Electroreductive Intramolecular Coupling of Nonconjugated Aromatic Ketones

Article abstract of DOI:10.1021/jo00085a033

The electroreduction of nonconjugated aromatic ketones gave intramolecularly coupled products.The best result was obtained using an Sn cathode in i-PrOH containing tetraalkylammonium salt as a supporting electrolyte.This reductive cyclization proceeded with remarkable stereoselectivity, and the cis isomer was obtained exclusively.A variety of new bi- and polycyclic compounds were synthesized.The reaction mechanism was studied, and it was suggested that the anion radical generated by one-electron transfer to a carbonyl group attacks an aromatic ring intramolecularly.The choice of counter cation of the anion radical was critical for the reductive cyclization.Other reductive methods employing metal reducing agents were also studied.Reduction with Na in HMPA-THF gave the same cyclized product, though the yield was lower than that with the electroreduction.