Asymmetric catalytic [3 + 3]-cycloaddition of γ-hydroxy-α,β-unsaturated ketones with azaoxyallyl cations

Abstract

An organocatalytic asymmetric [3 + 3]-cycloaddition between γ-hydroxy-α,β-unsaturated ketones and in situ generated azaoxyallyl cations has been developed for the enantioselective synthesis of functionalized morpholin-3-ones. The asymmetric reaction using cinchonidine-derived squaramide as an organocatalyst was tolerant to various γ-hydroxy-α,β-unsaturated ketones and α-bromodimethylhydroxamates, providing access to the desired functionalized morpholin-3-ones in moderate yields with good-to-excellent enantioselectivities (up to 90% ee).