Synthesis of 6‐R‐5‐Aryl‐1,3‐dioxo‐1,2,3,4‐tetrahydro[1]benzothieno[3′,2′:4,5]pyrido [2,3‐d]pyrimidin‐5‐ium Salts and 6‐R‐5‐Aryl‐5,6‐dihydro[1]benzothieno[3′,2′:4,5]pyrido [2,3‐d]pyrimidine‐1,3(2H,4H)‐diones.

Acylation of 5-(benzothiophen-3-yl)pyrimidine-2,4,6(1H,3H,5H)-trione using acetic and propionic anhydride in the presence of 70% perchloric acid gave the 6-methyl(ethyl)-1,3-dioxo-1,2,3,4-tetra-hydro[1]benzothieno[3',2':4,5]pyrano[2,3-d]pyrimidin-5-ium perchlorates. Hydrolysis of the pyrano[2,3-d]pyrimidin-5-ium salts in aqueous alcohol solution gave 5-(2-acylbenzothiophen-3-yl)-pyrimidine-2,4,6(1H,3H,5H)-triones. Cyclocondensation of the latter with aromatic amine hydrochlorides produced 6-R-5-aryl-1,3-dioxo-1,2,3,4-tetrahydro[1]benzothieno[3',2':4,5]pyrido[2,3-d]-pyrimidin-5-ium chlorides. 6-R-5-Aryl-5,6-dihydro[1]benzothieno[3',2':4,5]pyrido[2,3-d]pyrimidine-1,3(2H,4H)-diones were synthesized by reduction of the pyrimidinium chlorides using sodium borohydride.