3.76 g of 50% sodium hydride in mineral oil were added to 250 ml. of dimethylforamamide cooled to about 0° C. The temperature of the suspension was maintained at about 0° C., while a solution of 27.05 g (0.1 mol) of 7-chloro-2,3-dihydro-5-phenyl-1H-1,4-benzodiazepin-2-one in 50 ml. of dimethylformamide was added dropwise to it. The resulting mixture was stirred for 2 hours, and then 10 ml. of propargyl bromide were added dropwise while maintaining the temperature at 10°-15° C. The reaction mixture was stirred for about 4 hours and then poured over ice. The product was filtered and dissolved in chloroform; and the chloroform solution was separated from the aqueous layer, and dried over sodium sulphate. The chloroform was evaporated off from the solution and the residue was dissolved in the minimum quantity of a 7:3 (by volume) mixture of benzene and ethyl acetate. This solution was chromatographed on a column of silica gel and eluted with a 7:3 (by volume) mixture of benzene and ethyl acetate. The portion of eluate containing the desired product, as determined by thin-layer chromatography, was collected and evaporated under reduced pressure. The residue was recrystallized from a 1:1 (by volume) mixture of benzene and hexane, giving 16 g of the pure desired product with a melting point of 141°-143° C.
