tert-Butylation of α,β-Unsaturated Nitriles by tert-Butylmercury Halides in the Presence of Iodide Ion

Iodide ion promotes the free radical addition of t-BuHgI to acrylonitrile to form t-BuCH₂CH (CN)HgI. A facile reaction of the adduct 1-cyanoalkyl radical with t-BuHgI₂^-is indicated. Further promotion is observed in the presence of NH₄I or PTSA/KI in a reaction now leading directly to t-BuCH₂CH₂CN. Protonation of the intermediate adduct radical followed by electron transfer from t-BuHgI₂^-is postulated. With fumaronitrile reaction of the adduct, radical [t-BuCH (CN)C·HCN] with t-BuHgI can be promoted by the addition of acids or bases. In the presence of NH₄I or PTSA/KI, the reductive alkylation product is formed, while in the presence of DABCO, oxidative alkylation occurs to yield t-BuC (CN)=CHCN and t-BuC (CN)=C (CN)Bu-t. Protonation of [t-BuCH (CN)C·HCN] increases the ease of reduction while deprotonation yields an easily oxidized radical anion.