| Abstract: | Photochemical Reactions of 3-Pyrazolidone Betains. V. Photooxidation of Heteroaromatic N-Ylids The dye-sensitized photooxidation of the heteroaromatic N-ylids 3a and 3b yields 1-isoquinolone 8 together with ethyl mesoxalate 13 and bis(benzoyl-isoquinol-1-on-2-yl-methyl)ether 10 , respectively. These are decomposition products of fivemembered ring peroxides, formed by reaction of singlet oxygen with the N-ylids. One mole of the ylids 3c, 4 and 5 gives complete conversion with 0.5 moles of singlet oxygen, yielding the corresponding heteroaromatic and mesoxalic acid derivatives, respectively. The products and the oxygen consumption are discussed to be due to reaction of one molecule of the ylid with one molecule of alkylhydroperoxide 18 , formed as a primary product. N-Ylids 3c, 4 and 5 react in the same manner with hydrogen hydroperoxide or perbenzoic acid to the corresponding heteroaromatic and mesoxalic acid derivatives. For the reaction between 3c and substituted perbenzoic acids the HAMMETT correlation gives ϱ = +0.94. |
