A STUDY OF THE REGIOSELECTIVITY OF THE RADICAL-ADDITION OF RSAR DERIVED FROM THE PHOTOLYSIS OF TERT-HOMOALLYL AND TERT-ALKYL 4-NITROBENZENESULFENATES TO SUBSTITUTED ALLENES AND ALKENES

The regioselectivity of the free radical addition of ''RSAr'' derived from the photolysis of tert-homoallyl and tert-alkyl 4-nitrobenzenesul fenates, followed by beta-scission of the alkoxy radicals to produce t he allyl or alkyl radicals R. to 1,1- and 1,3-dimethylallene and acryl onitrile and methyl acrylate has been determined. The regioselectivity of addition of ''RSAr'' to 1,1- and 1,3-dimethylallene occurs by the addition of the arylthiyl radical to the-center carbon atom of the all ene chromophore, whereas the regioselectivity of the addition to acryl onitrile and methyl acrylate varies with the nature of the R.. The res ults are interpreted in terms of the relative reactivities of the pi s ystems toward radical addition and the relative rates of beta-scission of the intermediate alkoxy radicals versus the rates of addition of t he 4-nitrobenzenethiyl radical and R. to the pi systems.