continued stirring for 2hat room temperature. After consumption of aniline, all the volatiles were removed under reduced pressure and the crude product was directly used in the next step without further purification.

To a stirred solution of crude product in dry THF at 0 °C were added Et₃N (5.0 equiv.) and POCl₃ (1.2 equiv.) dropwise sequentially. After stirring for 2hat 0 °C, the reaction was quenched with water and extracted with ethylacetate (EA) for three times. The organic layer was washed with brine and dried over anhydrous Na₂SO₄ and concentrated under reduced pressure. The crude product was purified by column chromatography on silica gel to observed pure product 2. In addition, 2a-2s are known compound.

Synthesis of compounds 3

To a stirred solution of 1 (0.15 mmol, 1.5 equiv.) in mixed solvent (1 mL, THF: H₂O = 10:1) were added 2 (0.1 mmol, 1.0 equiv.) and boron catalyst (10 mol%). The resulting solution was stirred in the presence of O₂ under blue light irradiation. The reaction was monitored by TLC, the crude products were purified by flash column chromatography to provide a series of amide compounds 3. In addition, 3aa was known compound.

Gram scale reaction

To a stirred solution of 2a (6 mmol, 1.074 g) in mixed solvent (50 mL, THF: H₂O = 10:1) were added to 1a (7 mmol, 1.463 g) and boron catalyst (10 mol%, 0.307 g). The resulting solution was stirred at blue LED and O₂ for 36 h. The crude product was purified by flash column chromatography to provide a series of amide compound 3aa (1.502 g, 62%).

Oxidation reaction of 1a

To a stirred solution of 1a (0.1 mmol, 20.9 mg, 1.0 equiv.) in mixed solvent (1 mL, THF: H₂O = 10:1) was added to boron catalyst (10 mol%). The resulting solution was stirred at blue LEDs and 1 atm O₂ for 12 h. The crude product was purified by flash column chromatography to provide 1aa (6.6 mg, 30%) and 1a (12.7 mg, 61%).

X-ray crystal structure analysis for 1aa

X-ray crystal structure analysis of C1. A clear colorless plate. Formula C₃₃H₁₅BF₁₅NO₂, M = 753.27, 0.25∗0.2∗0.05 mm, a = 12.0787(1), b = 11.9169(1), c = 41.6237(3) Å, β = 97.510(1)°, V = 5939.95(8) Å³, μ= 1.518 mm^-1, 0.651 ≤ T ≤ 1.000, Theta(max) = 74.296°, R = 0.0381, wR² = 0.1036, temperature = 293 K, hydrogen atoms calculated and refined as riding atoms.

Light on/off experiments

To a stirred solution of the 1-isocyano-4-methoxybenzene (2b, 0.1 mmol, 1.0 equiv.) and boron catalyst (10 mol%) in mixed solvent (1mL, THF: H₂O = 10:1) was added the N-phenyl-1,2,3,4-tetrahydroisoquinoline (1a, 0.15 mmol, 1.5 equiv.). Besides, 0.1 mmol dodecane was added as internal standard. The light was kept on for ten minutes then kept off for thirty minutes. The reaction mixture 0.05 mL was taken and diluted with 1,2-dichloroethane (DCE) to 2 mL for gas chromatography (GC) monitoring.

Spectroscopic data

N-([1,1'-biphenyl]-4-yl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3aa)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (33.7 mg, 84% yield). m.p.: 192−194 °C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.88 (s, 1H), 7.65 (d, J = 6.8 Hz, 1H), 7.57−7.49 (m, 6H), 7.36−7.27 (m, 4H), 7.26−7.23 (m, 1H), 7.18 (d, J = 7.2 Hz, 1H), 7.02 (d, J = 8.0 Hz, 2H), 6.95 (dd, J₁ = J₂ = 7.6 Hz, 1H), 5.09 (s, 1H), 3.94 (dt, J = 9.6 Hz, J = 4.4 Hz, 1H), 3.40 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.16-3.00 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.6, 149.4, 140.5, 137.3, 136.7, 134.5, 132.1, 129.6, 129.1, 127.8, 127.7, 127.5, 127.1, 126.9, 120.4, 120.1, 115.3, 66.5, 45.4, 28.8. IR ν 3298, 3034, 2251, 2228, 1662, 1287, 858, 690 cm^-1. HRMS (ESI) m/z: calcd for C₂₈H₂₅N₂O [M+H]⁺ 405.1961; found 405.1960.

N-([1,1'-biphenyl]-4-yl)-2-(naphthalen-2-yl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ba)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (37.6 mg, 83% yield). m.p.: 141−143 °C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.89 (s, 1H), 7.79 (d, J = 8.8 Hz, 1H), 7.75−7.67 (m, 3H), 7.54−7.45 (m, 6H), 7.44−7.35 (m, 3H), 7.33−7.24 (m, 6H), 7.17 (d, J = 7.2 Hz, 1H), 5.24 (s, 1H), 4.03 (dt, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.50 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.18−3.01 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 147.0, 140.5, 137.4, 136.7, 134.5, 134.4, 132.0, 129.5, 129.2, 128.8, 128.6, 127.9, 127.8, 127.6, 127.5, 127.1, 126.94, 126.9, 126.8, 126.7, 123.9, 120.1, 117.5, 66.2, 45.9, 28.8. IR ν 3303, 3052, 2924, 1667, 1596, 1386, 1112, 834 cm^-1. HRMS (ESI) m/z: calcd for C₃₂H₂₇N₂O [M+H]⁺ 455.2118; found 455.2117.

N-([1,1'-biphenyl]-4-yl)-2-(4-cyanophenyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ca)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (24.5 mg, 57% yield). m.p.: 137−139 °C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.37 (s, 1H), 7.61−7.58 (m, 1H), 7.55−7.48 (m, 8H), 7.40 (dd, J₁ = J₂ = 8.0 Hz, 2H), 7.33−7.28 (m, 3H), 7.23−7.20 (m, 1H), 6.95 (d, J = 8.8 Hz, 2H), 5.18 (s, 1H), 4.06−4.00 (m, 1H), 3.43 (td, J = 11.2 Hz, J = 3.6 Hz, 1H), 3.25−3.16 (m, 1H), 3.07 (dt, J = 15.6 Hz, J = 3.6 Hz, 1H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 169.4, 152.0, 140.3, 137.8, 136.3, 134.4, 133.8, 131.7, 128.8, 128.4, 127.8, 127.6, 127.3, 127.27, 126.9, 120.4, 119.8, 113.7, 101.5, 65.6, 44.5, 28.7. IR ν 3319, 3026, 2831, 2246, 1662, 1318, 904, 722 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₄N₃O [M+H]⁺ 430.1914; found 430.1907.

N-([1,1'-biphenyl]-4-yl)-2-(4-chlorophenyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3da)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (14.9 mg, 34% yield). m.p.: 188−190 °C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.72 (s, 1H), 7.63 (d, J = 6.8 Hz, 1H), 7.55−7.48 (m, 6H), 7.42−7.37 (m, 2H), 7.33−7.24 (m, 5H), 7.17 (d, J = 6.8 Hz, 1H), 6.92 (d, J = 9.2 Hz, 2H), 5.03 (s, 1H), 3.94−3.88 (m, 1H), 3.35 (td, J = 10.8 Hz, J = 3.6 Hz, 1H), 3.16−3.08 (m, 1H), 3.01 (dt, J = 12.0 Hz, J = 3.2 Hz, 1H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.2, 148.0, 140.4, 137.5, 136.6, 134.3, 131.8, 129.4, 129.0, 128.8, 127.9, 127.8, 127.6, 127.2, 127.0, 126.9, 125.5, 120.1, 116.4, 66.4, 45.6, 28.8. IR ν 3255, 3061, 2920, 2851, 1596, 1331, 1052, 840 cm^-1. HRMS (ESI) m/z: calcd for C₂₈H₂₄N₂OCl [M+H]⁺ 439.1572; found 439.1571.

N-([1,1'-biphenyl]-4-yl)-2-(2-methoxyphenyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ea)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (28.6 mg, 66% yield). m.p.: 66-68°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.98 (s, 1H), 7.72 (d, J =7.2 Hz, 1H), 7.60-7.50 (m, 6H), 7.40 (dd, J₁ = J₂ = 7.6 Hz, 2H), 7.32-7.22 (m, 3H), 7.17-7.10 (m, 3H), 6.97-6.87 (m, 2H), 5.08 (s, 1H), 4.00 (s, 3H), 3.48-3.31 (m, 2H), 3.03-2.84 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.5, 153.8, 140.6, 139.0, 137.6, 136.6, 134.6, 132.1, 129.0, 128.7, 128.6, 127.5, 127.2, 127.0, 126.8, 126.2, 125.6, 123.3, 121.3, 119.5, 111.5, 65.2, 55.6, 47.7, 28.0. IR ν 3298, 3026, 2849, 2228, 1490, 1035, 904, 720 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₇N₂O₂[M+H]⁺ 435.2067; found 435.2066.

N-([1,1′-biphenyl]-4-yl)-2-(3-methoxyphenyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3fa)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (16.1 mg, 37% yield). m.p.: 64-66°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.81 (s, 1H), 7.63 (d, J = 7.2 Hz, 1H), 7.57-7.48 (m, 6H), 7.42-7.38 (m, 2H), 7.33-7.21 (m, 4H), 7.17 (d, J = 6.8 Hz, 1H), 6.62-6.56 (m, 2H), 5.10 (s, 1H), 3.95-3.89 (m, 1H), 3.80 (s, 3H), 3.39 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.15-2.99 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.4, 160.8, 150.8, 140.5, 137.3, 136.7, 134.5, 132.1, 130.3, 129.1, 128.8, 127.7, 127.5, 127.1, 126.8, 120.1, 108.0, 105.0, 101.9, 66.4, 55.3, 45.3, 28.8. IR ν 3319, 3025, 2920, 2847, 1662, 1445, 1166, 757 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₇N₂O₂[M+H]⁺ 435.2067; found 435.2066.

N-([1,1'-biphenyl]-4-yl)-2-(p-tolyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ga)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (22.9 mg, 55% yield). m.p.: 160-162°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.94 (s, 1H), 7.65 (d, J = 7.2 Hz, 1H), 7.56-7.47 (m, 6H), 7.41-7.37 (m, 2H), 7.32-7.22 (m, 3H), 7.17-7.11 (m, 3H), 6.93 (d, J = 8.8 Hz, 2H), 5.04 (s, 1H), 3.88 (dt, J = 10.4 Hz, J = 4.4 Hz, 1H), 3.35 (td, J = 11.2 Hz, J = 4.0 Hz, 1H), 3.13-2.96 (m, 2H), 2.28 (s, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.7, 147.3, 140.5, 137.2, 136.8, 134.5, 132.1, 130.1, 129.0, 128.8, 127.8, 127.6, 127.5, 127.1, 126.8, 126.77, 120.1, 115.8, 66.5, 45.9, 28.8, 20.4. IR ν 3303, 3022, 2920, 2850, 1913, 1671, 1499, 1149 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₇N₂O [M+H]⁺ 419.2118; found 419.2119.

N-([1,1'-biphenyl]-4-yl)-2-(m-tolyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ha)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (19.3 mg, 46% yield). m.p.: 137-139°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.88 (s, 1H), 7.66-7.63 (m, 1H), 7.58-7.49 (m, 6H), 7.42-7.37 (m, 2H), 7.33-7.15 (m, 5H), 6.84-6.76 (m, 3H), 5.09 (s, 1H), 3.92 (dt, J = 11.2 Hz, J = 4.4 Hz, 1H), 3.40 (td, J = 10.4 Hz, J = 4.0 Hz, 1H), 3.14-2.99 (m, 2H), 2.35 (s, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.6, 149.5, 140.5, 139.4, 137.3, 136.8, 134.6, 132.2, 129.4, 129.2, 128.8, 127.7, 127.66, 127.5, 127.1, 126.85, 126.8, 121.3, 120.1, 116.0, 112.4, 66.4, 45.4, 28.8, 21.9. IR ν 3326, 3031, 2917, 2827, 1671, 1487, 1113, 835 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₆N₂ONa [M+Na]⁺ 441.1937; found 441.1935.

N-([1,1'-biphenyl]-4-yl)-6,7-dimethoxy-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ia)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 2:1 as the eluent). Yellow solid (24.1 mg, 52% yield). m.p.: 197-198°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.85 (s, 1H), 7.56-7.48 (m, 6H), 7.42-7.37 (m, 2H), 7.35-7.28 (m, 3H), 7.18 (s, 1H), 7.03 (d, J = 8.0 Hz, 1H), 6.95 (dd, J₁ = J₂ = 7.2 Hz, 1H), 6.65 (s, 1H), 5.01 (s, 1H), 3.93-3.86 (m, 7H), 3.44-3.37 (m, 1H), 3.07-2.90 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.8, 149.5, 148.5, 147.8, 140.5, 137.3, 136.8, 129.6, 128.8, 127.6, 127.1, 126.8, 126.6, 123.8, 120.5, 120.2, 115.6, 111.8, 110.6, 65.9, 56.1, 56.0, 45.6, 28.2. IR ν 3263, 3021, 2911, 2828, 1657, 1217, 1114, 992 cm^-1. HRMS (ESI) m/z: calcd for C₃₀H₂₉N₂O₃[M+H]⁺ 465.2173; found 465.2172.

N-([1,1'-biphenyl]-4-yl)-1-phenylpiperidine-2-carboxamide (3ja)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (11.4 mg 32% yield). m.p.: 139-141°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.45 (s, 1H), 7.55-7.48 (m, 6H), 7.41 (dd, J₁ = J₂ = 7.6 Hz, 2H), 7.33-7.29 (m, 3H), 7.07 (d, J =8.0 Hz, 2H), 6.94 (dd, J₁ = J₂ = 7.2 Hz, 1H), 4.19 (t, J = 5.2 Hz, 1H), 3.36-3.34 (m, 2H), 2.21-2.17 (m, 1H), 2.01-1.94 (m, 1H), 1.80-1.61 (m, 5H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 171.3, 150.7, 140.6, 137.1, 137.0, 129.6, 128.8, 127.6, 127.1, 126.8, 121.2, 120.0, 117.8, 62.8, 49.5, 26.4, 24.0, 21.7. IR ν 3323, 3025, 1671, 1484, 1241, 830, 759, 695. HRMS (ESI) m/z: calcd for C₂₄H₂₅N₂O [M+H]⁺ 357.1961; found 357.1958.

([1,1'-biphenyl]-4-yl)-1-phenylpyrrolidine-2-carboxamide (3ka)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (13.3 mg, 39% yield). m.p.: 207-208°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.44 (s, 1H), 7.59-7.51 (m, 6H), 7.41 (dd, J₁ = J₂ = 7.6 Hz, 2H), 7.33-7.27 (m, 3H), 6.89-6.84 (m, 1H), 6.73 (d, J = 8.0 Hz, 2H), 4.12-4.08 (m, 1H), 3.79-3.75 (m, 1H), 3.31-3.24 (m, 1H), 2.42-2.28 (m, 2H), 2.10-1.99 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.3, 147.6, 140.5, 137.4, 136.6, 129.5, 128.8, 127.6, 127.2, 126.9, 120.3, 118.9, 113.5, 65.4, 50.1, 31.6, 24.4. IR ν 3326, 2967, 2818, 1663, 1497, 1005, 755, 713. HRMS (ESI) m/z: calcd for C₂₃H₂₃N₂O [M+H]⁺ 343.1875; found 343.1803.

N-(4-methoxyphenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ab)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (30.7 mg, 86% yield). m.p.: 132-134°C . ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.70 (s, 1H), 7.63 (d, J = 8.4 Hz, 1H), 7.38-7.29 (m, 4H), 7.28-7.21 (m, 2H), 7.16 (d, J = 6.8 Hz, 1H), 6.99 (d, J = 8.0 Hz, 2H), 6.93 (dd, J₁ = J₂ = 6.8 Hz, 1H), 6.81-6.76 (m, 2H), 5.06 (s, 1H), 3.94-3.89 (m, 1H), 3.74 (s, 3H), 3.37 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.14-2.97 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.3, 156.5, 149.5, 134.6, 132.2, 130.6, 129.5, 129.1, 127.7, 127.6, 126.8, 121.6, 120.2, 115.1, 114.0, 66.3, 55.5, 45.3, 28.8. IR ν 3298, 3029, 2900, 2850, 1498, 888, 814 cm^-1. HRMS (ESI) m/z: calcd for C₂₃H₂₃N₂O₂[M+H]⁺ 359.1754; found 359.1753.

N-(4-bromophenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ac)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (22.7 mg, 56% yield). m.p.: 154-155°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.83 (s, 1H), 7.61 (d, J = 8.8 Hz, 1H), 7.36-7.22 (m, 8H), 7.17 (d, J = 6.8 Hz, 1H), 7.00-6.92 (m, 3H), 5.06 (s, 1H), 3.91 (dt, J =11.2 Hz, J = 4.4 Hz, 1H), 3.38 (td, J =10.8 Hz, J = 4.0 Hz, 1H), 3.12-2.97 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.7, 149.3, 136.5, 134.5, 131.9, 131.8, 129.6, 129.1, 127.81, 127.8, 126.9, 121.4, 120.5, 117.0, 115.3, 66.3, 45.4, 28.7. IR ν 3298, 3028, 2915, 2228, 1597, 1320, 992, 690 cm^-1. HRMS (ESI) m/z: calcd for C₂₂H₂₀N₂OBr [M+H]⁺ 407.0754; found 407.0752.

N-(4-iodophenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ad)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (19.0 mg, 42% yield). m.p.: 122-124°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.80 (s, 1H), 7.63-7.59 (m, 1H), 7.57-7.53 (m, 2H), 7.35-7.22 (m, 6H), 7.18-7.15 (m, 1H), 7.00-6.92 (m, 3H), 5.06 (s, 1H), 3.90 (dt, J = 11.2 Hz, J = 4.8 Hz, 1H), 3.42-3.35 (m, 1H), 3.11-2.97 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ. 170.6, 149.3, 137.8, 137.2, 134.5, 131.8, 129.6, 129.1, 127.8, 127.77, 126.9, 121.7, 120.6, 115.4, 87.6, 66.4, 45.4, 28.7. IR ν 3323, 3027, 2919, 2242, 2242, 1597, 1178, 818 cm^-1. HRMS (ESI) m/z: calcd for C₂₂H₂₀N₂OI [M+H]⁺ 455.0615; found 455.0614.

N-(4-cyanophenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ae)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (18.1 mg, 51% yield). m.p.: 74-76°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.05 (s, 1H), 7.62-7.58 (m, 3H), 7.55-7.51 (m, 2H), 7.36-7.30 (m, 2H), 7.28-7.24 (m, 2H), 7.19-7.16 (m, 1H), 7.02-6.94 (m, 3H), 5.09 (s, 1H), 3.91 (dt, J = 11.2 Hz, J = 4.8 Hz, 1H), 3.43-3.36 (m, 1H), 3.11-2.98 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 171.2, 149.2, 141.4, 134.5, 133.2, 131.4, 129.7, 129.1, 129.0, 128.0, 127.9, 126.9, 120.9, 119.7, 118.8, 115.6, 107.3, 66.4, 45.6, 28.7. IR ν 3323, 3030, 2915, 2224, 1921, 1672, 1402, 933 cm^-1. HRMS (ESI) m/z: calcd for C₂₃H₂₀N₃O [M+H]⁺ 354.1601; found 354.1602.

N-(3-cyanophenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3af)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (15.5 mg, 43% yield). m.p.: 138-140°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 8.97 (s, 1H), 7.88-7.87 (m, 1H), 7.67-7.60 (m, 2H), 7.37-7.31 (m, 4H), 7.30-7.23 (m, 2H), 7.19-7.16 (m, 1H), 7.02-6.94 (m, 3H), 5.09 (s, 1H), 3.92 (dt, J = 11.2 Hz, J = 4.4 Hz, 1H), 3.42-3.35 (m, 1H),3.13-2.99 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 171.2, 149.3, 138.3, 134.5, 131.5, 129.8, 129.7, 129.0, 127.94, 127.9, 127.8, 126.9, 123.9, 123.0, 120.8, 118.3, 115.5, 113.0, 66.3, 45.6, 28.7. IR ν 3298, 3043, 2899, 2251, 2227, 1499, 1036, 888 cm^-1. HRMS (ESI) m/z: calcd for C₂₃H₂₀N₃O [M+H]⁺ 354.1601; found 354.1599.

N-(4-nitrophenyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ag)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). Yellow oil (20.8 mg, 56% yield). ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.19 (s, 1H), 8.13 (d, J = 9.2 Hz, 2H), 7.67-7.60 (m, 3H), 7.34-7.25 (m, 5H), 7.18 (d, J = 6.8 Hz, 1H), 7.02-6.95 (m, 3H), 5.11 (s, 1H), 3.96-3.89 (m, 1H), 3.43-3.38 (m, 1H), 3.11-3.01 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 171.3, 149.2, 143.7, 143.2, 134.5, 131.3, 129.7, 129.0, 128.04, 128.0, 127.0, 121.0, 119.3, 115.7, 66.4, 45.7, 28.6.

N-([1,1'-biphenyl]-2-yl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ah)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (31.1 mg, 77% yield). m.p.: 53-54°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.18 (s, 1H), 8.50 (d, J = 8.4 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.34-7.24 (m, 4H), 7.23-7.13 (m, 5H), 7.09 (d, J = 7.2 Hz, 1H), 7.05-7.02 (m, 3H), 6.91 (dd, J₁ = J₂ = 7.2 Hz, 1H), 6.77 (d, J = 8.0 Hz, 2H), 4.91 (s, 1H), 3.28 (dt, J = 10.8 Hz, J = 3.6 Hz, 1H), 2.98 (td, J = 10.8 Hz, J = 3.2 Hz, 1H), 2.67 (dt, J = 10.2 Hz, J = 3.2 Hz, 1H), 2.46-2.38 (m, 1H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.5, 148.9, 137.8, 135.0, 134.4, 132.1, 131.7, 129.6, 129.3, 129.2, 129.1, 128.9, 128.8, 128.5, 127.7, 127.6, 127.5, 126.9, 123.8, 119.7, 119.3, 114.4, 66.6, 44.3, 28.6. IR ν 3323, 3028, 2916, 2242, 1672, 1489, 1295, 1037 cm^-1. HRMS (ESI) m/z: calcd for C₂₈H₂₅N₂O [M+H]⁺ 405.1961; found 405.1960.

N-(4'-methoxy-[1,1'-biphenyl]-2-yl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ai)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (36.4 mg, 84% yield). m.p.: 128-130°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.17 (s, 1H), 8.46 (dd, J₁ = 8.0 Hz, J₂ = 0.8 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.32-7.26 (m, 3H), 7.25-7.17 (m, 2H), 7.15-7.12 (m, 1H), 7.10-7.05 (m, 2H), 6.98-6.89 (m, 3H), 6.77 (d, J = 8.0 Hz, 2H), 6.71-6.67 (m, 2H), 3.82 (s, 3H), 3.34 (dt, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.03 (td, J = 11.2 Hz, J = 3.6 Hz, 1H), 2.73 (dt, J = 16.0 Hz, J = 3.2 Hz, 1H), 2.58-2.50 (m, 1H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.4, 159.0, 148.9, 135.1, 134.5, 132.2, 131.4, 130.3, 129.8, 129.7, 129.3, 128.8, 128.2, 127.6, 127.4, 126.9, 123.7, 119.6, 119.3, 114.3, 114.1, 66.6, 55.3, 44.3, 28.6. IR ν 3316, 3061, 2914, 2846, 2247, 1598, 1035, 834 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₇N₂O₂[M+H]⁺ 435.2067; found 435.2068.

N-(4'-methyl-[1,1'-biphenyl]-2-yl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3aj)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (30.5 mg, 73% yield). m.p.: 136-138°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.17 (s, 1H), 8.46 (d, J = 9.6 Hz, 1H), 7.56 (d, J = 7.2 Hz, 1H), 7.32-7.12 (m, 6H), 7.10 -7.04 (m, 2H), 6.98 (d, J = 8.0 Hz, 2H), 6.94-6.88 (m, 3H), 6.73 (d, J = 8.0 Hz, 2H), 4.90 (s, 1H), 3.29 (dt, J = 10.4 Hz, J = 4.4 Hz, 1H), 3.02 (td, J = 11.2 Hz, J = 3.2 Hz, 1H), 2.70 (dt, J = 15.6 Hz, J = 3.6 Hz, 1H), 2.54-2.45 (m, 1H), 2.37 (s, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.3, 148.9, 137.4, 135.1, 134.7, 134.5, 132.2, 131.8, 129.6, 129.5, 129.2, 129.0, 128.9, 128.3, 127.6, 127.5, 126.9, 123.7, 119.7, 119.3, 114.3, 66.5, 44.3, 28.5, 21.3. IR ν 3327, 3057, 2950, 2917, 1683, 1493, 1271, 930 cm^-1. HRMS (ESI) m/z: calcd for C₂₉H₂₇N₂O [M+H]⁺ 419.2118; found 419.2116.

N-([1,1':4',1''-terphenyl]-2-yl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ak)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (38.4 mg, 80% yield). m.p.: 119-121°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 9.23 (s, 1H), 8.50 (dd, J₁ = 8.8 Hz, J₂ = 1.2 Hz, 1H), 7.65-7.61 (m, 2H), 7.58 (d, J = 7.2 Hz, 1H), 7.54-7.49 (m, 2H), 7.44-7.39 (m, 3H), 7.36-7.31 (m, 1H), 7.28-7.16 (m, 5H), 7.13-7.08 (m, 3H), 7.04 (d, J = 7.2 Hz, 1H), 6.90 (dd, J₁ = J₂ = 7.2 Hz, 1H), 6.75 (d, J = 8.0 Hz, 2H), 4.92 (s, 1H), 3.28 (dt, J = 10.4 Hz, J = 4.4 Hz, 1H), 2.98 (td, J = 11.2 Hz, J = 3.2 Hz, 1H), 2.68 (dt, J = 15.6 Hz, J = 3.6 Hz, 1H), 2.55-2.46 (m, 1H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 170.4, 148.9, 140.4, 140.3, 136.7, 135.0, 134.4, 132.2, 131.4, 129.6, 129.54, 129.5, 129.3, 129.0, 128.9, 128.6, 127.7, 127.6, 127.53, 127.5, 127.4, 127.1, 127.0, 126.9, 123.8, 119.8, 119.4, 114.4, 66.6, 44.4, 28.5. IR ν 3300, 3025, 2849, 2247, 1685, 1111, 906, 841 cm^-1. HRMS (ESI) m/z: calcd for C₃₄H₂₉N₂O [M+H]⁺ 481.2274; found 481.2273.

N-benzyl-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3al)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 10:1 as the eluent). White solid (29.3 mg, 86% yield). m.p.: 154-156°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.64-7.61 (m, 1H), 7.32-7.14 (m, 9H), 7.04-7.00 (m, 2H), 6.93-6.88 (m, 3H), 5.06 (s, 1H), 4.43-4.32 (m, 2H), 3.82 (dt, J = 10.8 Hz, J = 4.4 Hz, 1H), 3.28 (td, J = 10.4 Hz, J = 3.6 Hz, 1H), 3.07-2.91 (m, 2H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.4, 149.4, 138.1, 134.5, 132.6, 129.4, 128.9, 128.6, 127.7, 127.5, 127.4, 127.3, 126.8, 119.7, 114.9, 65.6, 45.2, 43.4, 29.0. IR ν 3319, 3025, 2831, 2247, 1489, 1055, 903, 756 cm^-1. HRMS (ESI) m/z: calcd for C₂₃H₂₃N₂O [M+H]⁺ 343.1805; found 343.1803.

N-phenethyl-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3am)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). White solid (19.9 mg, 56% yield). m.p.: 123-125°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.60-7.57 (m, 1H), 7.32-7.23 (m, 4H), 7.19-7.11 (m, 4H), 6.93-6.84 (m, 6H), 4.94 (s, 1H), 3.71 (dt, J = 11.2 Hz, J = 4.0 Hz, 1H), 3.52-3.36 (m, 2H), 3.19 (td, J = 11.2 Hz, J = 3.6 Hz, 1H), 2.89-2.60 (m, 4H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.3, 149.2, 138.7, 134.6, 132.6, 129.4, 128.8, 128.7, 128.5, 127.5, 127.46, 126.8, 126.4, 119.4, 114.3, 65.6, 44.6, 40.6, 35.4, 28.8. IR ν 3298, 3028, 2899, 2228, 1663, 1516, 943, 791 cm^-1. HRMS (ESI) m/z: calcd for C₂₄H₂₅N₂O [M+H]⁺ 357.1961; found 357.1960.

N-(4-methylphenethyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3an)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). White solid (28.5 mg, 77% yield). m.p.: 97-99°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.59-7.56 (m, 1H), 7.31-7.21 (m, 4H), 7.14-7.11 (m, 1H), 6.97 (d, J = 7.6 Hz, 2H), 6.90-6.79 (m, 6H), 4.93 (s, 1H), 3.71 (dt, J = 11.2 Hz, J = 4.8 Hz, 1H), 3.49-3.34 (m, 2H), 3.20 (td, J = 10.4 Hz, J = 4.4 Hz, 1H), 2.90-2.75 (m, 2H), 2.71-2.55 (m, 2H), 2.29 (s, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.3, 149.3, 135.8, 135.6, 134.6, 132.7, 129.4, 129.2, 128.9, 128.7, 128.6, 127.5, 127.4, 126.7, 119.4, 114.3, 65.6, 44.7, 40.7, 35.0, 28.8, 21.0. IR ν 3262, 3063, 2831, 2241, 1598, 1442, 1426, 987 cm^-1. HRMS (ESI) m/z: calcd for C₂₅H₂₇N₂O [M+H]⁺ 371.2118; found 371.2120.

N-(3,4-dimethoxyphenethyl)-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ao)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 2:1 as the eluent). White solid (23.3 mg, 56% yield). m.p.: 105-106°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.58-7.55 (m, 1H), 7.31-7.20 (m, 4H), 7.13-7.10 (m, 1H), 6.93-6.82 (m, 4H), 6.66 (d, J = 8.4 Hz, 1H), 6.54 (d, J = 2.0 Hz, 1H), 6.46 (dd, J = 8.0 Hz, J = 1.6 Hz, 1H), 4.93 (s, 1H), 3.84 (s, 3H), 3.72-3.65 (m, 4H), 3.48-3.41 (m, 2H), 3.20 (td, J = 11.2 Hz, J = 3.6 Hz, 1H), 2.89-2.57 (m, 4H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.3, 149.3, 148.9, 147.5, 134.5, 132.7, 131.1, 129.4, 128.9, 127.5, 127.4, 126.7, 120.6, 119.4, 114.2, 111.6, 111.2, 65.7, 55.9, 55.7, 44.6, 40.5, 35.0, 28.8. IR ν 3028, 2915, 2850, 2251, 1662, 1061, 889, 752 cm^-1. HRMS (ESI) m/z: calcd for C₂₆H₂₉N₂O₃[M+H]⁺ 417.2173; found 417.2171.

2-phenyl-N-(4-phenylbutyl)-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ap)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). White solid (23.8 mg, 62% yield). m.p.: 146-148°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.60-7.57 (m, 1H), 7.31-7.19 (m, 6H), 7.17-7.12 (m, 2H), 7.05-7.02 (m, 2H), 6.91-6.84 (m, 4H), 4.96 (s, 1H), 3.83 (dt, J = 11.2 Hz, J = 4.4 Hz, 1H), 3.31-3.11 (m, 3H), 3.06-2.91 (m, 2H), 2.50 (t, J = 6.8 Hz, 2H), 1.51-1.36 (m, 4H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.2, 149.4, 142.1, 134.4, 132.8, 129.4, 128.9, 128.3, 127.5, 127.4, 126.8, 125.7, 119.6, 114.5, 65.6, 45.0, 39.2, 35.4, 29.1, 29.0, 28.5. IR ν 3254, 3061, 2941, 2828, 1676, 1559, 1217, 827 cm^-1. HRMS (ESI) m/z: calcd for C₂₆H₂₉N₂O [M+H]⁺ 385.2274; found 385.2272.

N-octyl-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3aq)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). White solid (32.8 mg, 90% yield). m.p.: 129-130°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.60-7.57 (m, 1H), 7.32-7.27 (m, 2H), 7.25-7.19 (m, 2H), 7.15-7.12 (m, 1H), 6.92-6.87 (m, 4H), 4.97 (s, 1H), 3.85 (dt, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.28 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.23-3.11 (m, 2H), 3.10-2.94 (m, 2H), 1.41-1.32 (m, 2H), 1.26-1.10 (m, 11H), 0.86 (t, J = 7.2 Hz, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.1, 149.4, 134.4, 132.8, 129.4, 128.9, 127.5, 127.4, 126.7, 119.5, 114.5, 65.6, 45.0, 39.5, 31.7, 29.5, 29.2, 29.1, 29.0, 26.8, 22.6, 14.1. IR ν 3264, 3060, 2950, 2847, 1673, 1425, 1220, 1053 cm^-1. HRMS (ESI) m/z: calcd for C₂₄H₃₃N₂O [M+H]⁺ 365.2587; found 365.2585.

N-dodecyl-2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carboxamide (3ar)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). White solid (32.3 mg, 77% yield). m.p.: 101-103°C. ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.61-7.57 (m, 1H), 7.33-7.20 (m, 4H), 7.16-7.13 (m, 1H), 6.92-6.87 (m, 4H), 4.97 (s, 1H), 3.86 (dt, J = 10.8 Hz, J = 4.4 Hz, 1H), 3.30 (td, J = 10.8 Hz, J = 4.0 Hz, 1H), 3.25-3.11 (m, 2H), 3.10-2.94 (m, 2H), 1.43-1.12 (m, 20H), 0.88 (t, J = 7.2 Hz, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.1, 149.4, 134.4, 132.8, 129.4, 128.9, 127.5, 127.4, 126.7, 119.5, 114.5, 65.6, 44.9, 39.5, 31.9, 29.65, 29.64, 29.54, 29.51, 29.49, 29.4, 29.2, 29.0, 26.8, 22.7, 14.2. IR ν 3317, 3027, 2918, 2246, 1663, 1488, 904, 723 cm^-1. HRMS (ESI) m/z: calcd for C₂₈H₄₁N₂O [M+H]⁺ 421.3213; found 421.3212.

Ethyl (2-phenyl-1,2,3,4-tetrahydroisoquinoline-1-carbonyl)glycinate (3as)

Purified by silica gel chromatography (petroleum ether/ethyl acetate 5:1 as the eluent). Colorless oil (31.1 mg, 92% yield). ¹H NMR (400 MHz, CDCl₃, TMS) δ 7.55-7.52 (m, 1H), 7.45-7.42 (m, 1H), 7.33-7.22 (m, 4H), 7.17-7.13 (m, 1H), 6.96-6.87 (m, 3H), 5.03 (s, 1H), 4.16-4.06 (m, 3H), 3.91-3.83 (m, 2H), 3.37-3.30 (m, 1H), 3.20-3.11 (m, 1H), 3.02-2.95 (m, 1H), 1.20 (t, J = 7.2 Hz, 3H). ¹³C{¹H} NMR (100 MHz, CDCl₃, TMS) δ 172.6, 169.6, 149.3, 135.0, 132.5, 129.4, 129.1, 127.6, 127.56, 126.7, 119.5, 114.4, 65.4, 61.5, 44.8, 41.3, 28.6, 14.1. IR ν 3298, 2918, 2250, 1598, 1318, 1036, 791, 692 cm^-1. HRMS (ESI) m/z: calcd for C₂₀H₂₃N₂O₃[M+H]⁺ 339.1703; found 339.1701.

Acknowledgments

We are grateful for the financial support provided by the National Natural Science Foundation of China (22271108, 21871100, 21901079), the Fundamental Research Funds for the Central Universities (2017KFYXJJ166, 2019kfyRCPY096), Huazhong University of Science and Technology (HUST), Hubei Technological Innovation Project (2019ACA125), and the Opening Fund of Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica (No. BCMM201805). We also thank the Analytical and Testing Center of HUST, Analytical and Testing Center of the School of Chemistry and Chemical Engineering (HUST) for access to their facilities.

Author contributions

X-Y.T. conceived and supervised the study. S-J.W. performed the syntheses, the spectroscopic characterizations and the X-ray crystal diffraction analysis. S-J.W., L.W., and X-Y.T. analyzed the data and wrote the manuscript.

Declaration of interests

The authors declare no competing interest.

Published: March 30, 2023

Footnotes

Supplemental information can be found online at https://doi.org/10.1016/j.isci.2023.106528.

Supplemental information

Document S1. Figures S1–S25, Tables S1–S3, Scheme S1, and Data S1

mmc1.pdf^{(5.7MB, pdf)}

Data and code availability

•
The original crystal structure of B(C₆F₅)₃^.H₂O with 1aa has been deposited at CCDC and is publicly available as of the date of publication. CCDC number is listed in the key resources table.
•
This paper does not report original code.
•
Any additional information required to reanalyze the data reported in this paper can be obtained from the lead contact upon request.

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