Studies on Pyrimidine Derivatives. XXIX. Synthesis of Pyrimidines fused with Five-membered Heterocycles by Cross-coupling of 5-Iodopyrimidines with Phenylacetylene and Styrene

2,4-Dimethyl-6-phenyl-furo- and -thieno-[2,3-d]-pyrimidine were synthesized by cross-couping of 2,6-dimethyl-5-iodopyrimidines with phenylacetylene in the presence of palladium catalyst, followed by cyclization of the resulting phenylethynylpyrimidines. 2,4-Dimethyl-6-phenyl[2,3-d]pyrimidine was also synthesized by the thermal decomposition of 4-azido-2,6-dimethyl-5-styrylpyrimidine, which was obtained from the 4-chloro derivative.