B(C₆F₅)₃-Catalyzed Sequential Additions of Terminal Alkynes to <i>para</i>-Substituted Phenols: Selective Construction of Congested Phenol-Substituted Quaternary Carbons

Abstract

We have developed a borane-catalyzed sequential addition of terminal alkynes to <i>para</i>-substituted phenols, which affords a wide range of <i>ortho</i>-propargylic alkylated phenols bearing congested quaternary carbons. Control experiments combined with DFT calculations suggest that the reaction undergoes a sequential phenol alkenylation/hydroalkynylation process. Further extension of this strategy to the construction of triaryl-substituted quaternary carbons demonstrates the broad utility of this method.