Copper(i)/phosphine-catalyzed tandem carboxylation/annulation of terminal alkynes under ambient pressure of CO2: one-pot access to 3a-hydroxyisoxazolo[3,2-a]isoindol-8(3aH)-ones†
An efficient method for the synthesis of 3a-hydroxyisoxazolo[3,2-a]isoindol-8(3aH)-ones from CO2, terminal alkynes, EtBr, and NHPI (N-hydroxyphthalimide) was developed through a tandem carboxylation/annulation strategy catalyzed by a copper(I)/phosphine system. This one-pot multicomponent reaction was conducted at atmospheric CO2 pressure to afford the target products in good to excellent yields under mild conditions. Notably, a wide range of functional groups were tolerated in this procedure. This protocol with simultaneous formation of four novel bonds i.e. two C–C bonds and two C–O bonds represents an efficient methodology for upgrading CO2 into heterocycles.