Site-selective mono-oxidative addition of active zinc into carbon–bromine bond of dibrominated-thiophenes: preparation of thienylzinc reagents and their applications

A facile protocol for the preparation of 3-bromo-2-thienylzinc bromide A and 5-bromo-2-thienylzinc bromide B has been developed. It has been successfully accomplished by a site-selective oxidative addition of active zinc into a chemically pseudo-equivalent or equivalent carbon–bromine bond, respectively. The subsequent cross-coupling reactions of the organozincs were also successfully carried out under mild conditions providing the corresponding products in moderate to high yields.