Carvone enol acetate

Bicyclic compounds have apparently never been detected in the products resulting from the carbonium ion reactions of either acyclic precursors [e.g., (33-X) or (34-X)], or monocyclic menthane reactants [e.g., (35-X)] under quite a variety of conditions (77, 84, 86, 87), It appears to be necessary to provide additional driving force as in the acid-catalyzed cyclization of carvone enol acetate (44) 87) or the intramolecular enolate alkylation of keto tosylate (45) 88, 89) in order to overcome the strain energy of the bicyclo[2.2.1]heptane and bicyclo-[3.1.1]heptane rings. An additional factor in the latter case is, of course, increased electrophilic demand at a primary, as opposed to a tertiary, center. 

The electrooxidation of the enol acetate 23 of isopinocamphone generally leads to three different types of products 7-carvone 7, 8-acetoxy-p-menth-6-en-2-one 24, and 2-acetoxy-2,6,6-trimethylbicyclo[3.1.1]heptan-3-one. The product distribution is largely dependent on the combination of solvent and electrolyte. It is found that the enol acetate 23 leads to /-carvone 7 selectively, if electrolysis is performed in a CH2C12/ AcOH(8/l)—Et4NOTs—(C) system (Scheme 3-8)55>. 

A useful synthesis (ref.ll)of patchouli alcohol, an important fragrant constituent of patchouli oil, from (+)-camphor, that onetime important natural product which was employed as a plasticiser for nitrocellulose (itself a semi-synthetic polymer), was complicated by structural revision of the sesquiterpene alcohol. Dihydrocarvone (14) obtained by saturation of the ring double bond in carvone, a major constituent of oil of spearmint has been employed for two very different sesquiterpenes, the ketone campherenone (15) and the alcohol, occidentalol (16). In the first case an enol acetate was converted to a bicyclic intermediate by earlier established methodology and the route emulated a plausible biogenetic sequence giving racemic campherenone (ref.12) as shown. Any chirality in (14) is apparently lost. 

A simple one-step synthesis of (-)-A -tetrahydrocannabinol from chrysanthenol and olevitol has been reported. The anodic oxidation of the enol acetate of iso-pinocamphone (613), obtained in three steps by standard methods from l-oc-pinene, provides a novel synthesis of /-carvone (614 34% overall) in essentially quantitative optical yield. The choice of solvent (CH2CI2-ACOH) and supporting electrolyte (Et4NOTs) is important. Treatment of a-pinene with Bu OK/Bu"Li gave (615) which... 

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