STEREOCHEMISTRY OF ELECTROPHILIC SUBSTITUTION OF (+)-3-CARENE - PRINS AND FRIEDEL-CRAFTS-ACETYLATION REACTIONS

Evidence is presented that the previously studied Prins and Friedel-Crafts-acetylation reactions of (+)-3-carene (IV) each involve electrophilic attack trans to the cyclopropyl ring to give the products I and IX, having the newly introduced C-4 substituents in an α-orientation. Through oxidation, I and IX were converted to a common intermediate, the ester VI. Analysis of the NMR spectra of the epimeric esters VI and VII and ketones IX and X with the aid of double decoupling techniques permitted assignment of the 4α and 4β configurations, respectively. Additional support for the assignments I and IX is provided by examination of the NMR spectra of the epoxides XII and XIII. © 1968.