Intramolecular formal iron-catalyzed ene reactions: The stereoselective and regiocontrolled formation of substituted tetrahydropyrans

Abstract

The iron-catalyzed six-membered ring carbocyclizations of 5-oxa-2, 8, 10-undecatriene derivatives proceed with high regio- and stereoselectivity to yield trans-3, 4-disubstituted tetrahydropyrans. Substrates containing an alkyl substituent at the 4- or the 7-position of the starting triene ether cyclize with high secondary stereoinduction to produce trans, trans-trisubstituted derivatives. Diastereomeric (2 Z)- and (2 E)-substrates cyclize via complementary [4+4]- and [4+2]-ene reaction pathways.