Ferrocenyl-Substituted Tetrahydrothiophenes via Formal (3+2)-Cycloaddition Reactions of Ferrocenyl Thioketones With Donor-Acceptor Cyclopropanes

Abstract

Ferrocenyl thioketones react with donor-acceptor cyclopropanes in dichloromethane at room temperature in the presence of catalytic amounts of Sc(OTf)3 yielding tetrahydrothiophene derivatives, products of formal (3+2)-cycloaddition reactions, in moderate to high yields. In all studied cases, dimethyl 2-arylcyclopropane dicarboxylates react with corresponding aryl ferrocenyl thioketones in a completely diastereoselective manner to form single products in which (C-2)-Ar and (C-5)-ferrocenyl groups are oriented in a cis-fashion. In contrast, the same cyclopropanes undergo reaction with alkyl ferrocenyl thioketones to form nearly equal amounts of both diastereoisomeric tetrahydrothiophenes. Low selectivity was also observed in the reaction of 2-phthalimide-derived cyclopropane with ferrocenyl phenyl thioketone.