Identification of phenylmethylene as an active intermediate of the acid-catalyzed styrene epoxide oxidation in polar solvents

Abstract

After the acid-catalyzed conversion of styrene epoxide under the action of p-toluenesulfonic acid (acetonitrile, ButOH (90%) + chlorobenzene (10%) (v/v), 343 K) in the presence of pyridine, a spectrum of iminium ylide was obtained (λmax = 450 nm), coinciding with the spectrum of the ylide product formed upon the reaction of pyridine with phenylmethylene (published data) during generation of carbenes from diazo compounds by flash photolysis. In an oxygen atmosphere, no ylide absorption band is recorded. This result confirms the previous assumption according to which in epoxide–acid systems, carbene species are formed, react with O2 in an oxygen atmosphere, and destroy the added hydroperoxides in the absence of O2.