Regioselective reductions of β,β-disubstituted enones catalyzed by nonracemically ligated copper hydride
作者:Karl R. Voigtritter、Nicholas A. Isley、Ralph Moser、Donald H. Aue、Bruce H. Lipshutz
DOI:10.1016/j.tet.2011.10.056
日期:2012.4
2-additions to β,β-disubstituted α,β-unsaturated ketones have been further explored. Asymmetric reductions of enones lacking an α-substituent can be achieved with CuH complexed by DTBM-SEGPHOS in Et2O at −25 °C leading to the generation of highly valuable nonracemic allylic alcohols. The corresponding 1,4-reductions can also be achieved using the same reaction conditions by switching the ligand to a JOSIPHOS
进一步研究了CuH催化的β,β-二取代的α,β-不饱和酮的1,2-加成反应。在-25°C下,由DTBM-SEGPHOS在ET 2 O中与DTBM-SEGPHOS络合的CuH可以实现缺少α-取代基的烯酮的不对称还原,从而生成了高价值的非外消旋烯丙醇。通过将配体切换为提供非外消旋β,β-二取代的酮的JOSIPHOS类似物,也可以在相同的反应条件下实现相应的1,4-还原。对模型1,2-和1,4-加成的烯酮构象和过渡态能量进行DFT计算,以阐明影响产物比率的因素。