Catalytic Enantioselective Nitroso Diels–Alder Reaction

The nitroso Diels-Alder (NDA) reaction is an attractive strategy for the synthesis of 3,6-dihydro-1,2-oxazines and 1-amino-4-hydroxy-2-ene derivatives. Herein we report the Cu(I)-DTBM-Segphos catalyzed asymmetric intermolecular NDA reaction of variously substituted cyclic 1,3-dienes using highly reactive nitroso compounds derived from pyrimidine and pyridazine derivatives. In most of the cases studied, the cycloadducts were obtained in high yields (up to 99%) with very high regio-, diastereo-, and enantioselectivities (up to regioselectivity > 99:1, d.r. > 99:1, and >99% ee). As an application of this methodology, formal syntheses of conduramine A-1 and narciclasine were accomplished.