Electrolysis of dimethyl alkylidenemalonates RCH=C(COOMe)(2) (R=n-Alk,
Ph) in an undivided cell in MeOH in the presence of alkali metal hali
de as mediator, leads to the formation of cyclic dimers, i.e., 3,4-dis
ubstituted 1,1,2,2-cyclobutanetetracarboxylates. The reaction proceeds
via the reductive coupling of two substrate molecules at cathode and
the cyclization of a hydrodimer dianion by its interaction with an act
ive form of a mediator, an anode-generated halogen.