Highly enantioselective catalytic asymmetric [2+2] cycloadditions of cyclic α-alkylidene β-oxo imides with ynamides

Highly enantioselective catalytic asymmetric [2+2] cycloadditions of cyclic α-alkylidene β-oxo imides with ynamides are described. The high reactivity of the cyclic α-alkylidene β-oxo imide allows the [2+2] cycloadditions of a hindered substrate with unreactive ynamides at low temperature. The X-ray crystallographic analysis of the product suggests that the enantioselectivity of the [2+2] cycloaddition can be well explained by the chelate model comprising the intramolecular hydrogen bond, wherein the cyclic α-alkylidene β-oxo imide coordinates with Cu^II through the two imide carbonyls. The imide group in the product can be transformed to amide, nitrile, and ester groups; moreover, it is removable.