Free-radical chain substitution reactions involving organomercurials

Substituted 1-alkenyl compounds of the type R(\u271)R(\u272)C=CHQ (Q = I, Br, HgX, SPh, S(O)Ph, SO(,2)Ph, SnBu(,3)) undergo photostimulated substitution reactions with organomercurials (RHgX and R(,2)Hg). The reactions are inhibited by di-tert-butyl nitroxide and do not occur in the dark. The evidence supports a free-radical chain mechanism. The proposed mechanism involves regioselective (alpha)-addition of the alkyl radicals followed by (beta)-elimination of Q(.). The chain carrier Q(.) reacts with the mercurials by either a S(,H)2 or an electron transfer process. In the electron transfer process, the reaction is believed to occur in a concerted manner. The initial kinetic chain length of the reactions of 2,2-diphenylethenyl iodide and tri-n-butyl-(E)-2-phenylethenylstannane with t-butylmercury chloride are determined to be 100 and 71, respectively.;Heteroatom-centered radicals (PhS(.), PhSe(.), PhSO(,2)(.), (EtO)(,2)PO(.)) add efficiently to the double bonds of the alkenyl compounds followed by (beta)-elimination of Q(.) to give the substitution products in excellent yields. Other substrates which react with 1-alkenyl compounds include triisopropylaluminum, tricyclohexylborane, and isopropylmagnesium iodide. These reactions, however, are limited to alkenyl sulfones and mercurials.;The substitution reactions of (E)- and (Z)-1,2-disubstituted ethylenes (XCH=CHZ where X = CO(,2)Me, Cl; Z = I, Cl, SnBu(,3), HgCl) with organomercurials and phenyl disulfide occur in a stereospecific manner. The reactions have been extended to include allyl and alkynyl systems.;The relative reactivities of the alkenyl and alkynyl derivatives towards cyclohexyl and thiophenoxy radicals have been determined. With cyclohexyl radical, the relative reactivities are in the order SO(,2)Ph \u3e I \u3e SnBu(,3) for the alkynyl system and SO(,2)Ph \u3e SPh \u3e HgCl \u3e I \u3e SnBu(,3) for the alkenyl system. With thiophenoxy radical, the reactivity order is SO(,2)Ph \u3e I \u3e SnBu(,3) for the alkynyl series and HgCl \u3e SnBu(,3) \u3e I \u3e SO(,2)Ph for the alkenyl system.;Mercuric carboxylates can provide alkyl radicals by the decarboxylation of carboxy radicals in a Hunsdiecker type process. The resulting alkyl radicals will react with alkenyl derivatives, phenyl disulfide, phenyl diselenide and N-(phenylthio)phathalimide to give the substitution products