4-Methyl-6-mercapto-2-phenylpyrimidine-5-carbonitrile ( 1 ) was reacted with different halo compounds, namely ethylchloroacetate, chloroacetone, bromoacetanilide, p-chlorobromoacetanilide, and p -methoxy chloroacetanilide in ethanol in the presence of sodium acetate yielded the corresponding S-alkylated derivatives ( 2a-e ). The latter compounds underwent cyclization into thienopyrimidines ( 4a-e ) upon treatment with sodium ethoxide in ethanol. The reaction of ( 4a ) with hydrazine hydrate led to the formation of 5-amino-4-methyl-2-phenylthieno[2,3-d]pyrimidine-2-carbohydrazide ( 5 ). Compound ( 5 ) was reacted with a variety of reagents to produce other new thienopyrimidines as well as oxadiazolylthienopyrimidines ( 6, 11 ).