Synthesis of fused-tetrahydropyrimidines: one-pot methylenation-cyclization utilizing two molecules of CO.

A methylenation-cyclization reaction, employing cyclic enaminones with primary aromatic amines and two molecules of CO, furnishing fused-tetrahydropyrimidines, is discussed. In this CsCO and ZnI catalyzed one-pot two-step procedure, two molecules of CO were selectively converted to methylene groups. The multi-component reaction might proceed through the formation of bis(silyl)acetal which was followed by condensation and further aza-Diels-Alder reaction. Hydroquinazoline, hydrocyclopenta[d]pyrimidine and hydroindeno[1,2-d]pyrimidine derivatives could be prepared with CO as the C1 source, effectively.