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. 2026 Jul 13;16(37):40076–40084. doi: 10.1039/d6ra04323b

Direct halo-/seleno-sulfonylation and diselenylation of ynamides mediated by visible light

Lucie Almeida Do Amaral a, Dominique Mouysset a, Didier Siri a, Jean-Simon Suppo a,✉, Stéphane Gastaldi a,✉, Michèle Bertrand a,✉, Laurence Feray a,✉
PMCID: PMC13359595  PMID: 42444706

Abstract

Blue LED light-induced double functionalization of ynamides in the presence of tosyl iodide, tosyl bromide, tosyl phenyl selenide, tosyl benzyl selenide, and diphenyl diselenide is reported. The strategy, based on the photoinduced cleavage of the tosyl derivatives (TsY), or diselenide derivative, involves radical addition to the triple bond of ynamides followed by atom/group transfer. It allows the increase of molecular complexity in a simple, clean, and atom economical manner. These atom-transfer-radical-addition (ATRA) processes occur in the absence of initiator or catalyst with high yield and high regio- and stereoselectivity leading to complex tetrasubstituted alkenes bearing no less than three heteroatoms. Theoretical support to the mechanism and the scope and limitation of the reaction are discussed.

Blue LED light induced regio- and stereoselective double functionalization of ynamides in the presence of tosyl halides, tosyl selenides, and diphenyl diselenide. These ATRA processes occur with high yield leading to complex polysubstituted enamides.graphic file with name d6ra04323b-ga.jpg

Introduction

Installing molecular diversity while respecting the principles of green chemistry is an ongoing challenge for organic chemists. Thus, strategies that enable the rapid generation of structural complexity while minimizing the number of steps, reagents, and waste are therefore highly desirable. Among them, atom transfer radical addition (ATRA) reactions stand out as highly efficient and environmentally attractive transformations. By enabling the direct difunctionalization of unsaturated systems, ATRA processes combine high atom economy, operational simplicity, and step economy, making them particularly well aligned with the goals of sustainable synthesis. In this context, double hetero functionalization of alkynes has emerged as a powerful strategy for the selective construction of two new carbon–heteroatom bonds within a single operation.1 Among these transformations, direct two-component halo- and seleno-sulfonylation of alkynes is a specific class that allows rapid construction of β-halo- and seleno-vinyl sulfone derivatives, powerful building blocks for organic synthesis2 and precursors of biologically active compounds3 in a single and cost-effective step.

Amiel pioneered the direct halosulfonylation of alkynes by describing the first chlorosulfonylation of phenylacetylene using sulfonyl chlorides under copper catalysis in 1971.4 The same strategy was then applied in 1974 to obtain β-bromo-vinyl sulfones from sulfonyl bromides (Scheme 1a and b).5 The reactions were then carried out at 100 °C to give a E : Z mixture of addition products. At the same time, Truce's work showed that it was possible to perform the iodosulfonylation of alkynes using sulfonyl iodides under visible light activation (Scheme 1c).6 In 2005, 35 years later, Liang's group proposed a stereoselective version of the direct chlorosulfonylation reaction of arylacetylenes, highlighting the importance of using copper catalysis in the presence of 1 equivalent of Me2S at 110 °C to form the corresponding (Z)-β-chloro-vinyl sulfones as the only isomer.7 The work of Nakamura, who developed an iron-catalyzed version of this reaction in 2012, successfully yielded the E-isomer exclusively by working at 110 °C in toluene.8 Finally, with the emergence of redox photocatalysis, an iridium-photocatalyzed version of this transformation was described in 2018 by Kim and Han's group,9 followed by a similar strategy developed by Hu, involving a heteroleptic copper(i) as photocatalyst.10 In these two cases long reaction time, i.e. 24 h was required to reach good yields. Since Amiel's and Truce's pioneering work, direct bromo- or iodo-sulfonylation of alkynes has been studied much less extensively. An example of bromosulfonylation of phenylacetylene under UV activation was described by Vasin in 2003,11 followed by the work of Alabugin, realized on terminal alkynes, which showed that this reaction could be initiated by the oxidation of triethylborane at room temperature.12 More recently, a photoinitiated version of this transformation under visible light, involving terminal triple bonds without any additives or in the presence of a bis-imine has been proposed by Asachenko.13

Scheme 1. Two component chloro-, bromo-, iodo-, seleno-sulfonylation and diselenylation of triple bonds.

Scheme 1

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Back demonstrated in 1983 that the direct two-component selenosulfonylation of alkynes using sulfonylselenide derivatives (Scheme 1d) could be carry out under thermal activation in the absence or in the presence of azobisisobutyronitrile (AIBN) as a free radical initiator.14 Later on, Wang and Ji, followed by Niu, Li, and Xia, proposed two photocatalyzed versions of this transformation using a copper or cobalt complex15 or graphitic carbon nitride16 as photocatalysts. It is to be noted that although these reactions were conducted at room temperature, the time required to obtain satisfactory yields is relatively long, up to 17 h.

Despite the decades separating recent works from older ones, all these transformations share a radical mechanism, in which sulfonyl radical adds to a triple bond. Except for iodosulfonylation and, to a lesser extent, bromosulfonation, all these processes require either thermal activation or UV irradiation to promote the homolytic cleavage of the halogen–sulfur bond that generates sulfonyl radical or the addition of a partner that serves as an initiator or catalyst to form the same radical through atom transfer or single electron transfer.

Due to the electron-donating effect of the nitrogen atom, tempered by the nature of its electron-withdrawing substituent, ynamides behave as activated polarized alkynes that have been extensively used to perform regioselective, rapid, and elegant constructions of versatile N-containing molecules. Compared to simple alkynes, ynamides are especially interesting substrates as they inherently introduce an additional heteroatom into the molecular framework, thereby increasing structural complexity and synthetic versatility. However, to the best of our knowledge, none of these methods involves the use of a C–C triple bond of ynamides as substrate. Only one example has been reported to date by Wang's group,17 which showed for the purposes of mechanistic investigation17a in 2022 that, under activation by visible light, the addition of TsI to the N-phenyl tosyl ynamide derived from phenylacetylene led to the iodo-vinyl sulfone with the opposite selectivity compared to that obtained in the present report (vide infra) (Scheme 1f). This work was extended to other sulfonyl ynamides and terminal aromatic alkynes thus demonstrating the full value of this process.17b

As halo- and seleno-sulfonylation of triple bonds, the direct diselenylation reaction allows for the environmentally friendly and atom economical preparation of di hetero-substituted alkenes. In particular, 1,2-diselenylated alkenes are important intermediates in organoselenium chemistry and are widely used in organic synthesis because the C–Se bond is highly versatile and can be selectively transformed.1b,c Regarding the direct two-component diselenylation of triple bonds (Scheme 1e), Back reported in 1988 the first transformation involving methyl propriolate and dimethyl maleate as substrates.18 Under UV irradiation for 24 h the resulting diselenide adducts were isolated as mixture of E : Z isomers through ATRA mechanism involving the addition of phenylselenyl radical to these electron poor alkynes. Following this initial result, various methods based on the use of a metal such as palladium,19 iron,20 copper,21 copper/zinc couple,22 or even gold23 were developed. Most of these transformations, involving a polar mechanism, require long reaction times and high temperatures to be effective. More recently, Niu, Song, and Wang24 proposed a clean electrochemical protocol to perform this transformation at room temperature. However, the optimized conditions only worked with terminal arylacetylenes and required 15 h of reaction time. The proposed mechanism involves radical addition of phenylselenyl radical to the triple bond of the substrates. Surprisingly, in the development of these triple bond diselenylation reactions, as with those dedicated to halo-sulfonylation seen above, ynamides have not been the subject of any specific study.

In this context, we describe herein the direct visible light-induced two component stereoselective difunctionalization of various N-cyclic and N-acyclic ynamides by using tosyl derivatives (TsY) and diselenide derivative (PhSe)2 at room temperature, in the absence of any other reagents or photocatalysts or other costly energy activation methods (Scheme 1g).

Results and discussion

We started our investigations by selecting ynamide 1a derived from oxazolidinone and 1-hexyne as the model substrate (Table 1). Reacting 1a (0.2 M in degassed dichloromethane) in the presence of 0.2 equiv. of AIBN and 1.2 equiv. of TsBr led after 4 h irradiation with a 365 nm Lamp to the formation of the desired adduct 3aa with 67% isolated yield (Table 1, entry 1). Only one isomer was detected from the 1H NMR spectrum of the crude reaction mixture. In absence of AIBN, the process remained effective leading to 3aa in 69% yield after 6 h irradiation (Table 1, entry 2). Surprisingly, by using a wavelength for irradiation with lower energy, i.e., 405 nm, the expected product 3aa was isolated with a significant increase in yield after 6 h (Table 1, entry 3). The reaction time could be reduced to 2 h without loss of efficiency (Table 1, entry 4). Even at 450 nm, the reaction occurred but with a longer irradiation time for a moderate yield (Table 1, entry 5).

Table 1. Optimization of reaction conditions involving ynamide 1a.

graphic file with name d6ra04323b-u1.jpg
Entry Wavelength (nm) Y AIBN (equiv) t 3af or 1ag
1 365b Br 0.2 4 h 3aa (67%)
2 365b Br — 6 h 3aa (69%)
3 405c Br — 6 h 3aa (89%)
4 405c Br — 2 h 3aa (88%)
5 450d Br — 12 h 3aa (59%)
6 — Br — 2 h 1a (93%)h
7 405c Br — 2 h 1a (60%)i
8 405c SeBn — 30 min 3ac (70%)
9 — SeBn — 30 min 1a (68%)h
10 405c SeBn — 30 min 1a (64%)i
11 405c I — 30 min 3ab (77%)
12 405c Cl — 2 h 1a (90%)
13 365b Cl — 2 h 1a (85%)
14 365b Cl 0.2 2 h 1a (75%)
15 306e Cl 0.2 2 h 1a (77%)
16 — Cl 0.2 2 h 1a (68%)j
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a

[1a] = 0.2 M in degassed dichloromethane.

b

18 W LEDs (Evoluchem® lamps, 365 nm, light intensity: 16.7 mW cm−2 at 10 cm distance).

c

18 W LEDs (Evoluchem® lamps, 405 nm, light intensity: 22.9 mW cm−2 at 10 cm distance).

d

18 W LEDs (Evoluchem® lamps, 450 nm, light intensity: 29.3 mW cm−2 at 10 cm distance).

e

Rayonet apparatus (RPR-200, 16 UV lamps, 306 nm).

f

Isolated yield.

g

NMR yield with internal reference (pentamethylbenzene).

h

Under dark.

i

TEMPO (1 equiv.).

j

In toluene, 80 °C.

Optimized reaction conditions, i.e., irradiation at 405 nm in degassed dichloromethane were used to explore the reactivity of other tosyl derivatives (TsY). In the presence of TsSeBn or TsI, under these conditions, ynamide 1a was totally consumed after 30 min leading to the desired adducts 3ac and 3ab with good isolated yields. Again, the process was totally regio and stereoselective to give E-adducts exclusively (vide infra) (Table 1, entries 8 and 11). Our efforts then turned to the addition of TsCl. Experiments were conducted at different irradiation wavelengths, namely 405, 365, and 306 nm, in the absence or presence of AIBN. For each of these, only the starting material was recovered after 2 hours of reaction (Table 1, entries 12–15). Finally, a last reaction carried out under thermal activation in the presence of AIBN also failed to produce the desired product (Table 1, entry 16).

Optimized reaction conditions found for TsBr, TsSeBn, and TsI additions were used to explore the scope of the transformation. The results of irradiation experiments conducted with N-cyclic ynamides 1a–h prepared according to modified Stahl procedure25 and N-acyclic ynamide 1i prepared according to Hsung methodology26 are reported in Scheme 2.

Scheme 2. Scope of the di hetero-functionalization process. a30 min for 2b:TsI, 2c: TsSeBn, and 2d:TsSePh. 120 min for 2a:TsBr. bORTEP view of the single crystal X-ray structure of compounds 3cc, 3dd, and 3cd.

Scheme 2

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Reacting substrates derived from oxazolidinone 1a–b with TsY derivatives 2a–d led to the formation of trisubstituted enamides 3aa–ad and 3ba–bb with a total control of regio- and stereo-selectivity. The isolated yields varied from 70 to 93%. The process remained highly effective when phthalimide-derived ynamides 1c–e were used. Fortunately, among the adducts obtained, 3cc, 3cd, and 3dd were successfully recrystallized and the configuration of the double bond was assigned from their X-ray spectrum showing the trans addition of TsSePh and TsSeBn. Vinylogous ynamides 1f–h derived from 3-methyl-indole carboxylate also proved to be good partners in this transformation, enabling the formation of the desired adducts with yields of up to 95% for the addition of TsSeBn. We next explored the reaction scope using N-acyclic ynamide 1i. The process proved to be compatible with the use of this substrate leading to the formation of adducts 3ia–id with good yields and again a total regio- and stereo-selectivity.

We also showed that these experimental conditions, which use visible light, were compatible with a non-activated triple bond. Indeed, 1-hexyne (1j) was reacted in the presence of TsBr to give the corresponding adduct 3ja in 90% yield.

A mechanistic study was conducted to determine the key stages of this transformation (Scheme 3). The involvement of a radical mechanism takes into account the fact that reactions carried out on 1a in the presence of TsBr or TsSeBn in the absence of light or in the presence of 1 equiv. of TEMPO were completely inhibited (Table 1. Entries 6, 7, 9, and 10). The first step involves the homolytic cleavage of the Y–SO2Tol bond of 2a–d leading to a tosyl radical (Scheme 3a). The homolytic cleavage of TsI under visible light is a well-known process.6 Conversely, as described in the literature, the same cleavage involving brominated11 or selenated14 derivatives is most commonly carried out under UV irradiation or thermal activation. The UV-visible absorption spectrum of tosyl derivatives 2 clearly showed the influence of concentration on the maximum absorption wavelength (Scheme 3b). A bathochromic effect was observed with increasing concentration, probably due to π-stacking interactions.27 Since the addition reactions are conducted at 0.2 M, it can be assumed that at this concentration, TsBr and TsSePh absorb visible light and undergo homolytic cleavage.

Scheme 3. Mechanistic studies. (a) BDE(SO2–Y) calculated in kcal mol−1 at (M06-2X/def2-TZVP) level of theory. (b) Normalized UV visible absorption spectra of TsY at various concentrations in dichloromethane. (c) Radical addition of tosyl radical to ynamides: previous mechanistic studies. (d) Energy diagrams for competitive addition paths (relative enthalpies are given in kcal mol−1). (e) Reaction involving ynamides derived from cyclopropylacetylene (n.d.: not detected). (f) Energy profile for inversion of vinyl radical and bromine atom transfer (relative enthalpies are given in kcal mol−1).

Scheme 3

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Conversely, the UV visible absorption spectrum of TsCl in DCM showed a maximum absorption wavelength that is too low to expect reactivity under visible light. However, it should be noted that TsCl at this concentration (0.2 M) is not completely soluble in DCM, which may interfere with measurements. To rule out the possibility of an initiation step involving a visible light-reactive ynamide/TsY charge transfer complex, the absorption spectrum of an equimolar mixture of ynamide 1a and TsBr (2a) was measured in dichloromethane and compared to the spectra obtained for the two compounds taken individually at the same concentration. No effect on the maximum absorption wavelengths was observed (see SI).

Y–SO2Tol bond dissociation energy (BDE) for TsY derivatives were calculated at (M06-2X/def2-TZVP) level of theory (Scheme 3a) showing values lower or around 50 kcal mol−1 for TsI, TsBr, and TsSePh which is entirely consistent with a homolytic cleavage process. The value calculated for TsCl is in agreement to that previously determined experimentally and described in the literature for PhSO2Cl (BDE (Cl–SO2Ph) = 70.6 kcal mol−1).28 The lack of reactivity of TsCl upon light activation in our process was not surprising considering the reactivity of TsCl with regard to homolytic cleavage of the Cl–SO2 bond, which is much more difficult to break than its brominated, iodinated, or selenated Y–SO2 analogues.

The second step of the mechanism involves the addition of the sulfonyl radical to the triple bond of the substrate. During the course of our investigation on the reactivity of ynamides towards radical transformations, we have shown that sulfonyl radicals can add to the triple bond of N-sulfonyl ynamides to give α-sulfonyl amides in good yields.29 This step was totally regiospecific, involving the addition of sulfonyl radical to the carbon of the triple bond in beta position of the nitrogen atom (Scheme 3c). This reactivity of N-sulfonyl ynamides towards sulfonyl radicals was also explored by Zhu30 in 2021, Wang17 in 2022 and Chang31 and Wang in 2026. As part of Wang's study,17 an addition of the radical to the carbon of the triple bond in alpha position of the nitrogen atom was also proposed. In this particular case, the ynamide carried an aromatic group on the triple bond, thereby reversing the regioselectivity of the process.32

Theoretical calculations were performed to explain the total selectivity experimentally observed. DFT is a powerful tool for reaction mechanism investigation in predicting the regioselectivity and the stereoselectivity. The Gaussian 16 package33 was used to establish the potential energy profile for the addition of tosyl radical to model substrate 1a-Me where the n-butyl chain was replaced by a methyl group to simplify calculations (Scheme 3d). The structures of reactants, products, and transition states were optimized at the ωB97X-D/6-311++G(3df,3pd)//ωB97X-D/6-31G(d,p) level of theory. Intrinsic reaction coordinate (IRC) calculations, at the same level of theory, were performed to ensure that the transition states led to the expected reactants and products. The data are summarized in Scheme 3d and the following comments are worth being noted. Both addition processes have nearly no activation energies, however the addition of tosyl radical to Cβ leading to vinyl radical B1 is more exothermic by 5 kcal per mole than the addition to Cα leading to vinyl radical A. Although the addition of sulfonyl radical is known to be reversible,34 the exothermicity of the two addition paths makes both monomolecular reverse steps very slow35 compared to the rate of the subsequent bimolecular atom or group transfer which has nearly no activation barrier (vide infra). For a process under kinetic control the theoretical regioselectivity can be estimated >95 : 5 from the 1.7 kcal per mole difference in activation energy between the two competitive paths.

The ring-opening of cyclopropylcarbinyl36 or cyclopropylvinyl37 radicals (generally assumed to be diffusion-controlled processes) provides convenient radical clocks. Accordingly, addition to Cα of ynamides of type 1 derived from cyclopropylacetylene should result in the formation of allenic products 4 (Scheme 3e). When ynamides 1b, 1d, and 1g were submitted to the reaction conditions in the presence of TsI, TsSePh, and TsBr, respectively, no products resulting from ring opening were detected. Only the formation of adducts 3bb, 3dd, and 3ga was observed (Scheme 2). These results support the total regioselectivity in favor of the addition to Cβ regardless which TsY derivative is used.

A competitive experiment involving irradiation at 405 nm for 2 h of an equimolar mixture of ynamide 1a and 1-hexyne (1j) in the presence of 0.95 equiv. of TsBr (2a) led to 72% conversion of 1a in adduct 3aa while only 28% of 1-hexyne was consumed to give the corresponding adduct 3aj (see SI). This result is consistent with a lower reactivity of this latter compared to ynamides. This result is not surprising given the electrophilic nature of tosyl radical,38 which adds more rapidly to the electron-richest triple bond.39

The stereoselectivity of the process is determined by the competition between atom or group transfer from TsY and monomolecular interconversion of the vinyl radical intermediates B1 and B2. A scan, based on a regular variation of the radical-center valence angle, enabled the location of the interconversion transition state TSinv (Scheme 3f). The energy difference between the two sp2 conformations of the radical is low (3.7 kcal mol−1). However, the activation barriers for interconverting B1 into B2 (8.4 kcal mol−1) and B2 into B1 (4.7 kcal mol−1) are largely higher than the low barriers reported for simple alkenyl radicals (<2 kcal mol−1) which rapidly interconvert.40 The calculated barriers are consistent with the strongly bent conformation of both radical isomers. There is no activation enthalpy for bimolecular atom transfer to B1 (−0.2 kcal mol−1 for bromine atom transfer, Scheme 3f). Such a fast atom transfer would prevent the inversion process from B1 to B2. Even low, the activation barrier for bimolecular atom transfer to B2 (+2.1 kcal mol−1 for bromine atom transfer, Scheme 3f) might make the inversion process from B2 to B1 competitive with the transfer. It is reasonable to assume that for B2, the monomolecular inversion process, is faster than the bimolecular atom transfer. This would result in the selective formation of the trans adduct.

Based on this study, we proposed the ATRA mechanism described in Scheme 4. The first step involves the homolytic cleavage of the Y–SO2 bond of 2 under visible light, leading to tosyl radical. Once formed, the tosyl radical adds regioselectively to the triple bond of ynamides 1 to form vinyl radical B1, which evolves by halogen atom transfer or selenide group transfer to form the expected product.

Scheme 4. (a) Proposed mechanism.

Scheme 4

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Finally, the protocol was scaled up to 4 mmol of ynamide 1a that was reacted in the presence of TSBr (2a) or TsSePh (2d) (Scheme 5). Enamides 3aa and 3ad were isolated in 82% and 81% yield, respectively, showing the synthetic utility of the process. Post-functionalization reactions involving enamide 3ad were performed. The chemoselective oxidation was achieved in the presence of 1 equiv. of m-CPBA leading to selenoxide 4ad. Oxidation followed by hydration led to α-sulfonylated amide 5.

Scheme 5. Scaled-up reactions involving 1a and post-functionalization reactions of 3ad.

Scheme 5

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Hetero-difunctionalization reaction involving ynamides was extended to direct diselenylation in the presence of (PhSe)2. The results are reported in Scheme 6. Two-selenium-containing enamides 3ae, 3fe, and 3ie were isolated in excellent yields. In each case, a single isomer was obtained. The E stereochemistry was assigned based on results reported in the literature.18

Scheme 6. (a) Scope of the diselenylation process. 2e: (PhSe)2.

Scheme 6

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To rule out the possibility of a polar mechanism involving an electrophilic addition to the triple bond, two reactions were carried out on 1a in the presence of (PhSe)2 in the absence of light and under irradiation in the presence of 1 equivalent of TEMPO. The lack of reactivity in both cases suggests that an ATRA mechanism is again proceeding, involving the addition of phenylselenyl radical to the electron-rich triple bond of ynamide.

These results raise questions about the reactivity of the selenium-centered radical, long been known to add to electron-poor triple bonds such as methyl propiolate or dimethylacetylene dicarboxylate.18 A competitive experiment showed that ynamide 1a is twice as reactive as diethylacetylene dicarboxylate (1k) (Scheme 6). It is worth noting that no addition to 1-hexyne (1j) was observed under the very same experimental conditions as already observed by Back.18 Contrary to that of phenylsulfonyl radical, this specific behaviour of phenylselenyl radical towards triple bonds seems not to be related to polar effects. Phenylselenyl radical would rather be classified as an ambident radical. Theoretical calculations on model substrates 1a-Me, 1j-Me, and 1k-Me clearly showed that all these additions are exothermic processes with no activation energy (Scheme 7). However, the addition to both electron rich 1a-Me and electron poor 1k-Me substrates would be about twice as exothermic as the addition to 1j-Me. A kinetic study of the addition of phenylselenyl radical to a large panel of vinyl monomers had led Ito41 to point out the importance of the stability of the incoming radical adduct in determining reactivity. In the case of vinyl monomers, the reverse addition step is so fast that the kinetic measurements were only made possible in the presence of O2 as a radical trap. In the present work concerned with triple bonds, only the addition to 1-hexyne (1j) might be reversible so that no adduct could be detected.

Scheme 7. Energy diagrams for phenylselenyl radical addition to 1a-Me, 1j-Me, and 1k-Me (relative enthalpies are given in kcal mol−1).

Scheme 7

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Conclusions

In conclusion, we have developed a general protocol for the hetero-difunctionalization of ynamides, enabling the regioselective and stereoselective construction of tetrasubstituted alkynes bearing no less than three heteroatoms in good to excellent yields. The experimental conditions, which are mild and consistent with the principles of green chemistry, require only visible light as an additional reagent, resulting in a complete atom economy. At the same time, this study also advances our understanding of the particular reactivity of ynamides toward radicals, a growing field of interest to organic chemists. At last, the diselenylation of ynamides extend the panel of non-aromatic triple bonds to which phenylselenyl radical can add via an ATRA process.

Author contributions

All the authors contributed equally.

Conflicts of interest

There are no conflicts to declare.

Supplementary Material

RA-016-D6RA04323B-s001
RA-016-D6RA04323B-s002

Acknowledgments

The authors acknowledge Aix Marseille University for funding Lucie Almeida Do Amaral's thesis.

Data availability

The data supporting this article (experimental procedures, NMR spectra, UV-visible spectra, theoretical calculation) have been included as part of the supplementary information (SI).

CCDC 2551667, 2551668, 2551669 and 2565276 contain the supplementary crystallographic data for this paper.42a–d

Supplementary information: experimental procedures, NMR spectra, UV-visible spectra, theoretical calculation. See DOI: https://doi.org/10.1039/d6ra04323b.

Notes and references

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

RA-016-D6RA04323B-s001
RA-016-D6RA04323B-s001.pdf (13MB, pdf)
RA-016-D6RA04323B-s002
RA-016-D6RA04323B-s002.cif (136.3KB, cif)

Data Availability Statement

The data supporting this article (experimental procedures, NMR spectra, UV-visible spectra, theoretical calculation) have been included as part of the supplementary information (SI).

CCDC 2551667, 2551668, 2551669 and 2565276 contain the supplementary crystallographic data for this paper.42a–d

Supplementary information: experimental procedures, NMR spectra, UV-visible spectra, theoretical calculation. See DOI: https://doi.org/10.1039/d6ra04323b.

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