A suspension of 100 g of 7-chloro-5-phenyl-1-methyl-3-hydroxy-1,3-dihydro-
2H-1,4-benzodiazepin-2-one in 700 ml of anhydrous pyridine, kept stirred
between 0°C and +5°C, is slowly treated, during 20 to 30 minutes, with 54.5
ml phenyl chlorocarbonate. The temperature is gradually allowed to rise to
20°-25°C and stirring is maintained at this temperature during 24 hours.
2 l of water are then slowly added (during about 30 minutes) and stirring is
maintained during 1 hour. The precipitate which has been formed is collected
on a filter, washed thoroughly with water, dried in a vacuo at 50°C and
recrystallized by dissolving it at 60°C in 1,400 ml dioxane, the solution thus obtained being evaporated under reduced pressures to one-half of its volume,
and 1,700 ml of ligroin (BP 80°C to 120°C) being added thereto.
7-chloro-5-phenyl-1-methyl-3-phenoxycarbonyloxy-1,3-dihydro-2H-1,4-
benzodiazepin-2-one is thus obtained, with a melting point of 162°C to 164°C.
A suspension of 45 g 3-phenoxycarbonyloxy-1-methyl-7-chloro-5-phenyl-1,3-
dihydro-2H-1,4benzodiazepin-2-one in 450 ml methanol is treated with
stirring, with 43 ml of a solution of dimethylamine in methanol (containing 31
g dimethylamine in 100 ml). Stirring is maintained at 20°C to 25°C during 5
hours. The reaction mixture is filtered, and the filtrate is diluted with 450 ml
water. The precipitate thus formed, is 3-(N,N-dimethylcarbamoyloxy)-1-
methyl-7-chloro-5-phenyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one, which is
collected on a filter, dried and recrystallized from ethyl acetate, and has a
melting point of 173°C to 174°C.
