Palladium-Catalyzed Amination of Aromatic C−H Bonds with Oxime Esters

摘要

Aromatic amines and their derivatives are common in pharmaceu-nticals, agrochemicals, dyes, herbicides, and conducting polymers.n1nTherefore, intense effort has been focused on the development ofnmethods for the synthesis of the C N bonds in aromatic amines.nTraditional routes to aromatic amines by nitration, reduction, andnalkylation have been largely displaced by catalytic amination of arylnhalides and pseudohalides.n2nHowever, the direct amination of C Hnbondsn3nwould provide a complementary approach to the synthesis ofnarylamines by eliminating the need to prepare the aryl halides ornpseudohalides. Two general strategies for the direct amination of C Hnbonds have been followed: formal insertion of a nitrene into annaromatic C H bond (strategy A in Scheme 1)n4nand oxidative aminationnof arenes with amine derivatives (strategy B in Scheme 1).n5nIn thenformer, a highly active nitrene intermediate is involved, and in thenlatter, an external oxidant is required; both processes typically requirenhigh catalyst loadings (5 20%).