Chemical evolution. XVI. Photochemistry of ortho-substituted benzene derivatives and related heterocycles

Photochemistry of Salicylaldoxime in Solid Argon: An Experimental and Theoretical Study

“…The dehydration of salicylaldoxime may lead to the formation of 2-cyanophenol, which was postulated to be a minor photolysis product in irradiated hexane and aqueous base solution of salicylaldoxime. [19] The comparison of the frequencies characteristic for C with the reported infrared spectra of 2-cyanophenol [30,31] confirms, indeed, formation of the latter molecule in the studied photoreaction. The water and 2-cyanophenol molecules are both proton donors and acceptors, so, being trapped in the same matrix cage after salicylaldoxime is photodissociated, they may form a hydrogen-bonded complex.…”

“…Scheme 2 presents the reaction channel leading to a formation of the 2-cyanophenol-H 2 O complex. As already mentioned in the Introduction, earlier studies [18,19] indicate that the major result of salicylaldoxime photolysis in polar solvents like water or ethanol and nonpolar ones like hexane or pentane is cyclization to give benzoxazole. Photohydrolysis reaction leading to the formation of salicylaldehyde is a minor reaction channel, however, may become important in the acidified solutions.…”

“…[17] The photochemistry of o-hydroxy-substituted aromatic oximes in aqueous solutions exposed to 350, 300, and 254 nm radiation has also been reported. [18][19][20] The major result of photolysis of salicylaldoxime was cyclization to give benzoxazole; however, photohydrolysis producing salicylaldehyde was found to be competitive with cyclization, especially in acidified solutions. [18] In irradiated aqueous base solution of salicylaldoxime some amount of 2-cyanophenol and a trace amount of salicylaldehyde were identified in addition to the cyclization photoproduct benzoxazole.…”

“…[18] In irradiated aqueous base solution of salicylaldoxime some amount of 2-cyanophenol and a trace amount of salicylaldehyde were identified in addition to the cyclization photoproduct benzoxazole. [19] Haley and Yates [18] suggested the mechanism of the cyclization reaction of salicylaldoxime. On the basis of the fluorescence emission and excitation spectra of salicylaldoxime the authors put forward a hypothesis on the existence of two major ground-state conformers of the molecule, one having an intramolecular hydrogen bond and the other being hydrogen bonded to the solvent.…”

Reakcije oksazola i njihovih derivata u pobuđenom stanju. I. dio: Fototranspozicije u prstenu

“…23,24 istražuje izomerizacije izoksazola i benzizoksazola pomoću CASSCF i MP2-CAS računskih metoda. Stariji mehanizam 22,25,26 za te reakcije bio mehanizam je ciklizacije-izomerizacije (shema 3) koji uključuje prvotno nastajanje bicikličkog međuprodukta nakon kojeg slijedi [1,3]-pomak dušika u sekundarni biciklički međuprodukt koji podliježe otvaranju azirinskog prstena u produkte fototranspozicije (P 1 -P 3 ). Ti međuprodukti nisu nikad zamijećeni, te je autor predložio drugi, izravni mehanizam preko stožastog presjeka (CI).…”