Department of Organic Chemistry, Stockholm University , Stockholm SE-10691, Sweden.
Division of Theoretical Chemistry & Biology, School of Biotechnology, KTH Royal Institute of Technology , Stockholm SE-10691, Sweden.
J Am Chem Soc. 2016 Oct 12;138(40):13408-13414. doi: 10.1021/jacs.6b08350. Epub 2016 Sep 30.
A mild base-catalyzed strategy for the isomerization of allylic alcohols and allylic ethers has been developed. Experimental and computational investigations indicate that transition metal catalysts are not required when basic additives are present. As in the case of using transition metals under basic conditions, the isomerization catalyzed solely by base also follows a stereospecific pathway. The reaction is initiated by a rate-limiting deprotonation. Formation of an intimate ion pair between an allylic anion and the conjugate acid of the base results in efficient transfer of chirality. Through this mechanism, stereochemical information contained in the allylic alcohols is transferred to the ketone products. The stereospecific isomerization is also applicable for the first time to allylic ethers, yielding synthetically valuable enantioenriched (up to 97% ee) enol ethers.
已开发出一种温和的碱催化策略，用于烯丙醇和烯丙基醚的异构化。实验和计算研究表明，当存在碱性添加剂时，不需要过渡金属催化剂。与在碱性条件下使用过渡金属的情况一样，仅由碱催化的异构化也遵循立体专一的途径。该反应由限速的去质子化引发。烯丙基阴离子与碱的共轭酸之间形成紧密的离子对，导致手性的有效转移。通过这种机制，烯丙醇中包含的立体化学信息被转移到酮产物中。立体专一的异构化也首次适用于烯丙基醚，得到了具有合成价值的对映体过量（高达 97%ee）的烯醇醚。
