Organocatalytic domino formation of (3R,3aS,9bR)-configured 3-aryl-3a-benzamido-1,3a,4,9b-tetrahydrochromeno[4,3-b]pyrroles in carbon dioxide medium

Asymmetric cycloaddition/intramolecular rearrangement domino reaction of 2-(2-hydroxybenzylideneamino)- malonates with 4-arylidene-2-phenyloxazol-5(4H)-ones can be efficiently carried out in sub- or supercritical carbon dioxide to afford (3R,3aS,9bR)-3-aryl-3a-benzamido-4-oxo-1,3a,4,9b-tetrahydrochromeno[4,3-b]pyrrole-2,2(3H)- dicarboxylates in high yields with up to 99% ee. Excellent stereoinduction is provided in this process by the use of bifunctional hybrid organocatalyst consisting of squaramide (thiourea) and chiral tertiary amine units.