[Cl:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8]1[C:14]2[CH:15]=[C:16]([N+:19]([O-:21])=[O:20])[CH:17]=[CH:18][C:13]=2[NH:12][C:11](=O)[CH:10]([CH3:23])[N:9]=1.P12(SP3(SP(SP(S3)(S1)=S)(=S)S2)=S)=[S:25].C(N(CC)CC)C>O1CCOCC1>[Cl:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8]1[C:14]2[CH:15]=[C:16]([N+:19]([O-:21])=[O:20])[CH:17]=[CH:18][C:13]=2[NH:12][C:11](=[S:25])[CH:10]([CH3:23])[N:9]=12.6 g of (+)-5-(o-chlorophenyl)-1,3-dihydro-3-methyl-7-nitro-2H-1,4-benzodiazepin-2-one are dissolved in 40 ml of dioxane and treated with 1.6 g of phosphorus pentasulfide and 0.7 ml of triethylamine. The mixture is then heated to reflux for 20 minutes, cooled with ice and concentrated on a rotary evaporator. The residue is treated with 10% bicarbonate solution and ethyl acetate, and the ethyl acetate phase is washed twice with 10% bicarbonate solution, dried with sodium sulfate, filtered and concentrated. The residue is purified on a 60 g silica gel column using methylene chloride and methylene chloride/ethyl acetate (20:1) for the elution and then crystallised from methylene chloride/petroleum ether. There is obtained (+)-5-(o-chlorophenyl)-1,3-dihydro-3-methyl-7-nitro-2H-1,4-benzodiazepin-2-thione which melts at 258°-260° C and which exhibits a rotation of [α]25D =+160,6° (in methylene chloride, 1%).
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