is chromatographed on silica gel using 50 ethyl acetatecyclohexane to give 7 chloro 2 3 dihydro 5 phenyl 2 thioxo 1h 1 4 benzodiazepin 1 acetic acid methyl ester of melting point 188 u00b0 189 u00b0 c from ether anal calcd for c 18 h 15 cln 2 o 2 s c 60 24 h 4 21 cl 9 88 n 7 81 s 8 94 found c 60 14 h 4 40 cl 9 81 n 7 76 s 9 06 a mixture of 3 8 g 0 01 mole of 7 chloro 5 o chlorophenyl 2 3 dihydro 2 oxo 1h 1 4 benzodiazepin 1 acetic acid methyl ester 2 3 g 0 0105 mole of phosphorus pentasulfide and 100 ml of pyridine is heated under reflux for about 22 hours the reaction mixture is evaporated and the residue thus obtained is dissolved in chloroform and 100 ml of aqueous sodium bicarbonate solution the organic layer is separated washed with three 50 ml portions of aqueous sodium bicarbonate solution and with saturated salt solution dried over anhydrous magnesium sulfate and evaporated to remove the solvent the residue 4 1 g thus obtained is dissolved in about 20 ml of methylene chloride and chromatographed on 410 g of silica gel elution with 50 ethyl acetate methylene chloride gives 1 79 g of 7 chloro 5 o chlorophenyl 2 3 dihydro 2 thioxo 1h 1 4 benzodiazepin 1 acetic acid methyl ester recrystallization.