Molecular Iodine-Catalyzed 1,6-Conjugated Addition of Enaminones on para-Quinone Methides

Abstract

A highly efficient and metal-free protocol has been developed for the synthesis of a series of enaminone derivatives functionalized with unsymmetrical diarylmethyl units via 1,6-conjugate addition of enaminones viz. arylaminocyclohexenones and N-alkyl arylaminomaleimides, using molecular iodine (I₂) under mild conditions. This reaction proceeds at ambient temperature, yielding structurally diverse products with excellent functional group tolerance. The optimized conditions demonstrated remarkable substrate scope, including electron-donating and electron-withdrawing substituents on both para-quinone methides (p-QMs) and enaminones. The use of I₂ as a catalyst offers an environmentally benign and cost-effective alternative to transition metals, ensuring operational simplicity. The scalability of the method was successfully demonstrated through gram-scale synthesis.