Hydrochloric Acid → 6,11-dihydro-5H-pyrido[2,3-b][1,5]benzodiazepine

Participants

Reaction Steps

Diborane dimethylsulfide complex (35 mL) was added via syringe to a suspension of 6,11-dihydro-5H-pyrido[2,3-b][1,5]benzodiazepin-5-one 1:1 salt with hydrochloric acid of Step A (25 g, 0.1 mole) in dioxane (230 mL) under nitrogen. The mixture was sonicated overnight at room temperature and then evaporated to dryness in vacuo. The green residue was treated with cold 2N hydrochloric acid and diethyl ether. The cold aqueous layer was basified with 50% aqueous sodium hydroxide (to pH 9) and the basic layer extracted with ethyl acetate. The organic extracts were dried over anhydrous potassium carbonate, and evaporated to dryness to yield a burgundy solid (24.35 g). This crude material was purified by trituration with diethyl ether. The solid was collected, washed and dried in vacuo. The mother liquors from different runs were combined and the mixture (18.5 g) flash chromatographed (on silica Merck-60, eluant 20% ethyl acetate in hexane) to provide additional material homogeneous by TLC (yellow solid, 11 g).

Provenance & Evidence