Ethers rose oxide

The monoterpene ether rose oxide was isolated from Bulgarian rose oil. Since rose oxide has two asymmetric centers, there are four possible... 

Cyclic ethers used as fragrances include a number of terpenoid compounds. Some of them, such as 1,4-cineole [470-67-7] and 1,8-cineole, occur in essential oils in significant quantities. Others are only minor components examples are rose oxide, nerol oxide [1786-08-9], and rose furan [15186-51-3], which contribute to the specific fragrance of rose oil. Caryophyllene oxide [1139-30-6], which has a woody,... 

The electrolysis of citronellol 54 in methanol provides 55 (89 % yield) and subsequent demethoxylative cyclization with BF3-etherate (or EG Acid) gives dl-rose oxide 5 (cis/trans = 9 1) in 84% yield from 54 (Scheme 3-19)67>. 

Geraniol Citronellol beta Damascone Rose oxide Geranium Citronellyl acetate Phenyl ethyl alcohol Orthomethoxy benzyl ethyl ether... 

Anselmi et al. (02JCS(P2)1525), very recently published the conformational analysis and dynamics of cA/ rafts-4-methylcyclohexyl tetrahydro-pyranyl ethers (cf. Scheme 12) and compared their structures with the floral odors of the compounds. The cis isomer 40(cis), endowed with a main white flower note, has an bent, oval molecular shape. The trans derivatives 40(trans) and 41, exhibit different odors, possess an extended structure of cylindrical molecular shape. Brenna et al. (02CJC714) reexamined the configuration/conformation of rose oxide analogues. However, the conformational analysis provided poorer results than published previously (78JPC303) without even citing the previous paper. 

Rose oxide (240) (32% cis, 68% trans) and dihydrorose oxide were synthesized efficiently by the action of isobutenylmagnesium bromide or isobutylmagnesium bromide on the ether (24Synthesis of dehydrorose oxide, rose oxide (240), and... 

Ethers, such as diphenyl oxide and rose oxide... 

More original is the Claisen rearrangement of the vinyl ether of alcohol 927 (made by Grignard addition of isobutenylmagnesium chloride to 2-butenal), which yielded 58% of the aldehyde 928, needing only reduction to the alcohol before acid cyclization to iso-rose oxide (929) and rose oxide (909). ° ... 

There are several cyclic ethers derived from acyclic monoterpenes which are of importance at lower levels in fragrances. Allylic oxidation of citronellol can be used to introduce a leaving group which allows cyclization to form the pyran, rose oxide. Chlorination was one of the first oxidation techniques employed various others, including electrochemical methods, have since been developed. An outline of the synthesis is given in Scheme 4.16. Rose oxide occurs in rose and geranium oils, to which it imparts a characteristic dry, green, rosy top-note. 

The occurrence and syntheses of rose oxides, dihydrorose oxides, rosefuran, and nerol oxides, together with related compounds, have been reviewed. The structure of a cyclic monoterpenoid ether from Artemisia tridentata, which is related to the santolinyl monoterpenoids, has been confirmed (c/. Vol, 7, p. 20) as (227) and renamed artemiseole (c/. Vol. 8, p. 58 for an incorrect structural deduction).Interestingly, another new component of A. tridentata, the (3S)-diastereoisomer of (74), with formic acid yields (227) in contrast to (74) which yields the acyclic aldehyde (228). ° It is possible that some of the 31% of unidentified components in the essential oil of A. annua may correspond to these new compounds.The quinone (229) has been isolated from Lithospermum erythrofhizon, and further details on the presence of aeginetolide in Aeginetia indica have been published. 

At the beginning of the 1960s, Ervin Koviits (1927-2012) found that rose oil consists of at least 275 components (which led to certain disillusionment). These substances, characteristic of rose scent, were still unknown, and might, in an unfavomable case, be present in only trace amounts. The first important component to be discovered was rose oxide [27], a cyclic monoterpene ether, at a concentration of 0.5%. Rose oxide has an unpleasant smell, reminiscent of mineral oU. At high dilution however, it exudes a scent of beautifid freshness and a nuance reminiscent of green leaves. 

Three monoterpenoid ethers are shown in Figure 6.19.1,8 Cineole (98), more commonly referred to simply as cineole, comprises up to 95% of the oil of Eucalyptus globulus and about 40%-50% of cajeput oil. It also can be found in an extensive range of other oils and often as a major component. It has antibacterial and decongestant properties and consequently, eucalyptus oil is used in various paramedical applications. Menthofuran (99) occurs in mint oils and contributes to the odor of peppermint. It is also found in several other oils. Rose oxide is found predominantly in rose and geranium oils. There are four isomers, the commonest being the levorotatory enantiomer of cis rose oxide (100). This is also the isomer with the lowest odor threshold of the four. 

Numerous other ethers containing pyran or furan rings are formed by the dehydration of aliphatic diols (e.g. linalool oxides, rose oxide or nerol oxide) and are components of many essential oils. For example, the furanoid 2R,5R)- E)- and (2J ,5S)-... 

Epoxycaryophyllene (-l-)-DIII ether (-l-)-Menthofuran (H-)-1,8-Clneol (-)-Nerol oxide (-)-(Z)-Rose oxide... 

Hydroalkoxylation. The cycloisomerization of unactivated unsaturated alcohols has been achieved using Al(OTf)3 (eq Reaction with unsaturated oximes also led to 1,2-oxaza heterocycles with five-, six-, and seven-membered rings. This catalyst provided a straightforward route to cyclic ethers with a Markovnikov-type regioselectivity. Notably, these conditions were used for efficient synthesis of olfactory-active rose oxide derivatives. Mechanistic studies showed that Al(OTf)3 coordinates to the oxygen atom of the alcohol, leading to strong acidification of the hydroxyl proton. Intermolecular hydroalkoxylation with methanol has also been reported. ... 

Properties. Phenethyl alcohol is a colorless liquid with a mild rose odor. It can be dehydrogenated catalytically to phenylacetaldehyde and oxidized to phenylacetic acid (e.g., with chromic acid). Its lower molecular mass fatty acid esters as well as some alkyl ethers, are valuable fragrance and flavor substances. 

A former application of aniline, now mainly displaced, was conversion to hydroquinone. The hydroquinone is the starting point for a process developed by Rose at ICI s Plastics Division. The outcome, a high melting polymer, resistant to oxidation, is poly(ether-ether-ketone), or PEEK, made from hydroquinone. This high-performance thermoplastic, with fiber reinforcements such as Kevlar, is used in plastic kettles, nose-cones of missiles and engines. 

Diphenyl oxide, prepared from phenol, is important in rose and other floral fragrances. The addition of ethylene oxide to phenol gives phenoxyethanol and hence its esters, the most important of which is the isobutyrate (Scheme 4.56). Etherification gives materials such as anisole (methyl phenyl ether), estragole [3-(p-methoxyphenyl)prop-l-ene, a constituent of tarragon] and anethole [l-(/ -methoxyphenyl)-prop-l-ene, which occurs in and is strongly characteristic of aniseed]. 

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