Water → 2-phenyl-5,6-dihydro-4H-1,3,4-oxadiazin-5-one

Participants

Reaction Conditions

Reaction Steps

812 g (3.82 mol) of N′-(2-chloroacetyl)benzenecarbohydrazide were dissolved in 13 liters of dry DMF, and 384.95 g (4.58 mol) of sodium bicarbonate were added. The reaction solution was then heated to 100° C. and stirred at this temperature overnight. After the reaction had gone to completion (monitored by TLC, mobile phase dichloromethane/ethyl acetate 9:1), the reaction solution was cooled to room temperature, poured into 65 liters of water and extracted three times with in each case 17.5 liters of ethyl acetate. The combined organic phases were washed with 13.8 liters of saturated aqueous sodium bicarbonate solution, dried and concentrated to dryness under reduced pressure. The solid obtained was dissolved in a 9:1 mixture of dichloromethane and methanol and applied to 17 kg of silica gel. The product was chromatographed on two portions of silica gel (in each case 8 kg) using 260 liters of dichloromethane/ethyl acetate 9:1 as mobile phase. The combined product fractions were concentrated, and the solid obtained was triturated with 3 liters of diethyl ether. Filtration gave 247 g (1.40 mol, 35% of theory) of the title compound as a white solid.

Provenance & Evidence