Subscribe to RSS
DOI: 10.1055/a-1670-5829
The Silicon–Hydrogen Exchange Reaction: Catalytic Kinetic Resolution of 2-Substituted Cyclic Ketones
Generous support from the Max Planck Society, the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), Leibniz Award to B.L. and under Germany’s Excellence Strategy−EXC 2033−390677874−RESOLV, and the European Research Council (ERC, European Union’s Horizon 2020 research and innovation program ‘C−H Acids for Organic Synthesis, CHAOS’ Advanced Grant Agreement No.694228) is gratefully acknowledged.
Abstract
We have recently reported the strong and confined, chiral acid-catalyzed asymmetric ‘silicon−hydrogen exchange reaction’. One aspect of this transformation is that it enables access to enantiopure enol silanes in a tautomerizing σ-bond metathesis, via deprotosilylation of ketones with allyl silanes as the silicon source. However, until today, this reaction has not been applied to racemic, 2-substituted, cyclic ketones. We show here that these important substrates readily undergo a highly enantioselective kinetic resolution furnishing the corresponding kinetically preferred enol silanes. Mechanistic studies suggest the fascinating possibility of advancing the process to a dynamic kinetic resolution.
Supporting Information
- Supporting information for this article is available online at https://doi.org/10.1055/a-1670-5829.
- Supporting Information
Publication History
Received: 17 September 2021
Accepted after revision: 14 October 2021
Accepted Manuscript online:
15 October 2021
Article published online:
29 October 2021
© 2021. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)
Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany
-
References and Notes
- 1a Li L, Wei Y.-L, Xu L.-W. Synlett 2020; 31: 21
- 1b Ma J.-H, Li L, Sun Y.-L, Xu Z, Bai X.-F, Yang K.-F, Cao J, Cui Y.-M, Yin G.-W, Xu L.-W. Sci. China Chem. 2020; 63: 1082
- 2 Zhou H, Bae HY, Leutzsch M, Kennemur JL, Bécart D, List B. J. Am. Chem. Soc. 2020; 142: 13695
- 3 Ishihara K, Nakamura H, Nakamura S, Yamamoto H. J. Org. Chem. 1998; 63: 6444
- 4 Inanaga K, Ogawa Y, Nagamoto Y, Daigaku A, Tokuyama H, Takemoto Y, Takasu K. Beilstein J. Org. Chem. 2012; 8: 658
- 5 Boxer MB, Albert BJ, Yamamoto H. Aldrichimica Acta 2009; 42: 1
- 6a Cheon CH, Yamamoto H. J. Am. Chem. Soc. 2008; 130: 9246
- 6b Ye F, Zheng ZJ, Deng WH, Zheng LS, Deng Y, Xia CG, Xu LW. Chem. Asian J. 2013; 8: 2242
- 7 Amatov T, Tsuji N, Maji R, Schreyer L, Zhou H, Leutzsch M, List B. J. Am. Chem. Soc. 2021; 143: 14475
- 8 Example Synthetic ProcedureMethallyl TBS reagent 2 (46 μL, 0.2 mmol, 2.0 equiv.) was placed in a flame-dried Schlenk flask, equipped with a Teflon-coated magnetic stirring bar. IDPi 5e (0.01 equiv.) and toluene (0.1 M, 1.0 mL) were added at 25 °C and stirred for 30 min. The resultant mixture was cooled to 0 °C for 10 min, and the appropriate ketone 1a–1e (0.1 mmol, 1.0 equiv.) was slowly added. Then the reaction was stirred for indicated time at 0 °C. The reaction was monitored by GC, calibrated with 1,3,5-trimethoxybenzene as internal standard. When the conversion of ketone was around 50%, the reaction was quenched by addition of three drops of triethylamine by pipet. Crude NMR was performed to confirm the conversion of ketone and determine the NMR yield with CH2Br2 as internal standard after all organic volatiles were evaporated in vacuo. The crude residue was purified by preparative TLC to afford the desired enol silane 3a–3e, and r.r. was determined by 1H NMR analysis. e.r. of the enol silane product and recovered ketone were determined by HPLC analysis.Spectral Information for Compound 3a 1H NMR (501 MHz, CD2Cl2): δ = 7.29–7.23 (m, 2 H), 7.23–7.19 (m, 2 H), 7.18–7.13 (m, 1 H), 5.04 (td, J = 4.0, 1.2 Hz, 1 H), 3.35 (tq, J = 6.0, 1.9 Hz, 1 H), 2.24–2.05 (m, 2 H), 2.05–1.96 (m, 1 H), 1.72–1.63 (m, 1 H), 1.63–1.54 (m, 1 H), 1.50 (d, J = 6.4 Hz, 1 H), 0.68 (s, 9 H), 0.08 (s, 3 H), 0.00 (s, 3 H). 13C NMR (126 MHz, CD2Cl2): δ = 150.9, 144.7, 128.4, 127.8, 125.7, 105.4, 46.3, 33.2, 25.2, 24.1, 19.8, 17.7, –4.9, –5.1. Rf = 0.41 (hexanes). ESI-HRMS: m/z calcd for C18H29O1Si1 ([M + H]+): 289.1982; found: 289.1977. HPLC (OD-3R, MeCN–H2O = 65:35, 1.0 mL/min, 298 K, 220 nm): t R1 = 15.0 min, t R2 = 14.0 min; e.r. = 96:4; r.r. = 56:1. [α]D 25 = –66.3 (c 0.35, CHCl3).
- 9 Akiyama T. Chem. Rev. 2007; 107: 5744
- 10 Čorić I, List B. Nature 2012; 483: 315
- 11a James T, van Gemmeren M, List B. Chem. Rev. 2015; 115: 9388
- 11b Wakchaure V, Obradors C, List B. Synlett 2020; 31: 1707
- 11c Zhang Z, Klussmann M, List B. Synlett 2020; 31: 1593
- 12 Schreyer L, Properzi R, List B. Angew. Chem. Int. Ed. 2019; 58: 12761
- 13 Zhu C, Mandrelli F, Zhou H, Maji R, List B. J. Am. Chem. Soc. 2021; 143: 3312