Theoretical Study of the Reaction Formalhydrazone with Singlet Oxygen. Fragmentation of the C=N Bond, Ene Reaction and Other Processes
Year: 2013
Type: article
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.
Source: Photochemistry and Photobiology
DOI: 10.1111/php.12199
Language: English
Subfield: Physical and Theoretical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2167726005