A reexamination of Biginelli-like multicomponent condensation reaction: one-pot regioselective synthesis of spiro heterobicyclic rings.

A pseudo four-component reaction is described, leading to the efficient regioselective synthesis of sigma symmetric spiro heterobicyclic rings using aldehydes and urea in the presence of cyclic beta-diester or beta-diamides such as Meldrum's acid or barbituric acid derivatives. The reaction needs no added catalyst and proceeds solvent-free conditions at 80 degrees C.