Photochemical Alkylation, Hydroxyalkylation, and Alkoxylation of Pyridinecarboxamides in Alcohol

Abstract

The UV-irradiation of 2- and 4-pyridinecarboxamides in alcohol brings about alkylation and/or hydroxyalkylation in the pyridine ring. In the irradiation of 3-pyridinecarboxamide in the presence of sulfuric acid, ionic reaction (alkoxylation at the 2- and 6-position) and radical reaction (alkylation at the 4- and 6-position) occur in parallel. The effects of quenchers indicate that two alkylation products originate from one excited triplet state which is quenched by energy-transfer mechanism and that two alkoxylation products originate from the excited singlet state.

Photodegradation of pyridylketoximes in methanolic solutions under UV–Vis radiation

“…After photodegradation, the samples were analyzed using LC-MS/MS and UV-Vis techniques in 0, 5,10,15,20,25,30,45, and 60 min of radiation. Additionally, the samples obtained after 60 min of the photodegradation were analyzed using the GC-MS technique.…”

“…The mechanism of photosubstitution to the pyridine ring in the presence of oxime moiety seems to be different from that for other pyridine derivatives. The UV radiation of pyridine-3-and -4-pyridinecarboxylic acids, esters and amides, depends on the pH of alcoholic solution and also leads to hydroxyalkylation and alkoxylation [23][24][25][26][27][28][29]. However, the hydroxymethylation is combined with the photoreduction (radical not ionic reaction) to the alkyl substituent.…”