Fragrances myrcene

Dimerization of Isoprene. Isoprene is becoming an increasingly important raw material for the production of terpenes. For example, myrcene (7) can be produced by the dimerization of isoprene (2-methyl-1,3-butadiene) (42—44) and myrcene is very useful for synthesizing a number of oxygenated terpenes important in the flavor and fragrance industry. 

Uses ndReactions. Some of the principal uses for P-pinene are for manufacturing terpene resins and for thermal isomerization (pyrolysis) to myrcene. The resins are made by Lewis acid (usuaUy AlCl ) polymerization of P-pinene, either as a homopolymer or as a copolymer with other terpenes such as limonene. P-Pinene polymerizes much easier than a-pinene and the resins are usehil in pressure-sensitive adhesives, hot-melt adhesives and coatings, and elastomeric sealants. One of the first syntheses of a new fragrance chemical from turpentine sources used formaldehyde with P-pinene in a Prins reaction to produce the alcohol, Nopol (26) (59). 

The production of myrcene (7) from P-pinene is important commercially for the synthesis of a wide variety of flavor and fragrance materials. Some of those include nerol and geraniol, citroneUol (27) and citral (5). 

Purified myrcene has minimal use in flavor and fragrance appHcations. Production and cost figures for cmde myrcene from P-pinene are not pubhshed to avoid disclosure of individual company operations, but the production volume is large (- SO, 000 t). 

Uses ndReactions. The largest use of myrcene is for the production of the terpene alcohols nerol, geraniol, and linalool. The nerol and geraniol are further used as intermediates for the production of other large-volume flavor and fragrance chemicals such as citroneUol, dimethyloctanol, citroneUal, hydroxycitroneUal, racemic menthol, citral, and the ionones and methylionones. 

Myrcene with its conjugated diene system readily undergoes Diels-Alder reactions with a number of dienophiles. For example, reaction with 3-meth.5i-3-pentene-2-one with a catalytic amount of AlCl gives an intermediate monocyclic ketone, which when cyclized with 85% phosphoric acid produces the bicycHc ketone known as Iso E Super [54464-57-2] (49). The product is useful in providing sandalwood-like and cedarwood-like fragrance ingredients (91). 

The wonderful fragrance of leaves from the California bay tree is due primarily to myrcene, a simple terpene. 

Pinene is similar to a-pinene in its reactions. Pyrolytic cleavage to myrcene, the starting material for acyclic terpenes, is used on an industrial scale. Addition of formaldehyde results in the formation of nopol nopyl acetate is used as a fragrance material. /3-Pinene is produced in large quantities by distillation of turpentine oils. It is used as a fragrance material in household perfumery. However, most /3-pinene is used in the production of myrcene. 

Noyori s BINAP catalysts deserve special attention because their chirality is based on the bulkiness of the naphthalene groups, rather than on carbon or phosphorus asymmetric centers (Figure 3.28, inset) [77]. One of the many examples of asymmetric catalysis using BINAP is the synthesis of (—)-menthol, an important additive for flavors, fragrances, and pharmaceuticals. Starting from myrcene, the process is carried out by Takasago International on a multi-ton scale. The key step is the isomerization of geranyldiethylamine to (R)-citronellal enamine [78], which is then hydrolyzed to (R)-citronellal with nearly 99% ee. 

Terpenes are obtained either by processing wood in the kraft process in paper production or by collecting resins and turpentine from conifers. The scale of produced terpenoids in comparison with fats and oils is small. Applications for terpenes are in pure form as solvents, as odorous substances, or in dyes. Most terpenoids contain double bonds which are readily available to perform chemical reactions. A widespread component of turpentine is a-pinene, from which many fragrances are produced. A further often-used resource is myrcene, which is obtained by pyrolysis of (3-pinene. Myrcene is an important base chemical to produce, for example, the fragrances nerol and geraniol [7]. 

Thermal rearrangement of / -pinene affords myrcene (Fig. 8.43) which is the raw material for a variety of flavor and fragrance compounds, e.g. the Takasago process for the production of optically pure L-menthol (see Chapter 1). Dehydro-... 

Monoterpenoids are responsible for fragrances and flavors of many plants and thus their products are used in perfumery and as spices. To date over 1,500 monoterpenoids are known, and these constitute acyclic, monocyclic, and bicyclic monoterpenoids (32), which occur in nature as hydrocarbons, alcohols, aldehydes, and carboxylic acids and their esters. Several acyclic monoterpenoid hydrocarbons are known, and these include trienes such as 3-myrcene (Cl), a-myrcene (C2), (Z)-a-ocimene (C3), ( )-a-ocimene (C4), (Z)-3-ocimene (C5), and ( )-P-ocimene (C6). 3-Myrcene and 3-ocimene are constituents of basil (Oci-mum basilicum, Labiatae) and bay (Pimenta acris, Myrtaceae), pettitgrain (Citrus vulgaris, Rutaceae) leaves, strobiles of hops (Humulus lupulus, Cannabaceae), and several other essential oils. Unsaturated acyclic monoterpene alcohol constituents of plants and their derived aldehydes play a signihcant role in the perfume industry. Some common acyclic monoterpene alcohols and aldehydes include geraniol (C7), linalool (C8) (a... 

The epoxidation of terpenic substrates is of interest in the flavor and fragrance industry [55,56]. Terpenes are derivatives of isoprene, which has formula CsHg (2-methyl-frans-butadiene). There are tens of examples of terpenes, including limonene, a-pinene, geraniol, citronellol, myrcene, ocimene, camphene, a-terpin-eol, menthol, and isopugelol. Limonene is an abundant monoterpene extracted from citrus oil, which can be epoxidized to obtain fragrances, perfumes, and... 

A number of hydrocarbons of this family add oily, green or herbaceous notes to essential oils. Two hydrocarbons, myrcene and dihydromyrcene (also known as citronellene), deserve mention as feedstocks for other fragrance ingredients. 

Geranylacetone is an intermediate in the synthesis of other fragrance substances. It is mainly produced from linalool. Another route starts from myrcene, to which methyl acetoacetate is added under rhodium catalysis geranylacetone is subsequently obtained after saponification and decarboxylation [70a]. It is used in perfumery in rose compositions, for example, in soap perfumes. 

Another synthetic method for the production of pseudoionone, which starts from myrcene [94a], [94b], has never been commercialized for the production of fragrance materials (see also p. 45, geranylacetone). The process consists of a rhodium-catalyzed addition of methyl acetoacetate to myrcene, transesterification of the resulting ester with allyl alcohol, and an oxidative decarboxylation of the allyl ester under palladium catalysis to obtain pseudoionone. 

C16H260, Mr 234.38, bp031 kpa 134-135 °C, reg° 1.498-1.500, is a synthetic amber fragrance. It is prepared by a Diels-Alder reaction of myrcene and 3-methyl-3-pen-ten-2-one in the presence of aluminum chloride and cyclization of the substituted... 

Hydroxycitronellal is generally considered to have the odour closest in character to that of the natural product and has been used in such fragrances as Diorissimo which is a classic muguet type of perfume. Hydroxycitronellal is clearly terpenoid in origin, Lyral is prepared from a terpene, myrcene, and the structure of Lilial is very reminiscent of that of the p-menthane family of terpenoids. The syntheses of hydroxycitronellal and Lyral are both described in Chapter 3. All three of these materials contain aldehyde functions which limits their stability in oxidising media and in products where the pH is not neutral. There has therefore been a considerable amount of work on trying to find replacements for them and some examples are shown in Figure 10.11. 

Oil of thyme contains p-myrcen-8-ol derived from p-myrcene, and (i )-(-)-ipsdienol as well as its non-chiral regioisomer is not only the aggregation pheromone of the bark beetle Ips confusus, but also the fragrance of the blossoms of many orchids. Terpenoid pyran derivatives include diastereomeric rose oxides [(2/ ,4/ )-trans- and (2S,4R)-cis-] as well as racemic nerol oxide, which essentially contribute to the pleasantly flowery green smell of the Bulgarian oil of rose... 

Bromo-2-fluoro biphenyl intermediate, foam builders Alkenyl succinic anhydride intermediate, food additives Soy acid Stearyl alcohol intermediate, food emulsifiers Caprylic/capric acid Tallow acid intermediate, food supplements (tablet form) Cetyl alcohol intermediate, food wrap Vinylidene chloride monomer intermediate, fragrances p-t-Butyl toluene t-Butyl-m-xylene Citral Cyclopentanone Diethyl toluene diamine Dimethyl hexynediol 1,2-Methylenedioxybenzene 2-Methylpentanal Myrcene n-Propyl bromide intermediate, fragrances cosmetics Acetic anhydride n-Butyraldehyde n-Butyric acid Butyric anhydride 2-Ethylhexoic acid Isobutyric anhydride 2-Methylpropanal Propionic anhydride intermediate, fragrances personal care Butyric anhydride Isobutyric anhydride intermediate, free-radical polymerization initiators... 

Among the vast number of applications, an important example is the production of the so-called rose alcohols from p-pinene, viz. nerol, geraniol and linalool, key intermediates in the synthesis of many major fragrances. This process involves the thermal isomerization to myrcene, followed by addition of HCI, substitution by acetate and alkaline hydrolysis, as shown in Fig. 2.5 [3]. 

The main industrial application of P-pinene is the noncatalytic thermal isomerization reaction in the vapor phase to yield P-myrcene (besides limonene and p-menthadiene) as an intermediate for the commercial production of flavor and fragrance chemicals (Figure 3B.6), such as the terpenic alcohols geraniol, nerol and linalool, and synthetic aromas (citral, citronellal, menthol, and myrcenol). ... 

Turpentine is mostly composed of monoterpenes and these can have different industrial applications. Bomeol is used in cosmetics and in non-cosmetic products, such as household cleaners [145]. Carveol, linalool, myrcene, a- and (3-pinene, phellandrene and terpineol are used in the food, perfume, and cosmetics industry as fragrance and to impart flavors to foods [133, 146-149]. Also, it has been reported that turpentine could be an interesting resource for the pharmaceutical industry due... 

Myrcene is a very abundant acyclic monoterpene available from the essential oils of various plants including wild thyme and hops. Recently, an excellent overview on the manufacture and transformation of this natural product was given by Behr and Johnen [125]. Commercially, myrcene is produced by the pyrolysis of pinenes [126]. The rhodium-catalyzed hydroformylation of myrcene gives usually a mixture of fragrance aldehydes in more than 90% combined yields (Scheme 6.37) [127, 128]. The main aldehyde, which accounted for 70 - 80% of the mass balance, results from the reaction with the less substituted C=C bond through the formation of a T) -allyl rhodium intermediate complex [127]. The reaction was also performed in a toluene/water biphasic system using the water-soluble TPPTS ligand and a cationic surfactant [84]. 

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