Polycondensed nitrogen heterocycles. XXII. A new synthesis of 5,6-dihydro-7H-pyrazolo[1,5-d][1,4]benzodiazepin-6-ones

A new synthesis of 2-methyl-9-R'-10-R-5,6-dihydro-7H-pyrazolo1,5-d]1,4]benzodiazepin-6-ones ( 4a-c ) is deserved. Reaction of ethyl hydrazinoacetate hydrochloride with 1,3-diketones 1a-c gave both 3-methyl-5-(4R'-5-R-2-nitrophenyl)pyrazol-1-yl-acetate acids ( 2a-c ) and the corresponding ethyl esters 3a-c . Reduction with the appropiate reducing agent of compounds 2a-c and 3a-c directly gave the title compounds. Compound 4a showed insecticidal properties against the house fly.