Highly Stereoselective Addition of Stannylcuprates to Alkynones
摘要:
The addition of stannylcuprate reagents such as (Bu3Sn)(PhS)CuLi to alkynones has been found to proceed in high yield and with excellent stereoselectivity for the Z isomer of the product (>95%). The behavior of the stannylcuprates is thus very different from that of their "carbocuprate" counterparts such as Me2CuLi or Me2Cu(CN)Li-2 which are nonstereoselective. Furthermore, in contrast to the reactions of (R3Sn)(PhS)CuLi with the corresponding alkynoates, the presence of a proton source in the reaction medium has no effect on the stereos electivity of the reaction of alkynones.
A first observation of the direct alkynyl group transfer from silicon to copper is reported. The silicon group of alkynylsilanes was smoothly replaced by copper (I) chloride in DMI to give the corresponding copper (I) acetylides. This transformation was applied to the synthesis of alkynyl ketones catalyzed by CuCl. (C) 1997 Elsevier Science Ltd.