Ot-pinene

The epoxidation method developed by Noyori was subsequently applied to the direct formation of dicarboxylic acids from olefins [55], Cyclohexene was oxidized to adipic acid in 93% yield with the tungstate/ammonium bisulfate system and 4 equivalents of hydrogen peroxide. The selectivity problem associated with the Noyori method was circumvented to a certain degree by the improvements introduced by Jacobs and coworkers [56]. Additional amounts of (aminomethyl)phos-phonic acid and Na2W04 were introduced into the standard catalytic mixture, and the pH of the reaction media was adjusted to 4.2-5 with aqueous NaOH. These changes allowed for the formation of epoxides from ot-pinene, 1 -phenyl- 1-cyclohex-ene, and indene, with high levels of conversion and good selectivity (Scheme 6.3). 

Fig. 2.1.6.7 Epoxidation of (-)-ot-pinene over various homogeneous and immobilized transition metal-salen complexes. = homogeneous complex (QH F, 4.6 mmol pivalic aldehyde, 1.85 mmol (-)-ot-pinene, 25 mg catalyst,...

Finally, an interesting attempt has been carried out using chiral nitrogen bases in order to induce chirality in the oxidation reaction. Using (+)-2-aminomethylpyr-rolidine as the chiral nitrogen base and UHP as the oxidant in CH2CI2 at —5°C, a moderate diastereomeric excess of 41% is obtained at 11% conversion of ot-pinene. This study shows the feasibility of inducing enantioselectivity in this reaction by means of the use of chiral amine bases [34],... 

As with ot-pinene, a very well-performing system can be obtained by using either 2-aminomethylpyridine or irons-1,2-diaminocyclohexane as the nitrogen base in a CH2C12/CH3CN solvent mixture (entries 6 and 7). Especially, the latter gives excellent results with full conversion and selectivity for the monoepoxide [53],... 

Both antipodes of ot-pinene are available, which upon hydroboration with borane leads to both forms of diisopinocampheylborane (IPC2BH) depicted below ... 

D-Limonene and ot-pinene have been used as renewable solvents and chain transfer agents in metallocene-methylaluminoxane (MAO) catalysed polymerization of ot-olefins. Chain transfer from the catalyst to the solvent reduces the achieved in limonene compared with toluene and also reduces the overall catalyst activity. This was confirmed, as in the ROMP studies, by performing identical reactions in hydrogenated limonene. However, an increase in stereospecificity was seen when D-limonene was used as the solvent. This is measured as the mole fraction of [mmmm] pentads seen in NMR spectra of the polymer. 100% isotactic polypropylene would give a value of 1.0. On performing the same propylene polymerization reactions in toluene and then in limonene, the mole fraction of [mmmm] pentads increased from 0.86 to 0.94, indicating that using a chiral solvent influences the outcome of stereospecific polymerizations. Unfortunately, when a-pinene was used, some poly(a-pinene) was found to form and this contaminates the main polymer product. 

Dilongifolylborane is simply prepared by admixture of borane-dimethyl sulfide and 2 equiv. (+)-lon-gifolene in THF, whereupon the product crystallizes out of solution as the dimer, and can readily be separated from the solvent. It is used as a suspension for hydroboration reactions. Diisopinocampheylborane can be prepared in a similar way from (+)- or (-)-a-pinene, and early work was carried out with reagent so prepared. However, ot-pinene is often available only in purities up to ca. 95%, so that Ipc2BH produced by direct hydroboration can also be somewhat impure. Fortunately, equilibration of the reagent (dimethyl sulfide must first be removed if borane-dimethyl sulfide is used for the hydroboration) with cn-pinene, at 0 C over several days, results in preferential incorporation of the major enantiomer of a-pinene into the Ipc2BH. This then becomes available in 98-99% enantiomeric purity. 

Figure 23 Enanriomer separation of ot-pinene, P-pinene, and limonene on a 25-m Pyrex glass capillary with 6-me-2,3-pe-7-CD at 55 C,...

Bomeol, camphene, and a-pinene are made in nature from geranyl pyrophosphate. The biosynthesis of ot-pinene and the related camphor are described in the chapter. In the laboratory bornyi chloride and camphene can be made from a-pinene by the reactions described below. Give mechanisms for these reactions and say whether you consider them to be biomimetic. 

Decarbonylation of the ozonolysis product of ot-pinene gives a methyl trimethylcyclobutyl ketone. Addition of acetylene to this, followed by the Carroll reaction, gives (trimethylcyclobutyl)heptadienone. The cyclobutane ring is opened by acid to give a methylated /-ionone which, on cyclization, produces irones. Once again, the Greek prefixes have the same significance as in the ionone series. 

Among dialkylboranes, diisopinocampheylborane (lpc2BH, 1) is most often used for asymmetric hydroboration and several procedures for its synthesis are known2 67-71. The most convenient one, providing a product of essentially 100% ee, involves the hydroboration of ot-pinene with boranc-dimethyl sulfide complex71. 

The repeatability of the Ir values for various monoterpene hydrocarbons was examined. The concentrations of the standard samples for GC-MS of ot-pinene, P-pinene, sabinene, myrcene, a-phellandrene, a-terpinene, limonene, y-terpinene and terpinolene were within the range of 0.5-1.8% (w/w). The Ir value for each monoterpene hydrocarbon was plotted in Fig. 1, where the coefficient of variation (CV) is also presented. These Ir values only seem to vary over a narrow range, since their CVs were not more than 0.61% (limonene). 

FIGURE 14.10 Left Effect of a chiral guest molecule on the M/P equilibrium for a helical polymer. (Reprinted from Prince, R.B., S.A. Barnes, and J.S. Moore. /. Am. Chem. Soc., 122, 2758-2762, 2000. With permission.) Right. Effect of added (-)-a-pinene on the absorption (a) and circular dichroism, (b) spectra of m-PPE-CX)2 (structure shown in panel (a). (-)-ot-Pinene concentration ranges from 0 to 6 p,M. 

FIGURE 14.45 Epoxidation of limonene (68), Ot-pinene (4) and 3-carene (336) with p38 from the cultured cells of Nicotiana tabacum. (Modified from Yawata, T. et ah, 1998. Proc. 42nd TEAC, pp. 142-144.)... 

It has been proposed that some monoterpenoid constituents of Cannabis, such as ot-pinene or limonene, may synergize the antibacterial action of CBD, CBG, and CBN [79]. Interestingly, a potentiating effect of mono- or sesquiterpenoids present in Cannabis has been postulated also for other activities, and this observation supports arguments that whole plants and their complex preparations are better drugs than individual components isolated from them. 

Isobutene can also be copolymerized with 1,3-butadiene, cyclopentadiene, indene, or ot-pinene [589-593],... 

To be truly consistent with partitioning theory, particles must also shrink upon dilution, much like POA described above. Different experiments have confirmed that ot-pinene + ozone SOA particles do evaporate upon dilution, but not in the minute or so suggested by the volatility distribution in Fig. 5 and the timescales in Fig. 3. Rather, particles relax back to equilibrium after dilution over hours [31,108], though they do eventually reach the size predicted from equilibrium partitioning theory [108]. This delay is consistent with some phenomenon slowing evaporation by at least a factor of 100. Potential causes for this delay include dissociation of weakly bound oligomers [108] or slowed diffusion in the particles themselves... 

Hydroboration of Ketones with Boranes from ot-Pinenes and the Non-linear Effect in Asymmetric Reactions... 

This chiral reducing agent was developed by Chandrasekharan and Brown [22, 23] and can be prepared in situ from both enantiomers of ot-pinene. Later, the Merck group made an important observation on the (—)-isomer the reducing agent prepared from 98% optically pure (—)-a-pinene gave benzylic alcohol 5-16... 

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