Highly enantioselective [4 + 2] annulations catalyzed by amino acid-based phosphines: Synthesis of functionalized cyclohexenes and 3-spirocyclohexene-2-oxindoles

Highly enantioselective [4 + 2] annulation of activated alkenes with α-substituted allenoates catalyzed by amino acid-based bifunctional phosphines has been developed for the first time, which provides an easy access to optically enriched functionalized cyclohexenes. In particular, 3-spirocyclohexene-2-oxindoles were prepared in high yields and with excellent enantioselectivities.