Enantioselective, Electrocatalytic Lactonization of Methyl-Substituted Diols on a TEMPO-Modified Graphite Felt Electrode in the Presence of (- )-Sparteine.

A TEMPO (2,2,6,6-tetramethylpiperidin-1-yloxyl)-modified graphite felt electrode afforded enantioselective, electrocatalytic lactonized products of (S)-(−)-3,4,5,6-tetrahydro-4-methyl-2-pyranone, (S)-(−)-4,5-dihydro-4-methyl-2(3H)-furanone and (S)-(−)-4,5-dihydro-5-methyl-2(3H)-furanone from 3-methylpentane-1,5-diol, (S)-(−)-2-methylbutane-1,4-diol and racemic pentane-1,4-diol, respectively, in enantiomeric excess more than 95%, in the presence of (−)-sparteine in acetonitrile. The current efficiency and isolated yield of former two lactones were more than 90%.