作者:Fuyuhiko Matsuda、Motoi Kawatsura、Ken-ichi Hosaka、Haruhisa Shirahama
DOI:10.1002/(sici)1521-3765(19991105)5:11<3252::aid-chem3252>3.0.co;2-d
日期:1999.11.5
SmI2-promoted intermolecular ketone-olefin couplings are facilitated and stereocontrolled by hydroxyl groups incorporated within the starting materials. For example, the SmI2-induced ketone - olefin coupling reactions of alpha-hydroxy ketone 5 with ethyl acrylate, acrylonitrile, ethyl crotonate, and 2(5 H)-furanone proceeded with high stereocontrol to afford the syn-1,2-diol products 6-9 in good yields. Excellent diastereoselectivity was achieved in the reductive couplings of beta-hydroxy aldehyde 21 and erythro-beta-hydroxy ketone 24 with acrylonitrile using SmI2, to produce the anti-1,3-diols 22 and 25 in good yields. The sense of the stereo-selectivity was in full accord with a chelation-control model. In the proposed model, the stereochemistry of the reaction product is explained by assuming that a cyclic ketyl radical is generated during the initial single-electron reduction by SmI2. This radical species results from the chelation of the Sm-III cation, attached to the ketyl radical, with the hydroxyl group.