Control of 6-Exo and 7-Endo cyclizations of alkynylamides using platinum and bismuth catalysts

Article abstract of DOI:10.1002/asia.201100209

The rules of cyclization: Alkynylamides are regioselectively cycloisomerized into piperazin-2-one and 1,4-diazepan-2-one derivatives by using catalytic amounts of appropriate metal catalysts. A 6-exo-dig addition proceeds in the presence of Bi(OTf)₃, while the 7-endo-dig addition occurs with PtCl₂ for the same substrate. (see scheme; Ns=o- nitrobenzenesulfonyl, Ts=p-toluenesulfonyl, Cbz=benzyloxycarbonyl, DCE=dichloroethane) Copyright