3-Carene allylic oxidation

Allylic oxidation reactions employing chiomium(VI) reagents therefore appear to be very much dependent upon the intrinsic nature of the substrate as to their regiochemical outcome. This is exemplified by the r-butyl chromate allylic oxidation of (+)-3-carene (67 equation 28) where no great preference for either piquet exists. 

PFC is also a reasonable oxidant for activated C— H bonds. Allylic oxidation to a variety of ketonic products was observed upon treatment of A -carene with PFC." Benzylic C— H oxidation with PFC is also known. 

Using the most active catalyst (CoNaY) we have studied the oxidation of olefins of different structure and size of molecules, including a number of natural terpenes, namely, (+)-a-pinene (1), (+)-3-carene (2), (-)-caryophyllene (3) and dipentene (4). We have found that even acid-sensitive epoxides that are known to be prone to ring cleavage (caryophyllene epoxide, for example) can be obtained with high-to-exceUent selectivity (Table 2). It is noteworthy that neither allylic oxidation nor overoxidation occurs in the systems studied. Diolefins give mono-... 

Oxidation with singlet oxygen is subject to sterk effects but can show poor regioselectivity. For example, (+)-3-carene (52) is oxidized to produce a mixture of all three possible regioisomeric hydroperoxides with oxygenation occurring at the face of the allyl systm 0 qx>site the gem-dimethylcyclo-propane unit in each case (equation 22). - ... 

Japanese authors have made comprehensive investigations of the rearrangements of oxiranes in the presence of solid acids, bases, and salts.The model compounds employed were cyclohexene oxide and 1-methylcyclohexene oxide. The effects of the acidic and basic properties of the catalysts on the selectivity were interpreted on the basis of the products obtained. The main products are carbonyl compounds and allyl alcohol isomers. Rearrangements of limonene oxide over acids and bases were studied on five different types of Al203 similar research has been carried out on 2- and 3-carene oxides, cis- and trans-carvomenthene oxides and a-pinene oxide. ... 

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