Linalool epoxidation

Two simple constituents that appear to contain epoxide unit. have been detected in essential oils. These arc linalool epoxide (VX)1E,li and 1,2-epoxypulegone (VII). 47 The substance once formulated as 5,6-epoxycar-3-ene (VIII) by Penfold and Simonsen13 8 has reoentlv been reformulated a chrysanthonone (IX) by Blanchard,1 howevr -... 

Many hydroxylated linalools [including compounds 105, 106, 108, and 110, both (Z)- and ( )-isomers], as well as the epoxides of both furanoid (109) and pyranoid (see section on pyrans) linalyl oxides, have been identified in papaya fruit (Carica papaya). At the same time, the first reported occurrence of die two linalool epoxides (112) in nature was made. These epoxides are well known to be unstable and easily cyclized (see Vol. 2, p. 165) and have been made by careful peracid oxidation of linalool. An interesting new method has now been described. While the vanadium- or titanium-catalyzed epoxidation of geraniol (25) gave the 2,3-epoxide (see above), as does molybdenum-catalyzed epoxidation with hydrogen peroxide, the epoxidation of linalool (28) with molybdenum or tungsten peroxo complexes and hydrogen peroxide led, by reaction on the 6,7-double bond, to 112. ... 

As a test reaction a mixture of cis- and trans-carveol was oxidized with TBHP. Analogous to what has previously been observed for compounds like geraniol and linalool, epoxidation was fast and selective (reaction 8). Trans-carveol was converted only to the corresponding epoxide, whereas cis-carveol gave a mixture of cis-epoxide and carvone. 

Scheme 1 Oxidative cyclisation of geranyl linalool epoxide.

Linalool, 3 231, 232, 233 24 477, 495, 496, 500-503, 546 acid treatment of, 24 502 epoxidation of, 24 502 main producers of, 24 501 Linalool oxide, 24 502 Linalyl, 24 479 Linalyl acetate, 24 501 Linalyl alcohol, 24 500 Linalyl esters, 3 231 Linalyl oxide, 24 503 Lincomycin, registered for use in aquaculture in Japan, 3 221t Lincosamide, bacterial resistance mechanisms, 3 32t Lindane, 13 145-147... 

The interdigital secretion of the red hartebeest, A. b. caama, consists of fewer compound classes. It contains a few alkanes and short-chain, branched alcohols, fatty acids, including a few of the higher fatty acids up to octadecanoic acid, an epoxide and the cyclic ethers, rans-(2 ,5.R)-furanoid linalool oxide 23, as-(2JR,5S)-furanoid linalool oxide 24 and ds-(2S,5i )-furanoid linalool oxide 25 (Fig. 5) in a ratio of 2.5 1 1.5 respectively [138]. From the point of view that many of the constituents of the interdigital secretion of this animal are probably of microbial origin, it is interesting that cis- and trans- furanoid linalool oxides have also been found in castoreum [77]. 

Optically pure trans- and czs-linalool oxides, constituents of several plants and fruits, are among the main aroma components of oolong and black tea. These compounds were prepared from 2,3-epoxylinalyl acetate (9) (Scheme 17) [102]. The key step consist of a separation of the diastereomeric mixture of 9 by employing an epoxide hydrolase preparation derived from Rhodococcus sp. NCIMB 11216, yielding the product diol and remaining epoxide in excellent diastereomeric excess (de>98%). Further follow-up chemistry gave both linalool... 

Scheme 17. Synthesis of cis- and frans-linalool oxide using bacterial epoxide hydrolase...

The synthesis of tetrahydrofurans through cyclization via epoxide ring opening has been well investigated and has been applied to the preparation of a-bisabolol oxides (69IJC1060) and linalool oxides (77H(6)1365) and by Kishi et al. in the synthesis of lasalocid A (195), where the epoxide pathway resulted in a stereospecific construction of six out of the ten chiral centers (Scheme 93) (78JA2933). 

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

Some of the chemistry developed by the industry more recently, to produce new monohydric alcohols, is just as interesting as the linalool chemistry. Sandalore, a recent new Givaudan chemical with a persistent, sandalwood odor is made according to the scheme in Figure 15 (9). Alpha-pinene, the starting material, is converted to the epoxide which is catalytically rearranged to campholen-ic aldehyde. Aldol condensation with methyl ethyl ketone followed by hydrogenation yields Sandalore . 

Ti, Al-MCM-41 Ti-BEA Linalool Furan and pyran hydroxy esters Epoxidation + ring closure 80 >99 MeCN solvent TBHP/linalool = 1.1 1 bar 353 K 24 h glass batch reactor [24]... 

The exceptionally facile epoxidation of allylic alcohols by tert-butyl hydroperoxide in the presence of vanadium catalysts, discussed earlier, has been used466,467 for the synthesis of complex molecules. Thus, geraniol (X) and linalool (XI) are selectively epoxidized to the previously unknown monoepoxides with f-Bu02 H-V 0(acac)2 466 ... 

The Ti,Al-Beta shows both acidic and oxidative properties which is reflected in unwanted side-reaction. The group of Corma used the bifunctionality in the epoxidation/rearrangement of cx-terpineol to cineol alcohol and in the formation of furans from linalool.81,82 Similarly van Klaveren et al. applied Ti,Al-Beta in the one-pot conversion of styrene to phenyl acetaldehyde.83 Sato et alM solved the unwanted acid-catalyzed side reaction by neutralizing the acid site by ion exchange with alkali metals. Nevertheless the bifunctionality restricts the use of this catalyst to a limited number of reactions. 

The reaction of linalool with boron trifluoride etherate has been re-examined no pinenes or camphene were obtained.146 Dehydrolinalool reacts with methyl iso-propenyl ether under acidic conditions by Claisen rearrangement to give the allene (58).147 Further papers in this section include reaction of monoterpenoid alcohols with paraformaldehyde-acetic anhydride-sodium acetate,148 rearrangement of the alcohol (47 X = OH) to the oxabicycloheptane (59) and the ketone (60),149 and the rearrangement of a typical monoterpenoid vicinal hydroxy-ester to an epoxide.150... 

The one-pot epoxidation/cyclization of unsaturated terpene alcohols, for example linalool and a-terpineol, to mono- and bicyclic derivatives also required the catalysis of large-pore Ti,Al-P (Scheme 18.10) [93, 107]. 

The reaction was carried out in acetonitrile at 353 K using TBHP as oxidant. Conversions as high as 80 % were obtained. As shown in Scheme 6, it was postulated that the reaction takes place via epoxidation over Ti sites foUowed by acid catalyzed intramolecular opening of the epoxide ring by the 3-hydroxy group. Ti-6 zeolite gave somewhat lower conversions in addition to the preferential formation of furans over pyrans (ratio of ca. 1.5) due to shape selectivity. Ti-MCM-41 and gave furan to pyran ratios of ca. 0.9, comparable to those obtained by the epoxidase conversion of linalool. 

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