The first intermolecular reactions of the excited state of a silicon divalent compound (silylene) with benzene derivatives were discovered. Typically, when a benzene solution of an isolable silylene is irradiated with light of wavelengths longer than 420 nm at room temperature, the corresponding silacyclohepta-2, 4, 6-triene (silepin) is yielded quantitatively. The photochemical insertion of the silylene toward substituted benzenes ...