Michael–Michael Addition Reactions Promoted by Secondary Amine-Thiourea: Stereocontrolled Construction of Barbiturate-Fused Tetrahydropyrano Scaffolds and Pyranocoumarins

Bifunctional
secondary amine-thiourea organocatalysts were successfully
applied in the stereocontrolled synthesis of barbiturate-fused tetrahydropyrano
scaffolds. Compared with typically used tertiary amine-thiourea organocatalysts,
the developed catalysts exhibited excellent catalytic performance
in the domino Michael–Michael reaction between N, N′-dimethylbarbituric acid and Morita–Baylis–Hillman
acetates of nitroalkenes to yield pharmaceutically important heterocycles
in good yields with excellent enantioselectivities. Moreover, this
catalytic protocol can also be applied to synthesize biologically
active pyranocoumarin compounds.