Pinan

Pinan J P, Ouillon R, Ranson P, Becucci M and Califano S 1998 High resolution Raman study of phonon and vibron bandwidths in isotropically pure and natural benzene crystal J. Chem. Phys. 109 1-12... 

CIS Pinane and trans pinane are common names that de note the relationship be tween the pair of methyl groups on the bridge and the third methyl group... 

In practice hydrogenation of a pinene is observed to be 100% stereoselective The only product obtained is cis pinane No trans pinane is formed... 

Commercially, autoxidation is used in the production of a-cumyl hydroperoxide, tert-huty hydroperoxide, -diisopropylbenzene monohydroperoxide, -diisopropylbenzene dihydroperoxide, -menthane hydroperoxide, pinane hydroperoxide, and ethylbenzene hydroperoxide. 

Fig. 3. Conversion of a-pinene (8) to P-pinene (20) and to i j -pinane (21) and subsequent reactions.

Another important use of a-pinene is the hydrogenation to i j -pinane (21). One use of the i j -pinane is based on oxidation to cis- and /n j -pinane hydroperoxide and their subsequent catalytic reduction to cis- and /n j -pinanol (22 and 23) in about an 80 20 ratio (53,54). Pyrolysis of the i j -pinanol is an important route to linalool overall the yield of linalool (3) from a-pinene is about 30%. Linalool can be readily isomerized to nerol and geraniol using an ortho vanadate catalyst (55). Because the isomerization is an equiUbrium process, use of borate esters in the process improves the yield of nerol and geraniol to as high as 90% (56). 

Pyrolysis of the i j -pinane produces dihydromyrcene (24) (citroneUene) as the major product in 50—60% yield. Fractionation of the cmde product then gives an 87 wt % dihydromyrcene (57). Dihydromyrceno1 (25) produced from the dihydromyrcene is becoming increasingly important as a fragrance material. It has excellent stabiUty and has a powerhil, fresh, lime-like aroma. Hydration of citroneUene using formic acid has become an important commercial method for producing dihydromyrcenol (58). 

Dihydromyrcene Manufacture. 2,6-Dimethyl-2,7-octadiene, commonly known as dihydromyrcene (24) or citroneUene, is produced by the pyrolysis of pinane, which can be made by hydrogenation of a- or P-pinene (101). If the pinene starting material is optically active, the product is also optically active (102). The typical temperature for pyrolysis is about 550—600°C and the cmde product contains about 50—60% citroneUene. Efficient fractional distUlation is requited to produce an 87—90% citroneUene product. 

Another important process for linalool manufacture is the pyrolysis of i j -pinanol, which is produced from a-pinene. The a-pinene is hydrogenated to (73 -pinane, which is then oxidized to cis- and /n j -pinane hydroperoxide. Catalytic reduction of the hydroperoxides gives cis- and /n j -pinanol, which are then fractionally distilled subsequendy the i j -pinanol is thermally isomerized to linalool. Overall, the yield of linalool from a-pinene is estimated to be about 30%. 

Products formed by reaction of NO3 radicals with a-pinene have been identified and include pinane epoxide, 2-hydroxypinane-3-nitrate, and 3-ketopinan-2-nitrate formed by reactions at the double bond, and pinonaldehyde that is produced by ring fission between C-2 and C-3 (Wangberg et al. 1997). These reactions should be viewed in the general context of odd nitrogen to which alkyl nitrates belong (Schneider et al. 1998). 

The hydroxylation of cyclohexane by a strain of Xanthobacterium sp. (Trickett et al. 1990). In cell extracts, a range of other substrates was oxidized including cyclopentane, pinane, and toluene (Warburton et al. 1990). 

The linear co-oxidation dependence was observed for the following pairs of hydrocarbons (333 K, initiator AIBN) tetralin-ethylbenzene, phenylcyclopentane-ethylbenzene, phenyl-cyclohexane-ethylbenzene, tetralin-phenylcyclohexane, cyclohexene-2-butene, 2,3-dimethyl, and cyclohexene-pinane [8]. 

Pinane, 3 231 24 487 cis-Pinane, 24 495 Pinanols, 24 477, 495 Pinch, making stream matches at, 13 199-200. See also Pinch point Pinch analysis, 10 163 20 735-737 applications of, 20 763 total site, 20 751... 

An unusually large ( + 7.45 ppm) 7-SCS of a methyl group at C(7) was observed in cis-pinane (327) when compared with norpinane (326) (499). This difference does not originate only in the methyl effect transmitted through the bonds also, the 7g-effect from C(3) is missing due to the flip of the six-membered ring (499). In the trans isomer 328 the C(7) signal shows an upfield shift of 3.5 ppm, as expected (499). 

Rienacket R, Ohloff G, Opticsch actives fi-cittonellol aus (- -)-odet (—)-pinan, Angew ChemU HAQ, 1961. 

The enantioselectivity of these reagents is explained by comparison of transition structures 72 and 73 shown in Scheme 7. The disfavored transition structure 73 leading to the minor enantiomer displays a steric interaction between the methylene of the allylic unit and the methyl group of one of the pinane units. Unlike the tartrate boronates described above, the directing effect of the bis(isopinocampheyl) allylic boranes is extremely powerful, giving rise to high reagent control in double diastereoselective additions (see section on Double Diastereoselection ). 

In the case of diastereomeric mixtures of chiral hydroperoxides, standard chromatography on achiral phase can be employed to separate the diastereomers. As one example for the preparation of optically pure hydroperoxides via this method, the ex-chiral pool synthesis of the pinane hydroperoxides 11 is presented by Hamann and coworkers . From (15 )-cw-pinane [(15 )-cw-10], two optically active pinane-2-hydroperoxides cA-lla and trans-llb were obtained by autoxidation according to Scheme 17. Autoxidation of (IR)-c -pinane [(17 )-cw-10] led to the formation of the two enantiomers ent-lla and ent-llh. The ratio of cis to trans products was 4/1. The diastereomers could be separated by flash chromatography to give optically pure compounds. 

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