Catalytic Enantioselective 3 + 2 Cycloaddition of α–Keto Ester Enolates and Nitrile Oxides

摘要

An enantioselective [3 + 2] cycloaddition reaction between nitrile oxides and transiently generated enolates of α-keto esters has been developed. The catalyst system was found to be compatible with in situ nitrile oxidegeneration conditions. A versatile array of nitrile oxides and α-keto esters could participate in the cycloaddition, providing novel 5-hydroxy-2-isoxazolines in high chemical yield with high levels of diastereo- and enantioselectivity. Notably, the optimal reaction conditions circumvented concurrent reactions via Oimidoylation and hetero-[3 + 2] pathways.