Cooperative Photo-/Lewis Acid Catalyzed Tandem Intramolecular [3+2] Cross-Cycloadditions of Cyclopropane 1,1-Diesters with α,β-Unsaturated Carbonyls for Medium-Sized Carbocycles

A tandem isomerization/intramolecular [3 + 2] cross-cycloaddition (IMCC) of cydopropane 1,1-diesters with alpha,beta-unsaturated ketones/aldehydes under a cooperative catalysis of photo and Lewis acids has been successfully developed. This supplied a general and efficient strategy for construction of medium-sized carbocyclic (8-, 9-, and 10-membered) skeletons as well as such carbocyde-based bridged oxa-bicyclo [n.2.1] (n = 4-6) skeletons.