New route to 4-alkoxyquinazoline-2-carbonitriles

A new, direct synthesis is described for the relatively rare but synthetically very versatile quinazoline-2-carbonitriles from anthranilonitriles and 4,5-dichloro-1,2,3-dithiazolium chloride 1. Treatment of iminodithiazole 6, from 4,5-dimethoxyanthranilonitrile and the salt 1, with alcohols and a base gives 4-alkoxyquinazoline-2-carbonitriles 8 in good yield. Treatment of the parent iminodithiazole 2 (R = H; X = CN) with alcohols and sodium hydride gives the analogous quinazolines 12 in lower yield, though these yields are much improved and the reaction times reduced under microwave irradiation. Alternatively the imine 6 can be converted into the more reactive cyanothioformamide 7 which on brief heating in alcohols gives the same quinazolines 8 in high yield.