Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond,Ene Reaction and Other Processes |
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Authors: | Benjamin Rudshteyn Álvaro Castillo Ashwini A Ghogare Joel F Liebman Alexander Greer |
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Institution: | 1. Department of Chemistry, Graduate Center & The City University of New York (CUNY), , Brooklyn, NY;2. Department of Chemistry and Biochemistry, University of Maryland, , Baltimore, MD |
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Abstract: | Photobiologic and synthetic versatility of hydrazones has not yet been established with 1O2 as a route to commonly encountered nitrosamines. Thus, to determine whether the “parent” reaction of formalhydrazone and 1O2 leads to facile C=N bond cleavage and resulting nitrosamine formation, we have carried out CCSD(T)//DFT calculations and analyzed the energetics of the oxidation pathways. A 2 + 2] pathway occurs via diradicals and formation of 3‐amino‐1,2,3‐dioxazetidine in a 16 kcal/mol?1 process. Reversible addition or physical quenching of 1O2 occurs either on the formalhydrazone carbon for triplet diradicals at 2–3 kcal mol?1, or on the nitrogen (N(3)) atom forming zwitterions at ~15 kcal/mol?1, although the quenching channel by charge‐transfer interaction was not computed. The computations also predict a facile conversion of formalhydrazone and 1O2 to hydroperoxymethyl diazene in a low‐barrier ‘ene’ process, but no 2‐amino‐oxaziridine‐O‐oxide (perepoxide‐like) intermediate was found. A Benson‐like analysis (group increment calculations) on the closed‐shell species are in accord with the quantum chemical results. |
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