Sydnon-äthylene. III. Chemische Reaktionen elektronisch angeregter 4-Styryl-sydnone

Sydnone Ethylenes. III. Chemical Reactions of Excited 4-Styryl-sydnones Dependent on the character of the substituents in the photo reactions of 4-styryl sydnones Z/E-isomerism competes with CO2-elimination. Excited p-nitrostyryl sydnones exhibit a relatively strong degradation of the bond order in the CC region. Their quantum yields of Z/E-isomerism are therefore much higher than those of compounds with p-substituents of lower acceptor effect. In these compounds the cleavage of the sydnone ring with elimination of carbon dioxide is favoured especially if a methyl group is in 3-position of the sydnone.