Asymmetric phase-transfer reactions under base-free neutral conditions

作者：Shirakawa Seiji; Maruoka Keiji^*

来源：Tetrahedron Letters, 2014, 55(29): 3833-3839.

DOI：10.1016/j.tetlet.2014.05.014

• Phase-transfer catalysis
• Organocatalysis
• Asymmetric synthesis
• Bifunctional catalyst
• Onium salt

Although quaternary onium salt-catalyzed phase-transfer reactions are generally believed to require base additives, we discovered even without any base additives conjugate additions of 3-substituted oxindoles proceeded smoothly in the presence of lipophilic quaternary onium bromide under water-organic biphasic conditions. The mechanism of this novel base-free neutral phase-transfer reaction system was investigated, and the assumed catalytic cycle was presented together with interesting effects of water and lipophilicity of the phase-transfer catalyst. The base-free neutral phase-transfer reaction system could be applied to highly enantioselective conjugate additions, aldol reaction, sulfenylation, and chlorination under the influence of chiral bifunctional onium bromides as key catalysts.

• 出版日期2014-7-16