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DFT Study on the Cycloreversion of Thietane Radical Cations

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journal contribution
posted on 02.06.2011 by Luis R. Domingo, Raúl Pérez-Ruiz, Juan E. Argüello, Miguel A. Miranda
The molecular mechanism of the cycloreversion (CR) of thietane radical cations has been analyzed in detail at the UB3LYP/6-31G* level of theory. Results have shown that the process takes place via a stepwise mechanism leading to alkenes and thiobenzophenone; alternatively, formal [4 + 2] cycloadducts are obtained. Thus, the CR of radical cations 1a,b•+ is initiated by C2–C3 bond breaking, giving common intermediates INa,b. At this stage, two reaction pathways are feasible involving ion molecule complexes IMCa,b (i) or radical cations 4a,b•+ (ii). Calculations support that 1a•+ follows reaction pathway ii (leading to the formal [4 + 2] cycloadducts 5a). By contrast, 1b•+ follows pathway i, leading to trans-stilbene radical cation (2b•+) and thiobenzophenone.