Intramolecular addition of alkoxyl radicals. Part 4. Reductive cyclisation of olefinic hydroperoxides

Abstract

Pent-4-enyl hydroperoxide reacts with reducing salts (FeX₂, TiCl₃) to afford tetrahydrofurfuryl compounds (halides or dimers) in high yield from the selective cyclisation of the pent-4-enyloxyl radical. Analogous behaviour is observed for photolysis although the yields of cyclic products are lower. The photolysis of hex-5-enyl hydroperoxide does not yield cyclic products but these are observed when this hydroperoxide is reduced by FeCl₂. It is suggested that metallic salts are able to complex the alkoxyl radicals thereby making them more electrophilic and hence more prone to cyclise.