Theoretical Calculations on the Cycloreversion of Oxetane Radical Cations

Abstract

The molecular mechanism for the cycloreversion of oxetane radical cations has been studied at the UB3LYP/6-31G* level. Calculations support that the cycloreversion takes place via a concerted but asynchronous process, where C-C bond breaking at the transition state is more advanced than O-C breaking. This allows a favorable rearrangement of the spin electron density from the oxetane radical cation (with the spin density located mainly on the oxygen atom) to the alkene radical cation which is one of the final products. Inclusion of solvent effects does not modify the gas-phase results.

Hetero-cycloreversions Mediated by Photoinduced Electron Transfer

“…The molecular mechanism for this CR has been studied at the UB3LYP/6-31G* level. 50 Calculations are in agreement with an asynchronous process, which allows a favorable rearrangement of the spin electron density from the oxygen atom of the oxetane radical cation to the  system of the alkene radical cation.…”

Oxetane Ring Enlargement through Nucleophilic Trapping of Radical Cations by Acetonitrile

“…the UB3LYP/6-31G* level point to CR taking place in a concerted but asynchronous process, where CÀC breaking is more advanced than OÀC breaking at the transition state. 7 Experimental work on the PET CR of 2,3-diphenyloxetanes with (thia)pyrylium salts are in better agreement with an initial OÀC 2 cleavage. 4b With this background, we have undertaken an experimental and theoretical investigation on the PET CR of oxetane 1.…”

“…Semiempirical AM1 and PM3 calculations on the photoenzymatic repair of (6-4) DNA photoproducts by photolyases point to a nonconcerted, two-step mechanism for cleavage of oxetane radical cations via initial C–C bond cleavage. In addition, DFT calculations at the UB3LYP/6-31G* level point to CR taking place in a concerted but asynchronous process, where C–C breaking is more advanced than O–C breaking at the transition state . Experimental work on the PET CR of 2,3-diphenyloxetanes with (thia)pyrylium salts are in better agreement with an initial O–C 2 cleavage…”

Reaction mechanisms : Part (i) Radical and radical ion reactions

“…Computational studies on the cycloreversion of oxetane radical cations [eqn (14)], 79 and the electron transfer chemistry of cyclobutane pyrimidine dimers from the perspective of the mechanism of action associated with the enzyme DNA photolyase 80…”