Regioselective preparation of 1-(bromomethyl)-5H-thiazolo[3,2-a]quina 5-ones and analogous 5H-thieno[3,2-e]thiazolo[3,2-a]pyrimidin-5-ones from fused2-(alkenylthio)pyrimidin-4-ones

A convenient procedure For the regioselective preparation of polycyclic ang ular thiazolo[3,2-a]pyrimidin-5-ones is reported. 2-(Alkenylthio)quinazolin -4(3H)-ones and analogues thieno[2,3-d]pyrimidines were treated with bromin e in acetic acid to obtain 1-(bromomethyl)-5H-thiazolo[3,2-a]quinazolin-5-o nes 8a,d, and 1-(bromomethyl)-5H-thieno[3,2-e]thiazolo[3,2-a]pyrimidin-5-on es 8b,c,e,f, respectively. A route starting from 2-(alkenylamino)benzamides , which were converted to corresponding 2-thioxoquinazolin-4-ones and subse quently treated with bromine in acetic acid furnished angular 2-(bromomethy l)thiazolo[3,2-a]quinazolin-5-ones 11, or 3-(bromomethyl)[1,3]thiazino[3,2- a]quinazolin-6-one 14, respectively.