Development of novel synthetic approaches in nickel-catalyzed cross-coupling reactions.

摘要

Nickel-catalyzed cross-coupling reactions of aryl halides with organometallic reagents are recognized to be highly versatile and practical methods for construction of various aromatic molecules.; Carbon-carbon bond formation is among the most important types of transformations in organic synthesis. Employing an operationally simple and environmentally benign heterogeneous nickel catalyst, Kumada-Corriu type couplings between aryl chlorides and Grignard reagents has been effectively achieved.; Many hydrodechlorination methods have been driven by environmental issues, such as removal of poisonous dioxins and PCBs, where only reduction of the carbon-chlorine bond(s) is of paramount concern and functional group compatibility is rarely considered. In fine chemical synthesis, however, clean and chemoselective reductive methods which tolerate a variety of functionality are valuable. A mild reducing system using Me₂NH·BH₃/K ₂CO₃ under either homogeneous or heterogeneous nickel catalyzed conditions, which tolerates a variety of common functionalities, yielded the corresponding reduced aromatics in excellent yields.; Vancomycin is a clinically important antibiotic. The structure consists of nine sp3 chiral centers and three additional elements of stereochemistry. Syntheses have been achieved by three groups independently, but each reported low levels of selectivities in biaryl bond formation in the AB ring portion of the molecule. A novel chiral tethered internal phosphine for stereoselective biaryl bond formation was proposed and developed as a new class of auxiliary. This chiral auxiliary system participated in nickel-catalyzed Suzuki-like couplings to provide the desired natural S-configuration of the AB biaryl unit of vancomycin in a stereoselective manner.