Synthesis and Heterocyclization of4-(Alkenylsulfanyl)quinazolines

Alkylation of quinazoline-4(3H)-thione with 3-chloro-2-methylpropene and 2,3-dibromopropene afforded previously unknown 4-[(2-methylprop-2-en-1-yl)sulfanyl]quinazoline and 4-[(2-bromoprop-2-en-1-yl)sulfanyl]quinazoline, respectively. 4-[(Prop-2-en-1-yl)sulfanyl]quinazoline reacted with bromine to give bromocyclization product and product of bromine addition to the exocyclic double bond. The reaction of 4-[(2-methylprop-2-en-1-yl)sulfanyl]quinazoline with halogens involved thiazole ring fusion. 5-Bromo-3-methylidene-2,3-dihydro[1,3]thiazolo[3,2-c]quinazolinium bromide was isolated in the reaction of 4-[(2-bromoprop-2-en-1-yl)sulfanyl]quinazoline with bromine, and the reaction of the same substrate with iodine gave a mixture of 3-bromo-3-iodomethyl-2,3-dihydro[1,3]thiazolo[3,2-c]quinazolinium and 3-methylidene-2,3-dihydro[1,3]thiazolo[3,2-c]quinazolinium iodides. 4-[(2-Methylprop-2-en-1-yl)sulfanyl]quinazoline reacted with 2 equiv of iodine to produce 3-methyl-3-iodomethyl-2,3-dihydro[1,3]thiazolo[3,2-c]quinazolinium triiodide and pentaiodide; the structure of the latter was studied by X-ray diffraction.