SINGLE-ELECTRON TRANSFER IN NUCLEOPHILIC ALIPHATIC SUBSTITUTION - EVIDENCE FOR SINGLE-ELECTRON TRANSFER IN THE REACTIONS OF 1-HALONORBORNANES WITH VARIOUS NUCLEOPHILES

A series of 1-halonorbornanes was used as a model system in reactions with several nucleophiles in order to determine the involvement of single electron transfer (SET) in nucleophilic aliphatic substitution in the absence of light. The 1-halonorbornanes were allowed to react with Me3Sn-, Ph2P-, AlH4-, N(iPr)2-, SPh-, and the 2-nitropropyl anion in ether solvents at room temperature to 0-degrees-C. The results of product analyses, the use of radical and radical anion trapping reagents, the results of deuterium labeling studies, and the nucleofugality effect support a SET mechanism for the reactions involving 1-iodonorbornane. Convincing evidence that reduction of hindered alkyl iodides with LiAlH4 takes place by a SET pathway rather than by an impurity-initiated halogen atom radical chain process followed by an S(N)2 pathway, is presented.