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Catalytic Enantioselective [3 + 2] Cycloaddition of α‑Keto Ester Enolates and Nitrile Oxides

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posted on 2017-06-05, 00:00 authored by Samuel L. Bartlett, Yoshihiro Sohtome, Daisuke Hashizume, Peter S. White, Miki Sawamura, Jeffrey S. Johnson, Mikiko Sodeoka
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 oxide-generation 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 O-imidoylation and hetero-[3 + 2] pathways.