Gem-Difluoroallyllithium: Preparation by Lithium-Halogen Exchange and Utilization in Organosilicon and Organic Synthesis

摘要

gem-Difluoroallyllithium may be generated by lithiumbromine exchange between n-butyllithium and CH2=CHCF2Br at -95 degrees C using an in situ procedure. When this Li(CF2CHCH2) preparation is carried out in the presence of chlorosilanes, aldehydes, ketones and esters, products of type R3SiCF2CH=CH2, RCH(OH)CF2CH=CH2, RR'C-(OH)CF2CH=CH, respectively, are formed, often in good yield. The factors determining the regioselectivity in additions to C=0 of unsymmetrically substituted allylic lithium reagents are discussed. (Author)