Hydrogenation of limonene

Scheme 4-331. Hydrogenation of (+)-(/ )-limonene catalyzed by a [bis(imino)pyridine]bis(dinitrogen)iron complex.

By oxidation with permanganate it forms pinonic acid, C,oH,<503, a monobasic acid derived from cyclobutane. With strong sulphuric acid it forms a mixture of limonene, dipentene, terpinolene, terpinene, camphene and p-cymene. Hydrogen chloride reacts with turpentine oil to give CioHijCl, bomyl chloride, artificial camphor . 

To 0.165 mole of BMB (prepared as in the preceding experiment) maintained at 0°, is added 20.4 g (0.15 mole) of /-limonene over a period of 5 minutes. The reaction mixture is allowed to stand at room temperature for approximately 3 hours. It is then oxidized by the addition of 50 ml of 3 A sodium hydroxide followed by 50 ml of 30% hydrogen peroxide. The alcohol is worked up in the usual manner. Upon distillation, the primary terpineol is obtained, bp 115-116710 mm. 

It is generally observed that the less hindered double bond in a diolefin is preferentially hydrogenated as found in the reaction of limonene (equation 16)56. 

Both uncalcined and calcined LDHs have also been shown to be effective supports for noble metal catalysts [18-25]. For example, palladium supported on Cu/Mg/Al LDHs has been used in the liquid phase oxidation of limonene [24], and on calcined Mg/Al LDHs for the one-pot synthesis of 4-methyl-2-pentanone (methyl isobutyl ketone) from acetone and hydrogen at atmospheric pressure [25]. In the latter case, the performance depends on the interplay between the acid-base and hydrogenation properties. More recently. 

The preferred industrial method of carvone synthesis utilizes the selective addition of nitrosyl chloride to the endocyclic double bond of limonene. If a lower aliphatic alcohol is used as solvent, limonene nitrosochloride is obtained in high yield. It is converted into carvone oxime by elimination of hydrogen chloride in the presence of a weak base. Acid hydrolysis in the presence of a hydroxylamine acceptor, such as acetone, yields carvone [88]. 

The catalytic performance of the supported bimetallic nano-particles in the hydrogenation of unsaturated molecules was tested on a wide variety of unsaturated species hex-l-ene, phenyl acetylene, diphenyl acetylene, trans-stilbene, cis-cyclooctene and D-limonene. The highly efficient hydrogenation of hex-1 -ene was accompanied by the isomerisation reaction to cis-and trans-hex-2-ene, which were subsequently hydrogenated (albeit at a much slower rate) as reaction ensued. 

As already noted by Verkuijlen and Boelhouwer in 1974 [29], the SM of highly unsaturated fatty esters produces, among other compounds, considerable amounts of 1,4-cyclohexadiene (1,4-CHD). This fact has been exploited by Mathers et al. for the production of 1,3-cyclohexadiene (1,3-CHD) via metathesis and isomerization reactions of plant oils [141]. For instance, 1,4-CHD was obtained by treatment of soybean oil with C4 and was subsequently isomerized with RuHCl(CO)(PPh3)3. Then, the produced 1,3-CHD was polymerized with nickel(II)acetylacetonate/ methaluminoxane. Interestingly, the polymerizations could be carried out in bulk and using hydrogenated D-limonene as renewable solvent. The polymers thus obtained presented / m around 300°C. 

The second double bond is not hydroaminomethylated because of the mild conditions at 80°C and 80 bar and due to steric hindrance [51]. Graebin describes seven different products of the hydroaminomethylation of limonene [52]. The reaction time was reduced to 10 h by optimization of the catalyst including stepwise hydroformylation for 5 h and hydrogenation with pure hydrogen gas for 5 h. Isomerization was reduced by adding triphenylphosphine as ligand. 

Smith et al. (14) have claimed that different temperatures of solution of the inactive portion of the alloy, different temperatures and lengths of digestion, and different methods of washing have little effect on the catalytic activity as measured by the rate of hydrogenation of d-limonene. In their procedure the alcohol was evaporated under vacuum from the catalyst after which the terpene was added. With the probable large loss of hydrogen under these conditions, it is doubtful that these authors were investigating actual Raney nickel of the W-6 type. 

One of the principal components of lemon grass oil is limonene, C10H16. When limonene is treated with excess hydrogen and a platinum catalyst, the product is an alkane of formula CioH2o- What can you conclude about the stmcture of limonene ... 

Bregeault and co-workers have reported supporting [HP04 W0(02)2 2]2 species on resins and silica (Table 4.6).64 Amberlyst A26 was the macro-reticular resin used. The PW2 species was supported onto dehydrated porous silica. The catalysts were found to be highly selective for the epoxidation of limonene by hydrogen peroxide. 

However, in this section, the total synthesis of yingzhaosu A, the lead compound of a particular class of antimalarial 1,2-dioxocins, is reported. The synthesis involves eight steps and a 7.3% overall yield starting from (A)-limonene (Scheme 64). Besides the TOCO procedure that allowed the formation of five bonds in one step, the most intriguing steps involved the selective hydrogenation of a C-C double bond in the presence of a peroxide and an aldehyde functionalities (step vi) and the stereoselective reduction of the side-chain carbonyl with (R)-CBS catalyst (step viii). Last but not least, the old classical fractional recrystallization allowed the separation of yingzhaosu A from its C-14 epimer and saved two synthetic steps <2005JOC3618>. 

The selective hydrogenation of the disubstituted double bond of limonene (52) took place over a platinum catalyst at 60°C and 3 atmospheres pressure (Eqn. 15.33). 5 1,5-Undecadiene was hydrogenated to 5-undecene with 78% selectivity at 97% conversion over a Pt/A 2eolite catalyst that was treated with diphenyldiethoxysilane. 9... 

Finally, the cycloisomerization of 4-vinylcyclohexene (a butadiene dimer) to bicyclo[3.3.0]-2-octene (6) was found to occur at 250° over a silicophosphoric acid catalyst (11), along with a very large amount of hydrogen transfer (ethylcyclohexenes, methylethylcyclopentenes, ethylbenzene) and polymerization, a reaction closely related to that of limonene (5). A much better yield of the same hydrocarbon (6) was obtained from 1,5-cyclooctadiene (72% at 200°) with the same catalyst (25). 

Various chemical processes of limonene, which lead to the obtainment of useful chemicals and some analytical methods, are based on these reactions. Many flavor chemicals are synthesized from limonene by reaction with water, sulfur and halogens, or hydrolysis, hydrogenation, boration, oxidation and epoxide formation (Thomas and Bessiere, 1989). Hydroperoxides have also been studied and isolated because of their effect on off-flavor development in products containing citrus oil flavoring agents (Clark et al., 1981 Schieberle et al., 1987). Hydration of d-limonene produces alpha-terpineol, a compound that gives off an undesirable aroma in citrus-flavored products. It is also possible to produce alpha-terpineol and other useful value-added compounds... 

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