ortho-DIRECTED C-H ALKYLATION OF SUBSTITUTED BENZENES

摘要

The direct functionalization of arene C(sp2)-H bonds using transition-metal catalysis is a powerful tool for the synthesis of arenes with multiple functional groups.1-26 The first example of carbon-carbon (C-C) bond formation by the orthzo-directed C-H functionalization of a substituted benzene compound was reported in 1955 by Murahashi, who described dicobalt octacarbonyl catalyzed cyclocarbonylations of aromatic imines with carbon monoxide (Scheme l).27 The mechanism responsible for the cleavage of C-H bonds is not addressed; the concepts of C-H activation and C-H functionalization did not yet exist. The importance of this work was not recognized at the time, and remarkably, this ground-breaking catalytic reaction was reported prior to any stoichiometric cyclometalation reactions involving C-H activation. These cyclometalation reactions led to the production of orfto-metalated complexes involving nickel,28 palladium,29 or ruthenium,30 among other metals.