An effective method for accessing novel substituted thieno[2,3-d]pyrimidine-4-carboxylic acids in 63–71% yields based on Pd(dppf)Cl2-catalyzed carbonylation of substituted 4-chlorothieno[2,3-d]pyrimidines has been proposed; a procedure has been developed for obtaining the amides of these acids, suitable for liquid-phase combinatorial synthesis, in 53–77% yields. Compounds with antimicrobial activity against Pseudomonas aeruginosa similar to the reference drug streptomycin were found among the synthesized amides.
