Nitrones and oxazirans. III. Photolysis of 1-pyrroline 1-oxides and their related oxazirans

Abstract

Oxazirans have been prepared from a number of 1-pyrroline 1-oxides by photoisomerization and from the related 1-pyrrolines by oxidation with perbenzoic acid. This oxidation was found to be highly stereoselective in reaction with unsymmetrical pyrrolines, and 3,5-cis-disubstituted oxazirans were formed exclusively. A mixture of 3,5-cis- and trans-disubstituted oxazirans was formed in the photolysis of unsymmetrical 2-methyl-substituted pyrroline 1-oxides but stereo-selectivity was observed in the photolysis of similar 2-aryl-substituted pyrroline 1-oxides, in which cases only the trans-isomer was obtained. Photoisomerization of cis-5-phenyl-substituted oxazirans to their trans-isomers was also observed, while other oxazirans were found to be photo-stable.