Synthesis and S-methylation of 2-thioxopyrido[3',2':4,5]thieno[3,2-d]-pyrimidin-4(3H)-ones with and without a phase transfer catalyst

A number of 2-thioxopyrido[3',2':4,5]thieno[3,2-d]pyrimdin-4(3H)-ones (5) have been synthesized by cyclocondensation of 2-carbethoxy-3-amino-4-phenyl-6-substituted-thieno[2,3-b]pyridines (3) with various isothiocyanates. Compounds 5 were S-methylated routinely and the reactions compared under solid-liquid phase transfer conditions to obtain 2 -methylthiopyrido[3',2':4,5] thieno[3,2-d]pyrimidin-4(3H)-ones (6). The new triheterocyclic pyridothienopyrimidines were prepared with the objective to study their pharmacological properties.