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.