Creating Quaternary Centers with High Exo Stereoselectivity Using Activated α-Alkynyl Dienophiles

Ethynyl substituents were used to direct a highly exoselective creation of quaternary carbon centers in Diels−Alder cycloaddition reactions involving activated α-alkynyl dienophiles. The origins of electronic activation and the high stereoselectivities of these reactions were investigated by the B3LYP density functional method.