Addition - cyclization reaction of nitroalkane anions with o-quinone derivatives via electron transfer in the charge-transfer complexes

An addition - cyclization reaction of nitroalkane anions with tricyclic o-quinones occurs in acetonitrile to yield the corresponding 1,3-dioxole derivatives. The heat of formation of the charge-transfer complex formed between the 2-nitropropane anion and 1,7-phenanthroline-5,6-dione is of greater magnitude than the observed activation enthalpy of the addition reaction. Since such a relationship could only arise when the charge-transfer complex lies along the reaction pathway, the charge-transfer complex acts as a real intermediate rather than a bystander in the addition reaction of the 2-nitropropane anion with the o-quinone derivative. A comparison of the observed rate constants with those predicted for the electron transfer from nitroalkane anions to o-quinones indicates that the addition reaction proceeds via electron transfer in the charge-transfer complex formed between nitroalkane anions and the o-quinones, followed by C-O adduct formation and subsequent cyclization to afford the 1,3-dioxole derivatives.