Terpineol synthesis

A common industrial method of a-terpineol synthesis consists of the hydration of a-pinene or turpentine oil with aqueous mineral acids to give crystalline cis-terpin hydrate mp 117°C), followed by partial dehydration to a-terpineol. Suitable catalysts are weak acids or acid-activated silica gel [83]. 

In the eyent, TM 394A proyed to be a-terpineol and the shortest synthesis is by Alder and Vogt (Annalen. 1940, 564, 109) using the Diels-Alder reaction ... 

These researches on the synthesis of the terpenes were commenced in 1900, and has been carried on with considerable success and conspicuous ability ever since. It was considered necessary to synthesise terpineol, and BO establish the formula which analytic reactions supported. The first necessary step was to synthetically prepare the l-methyl-A -cyclo-hexene-4-earboxylic acid, of the formula—... 

Terpineol (that is a-terpineol) has been prepared synthetically by Perkin and his pupils, his method being described under the synthesis of limonene. 

Teeth whiteners, percarbamide, 623 Temperature, reaction rates, 903-12 Terminal olefins, selenide-catalyzed epoxidation, 384-5 a-Terpinene, peroxide synthesis, 706 a-Terpineol, preparation, 790 Terrorists, dialkyl peroxide explosives, 708 Tertiary amines, dioxirane oxidation, 1152 Tertiary hydroperoxides, structural characterization, 690-1... 

In the aromatic series, acetophenone and methyl iodide, for example, yield phenyldimethylcarbinol. An important step in the synthesis of i-terpineol is the preparation of ethyl-S-hydroxy-hexahydro-p-toluate from ethyl-S-ketohexahydrobenzoate and magnesium methyl iodide. 

Both a- and P-pinenes are popular starting materials for the synthesis of other monoterpene chiral synthons such as carvone, terpineol, and camphor (vide infra). Reactions leading to other monoterpenes are briefly summarized in Figure 5.1. Treatment of a-pinene with lead tetraacetate followed by rearrangement gives trans-verbenyl acetate (7), which is hydrolyzed to yield trans-verbenol (8) 8 Subsequent oxidation of 8 gives verbenone (9), which can be reduced to give cw-verbenol... 

In the synthesis of a-terpineol or limonene, for example, geranyl pyrophosphate isomerizes at one double bond to form neiyl pyrophosphate, a stereoisomer (Step [1] in the following reaction sequence). Neryl pyrophosphate then cyclizes to a 3° carbocation by intramolecular attack (Steps [2]-[3]). Nucleophilic attack of water on this carbocation yields a-terpineol (Step [4]) or loss of a proton yields limonene (Step [5]). Both products are cyclic monoterpenes. 

Derivatives of Menthene.— The most important alcohols and ketones derived from the menthene unsaturated group of terpenes are terpineol, di-hydro carveol, di-hydro carvone and pulegone. The first one, the alcohol terpineol, occurs in its dextro form in cardamon oil and marjoram oil, in its leoo form in neroU oil and in its inactive form in cajeput oil. The constitution is proven by Perkin s synthesis from As-tetra-hydro para-toluic acid by means of the Grignard reaction. 

The structure of the terpene a-terpineol (found in oils of cardamom and marjoram) was proved in part by the following synthesis ... 

Composition The European Pharmacopoeia lists linalyl acetate (56-78%), linalool (6.5-24%) and germacrene D (1.0-12%). a-Terpineol is limited to 5.0%, a- and P-thujone to 0.2%. Sclareol (0.4-2.6%) is found mainly in the concrete and is used for the synthesis of ambra fragrance materials. Further constituents are linalool oxide, geraniol, nerol, neryl and terpinyl acetate, citronellol, 1,8-cineole, benzaldehyde and n-nonanal. For further literature see [64, 65]. 

Use Solvent for protective coatings, polishes, and waxes synthesis of camphene, camphor, geraniol, terpin hydrate, terpineol, synthetic pine oil, terpene esters and ethers, lubricating oil additives, flavoring odorant. 

Tissue Cultures, Microbial Transformations.—Little success has rewarded the search for cell cultures that effectively biosynthesize monoterpenes de novo. The most impressive studies utilize cultures from a variety of Mentha spp. yields of oil were some 60 % (w/v) of those in the parent plants, but the monoterpene products were generally more oxidized (i.e. ketones extra C=C bonds predominated). In vitro, oxidation at C-3 of the menthane skeleton was also restricted, apparently owing to an inhibition of the enzymic reduction of the 4(8) double bond in the intermediates formed.925 926 Colchicine stimulated synthesis of essential oil by Mentha cultures.927 Iridoid glucosides have been produced by cultured cells of Gardenia spp.673 Menthone was biotransformed to neomenthol by Mentha suspension cultures,928 and Nicotiana lines oxidized linalool and its derivatives at C-10 to aldehydes and alcohols,929 and also foreign substrates such as a-terpineol (at C-6 and C-7) and /raw.s-/ -menthan-9-en-l-ol (at C-4 and C-10).930... 

Menthanes, which include menthol, menthonc, terpineol, and carvone, are some of the best known monoterpene-based chiral synthons in organic synthesis. They are all relatively inexpensive and are commercially available in bulk quantities. Menthols and their corresponding ketones, menthones. were first isolated from peppermint oils of various species of Mentha piperita L [30]. Menthones can exist in two diastereomeric forms, each with two enantiomers. The ones with the methyl and isopropyl groups in a Zrans-orientation are termed menthones, whereas those with the two in a cz.s-orientation are isomenthones. /-Menthone (22), also denoted as (7A,4S)-(-)-menthone. is the most abundant stereoisomer and is obtained by the dry distillation of the wood of Finns palustris Me II [31]. It can also be produced chemically by chromic acid oxidation of /-menthol (23) [32]. /-Menthone is commercially available in bulk quantities with optical purities of 90-98% ee [33]. 

Other lipases have also been tested in supercritical carbon dioxide for ester synthesis. In this context, the synthesis of terpinyl acetate from a-terpineol and acetic anhydride in supercritical carbon dioxide (scCO ) was carried out using five different lipases as catalysts (Candida rugosa type Vll, Amano PS, Amano AP-6,... 

Vol. 8, p. 40) work to synthesize the benzofuranone (139) and related compounds by acid ion-exchange resin rearrangement of the corresponding aldehydoacetate." Last year s Report omitted mention of the routine synthesis of (8i )-(- -)- and (85)-(+)-[9- Hi]-a-terpineol via epoxide reduction (Vol. 8, p. 42, ref. 371) and syntheses of some deuteriated pulegones and pulegone tosyl-hydrazones. ... 

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