title: Theoretical study of the reaction formalhydrazone with singlet oxygen. Fragmentation of the C=N bond, ene reaction and other processes.
abstract: Photobiologic and synthetic versatility of hydrazones has not yet been established with (1)O2 as a route to commonly encountered nitrosamines. Thus, to determine whether the "parent" reaction of formalhydrazone and (1)O2 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 (1)O2 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 (1)O2 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.
authors.affiliation: Department of Chemistry, Graduate Center & The City University of New York (CUNY), Brooklyn College, Brooklyn, NY.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Rudshteyn
authors.forename: Alvaro
authors.initials: A
authors.lastname: Castillo
authors.forename: Ashwini A
authors.initials: AA
authors.lastname: Ghogare
authors.forename: Joel F
authors.initials: JF
authors.lastname: Liebman
authors.forename: Alexander
authors.initials: A
authors.lastname: Greer
mesh_terms: D002244:Carbon / Q000737:chemistry*; D006835:Hydrazones / Q000737:chemistry*; D008962:Models, Theoretical; D009584:Nitrogen / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D006835:Hydrazones; D026082:Singlet Oxygen; D002244:Carbon; D009584:Nitrogen