Process for the manufacture of 4H-imidazo[1,5-A][1,4]benzodiazepines

A process for the manufacture of 4H-imidazo[1,5-a][1,4]benzodiazepine derivatives of formula I I wherein R1 is phenyl or mono- or disubstituted phenyl; R2 is hydrogen, halogen, nitro, cyano, trifluoromethyl or lower alkyl; R3 is hydrogen or lower alkyl; and R4 is hydrogen or lower alkyl and of pharmaceutically usable salts of these compounds by decarboxylating a 4H-imidazo[1,5-a][1,4]benzodiazepinecarboxylic acid of formula II II wherein R1, R2, R3 and R4 have the above significances, at elevated temperature and under elevated pressure in the presence of an organic solvent. The compounds of formula I and their pharmaceutically usable acid addition salts are known muscle relaxants, sedatives and anticonvulsants. A process for the manufacture of 4H-imidazo[1,5-a][1,4]benzodiazepine derivatives of formula I I wherein R1 is phenyl or mono- or disubstituted phenyl; R2 is hydrogen, halogen, nitro, cyano, trifluoromethyl or lower alkyl; R3 is hydrogen or lower alkyl; and R4 is hydrogen or lower alkyl and of pharmaceutically usable salts of these compounds by decarboxylating a 4H-imidazo[1,5-a][1,4]benzodiazepinecarboxylic acid of formula II II wherein R1, R2, R3 and R4 have the above significances, at elevated temperature and under elevated pressure in the presence of an organic solvent. The compounds of formula I and their pharmaceutically usable acid addition salts are known muscle relaxants, sedatives and anticonvulsants.