Huang Rui-Zhi, Lau Kai Kiat, Li Zhaofeng, Liu Tang-Lin, Zhao Yu
Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Republic of Singapore 117543.
School of Chemistry and Chemical Engineering , Southwest University , Chongqing 400715 , China.
J Am Chem Soc. 2018 Nov 7;140(44):14647-14654. doi: 10.1021/jacs.8b07007. Epub 2018 Oct 24.
We present herein an unprecedented enantioselective isomerization of homoallylic and bishomoallylic secondary alcohols, catalyzed by a commercially available rhodium-complex and a base. This catalytic redox-neutral process provides an effective access to chiral ketones in high efficiency and enantioselectivity, without the use of any stoichiometric reagent or generation of any waste. For the reaction of homoallylic alcohols, this system achieved not only a stereoconvergent access to chiral ketones bearing a β-stereocenter (up to 95%, 86% ee) but also a concomitant oxidative kinetic resolution of the alcohol substrates (S > 20). In the case of bishomoallylic alcohols, an intriguing ligand-induced divergent reactivity was observed. A terminal-to-internal alkene isomerization promoted by Rh/L7 followed by redox isomerization using Rh/BINAP system produced chiral ketones bearing a γ-stereocenter with high yield and enantioselectivity. Mechanistic studies provided strong support for the redox-isomerization pathway with chain walking of the key alkyl-Rh intermediate.
我们在此展示了一种前所未有的高烯丙基和双高烯丙基仲醇的对映选择性异构化反应，该反应由市售铑配合物和碱催化。这种催化的氧化还原中性过程提供了一种高效且对映选择性地有效合成手性酮的方法，无需使用任何化学计量试剂，也不会产生任何废物。对于高烯丙基醇的反应，该体系不仅实现了对带有β-立体中心的手性酮的立体汇聚合成（产率高达95%，对映体过量86%），还同时实现了醇底物的氧化动力学拆分（选择性因子S>20）。对于双高烯丙基醇，观察到了一种有趣的配体诱导的发散反应性。由Rh/L7促进的端烯到内烯异构化，随后使用Rh/BINAP体系进行氧化还原异构化，以高收率和对映选择性得到了带有γ-立体中心的手性酮。机理研究为关键烷基铑中间体链行走的氧化还原异构化途径提供了有力支持。
