Skip to main content
NCBI home page
ACS AuthorChoice logoLink to ACS AuthorChoice
. 2025 Nov 8;90(46):16568–16572. doi: 10.1021/acs.joc.5c02170

Platinum-Catalyzed Regio- and Stereoselective Diboration of Allenes by 1,8-Diaminonaphthalene-Protected Diboronic Acid (B2(dan)2)

Yuki Ito 1, Tairin Kawasaki 1, Yusuke Yoshigoe 1, Shinichi Saito 1,*
PMCID: PMC12645474  PMID: 41204906

Abstract

We report a regio- and stereoselective diboration of the terminal CC bond of allenes by B2(dan)2 (dan = naphthalene-1,8-diaminato) in the presence of a Pt catalyst. This reaction is applicable to a broad range of substrates, including 1-arylallenes and 1,1-disubstituted allenes. The two boryl groups in the product exhibit distinct reactivities, enabling chemoselective transformations.

graphic file with name jo5c02170_0008.jpg

graphic file with name jo5c02170_0006.jpg

Introduction

The transition-metal-catalyzed addition of diboronic acid derivatives to unsaturated hydrocarbons has attracted attention in recent years due to its ability to provide useful organodiboron compounds. Among such transformations, the diboration of allenes is a practical approach for the efficient synthesis of vinyl- and allylboron derivatives. Some challenges, however, remain to be addressed: (1) the control of regioselectivity arising from the presence of two different CC bonds in allenes and (2) the control of E/Z stereoselectivity of the resulting alkenes. Miyaura and co-workers reported the first example related to the platinum-catalyzed diboration of allenes with bis­(pinacolato)­diboron (B2(pin)2), demonstrating the selective addition to the internal double bond (Scheme a). Subsequently, Morken and Tang independently achieved the enantioselective diboration at the internal double bond by employing a platinum or palladium catalyst in combination with chiral phosphine ligands. In contrast, reports on the terminal diboration of allenes remain limited. For instance, Yang and Cheng developed the (Z)-selective diboration of the terminal CC bond by employing a palladium catalyst in combination with an alkenyl iodide (Scheme b). Stratakis reported that the use of gold nanoparticles with B2(pin)2 enabled terminal diboration of mono- and disubstituted allenes, affording mainly the (Z)-isomer. Platinum-catalyzed terminal diboration has also been achieved with only a limited range of substrates. For instance, Chen and co-workers developed the (Z)-selective terminal diboration of aminoallenes or alkoxyallenes in the presence of a platinum catalyst. Furthermore, Santos and co-workers achieved the regioselective terminal diboration of 1,1-disubstituted allenes using an unsymmetrical diboron compound, B­(pin)­B­(dan) (dan = naphthalene-1,8-diaminato), in the presence of a platinum catalyst (Scheme c). In reactions involving 1-arylallenes, however, precise control over both the regio- and stereoselectivity turned out to be difficult. Therefore, the development of a selective diboration reaction that can be applied to a broader range of substrates is highly demanding.

1. Diboration of Allenes with Diboron Compounds.

1

Open in a new tab

We have been interested in the chemistry of B­(dan) derivatives. The B­(dan) group, developed by Suginome and co-workers as a protected boronic acid, has recently been shown to be directly applicable to cross-coupling reactions, as demonstrated independently by our group , and Yoshida–Tsuchimoto group. Furthermore, we recently reported that B2(dan)2 (2) was readily available from B2(OH)4, which could be used as an efficient borylation reagent of styrenes or diborylating reagent of alkynes in the presence of transition-metal catalysts. Based on these findings, we envisioned that the diboration of allenes using B2(dan)2 would proceed in the presence of a platinum catalyst, providing stable yet reactive diborated compounds. In this article, we report the platinum-catalyzed terminal diboration of allenes using B2(dan)2 (Scheme d).

Results and Discussion

We examined the diboration of 4-methoxyphenylallene (1a) with B2(dan)2 (2) in the presence of a platinum catalyst. Reaction conditions previously optimized for the diboration of alkynes using B2(dan)2 were applicable to the reaction of 1a. Stirring a mixture of 1a (0.10 mmol), 2 (1.1 equiv), Pt­(dba)3 (3.0 mol %), and PPh3 (3.0 mol %) in toluene at 110 °C for 30 min led to (Z)-selective diboration of the terminal CC bond, affording 3a in 93% isolated yield (Scheme ). Although a trace amount of an isomer was detected in the crude mixture by 1H NMR spectroscopy, the pure product could be isolated by silica gel column chromatography. In contrast, when B2(pin)2 was employed under the same conditions, the combined yield of the products decreased (61%) and the internal diborated product (3r′) was formed as the major isomer in 40% yield. According to the report by Santos and co-workers, the diboration of phenylallene (1b) with B­(pin)­B­(dan) under similar conditions (Pt­(dba)3 (4.0 mol %), PPh3 (6.0 mol %), toluene at 80 °C for 24 h) afforded 3s in 10% yield and 3s′ in 42% yield. These results demonstrated that B2(dan)2 enables the terminal diboration of 1-arylallenes in the presence of a Pt catalyst with high regio- and stereoselectivity, which has not been achieved using other diboron compounds.

2. Comparison of the Reactivity of B2(dan)2 with Other Diboron Compounds.

2

Open in a new tab

a 1 (0.10 mmol), diboron reagent (1.1 equiv), Pt­(dba)3 (3.0 mol %), PPh3 (3.0 mol %), toluene (1 mL) at 110 °C for 30 min.

b Isolated yield.

c Determined by 1H NMR analysis using CH3NO2 as an internal standard.

d Reported by Santos et al.

e 1 (0.163 mmol), B­(pin)­B­(dan) (0.136 mmol), Pt­(dba)3 (4.0 mol %), PPh3 (6.0 mol %), toluene (1 mL) at 80 °C for 24 h.

f Determined by GC analysis.

Next, we investigated the substrate scope of this reaction (Scheme ). The scalability of the reaction was demonstrated by using a larger amount of 1a (10 mmol), affording 3a in 88% yield after stirring for 1 h in the presence of 1 mol % of Pt­(dba)3/PPh3. The reaction proceeded smoothly with phenylallene (1b) and 4-methylphenylallene (1c), providing the corresponding products 3b and 3c in 70% and 81% yields, respectively. When an electron-withdrawing group such as bromine (1d) or trifluoromethyl group (1e) was introduced at the para position of the phenyl group, the diborated product 3d or 3e was isolated in excellent yields of 91% or 93%, respectively. In contrast, substrates bearing an ethoxycarbonyl group (1f) or a cyano group (1g) showed slightly reduced reactivity. Under the standard reaction conditions, 3f was isolated in 74% yield after 1 h, while 3g was isolated in 60% yield after 30 min. These results imply that the coordination of the ester or cyano group to the platinum catalyst would result in the decreased rate of the reaction, which is consistent with our previous report. 2-Methoxyphenylallene (1h), 3-methoxyphenylallene (1i), and mesitylallene (1j) also reacted smoothly, affording products in 82–86% yields. The results indicate that the steric effect of the substituents bound to the aryl group has a minimal impact on the reactivity. It is noteworthy that the diborated compounds synthesized in this study were bench stable and readily purified by silica gel column chromatography.

3. Pt-Catalyzed Diboration of Allenes with B2(dan)2 .

3

Open in a new tab

a General reaction conditions: a mixture of 1 (0.10 mmol), 2 (1.1 equiv), Pt­(dba)3 (3.0 mol %), and PPh3 (3.0 mol %) in toluene (1 mL) was stirred for 30 min at 110 °C.

b Pt­(dba)3 (1.0 mol %)/PPh3 (1.0 mol %) was used.

c The reaction time was 1 h.

The scope of this reaction was further examined by using other allenes. The reaction of 1,3-diphenylallene (1k) afforded the corresponding product (3k) in 57% yield. The reactions of symmetrical 1,1-disubstituted allenes 1l and 1m proceeded smoothly to afford the corresponding diborated products in high yields (93% and 92%) with excellent regioselectivity. Although the reaction of unsymmetrical allene 1n was expected to give a mixture of E/Z isomers, only the terminal diborated (Z)-isomer was obtained in 87% yield. Unexpectedly, the reaction of 1-cyclohexyl-1-methylallene (1o) gave a mixture of E/Z isomers: (Z)-3o and (E)-3o were isolated in 45% and 36% yields, respectively. Interestingly, the reaction of cyclohexylallene 1p led to (Z)-selective terminal diboration, providing 3p in 87% yield. These results indicate that this reaction can be applied to a wide range of allenes, including 1-arylallenes, 1,3-disubstituted allenes, 1,1-disubstituted allenes, and monosubstituted allenes with a secondary alkyl group. When octylallene 1q was used, the internal diborated product 3q′ was obtained in 59% yield as the major isomer, while the terminal diborated product 3q was isolated in 23% yield under the standard conditions. This result implies that steric hindrance plays an important role for the observed regioselectivity.

The diborated compounds synthesized in this study are valuable synthetic intermediates (Scheme ). When Chan–Lam–Evans-type coupling of 3a was attempted with Cu­(OAc)2 (5.0 mol %), (t-BuO)2 (2.0 equiv), and N-methylaniline (4.0 equiv) at 100 °C, the coupling product 4a was obtained in 58% yield. Notably, the allyl-B­(dan) moiety was selectively transformed into a C–N bond. The remaining alkenyl-B­(dan) group in 4a was directly converted to styryl group via Suzuki–Miyaura coupling, demonstrating the orthogonal reactivity of the two B­(dan) groups. Both B­(dan) groups in 3a could also be directly converted into the corresponding B­(pin) derivative 3r. Treatment of 3a with KOt-Bu resulted in selective protodeboration of the allyl-B­(dan) to afford 6a. This compound was subsequently transformed into trisubstituted alkene 7a in 92% yield by direct Suzuki–Miyaura coupling.

4. Derivatization of 3a .

4

Open in a new tab

We assume that the mechanism of this reaction is similar to that reported for the platinum-catalyzed diboration of allenes using other diboron compounds (Scheme ). Thus, the oxidative addition of B2(dan)2 to a Pt(0) species (I) would generate a Pt­(II) complex (II), which then coordinate to the less sterically hindered terminal double bond of the allene to form intermediate III. In this intermediate, the substituent R and the platinum center would adopt an anti-configuration to minimize steric hindrance, which would determine the stereochemistry of the product to afford the (Z)-isomer. Subsequently, the insertion of the allene into the Pt–B bond would give the η1-allyl platinum intermediate (IV), which would further rearrange into a more stable η3-allyl platinum complex (Va). This complex would undergo reductive elimination to afford 3. Alternatively, a pathway from IV to Vb, followed by reductive elimination, would lead to a regioisomer 3′. This route, however, would likely be suppressed due to steric hindrance between the B­(dan) group bound to platinum and substituent R on the allene.

5. Proposed Mechanism for the Pt-Catalyzed Diboration of Allenes with B2(dan)2 .

5

Open in a new tab

Conclusion

In conclusion, we developed a terminal diboration of allenes using a platinum catalyst and B2(dan)2. This reaction proceeds with high regio- and stereoselectivity across a wide range of substrates, including 1-arylallenes that have posed challenges in terms of selectivity. The diborated compounds possess both alkenyl-B­(dan) and allyl-B­(dan) moieties, which could be derivatized in chemoselective manner. The study provides a complementary approach to the previously reported internal diboration of allenes, thereby contributing to the expansion of the chemistry of organodiboron compounds.

Supplementary Material

jo5c02170_si_001.pdf (70.2MB, pdf)

Acknowledgments

We thank Hattori Corporation for the gift of 1,8-diaminonaphthalene.

The data underlying this study are available in the published article and its Supporting Information.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.joc.5c02170.

  • General information, experimental procedures, characterization data, and NMR spectra for novel compounds (PDF)

†.

Center for Education, Faculty of Engineering, Chiba Institute of Technology, Chiba 275-0023, Japan

S.S. designed the project and directed the study. Y.I. performed all experimental studies. T.K. and Y.Y. assisted the study. Y.I. and S.S. wrote the manuscript.

The authors declare no competing financial interest.

References

  1. For recent reviews, see:; a Suginome, M. ; Ohmura, T. . Transition Metal-Catalyzed Element-Boryl Additions to Unsaturated Organic Compounds. Boronic Acids: Preparation and Applications in Organic Synthesis, Medicine and Materials, 2nd ed.; Hall, D. G. , Ed.; Wiley-VCH: Weinheim, 2011. [Google Scholar]; b Barbeyron R., Benedetti E., Cossy J., Vasseur J.-J., Arseniyadis S., Smietana M.. Recent developments in alkyne borylations. Tetrahedron. 2014;70(45):8431–8452. doi: 10.1016/j.tet.2014.06.026. [DOI] [Google Scholar]; c Neeve E. C., Geier S. J., Mkhalid I. A. I., Westcott S. A., Marder T. B.. Diboron­(4) Compounds: From Structural Curiosity to Synthetic Workhorse. Chem. Rev. 2016;116(16):9091–9161. doi: 10.1021/acs.chemrev.6b00193. [DOI] [PubMed] [Google Scholar]; d Xu, L. ; Zhang, S. ; Li, P. . Di- and Polyboron Compounds: Preparation and Chemoselective Transformations. In Boron Reagents in Synthesis; Coca, A. , Ed.; ACS Symposium Series 1236; American Chemistry Society: Washington, D.C., 2016. [Google Scholar]; e Yoshida H.. Borylation of Alkynes under Base/Coinage Metal Catalysis: Some Recent Developments. ACS Catal. 2016;6(3):1799–1811. doi: 10.1021/acscatal.5b02973. [DOI] [Google Scholar]; f Zhao F., Jia X., Li P., Zhao J., Zhou Y., Wang J., Liu H.. Catalytic and catalyst-free diboration of alkynes. Org. Chem. Front. 2017;4(11):2235–2255. doi: 10.1039/C7QO00614D. [DOI] [Google Scholar]; g Ansell M. B., Navarro O., Spencer J.. Transition metal catalyzed element–element′ additions to alkynes. Coord. Chem. Rev. 2017;336:54–77. doi: 10.1016/j.ccr.2017.01.003. [DOI] [Google Scholar]; h Wang X., Wang Y., Huang W., Xia C., Wu L.. Direct Synthesis of Multi­(boronate) Esters from Alkenes and Alkynes via Hydroboration and Boration Reactions. ACS Catal. 2021;11(1):1–18. doi: 10.1021/acscatal.0c03418. [DOI] [Google Scholar]; i Fernández E., Cuenca A. B.. Reactions of Diboron Reagents with Unsaturated Compounds. Org. React. 2021:267–425. doi: 10.1002/0471264180.or105.02. [DOI] [Google Scholar]
  2. Ishiyama T., Kitano T., Miyaura N.. Platinum­(0)-catalyzed diboration of allenes with bis­(pinacolato)­diboron. Tetrahedron Lett. 1998;39(16):2357–2360. doi: 10.1016/S0040-4039(98)00199-3. [DOI] [Google Scholar]
  3. Pelz N. F., Woodward A. R., Burks H. E., Sieber J. D., Morken J. P.. Palladium-Catalyzed Enantioselective Diboration of Prochiral Allenes. J. Am. Chem. Soc. 2004;126(50):16328–16329. doi: 10.1021/ja044167u. [DOI] [PubMed] [Google Scholar]
  4. Liu J., Nie M., Zhou Q., Gao S., Jiang W., Chung L. W., Tang W., Ding K.. Enantioselective palladium-catalyzed diboration of 1,1-disubstituted allenes. Chem. Sci. 2017;8(7):5161–5165. doi: 10.1039/C7SC01254C. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Yang F.-Y., Cheng C.-H.. Unusual Diboration of Allenes Catalyzed by Palladium Complexes and Organic Iodides: A New Efficient Route to Biboronic Compounds. J. Am. Chem. Soc. 2001;123(4):761–762. doi: 10.1021/ja005589g. [DOI] [PubMed] [Google Scholar]
  6. Kidonakis M., Stratakis M.. Regioselective Diboration and Silaboration of Allenes Catalyzed by Au Nanoparticles. ACS Catal. 2018;8(2):1227–1230. doi: 10.1021/acscatal.7b04084. [DOI] [Google Scholar]
  7. Chen J., Gao S., Gorden J. D., Chen M.. Stereoselective Syntheses of γ-Boryl Substituted syn-β-Alkoxy- and syn-β-Amino-homoallylic Alcohols via a Regio- and Stereoselective Allene Diboration and Aldehyde Allylboration Reaction Sequence. Org. Lett. 2019;21(12):4638–4641. doi: 10.1021/acs.orglett.9b01535. [DOI] [PubMed] [Google Scholar]
  8. Guo X., Nelson A. K., Slebodnick C., Santos W. L.. Regio- and Chemoselective Diboration of Allenes with Unsymmetrical Diboron: Formation of Vinyl and Allyl Boronic Acid Derivatives. ACS Catal. 2015;5(4):2172–2176. doi: 10.1021/acscatal.5b00387. [DOI] [Google Scholar]
  9. a Yamamoto K., Mohara Y., Mutoh Y., Saito S.. Ruthenium-Catalyzed (Z)-Selective Hydroboration of Terminal Alkynes with Naphthalene-1,8-diaminatoborane. J. Am. Chem. Soc. 2019;141(43):17042–17047. doi: 10.1021/jacs.9b06910. [DOI] [PubMed] [Google Scholar]; b Mutoh Y., Yamamoto K., Saito S.. Suzuki–Miyaura Cross-Coupling of 1,8-Diaminonaphthalene (dan)-Protected Arylboronic Acids. ACS Catal. 2020;10(1):352–357. doi: 10.1021/acscatal.9b03667. [DOI] [Google Scholar]; c Yasuda T., Yoshigoe Y., Saito S.. Copper-Catalyzed Borylation of Styrenes by 1,8-Diaminonaphthalene-Protected Diboronic Acid. Org. Lett. 2023;25(12):2093–2097. doi: 10.1021/acs.orglett.3c00451. [DOI] [PMC free article] [PubMed] [Google Scholar]; d Saito S., Koizumi Y., Ito Y., Yasuda T., Yoshigoe Y.. Platinum-Catalyzed Diboration of Alkynes by 1,8-Diaminonaphthalene-Protected Diboronic Acid (B2(dan)2) J. Org. Chem. 2024;89(22):16947–16951. doi: 10.1021/acs.joc.4c01939. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Noguchi H., Hojo K., Suginome M.. Boron-Masking Strategy for the Selective Synthesis of Oligoarenes via Iterative Suzuki–Miyaura Coupling. J. Am. Chem. Soc. 2007;129(4):758–759. doi: 10.1021/ja067975p. [DOI] [PubMed] [Google Scholar]
  11. a Yoshida H., Seki M., Kamio S., Tanaka H., Izumi Y., Li J., Osaka I., Abe M., Andoh H., Yajima T., Tani T., Tsuchimoto T.. Direct Suzuki–Miyaura Coupling with Naphthalene-1,8-diaminato (dan)-Substituted Organoborons. ACS Catal. 2020;10(1):346–351. doi: 10.1021/acscatal.9b03666. [DOI] [Google Scholar]; b Tomota K., Li J., Tanaka H., Nakamoto M., Tsushima T., Yoshida H.. Weak Base-Promoted Direct Cross-Coupling of Naphthalene-1,8-diaminato-substituted Arylboron Compounds. JACS Au. 2024;4(10):3931–3941. doi: 10.1021/jacsau.4c00665. [DOI] [PMC free article] [PubMed] [Google Scholar]; c Andoh H., Nakagawa R., Akutagawa T., Katata E., Tsuchimoto T.. Direct Suzuki–Miyaura cross-coupling of C­(sp2)–B­(dan) bonds: designed in pursuit of usability. Org. Chem. Front. 2025;12:3759–3774. doi: 10.1039/D5QO00230C. [DOI] [Google Scholar]
  12. a Sueki S., Kuninobu Y.. Copper-Catalyzed N- and O-Alkylation of Amines and Phenols using Alkylborane Reagents. Org. Lett. 2013;15(7):1544–1547. doi: 10.1021/ol400323z. [DOI] [PubMed] [Google Scholar]; b Yoshida H., Murashige Y., Osaka I.. Copper-Catalyzed B­(dan)-Installing Allylic Borylation of Allylic Phosphates. Adv. Synth. Catal. 2019;361:2286–2290. doi: 10.1002/adsc.201900342. [DOI] [Google Scholar]
  13. Lee J. C. H., McDonald R., Hall D. G.. Enantioselective preparation and chemoselective cross-coupling of 1,1-diboron compounds. Nat. Chem. 2011;3(11):894–899. doi: 10.1038/nchem.1150. [DOI] [PubMed] [Google Scholar]
  14. Wang M., Cheng L., Wu Z.. Theoretical Studies on the Reaction Mechanism of Platinum-Catalyzed Diboration of Allenes. Organometallics. 2008;27(24):6464–6471. doi: 10.1021/om800645v. [DOI] [Google Scholar]

Associated Data

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

Supplementary Materials

jo5c02170_si_001.pdf (70.2MB, pdf)

Data Availability Statement

The data underlying this study are available in the published article and its Supporting Information.

Articles from The Journal of Organic Chemistry are provided here courtesy of American Chemical Society

RESOURCES