ALLYLIC REARRANGEMENT OF TRANS-PINOCARVEOL ESTERS

摘要

The allylic rearrangement of trans-pinocarveol esters (I) to myrtenol esters (II), a reaction of interest in the chemistry of terpenes and cannabinoids, has been theoretically investigated. The intramolecular, cyclization-induced rearrangement results in equilibrium mixtures of the starting compounds and the products with the ratio of I vs. II in the equilibrium mixture being determined by their thermodynamic stabilities. The relative thermodynamic stabilities as reflected by calculated AM1 heats of formations (Delta Hf) were determined for various I-II ester pairs. The study, in agreement with available experimental evidence, indicates that generally I, which contain an endocyclic double bond, are more stable and thus predominantly form following rearrangements. In two cases (acetate and pivalate) the stability is reversed. Calculations performed for similar structures, esters of 2-methylene cyclohexane-1-ol (IV) and 1-cyclohexene-1-methanol (V) gave similar results. Structural and electronic factors which might influence the stability of these compounds were examined. Interestingly, a correlation between thermodynamic stability and dipole moments was observed. (C) 1996 John Wiley & Sons, Inc. [References: 13]