Carene epoxidation

Bicyclo[4,l,0]heptanes.—The hydrogenation, hydroboration, thermolysis, amination, oxidation, and photochemical isomerization of various carane derivatives has been reviewed by Cocker. Another case of the repetition of earlier work has appeared, this time concerning the catalytic reduction of car-3-ene (307). Further work on the acid- and base-catalysed ring-opening of carene epoxides is reported (Scheme 17). ... 

Cyclopropanes can also participate in epoxide openings, much like double bonds. The work of Ohloff and Giersch with carene epoxides illustrates this behavior, e.g. (25 equation 10) is converted to (26) and related carbenium ion derived products, and (27 equation 11) similarly forms (28). 

Carene is found as in various Pinaceae essential oils (+)-3-carene is a major compound of Pinus palustris essential and (-)-3-carene of Pinus sylvestris. It is used as raw material in perfumery (Bornscheuer et al, 2014). In rabbits, 3 carene is metabolized into 3-carene-9-ol and further oxi dized into 3-carene-9-carboxylic acid and 3-carene-9,10-dicarboxylic acid (Ishida et al., 1981). In vitro experiments with human liver microsomes revealed 3-carene-lO-ol and 3-carene-epoxide as metabolites (Figure 9.4). Hydroxylation was catalyzed by CYP2B6, CYP2C19, and CYP2D6, whereas epoxidation could be attributed to CYP1A2 (Duisken et al., 2005). 3-Carene-lO-ol could be detected as metabolite in human urine (Schmidt et al., 2013). 

Menthol from (+)-3-Carene. An Indian manufacturing process for (—)-menthol starts from 3-carene, the major component of Indian turpentine oil (55-65%). (+)-3-Carene isomerizes to (+)-2-carene, which can be pyrolyzed to (+)-tra s-2,8-/ -menthadiene. Isomerization of the latter yields (+)-isoterpi-nolene, which is hydrogenated to give >50% (+)-3-/ -menthene. Epoxidation and subsequent rearrangement lead to a menthone isomenthone mixture,... 

Pillay and Sunonsen18 8 have stated, for example, that a substance formulated by them ae d-A -carene oxide is stable to aqueous sgllurii aoid. Arbuzov and Michailov,30 on the other hand, also claim to have prepared this epoxide, but report success in forming the corresponding 1,2-diol on exposure to conventional hydrolysis conditions (Eq. 

Cyclodextrins have been covalently modified for catalytic oxidation, such as compounds 57, 62-65 (Schemes 3.14 to 3.16) [44, 45]. Enantioselective epoxidation of styrene derivatives, and carene using 20-100 mol% of the CD-ketoester 57 has been achieved. The inclusion-complex formation was confirmed by aH NMR titration experiments, confirming the 1 1 substrate catalyst stoichiometry under the reaction conditions. In the oxidation of carene, NOE and ROESY experiments showed different behavior according to the size of the R group (Scheme 13.14). Evidence was found for the formation of inclusion complexes with compounds 58 and 59. On the other hand, compounds 60 and 61 proved to interact with the catalyst via a tail inclusion vide infra). The increased diastereoselectivity observed with compounds 58 and 59 might be explained by a closer proximity to the covalently linked dioxirane. 

In the course of our earlier studies on terpenylboranes we developed a simple transformation of a- into 3-pinene," and a stereoselective synthesis of allylic alcohols by the reduction of vinylic epoxides.12 An extension of these studies to contrathermo-dynamic isomerization of a-thujene, 2- and 3-carene,13 and kinetic resolution of vinylic epoxides by the reduction with terpenylboranes,14 is described. 

SYNTHESIS OF (+)-3(10>CARENE, (+)-SABINENE, AND KINETIC RESOLUTION OF VINYLIC EPOXIDES... 

The synthesis of 8- and 9-substituted carenes (320) and (321) from the epoxide (322) has been described. 

Iona group -with jSJaotoma, 826 Carboxylic acida. reaction with axirMUnea, 653 epoxides, 366-82 etliylene auliidea. 612 o,CarboxyiitilbBne, perbenxoic acid Oxi-datlOD, 63, 373 Car-3 ene, epoxidation, 43 AB-Carene, peracetic acid oxidation, 381... 

The kinetic and stereochemical results on 2-methylenecyclohexanol derivatives have been utilized to interpret the stereoselective epoxidation of aliphatic a-ethylene-alcohols. The main product in the oxidation of 4-a-chloro-3(10)-carene 16 is 17 (Eq. 7). ... 

FIGURE 16.6 Epoxidation of 3-carene with H2O2 catalyzed by self-assembled sandwich POM plus Luviquat mono CP as cocatalyst, which accelerates the two-phase reaction by forming a stable emulsion that separates into a water and organic layer at full conversion. 

Many terpenoids in the correct oxidation state having also an oxygen atom at C-2 are converted to carvenone (578) with sulfuric acid. The epoxide (563) of 3-carene also undergoes this reaction, yielding the (— )-isomer 578, the (+ )-isomer being obtained fix)m (- )-4-caranone (579). ° ... 

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-... 

An amino ether 46, presumably derived from (+)-3-carene [( + )-40], has been used for asymmetric alkylation of azaenolates via imines (SectionD.1.1.1,4.1., ref 40). No details were given on the synthesis of 46, but it can be prepared by methylation of the corresponding amino alcohol which was probably obtained from the epoxide of ( + )-3-carene by ring opening with trimethylsilyl azide, followed by catalytic hydrogenation41,... 

Often terpenes may be included as additives, e.g. food additives licensed by the FDA. Terpenes detected in indoor air are mainly the monoterpenes alpha-, beta- pineries, 3 -carene and d-limonene which occur primarily in conifer products. Some of the monoterpenes may be converted into well-known epoxides and peroxides with high allergic potential. ... 

FIGURE 19.45 Epoxidation of limonene (68), a pinene (4), and 3-carene (336) with p38 from the cultured cells of Nicotiana tabacum. (Modi ed from Yawata, T. et al., Epoxidation of monoterpenes hy the peroxidase from the cultured cells oiNicotiana tabacum. Proceedings of 42nd TEAC, 1998, pp. 142-144.)... 

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