Electrochemical Studies of the Reduction of 6,6-Dimethyldibenzofulvene Oxide and Tetraphenyloxirane

Article abstract of DOI:10.1021/jo00199a016

The electrochemical reduction of 6,6-dimethyldibenzofulvene oxide (1) in dimethylformamide-0.1 M (n-Bu)4NClO4 is an overall two-electron process that affords 9-fluorenyl anion and acetone in the absence of an added proton donor and 2-(9-fluorenyl)propanol (2) in the presence of diethyl malonate.The initial electroreduction of tetraphenyloxirane (3) is also a two-electron process and gives Ph2C(-)CPh2(O-) as an unobserved intermediate.This dianioon reacts rapidly by abstracting a proton at either the benzhydryl carbon center (75percent) or the oxygen center (25percent) to give either Ph2CHCPh2(O-) or Ph2C(-)CPh2OH.The former anion then undergoes an elimination of Ph2CH(-) to afford Ph2C=O whereas Ph2C(-)CPh2(OH) eleminate OH- to give Ph2C=CPh2.Ph2C=O and Ph2C=CPh2 are then reduced at the applied potential to Ph2CHOH and (Ph2CH)2, respectively.Ph2CHCPh2OH (4) and 2 undergo electrochemically induced chain reactions in the potential range of interest with 4, affording equimolar amounts of Ph2C=O and Ph2CH2, whereas 2 gives equimolar amounts of fluorene and acetone.There is no evidence that carbene anion radicals are formed as transient intermediates in any of the electroreductions.