In the presence of a chiral thiourea as a bifunctional organocatalyst, Mannich reaction of N-Boc-imine with prochiral 1,3-dicarbonyl compounds proceeded with excellent enantio- and diastereoselectivities.
Both catalysts work: A highlyenantioselective direct Mannich‐type reaction of N‐Boc‐protected aldimines with 1,3‐dicarbonyl compounds has been developed with the use of a chiral phosphoric acid in the presence or absence of CaII. The absolute stereoselectivity of the phosphoric acid catalysis was found to be opposite to that of the calciumphosphate catalysis (see scheme; Boc=tert‐butoxycarbonyl)