Rose oxides

Reduction of (R)-(+)-citronellal by lithiumaluminumhydride yields (R)-(+)-citro-nellol which undergoes a photo ene reaction to the hydroperoxide in the presenee of the xanthene dye rose Bengal as a photosensitizer of singlet-oxygen. Sodium sulfite reduces hydroperoxide to the diol which is, when catalyzed by acids, dehydrated to the ir s-isomer of rose oxide 

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Review problem 34 Design a synthesis for rose oxide, TM 307, a perfiime occuring in rose and geranium oils which is made at present by the oxidation of another natural product, citronellol. 

In 1961, chemists (19) isolated a minor component of geranium oil, characterized it as rose oxide (1), and reported that this compound contributed to the characteristic geranium odor. Rose oxide (1) is manufactured by the photooxidation of citroneUol (8). 

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). 

Photooxidafions are also iudustriaHy significant. A widely used treatment for removal of thiols from petroleum distillates is air iu the presence of sulfonated phthalocyanines (cobalt or vanadium complexes). Studies of this photoreaction (53) with the analogous ziuc phthalocyanine show a facile photooxidation of thiols, and the rate is enhanced further by cationic surfactants. For the perfume iudustry, rose oxide is produced iu low toimage quantifies by singlet oxygen oxidation of citroneUol (54). Rose bengal is the photosensitizer. 

Bromisoval (h/ f 15-20) yielded dark brown chromatogram zones on a light brown background. Bromopride, bromazepam, bromhexine, bromocriptine, caryophyllene epoxide and rose oxide did not react. 

A number of useful reviews have appeared in the course of the last few years, and a number of chemicals, such as vitamin C, p-tetralone, hexafluoropropylene oxide, piperidine, glyoxalic acid, pinacol, p-hydroxypropiophenone, sebacic acid, p-anisaldehyde, maltol/ethyl maltol. Rose oxide, linalool, perfluorooctanoic acid, hydroquinone, etc., that are commercially made (or can be made) electrochemically have been catalogued. 

Defensive Compounds. In Cerambycinae, paired metasternal glands are situated in the thorax, while associated reservoirs open near the hind coxae [8]. Rose oxide 190 (Scheme 21) and iridodial 17 were identified from Aromia moschata... 

Essential oils are organic compounds derived from flowers, seeds, leaves, roots, resins, and citrus fruits. The structures of many fragrant compounds have been studied, and processes for making these valuable compounds in a laboratory have been developed. There are now approximately 5000 synthetically produced chemicals that are available to a perfumer. These chemicals include vanillin, rose oxides, and the damascenes, or rose ketones. 

Figure 3.4 Reactions of an excited state singlet oxygen (rose oxide).

The method of photosensitized oxygenation was successfully applied in the preparation of alcohols 265-270 from sylvestrene (264),207 and seems to be the most simple and successful method for the preparation of optically active rose oxides (272,273) from (+)- or (—)-citronellol C271).177 It may also be used for the preparation of certain organo-metallic hydroperoxides. Thus, the triphenyl-tin derivative of tri-methylethylene (274) undergoes a photosensitized oxygenation reaction with a rate similar to that of tetramethylethylene, giving rise to the hydroperoxides 275 and 276 219... 

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,... 

Rose oxide [16409-43-1], 4-methyl-2-(2-methyl-l-propenyl)tetrahydropyran... 

Rose oxide is usually prepared from citronellol which can be converted into a mixture of two allyl hydroperoxides (e.g., by photosensitized oxidation with oxygen). Reduction of the hydroperoxides with sodium sulfite yields the corresponding diols [183]. Treatment with dilute sulfuric acid results in allylic rearrangement and spontaneous cyclization of one of the isomers a mixture of diastereoisomeric rose oxides is thus formed. The unreacted diol isomer is separated by distillation. (—)-Citronellol as the starting material yields approximately a 1 1 mixture of (—)-cis- and (—)-tra s-rose oxide. 

Rose oxide is used in rose and geranium perfumes. 

In addition to the major components mentioned above, rose oil also contains a number of components which, although present in low concentrations, contribute to the characteristic fragrance [725-73 lb]. Among these are /3-damascenone (see p. 68) and rose oxide (see p. 143). 

This allyloxylation was used to produce d,l-rose oxide from citronellol (Eq. 50) 1 -Similarly d, 1-dihydroactinidiolide was formed in one step by the intramolecular oxyselenation-deselenation sequence (Eq. (51))... 

This reaction was used for a convenient synthesis of Rose oxide (equation 11)... 

In sensitized or photocatalyzed reactions, conditions of total or constant absorbance can easily be controlled by the concentration of the sensitizer or photocatalyst added. In addition, experience has shown that the concept of spatial separation between the light source and the reaction mixture is in general not required. Dragoco uses immersion-type annular reactor geometries [2, 3, 69, 70] for the production of ( —)-rose oxide by rose bengal sensitized oxidation of (— )-citronellol (Eqs. 45-48, Figure 23). 

Figure 23. Synthesis of (—)-rose oxide by sensitized oxidation of (-)-citronellol [2, 3,81].

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