Dimethyl acetylenedicarboxylate → 1-carbomethoxy-9-chloro-7-phenylpyrimido[1,2-a][1,4]benzodiazepin-3(5H)-one

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A mixture of 2-amino-7-chloro-5-phenyl-3H-1,4-benzodiazepine (13.5 g.; 0.05 mole), dimethyl acetylenedicarboxylate (7.1 g.; 0.05 mole) and 250 ml. of methanol were refluxed for 2 hours and evaporated. The residue was dissolved in 50 ml. of methylene chloride and chromatographed on 2 kg. of silica gel using 60% ethyl acetate 40% cyclohexane. Fractions 1-6 (4.5 l.) gave no material. Fractions 6-51 were discarded. Fraction 52-54 gave 6.3 g. of solids which were crystallized from methylene chloride ether to give 1-carbomethoxy-9-chloro-7-phenylpyrimido[1,2-a][1,4]benzodiazepin-3(5H)-one 3.1 g. of melting point 214°-215° C. dec., raised to 216°-217° C. on recrystallization from methanol-ether.

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