Regio‑, Diastereo‑, and Enantioselective Nitroso-Diels–Alder Reaction of 1,3-Diene-1-carbamates Catalyzed by Chiral Phosphoric Acids

Chiral phosphoric acid-catalyzed asymmetric nitroso-Diels–Alder reaction of nitrosoarenes with carbamate-dienes afforded cis-3,6-disubstituted dihydro-1,2-oxazines in high yields with excellent regio-, diastereo-, and enantioselectivities. Interestingly, we observed that the catalyst is able not only to control the enantioselectivity but also to reverse the regioselectivity of the noncatalyzed nitroso-Diels–Alder reaction. The regiochemistry reversal and asynchronous concerted mechanism were confirmed by DFT calculations.