Phosphorus sulfide (P2S5) → 7-Chloro-2,3-dihydro-5-phenyl-2-thioxo-1H-1,4-benzodiazepin-1-acetic acid methyl ester

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Reaction Steps

A mixture of 6.35 g. (0.0186 mole) of 7-chloro-2,3-dihydro-2-oxo-5-phenyl-1H-1,4-benzodiazepin-1-acetic acid methyl ester, 4.42 g. (0.0199 mole) of phosphorus pentasulfide and 185 ml. of pyridine is heated under reflux for about 19 hours. The pyridine is evaporated, 100 ml. of cold water is added, and the product is extracted with four 100-ml. portions of methylene chloride. The extracts are combined, washed with sodium bicarbonate solution and saturated salt solution, dried over anhydrous magnesium sulfate and evaporated to give 2.5 g. of residue. The residue thus obtained is extracted with eight 250-ml. portions of boiling ether. The extracts are combined and concentrated. On standing 2.1 g. of 7-chloro-2,3-dihydro-5-phenyl-2-thioxo-1H-1,4-benzodiazepin-1-acetic acid methyl ester of melting point 180°-182° c. crystallizes from solution; recrystallization from ether raises the melting point to 185°-187° C.

Provenance & Evidence