Generation and Application of o‐Quinone Methides Bearing Various Substituents on the Benzene Ring

Abstract o ‐Quinone methides ( o ‐QMs) are highly reactive, short‐lived intermediates, which have potential synthetic applicability. However, few studies on the generation of o ‐QMs bearing an electron‐withdrawing group have been reported. Herein we present a general method for the generation of o ‐QMs, particularly those substituted with an electrophilic substituent, from new precursors, 4 H ‐1,2‐benzoxazines 2 . We have also studied systematically the Diels–Alder reactions of o ‐QMs with various dienophiles, such as vinyl ethers, enamines and imines. The reactions provide a versatile route to substituted chromans, phenols and 3,4‐dihydro‐2 H ‐benzo[ e ][1,3]oxazines (3,4‐dihydro‐1,3‐benzoxazines). Furthermore, we applied the new method to the derivatization of some natural products.