Deconjugative Alkylation of α,β-Acetylenic Esters by Electrogenerated Base

Article abstract of DOI:10.1021/jo00210a006

Electrolysis of ethyl propiolate (1) and an excess of methyl iodide at a platinum cathode in hexamethylphosphoric triamide (HMPA) or N,N-dimethylformamide (DMF) solution containing tetra-n-butylammonium salt gave the acetylenic esters 2, 3, and 4.Similar electrochemical reactions of α,β-acetylenic esters 2, 5, and 9 with methyl iodide took place in good yields to give the corresponding α,α-dimethyl-β,γ-acetylenic esters 3 and 4, 4, and 10, respectively.Electrochemical reactions of 5 with ethyl, butyl, and allyl iodides also gave α,α-dialkyl β,γ-acetylenic esters 6, 7, and 8, respectively.These facile deconjugative alkylations appeared to take place by the action of the electrogenerated base (EGB) which was formed by the electrochemical reduction of alkyl iodides.Alkyl iodides worked as both a probasic compound of the EGB and as an electrophile.Reaction pathways of the present deconjugative alkylations are also discussed.