Yield:20197-84-6 2.48 g (46%)

Reaction Conditions:

in ice-water;trichlorophosphate;

Steps:

14.b 8,9-Dimethyl-2,3,5,6-tetrahydro-1,2,4-triazolo[4,3-c]quinazoline-3,5-dione

b) 4.5 g (0.023 mol) of 6,7-dimethyl-1,2,3,4-tetrahydroquinazoline-2,4-dione were suspended in 25 ml (0.27 mol) of phosphorus oxychloride and boiled under reflux for 16 hrs. The reaction mixture was left to cool to room temperature and poured on to ice-water. The brown precipitate was extracted with dichloromethane, chromatographed over silica gel with dichloromethane as the eluent and recrystallized from ethyl acetate/n-hexane. Yield: 2.48 g (46%) of 2,4-dichloro-6,7-dimethyl-quinazoline as white crystals; m.p. 140°-142° C.

References:

US5688803,1997,A