Phosphorus trichloride → 3-Fluoro-1,3-dihydro-1-methyl-7-chloro-5-phenyl-2H-1,4-benzodiazepin-2-one

Participants

Reaction Steps

A 580 μl (6.6 mmole) of phosphorous trichloride was added to a solution of 1.05 g (3.3 mmole) of 7-chloro-3-fluoro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one 4-oxide in 15 ml methylene chloride at 5°. The solution was stirred for 2 hr at 5° and then 20 hr at 25°, and then poured into 100 ml of cold aqueous 5% sodium bicarbonate solution. The organic layer was separated, washed with water, dried (MgSO4) and evaporated to dryness to give 800 mg (80%) of crude product. Recrystallization from heptane gave 650 mg (65%) of 7-chloro-3-fluoro-1.3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one as colorless crystals, mp 139°-140°. Even under these mild conditions, an appreciable amount of 3,7-dichloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one is formed as an impurity. If the reaction mixture is heated to 61° C. for only 10 min., none of the desired 3-fluoro compound is formed.

Provenance & Evidence