Linalool reactions

Uses ndReactions. Linalool can be estetified to linalyl acetate by reaction with acetic anhydride. Linalyl acetate [115-95-7] has a floral-fmity odor, reminiscent of bergamot and lavender. The price of the acetate in 1995 was 14.30/kg (45). Linalool is subject to dehydration and to isomerization to nerol and geraniol during the esterification. However, if the acetic acid formed during the esterification is removed in a distillation column, the isomerization can be minimized and good yields of the acetate obtained (130). 

Linalool can be converted to geranyl acetone (63) by the CarroU reaction (34). By transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give the geranyl acetone. 

Linalool has been used to prepare a mixture of terpenes useful for enhancing the aroma or taste of foodstuffs, chewing gums, and perfume compositions. Aqueous citric acid reaction at 100°C converts the linalool (3) to a complex mixture. A few of the components include a-terpineol (34%) (9), Bois de Rose oxide (5.1%) (64), ocimene quintoxide (0.5%) (65), linalool oxide (0.3%) (66), tij -ocimenol (3.28%) (67), and many other alcohols and hydrocarbons (131). 

Rapid reactions of linalool with OH radicals, NO3 radicals, and ozone in which the major products were acetone and 5-ethenyldihydro-5-methyl-2(3//)-furanone (Shu et al. 1997). 

Shu Y, ESC Kwok, EC Tuazon, R Atkinson, J Arey (1997) Products of the gas-phase reactions of linalool with OH radicals, NOj radicals, and O3. Environ Sci Technol 31 896-904. 

The Arabidopsis GES protein shares 40% sequence identity with two characterized linalool synthases from Clarkia breweri and Clarkia concinna [65], which together belong to the TPS-f family (Fig. 11.4). Linalool synthases catalyze a reaction analogous to that of GES by converting the 10-carbon substrate GPP into... 

Compounds 16 and 19 each deliver the expected six alcohols after reduction of the primarily formed hydroperoxide mixtures as a result of an oxygen attack on the trisubstituted A1 double bonds of these molecules. The ratio of tertiary/secondary hydroperoxides (or alcohols) is about 44 56, as has also been found with 1-methylcyclohexene (30)13S while open-chain olefins such as trimethylethylene (S3), 1,1-dimethyl-2-ethylethylene (id), 2,6-dimethyl-2-octene (39), myrcene (42), / -citronellol (45), linalool (48), and l,l-dimethyl-2-benzylethylene (51) give ratios of tertiary/secondary hydroperoxides between 54 46 and 60 40.104-1 7 7 1 79 The slight deviations from 1 1 ratios in all these cases are probably due to stereochemical rather than electronic effects exerted by the olefins on the reaction with oxygen. 

In this study we report on the reaction of selective hydrogenation of DHL (3,7-dimethyl-6-octaene-l-yne-3-ol, dehydrolinalool) to olefin alcohol LN (3,7-dimethyl-octadiene-1, 6-ol-3, linalool). Fig. 1 shows the way of the DHL hydrogenation. In this... 

Linalool is one of the most widely used fragrant substances in cosmetic and pharmaceutical industry (as a composite of many cosmetics and perfumes and as an intermediate in synthesis of vitamins (A, E)) (1). But natural resources can t supply the growing needs, so the necessity in synthetic LN has been increasing. Therefore the reaction of selective catalytic hydrogenation of DHL to LN is one of the most significant reactions in the chemistry of fragrant substances (2), and the main problem of this research is the development of modern catalytic technology for preparation of linalool. 

In the presence of acids, linalool isomerizes readily to geraniol, nerol, and a-terpineol. It is oxidized to citral by chromic acid. Oxidation with peracetic acid yields linalool oxides, which occur in small amounts in essential oils and are also used in perfumery. Hydrogenation of linalool gives tetrahydrolinalool, a stable fragrance material. Its odor is not as strong as, but fresher than, that of linalool. Linalool can be converted into linalyl acetate by reaction with ketene or an excess of boiling acetic anhydride [34]. 

Synthesis from (3-Pinene. For a description of this route, see under Geraniol. Addition of hydrogen chloride to myrcene (obtained from /3-pinene) results in a mixture of geranyl, neryl, and linalyl chlorides. Reaction of this mixture with acetic acid-sodium acetate in the presence of copper(I) chloride gives linalyl acetate in 75-80% yield [37]. Linalool is obtained after saponification. 

Esterification of linalool requires special reaction conditions since it tends to undergo dehydration and cyclization because it is an unsaturated tertiary alcohol. These reactions can be avoided as follows esterification with ketene in the presence of an acidic esterification catalyst below 30 °C results in formation of linalyl acetate without any byproducts [71]. Esterification can be achieved in good yield, with boiling acetic anhydride, whereby the acetic acid is distilled off as it is formed a large excess of acetic anhydride must be maintained by continuous addition of anhydride to the still vessel [34]. Highly pure linalyl acetate can be obtained by transesterification of tert-butyl acetate with linalool in the presence of sodium methylate and by continuous removal of the tert-butanol formed in the process [72]. 

The reaction of geraniol, nerol and linalool in the presence of VO(acac)2 -Me3SiOOSiMe3 in dichloromethane at 25 °C gave o -terpineol as the main product35. 

Uses Sind Reactions. a-Pinene (8) is useful for synthesizing a wide variety of terpenoids. Hydration to pine oil, acid-catalyzed isomerization to camphene, thermal isomerization to ocimene and alloocimene, and polymerization to terpene resins are some of its direct uses. Manufacture of linalool, nerol, and geraniol has become an economically important use of a-pinene. 

Uses and Reactions. 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 latge-volume flavor and fragrance chemicals such as citronellol, dimethyloctanol, citronellal, hydroxycitronellal, racemic menthol, citral, and the ionones and methylionones. 

In the eighties, the bioconversion of monoterpene alcohols by fungi had not been studied intensively [32]. However, a strain of Aspergillus niger was isolated from garden soil, able to transform geraniol, citronellol and linalool to their respective 8-hydroxy derivatives. This reaction was called fu-hydroxylation [39,40]. 

The reagent was used to obtain (R)-( + )-frontalin (5) from the aldehyde 2, available in two steps from (3R)-( —)-linalool. The adduct 3 from reaction of 2 with 1 was converted to the diol 4 by ozonation and reduction. Treatment of 4 with BF, etherate effects conversion to the methyl ketone and then cycli/ation to 5. 

Cyclization of unsaturated epoxides.1 Reaction of the epoxy alcohol (2) derived from linalool with cobaloxime(I), (1), forms the P-hydroxycobaloxime 3. 

The procedure usually is unsuitable for tertiary alcohols since the reaction with phthalic anhydride or succinic anhydride either fails or results in dehydration of the alcohol. A few tertiary alkyl phthalates, however, have been prepared and resolved by first converting the alcohols to sodium or potassium salts and allowing these to react79 80 with phthalic anhydride. This modification has been applied successfully to dUa- and /S-santalols81 and cB-linalool.81 As already mentioned, glycols cannot be resolved by this procedure because they form polymeric esters when heated with phthalic or succinic anhydride. Phenols also usually form phthaleins or other condensation products instead of simple acid esters. 

Scheme 10 Positive effect of the allylic alcohol of linalool in its RCM reaction [82]...

Potassium fluoride can also be used as a base in the Pd(0)-catalyzed reactions of 149 with allylic acetates, as shown in Scheme 33 (94MI1). Sinou and co-workers reported that the acetates of the isomeric geraniol, nerol, and linalool gave similar mixtures of final sulfides 150e (94MI1). 

---