Synthesis of (4 S *,5 S *)-Diphenyl-1,3,4,5-Tetrahydro-2 H -[1]Benzopyrano [4,3- d ]Pyrimidine-2-Thiones by Base-Catalysed Cyclocondensation of ( E )-3-Benzylideneflavanones with Thiourea,and Determination of Their Monoacetylation Site
Free accessResearch articleFirst published online March, 2004
Synthesis of (4 S *,5 S *)-Diphenyl-1,3,4,5-Tetrahydro-2 H -[1]Benzopyrano [4,3- d ]Pyrimidine-2-Thiones by Base-Catalysed Cyclocondensation of ( E )-3-Benzylideneflavanones with Thiourea,and Determination of Their Monoacetylation Site
Base-catalysed cyclocondensation of (E)-3-benzylideneflavanones with thiourea has been found to be highly stereoselective, producing (4S*,5S*)-diphenyl-1,3,4,5-tetrahydro-2H-[1]benzopyrano[4,3-d]pyrimidine-2-thiones in high yield, the structure of one of which has been determined by X-ray crystallography. Just like 4,6-diaryl-3, 4-dihydropyrimidine-2(1H)-thiones, the said products also undergo monoacetylation on treatment with Ac2O. The site of acetylation in both of these classes of compound are established by detailed NMR spectral studies.
