BF3<middle dot>OEt2 Promoted 1,6-Conjugate Addition of para-Quinone Methides: A Regioselective Approach to Diarylmethyl-Substituted Carbo- and Heterocycles

In this work, we report a base-free and transition metal-free 1,6-conjugate addition strategy for synthesizing unsymmetrical diaryl-substituted methanes possessing carbo- and heterocycles such as 1,3-indandione, aminouracils, and barbituric acid derivatives from para-quinone methides (p-QMs) using BF3<middle dot>OEt2 as promoter. The high functional group tolerance, good to excellent yields, and mild reaction conditions of this protocol underscore its significant potential for the synthesis of a broad spectrum of titled products. Furthermore, gram-scale synthesis and versatile subsequent conversions highlight the synthetic utility of these scaffolds.