Verbenol allylic oxidation

Oxygenated monoterpenes which are found in almost every bark beetle species attacking coniferous trees, include czs-verbenol 246, frans-verbenol 247, and myrtenol 248, representing primary products of allylic oxidation of the host terpene a-pinene 45. Further oxidation of 247 or 248 leads to the... 

Attempts to investigate boll weevil (Anthonomus grandis) pheromone biosynthesis have identified isomerization, dehydration, and oxidation of the pheromone alcohols, and anticipated allylic oxidation of myrcene and limonene, but no evidence for the cyclization of acyclic precursors. The aggregation pheromones of bark beetles have been reviewed. Ips calligraphus responds to ipsdienol only in the presence of the c/5-verbenol (32) large additional concentrations of the enantiomer (l/ ,4i ,5/ )-(32) reduce beetle response. 5-(-)-Ipsenol, the pheromone of Ips grandicollis, increases the response of /. avulsus to its own pheromone ipsdienol. ... 

Examples of the use of chromium(VI) reagents to effect the allylic oxidation of alkenes to give a,3-unsaturated carbonyl compounds are very common in the literature. The reaction was first reported by Treibs and Schmidt for the allylic oxidations of a-pinene to verbenone and verbenol, of dipentene to carvone and caiveol, and of cyclohexene to cyclohexenol and cyclohexenone, using a solution of chromium trioxide in a mixture of acetic anhydride and carbon tetrachloride. However, yields were low and no synthetic use of this observation was made. 

Oxidative cleavage of monocyclic and bicyclic allylic alcohols to keto acids and di-acids respectively is effected by RuClj/aq. Na(IO )/CCl -CH3CN thus trans-verbenol gave (+)-c/x-pinononic acid and (+)-frani-pinocarveol yielded (-)-cis-pinic acid (Table 3.6) [237]. The double bond in diphenylcholene was cleaved by RuOj/aq. Na(IO )/CCl to aldehyde and acid (Table 3.4) and the adjoining phenyl rings destroyed [238]. 

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