STEREO-REVERSED ELECTROPHILIC ADDITIONS TO 3-NORCARENES - INSIGHT INTO THE RELATIVE STERIC DEMANDS OF SINGLET OXYGEN IN THE ENE REACTION

Several snoutanes having a fused cyclohexene ring and therefore a 3-norcarene part structure entered into “ene” reaction with singlet oxygen and N-methyltriazolinedione with highly stereoselective or completely stereospecific approach to the anti surface (relative to the cyclopropane ring) of the double bond. When epoxidation and bromohydrin formation were examined, the preferred direction of electrophilic attack was shown to be syn. The several types of products were characterized spectroscopically and interrelated chemically. The absolute rates of reaction of the snoutanes and selected reference compounds toward 1O2 were determined by pulse radiolysis techniques. These data revealed that urazoles are not effective quenchers of singlet oxygen as previously proposed. Lastly, the causative factors underlying the striking reversal in the stereochemistry of electrophilic additions to the snoutanes are discussed. © 1979, American Chemical Society. All rights reserved.