Homogeneous Redox Catalysis Study of the Reductive Cyclization of 6-Hepten-2-one. Unusual Effects of the Nature and Concentration of the Catalyst

Article abstract of DOI:10.1021/ja00186a007

Electrochemical reductive cyclization of 6-hepten-2-one can be effected by homogeneous redox catalysts.Effective catalysts include biphenyl, 2-methoxybiphenyl, naphthalene, and phenanthrene.The reaction consumed 2 F mol^1-, and cis- and trans-1,2-dimethylcyclopentanol were formed as exclusive products.The percentage of the cyclic alcohol that was cis increased with increasing redox catalyst concentration, increasingly positive reduction potentials of the catalyst, and increasing amounts of water present in the medium.These results are explained by invoking amechanism involving reversible cyclization of the ketyl radical anion formed from reduction of 6-hepten-2-one.The cis or trans cyclized radical anions can be trapped by further reduction or by protonation to (ultimately) form the observed products.