An organocatalytic asymmetric tandem reaction for the construction of bicyclic skeletons.

Cyclic ketones react with (E)-2-nitroallylic acetates in the presence of catalytic pyrrolidine-thiourea, which affords bicyclic skeletons with four or five stereocenters in one single reaction with up to 98 % ee in moderate to high yields. The cooperative effects of both enamine and the Brønsted acid are found to be crucial for the high reactivity and enantioselectivity of this cascade reaction, which is demonstrated by both theoretical calculation and experimental data.