Donor‐Acceptor Cyclopropanes: Activation Enabled by a Single, Vinylogous Acceptor

Abstract

A novel class of highly activated donor‐acceptor cyclopropanes bearing only a single, vinylogous acceptor is presented. These strained moieties readily undergo cycloadditions with aldehydes, ketones, thioketones, nitriles, naphth‐2‐ols and various other substrates to yield the corresponding carbo‐ and heterocycles. Diastereocontrol can be achieved through the choice of catalyst (Brønsted or Lewis acid). The formation of tetrahydrofurans was shown to be highly enantiospecific when chiral cyclopropanes are employed. A series of mechanistic and kinetic experiments was conducted to elucidate a plausible catalytic cycle and to rationalize the stereochemical outcome.