Carboxamide-Directed Stereospecific Couplings of Chiral Tertiary Alkyl Halides with Terminal Alkynes

Herein, we report the stereospecific Sonogashira coupling of a chiral α-bromocarboxamide possessing a tert-alkyl moiety and an alkyne; this reaction produces a chiral tert-alkylated alkyne in a stereoretentive manner. In this reaction, both the CuBr/bathophen catalyst system and carboxamide directing group are essential for achieving the high enantiospecificities of the couplings. Mechanistic studies of this reaction revealed that the alkynyl copper species is the key intermediate that coordinates to the carboxamide group of chiral α-bromocarboxamide.