An efficient acceptor of 1-hydroxy(or alkoxy)alkyl radicals – ketene dithioacetal S,S-dioxide –

Photochemical Alkylation of Ketene Dithioacetal S,S-Dioxides. An Example of Captodative Olefin Functionalization

“…Another stoichiometric method for generating a radical is photochemical hydrogen abstraction by means of an nπ* triplet, e.g., benzophenone . Ogura reported the high yield functionalization of ketene thioacetal S , S -dioxides with various hydroxy (alkoxy)alkyl radicals generated from alcohols or ethers by irradiation with an equimolecular amount of benzophenone. , We explored whether the same scheme could be applied to hydrocarbons possessing no activated C−H bond. As it appears from Table and Scheme the result was positive.…”

“…These, in turn, are convenient synthetic intermediates in view of several possible elaborations, e.g., C -alkylation and -arylation, substitution of an allyl for a sulfone group, desulfurization, , pyrolysis to yield a carbonyl derivative, Pummerer rearrangement . Ketene dithioacetal S , S -dioxides have been shown to act as efficient acceptors of carbenes as well as of 1-hydroxy- (or alkoxy-)alkyl radicals. , Furthermore, intramolecular radical addition of β-(ω-iodoalkyl) derivatives has been shown to occur under classic radical chain conditions yielding five-, six-, and also four-membered cyclic derivatives, a result rationalized on the basis of the peculiar stability of the adduct radical due to the captodative effect . Somewhat surprisingly, no corresponding intermolecular radical alkylation has been reported except for the above-mentioned case of hydroxyalkyl radicals.…”