Organocatalytic enantioselective Michael addition of cyclic hemiacetals to nitroolefins: A facile access to chiral substituted 5- and 6-membered cyclic ethers

An efficient aminocatalytic enantioselective Michael addition of readily available cyclic hemiacetals to nitroolefins has been developed. The strategy serves as a powerful approach to synthetically valuable chiral 3-substituted tetrahydrofurans (THFs) and tetrahydropyrans (THPs). The synthetic utilities of the versatile Michael adducts also have been demonstrated in the synthesis of 2,3-disubstituted cyclic ethers, α-substituted lactones and venlafaxine analogues.