Palladium-Catalyzed Synthesis of 1,3,4-Benzotriazepines and Indazoles

Significance

Reported is the synthesis of either benzotriazepines or indazoles through the palladium-catalyzed reaction of ortho-halophenyl hydrazones with aromatic isocyanates. The reaction consists of a C-N bond forming step and isocya­nate condensation. The course of the reaction is very substrate-dependent, with both potential products often being formed. For benzotriazepine formation, the reaction gives better yields as the size of R increases. In the case of indazoles, yields improve when moving from R = Me to R = n-Pent, but then dramatically decrease when R = Ph. The nature of the aryl isocyanate also greatly affected the course of the reaction, with electron-donating groups increasing the yield dramatically in the case of the benzotriazepines, but less so in the case of the indazoles.