Aliphatic aldehydes, which normally show extremely poor
yields in the acid catalyzed Biginelli reaction due to decomposition
or polymerization under acidic conditions [33], were
also converted to their corresponding 3,4-dihydropyrimidin-2-
(1H)-ones, but with lower yields after longer reaction time than
the aromatic aldehydes. The procedure not only preserved the
simplicity of the Biginelli reaction, but also gave good yields of
3,4-dihydropyrimidin-2(1H)-ones.