Organocatalytic enantioselective Diels-Alder reaction between hydroxymaleimides and in situ generated nitrosoalkenes for direct preparation of chiral hemiketals with 1,2-oxazine skeleton

An organocatalyst promoted enantioselective inverse-electron-demand oxa-Diels-Alder (IEDDA) reaction between hydroxymaleimides and in situ generated nitrosoalkenes has been revealed, and a wide range of chiral hemiketals containing 5,6-dihydro-4H-1,2-oxazines and succinimide frameworks with two adjacent quaternary stereogenic centers have been effectively prepared for the first time with excellent results (up to 99% yield, up to 99 : 1 dr, up to >99% ee) even at a scale-up preparation under mild conditions.