Rhodium(III)-Catalyzed ortho-Alkylation of Phenoxy Substrates with Diazo Compounds via C-H Activation: A Case of Decarboxylative Pyrimidine/Pyridine Migratory Cyclization Rather than Removal of Pyrimidine/Pyridine Directing Group

Abstract

An efficient Rh(III)-catalyzed ortho-alkylation of phenoxy substrates with diazo compounds has been achieved for the first time using pyrimidine or pyridine as the directing group. Furthermore, bis-alkylation has also been achieved using para-substituted phenoxypyrimidine and 3 mol equiv of the diazo ester. The ortho-alkylated derivatives of phenoxy products possessing the ester functionality undergo decarboxylative pyrimidine/pyridine migratory cyclization (rather than deprotection of pyrimidine/pyridine group) using 20% NaOEt in EtOH affording a novel class of 3-(pyrimidin-2(1H)-ylidene)benzofuran-2(3H)-ones and 6-methyl-3-(pyridin-2(1H)-ylidene)benzofuran-2(3H)-one. The ortho-alkylated phenoxypyridine possessing ester functionality also undergoes decarboxylative pyridine migratory cyclization using MeOTf/NaOMe in toluene providing 6-methyl-3-(1-methylpyridin-2(1H)-ylidene)benzofuran-2(3H)-one.