Visible-Light-Induced Generation of <i>p-</i>Quinone Methides via Paternò–Büchi Reaction: Access to Quaternary Centers through Three-Component Coupling

A visible-light-mediated [2+2] Paternò-Büchi cycloaddition between <i>p</i>-benzoquinone and terminal and internal alkynes enables in situ generation of minimally substituted <i>p</i>-quinone methides (<i>p</i>QM). Subsequent 1,6-conjugate addition with diverse alcoholic nucleophiles forms quaternary centers under mild, metal-free conditions. Mechanistic investigations support a photocatalyst-independent pathway involving oxetene formation and electrocyclic ring opening, expanding the utility of <i>p</i>QM intermediates in complex molecule construction.