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DOI: 10.1055/s-0029-1220131
Hydrazone C-N Coupling Route to 3-Aminoindazoles
V. Lefebvre, T. Cailly, F. Fabis*, S. Rault
Université de Caen Basse-Normandie, France
Publication History
Publication Date:
22 June 2010 (online)

Significance
A general two-step synthesis of indazoles is described. The sequence involves palladium-catalyzed C-N coupling of benzophenone hydrazone with ortho-bromobenzonitriles, followed by an acidic deprotection-cyclization to afford the indazole products in good overall yields over two steps. In a synthetically useful observation, N1-alkylation of the intermediate hydrazone was demonstrated, which allowed the regioselective synthesis of an N1-alkylated indazole, thus avoiding protection-deprotection sequences for 3-aminoindazole. The substrate scope was moderately studied and the reaction was shown to tolerate both EDGs and EWGs. Unfortunately, no other halonitriles were tested in the reaction.