Acetohydrazide → Brotizolam

Participants

Reaction Conditions

Reaction Steps

A suspension of 50 g (0.14 mol) of (1) in 2.5 ml of pyridine and 200 ml of dichloromethane is added dropwise to a suspension of 36 g (0.183 mol) of phosphorus pentachloride in 250 ml of dichloromethane at 5-10° C. with cooling. The mixture is stirred for 1 hour at 10° C. and a solution of 17 g (0.28 mol) of acetic acid hydrazide in 170 ml of tetrahydrofuran, heated to 40-50° C., is added dropwise with cooling at 10-20° C. The mixture is then stirred for 1 hour at ambient temperature and then refluxed for 5 to 18 hours. It is then cooled to ambient temperature, 380 ml water are added with cooling and the mixture is adjusted to an alkaline pH with 45% sodium hydroxide solution. The phases are separated and the aqueous phase is extracted with 100 ml of dichloromethane. 5 g of activated charcoal are added to the combined organic phases which are then stirred for 10 minutes, filtered and evaporated to dryness in vacuo. The residue is taken up in 750 ml of boiling methylethylketone, 5 g of activated charcoal are added and the resulting mixture is refluxed for another 10 min. The suspension is filtered, then 570 ml of solvent are distilled off. The mixture is allowed to cool slowly to ambient temperature and then cooled to 5° C. and stirred for 2 hours at this temperature. The product that crystallises out is filtered off, washed with 30 ml of cold methylethylketone and 50 ml of cold ethyl acetate and dried overnight at 60° C. in vacuo. Yield: 36.6 g (66%) of brotizolam.

Provenance & Evidence