Vinylogous Reactivity of Cyclic 2-Enones: Organocatalysed Asymmetric Addition to 2-Enals to Synthesize Fused Carbocycles.

A method for asymmetric and site selective annulations at the γ and γ' positions of cyclic 2-enones with α,ß-unsaturated aldehydes has been developed. The organocatalysed [3+3]-annulations proceed with high levels of regio-, diastereo-, and enantioselectivity, affording a series of high value fused carbocycles. Further elaboration gave key lactones (both bridged and fused).