Vinylidene–Quinone Methides, Photochemical Generation and β-Silicon Effect on Reactivity

Irradiation of 2-alkynylphenols resulted in the generation of vinylidene−quinone methides (QMs), which were detected by laser flash photolysis in organic solvents and aqueous acetonitrile. QMs' spectroscopic properties and electrophilicity were both significantly affected by β-silicon effect. The hydration of the alkynyl moiety was an acid- and base-catalyzed process. The addition of amines was fast, yielding ketimines, with primary amines