Ir(III)-Catalyzed [4+2] cyclization of azobenzene and diazotized Meldrum's acid for the synthesis of cinnolin-3(2H)-one

The first report on Ir(III)-catalyzed C-H alkylation/cyclization of azobenzene with diazotized Meldrum's acid is described for the synthesis of cinnolin-3(2H)-one derivatives under mild conditions. Controlled experiments led to the isolation of intermediate ortho-alkylated product of azobenzene, which was converted to both cinnolin-3(2H)-one-4-carboxylic acid and its ester derivative. Additionally, the iridacyclic complex of azobenzene was isolated and found to be an active intermediate in the catalytic cycle.