THE MECHANISM OF REACTION OF GEMINAL DIHALIDES WITH SODIUM TRIMETHYLTIN - EVIDENCE FOR A SINGLE-ELECTRON TRANSFER INITIATED REACTION WHICH PRODUCES BOTH RADICAL AND CARBENE INTERMEDIATES

The reactions of two geminal dihalides, 6,6-dichloro-5,5-dimethyl-1-hexene (2a) and 6,6-diiodo-5,5-dimethyl-1-hexene (2b) with sodium trimethyltin (NaSnMe(3)), a known one-electron donor toward alkyl halides, have been studied. Evidence for a single electron transfer (SET) pathway has been obtained for both reactions. Although the monochloro analog of 2a, namely 7, was inert toward NaSnMe(3), 2a afforded 11 products. The nature of the products clearly indicates that the presence of two chlorine atoms on the same carbon atom results in a more favorable reduction potential than when just one chlorine atom is present. Both 2a and 2b on reaction with NaSnMe(3) also produced carbene-derived products, and evidence is presented that establishes that the carbene intermediate was in fact preceded by a radical intermediate. In addition, trimethyltin-substituted products (open chain as well as cyclized) were also obtained from both substrates and were found. to be derived from radical intermediates.