59467-94-6

The present invention refers to a process for the preparation of 4H-imidazo[1,5-a][1,4]benzodiazepines, in particular Midazolam, through an efficient and selective decarboxylation reaction of the derivative compound of the 5-aminomethyl-1-phenyl-1H-imidazole-4-carboxylic acid of formula (II) avoiding the formation of the 6H-imidazo[1,5-a][1,4]benzodiazepines by-products and the ensuing process for the isomerisation of a 4H-imidazo[1,5-a][1,4]benzodiazepine product.

The present invention refers to a process for the preparation of 4H-imidazo[1,5-a] [1,4]benzodiazepines, in particular Midazolam, through an efficient and selective decarboxylation reaction of the derivative compound of the 5-aminomethyl-1-phenyl-1H-imidazole-4-carboxylic acid of formula (II) avoiding the formation of the 6H-imidazo[1,5-a][1,4]benzodiazepines by-products and the ensuing process for the isomerisation of a 4H-imidazo[1,5-a][1,4]benzodiazepine product.

Novel Imidazobenzodiazepines and their analogs are useful as anticonvulsants, muscle relaxant, anxiolytic and sedative agents. Preferred compounds of this class belong to the imidazo[1,5-a][1,4]diazepine series which may have a very wide variety of organic substituents. An especially preferred genus included within the purview of the invention encompasses a compound of the formula STR1 wherein R1 is hydrogen and lower alkyl preferably methyl; R3 and R5 are hydrogen; R4 is hydrogen, nitro and halogen, most preferably, chlorine, and in a most preferred embodiment when positioned on the fused benzo portion of the imidazobenzodiazepine is in the 8-position thereof, R6 is phenyl or halo, nitro, or lower alkyl-substituted phenyl, preferably, halo, with fluorine being the preferred halogen, the substituted fluoro being positioned in the 2-position of the phenyl moiety and R2 is hydrogen and lower alkyl.

A multistep process is presented for the preparation of imidazobenzodiazepines of the formula STR1 wherein X is selected from the group consisting of hydrogen, halogen, nitro and trifluoromethyl, Y is selected from the group consisting of hydrogen, halogen and trifluoromethyl and R1 is selected from the group consisting of hydrogen, lower alkyl and aryl Also presented are novel intermediates utilized in the process. The end products are useful as sedatives, anxiolytics, muscle relaxants and anticonvulsants. The end products are especially useful in intravenous compositions for use in preoperative anesthesia.