R- -limonene

Several generalities can be formulated regarding selective reduction of polyolefins. Usually the least hindered double bond is hydrogenated pre ferentially (123), and, with steric hindrance about equal, the most strained bond will be reduced first. Exocyclic olefins are reduced more easily than those in the ring (R)-(+ )-Limonene, 190 g, was shaken with W-4 Raney nickel (12 g) under hydrogen at atmospheric pressure. After 31.9 1 of hydrogen had been absorbed, the solution was filtered. Essentially, pure (R)-( -i- )-carvomenthene was obtained in 96% yield (58). 

Chiral and achiral Jacobsen s catalysts exhibit similar diatereomeric excesses during the diastereoselective epoxidation of R-(+)-limonene using in situ prepared oxidizing agents. Therefore, the chiral center of the substrate appears to govern the chiral induction. In contrast, the chirality of the Jacobsen s catalyst appears to be responsible for the chiral induction when commercially available oxidants were used. 

Synonym d-p-mentha-l,8,-diene, (R)-(+)-p-mentha-l,8-diene, (+)-l-methyl-4-(l-methylethenyl)cyclohexene, p-mentha-1,8-diene, carvene, cinene, citrene, cajeputene, kautschin Chemical Name dextro-limonene, (R)-(+)-limonene CAS Registry No 5989-27-5 Molecular Formula C10H16 Molecular Weight 136.234 Melting Point (°C) ... 

The cycloaddition of nitrile oxides RCNO (R = alkyl, alkenyl, aryl), generated in situ from either RCH2NO2/PI1NCO or RCH=NOH/NaOCl to (R)-( + )-limonene, proceeds regioselectively at the extracyclic double bond, but not stereospecifically, to form (5R/S )-isoxazoles 78 in 64% to 81% isolated yield (241). 

In the search for environmentally benign chemicals that might deter birds such as starlings, crows, or pigeons from roosting en masse, spices and herbs such as rosemary, cumin, and thyme look promising. In some experiments, the birds feet were immersed in oil extracts of the spices. Starlings also avoided perches treated with starch mixes of (R)-limonene, (S)-limonene, (3-pinene, or methiocarb. The first three occur in rosemaiy, cumin, and thyme (Clark, 1997). 

HP IR measurements have recently been reported by workers at Sasol for cobalt-catalysed 1-dodecene hydroformylation reactions using bicyclic phosphines (4) derived from (R)-(+)-limonene [68]. Using Fourier deconvolution to separate absorptions due to [HCo(CO)4] and [Co2(CO)7(phosphine)], it was possible to estimate the ratio of modified [HCo(CO)3(phosphine)] to un-modified [HCo(CO)4] in the catalytic mixture, using peak areas. Values of this ratio ranged from ca. 2-20, depend-... 

A hydrocyclone system has been proposed for the separation of mixed plastics including among others HIPS. Both water and calcium chloride solutions have been used. A procedure for the determination of the HIPS content in a ABS/HIPS material has been proposed. The analysis method relies on the selective dissolution in R-limonene (44). 

Norgaard, A.W., Nojgaard, J.K., Larsen, K., Sporring, S., Wilkins, C.K., Clausen, P.A. and Wolkoff, P. (2006) Secondary limonene endo-ozonide a major product from gas-phase ozonolysis of R-(+)-limonene at ambient temperature. Atmospheric Environment, 40, 3460-6. 

Clausen, P.A., Wilkins, C.K., Wolkoff, P. and Nielsen, G.D. (2001) Chemical and biological evaluation of a reaction mixture of r-(+)-limonene/ozone-formation of strong airway irritants. Environment International,... 

Graebin CS, Eifler-Lima VL, da Rosa RG (2008) One-pot synthesis of secondary and tertiary amines from R(+)-limonene by tandem hydroformylation/reductive animation (hydroamino-methylation). Catal Commun 9 1066—1070. doi 10.1016/j.catcom.2007.10.008... 

These catalysts have been tested in the stereoselective epoxidation of R-(+)-limonene and (-)-a-pinene. Here only the epoxidation of (-)-a-pinene as depicted in Figure 4 is considered. The oxidant applied in the reaction is somewhat similar to the one introduced by Mukaiyama et al. and was favored over the system used by Jacobsen and coworkers14. 17. The major benefit of this system is that undesirable salt formation can be avoided by the use of environmentally benign molecular oxygen at RT instead of NaOCl as oxidant at 0°C. 

Renewable feedstocks can also be used as the raw materials for the synthesis of green, biodegradable polymers. A pertinent example is polylactate, derived from lactic acid which is produced by fermentation (see earlier). Another recent example is the production of polycarbonates by reaction of C02 with (R)-limonene oxide in the presence of a zinc catalyst (Fig. 8.47) [221]. 

Yue et al. reported on the total synthesis of / -(—)-cembrene A by using the mod-ihed Wittig reaction and titanium-induced intramolecular carbonyl coupling as key steps the overall yield is 29% starting from -geranylacetone (164) and R-(+)-limonene (168) (Scheme 6-15). ... 

Catalytic hydrogenation can be used for the selective reduction of a carbon-carbon double bond in the presence of other functional groups such as a carbonyl group or an aromatic ring. Selective reduction of one double bond in (R)-limonene (6.7), which contains two double bonds, gives (R)-carvomenthene (6.8) by hydrogenation over Ni metal. 

Matura M, Goossens A, Bordalo O, Garcia-Bravo B, Magnusson K, Wrangsjo K, Karlberg AT. Oxidized citrus oil (R-limonene) a frequent skin sensitizer in Europe. J Am Acad Dermatol 2002 47(5) 709-14. 

---