Geraniol synthesis

Hydroxylamines can be reduced electrochemically with N—O bond cleavage. This reaction was used in a geraniol synthesis (fragrance material) ... 

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). 

According to Example, it is possible to make 443 g of geranyl formate from 375 g of geraniol. A chemist making geranyl formate for the preparation of a perfume uses 375 g of starting material and collects 417 g of purified product. What is the percent yield of this synthesis ... 

A one-step synthesis of the triphenylphosphonium salt (81) from linalool or geraniol and triphenylphosphonium bromide, with simultaneous... 

The synthesis shown in Scheme 13.66 starts with the Sharpless asymmetric epoxidation product of geraniol. The epoxide was opened with inversion of configuration by NaBHjCN-BFj. The double bond was cleaved by ozonolysis and converted to the corresponding primary bromide. The terminal alkyne was introduced by alkylation of... 

Chakraborty has described the highly diastereoselective. Barrero and his group developed an approach to functionalized six-membered rings with exocyclic olefins from a-oxygenated derivatives of geraniol. The diastereo-selectivity observed is reasonable and thus the method holds promise for natural product synthesis [105]. 

Silica gel successfully catalyzed the stereoselective synthesis of several glucoside terpenoids. Treatment of 49a with propan-2-ol, geraniol, the tetrahydropyranyl (THP) ether of coniferyl alcohol, and (—)-perillyl alcohol gave glucosides 52a-d in good yields (Scheme 12). The acid-labile THP group was retained under these reaction... 

Takaya and co-workers46 found that BINAP-based Ru(II) dicarboxylate complexes 31 can serve as efficient catalyst precursors for enantioselective hydrogenation of geraniol (2E)-32 and nerol (2Z)-32. (R)- or (iS )-citroncllal 33 is obtained in nearly quantitative yield with 96-99% ee. The nonallylic double bonds in geraniol and nerol were intact. Neither double bond migration nor (fi)-/(Z)-isomerization occurred during the catalytic process. Furthermore, the S/C ratio was extremely high, and the catalyst could easily be recovered (Scheme 6-18). This process can be applied to the asymmetric synthesis of a key intermediate for vitamin E. 

The procedure for the synthesis of the title compound is a representative example of asymmetric hydrogenation in the presence of BINAP-Ru(ll) diacetate.5 The method is based on the synthesis of BINAP-Ru(ll) dicarboxylate complexes and enantioselective hydrogenation of geraniol.7 The present method provides the first practical means for asymmetric synthesis of (S)- and (R)-citronellol. (S)-(-)-Citronellol of optical purity up to 92% can be obtained in a limited quantity from rose oil. A microbiological reduction of geraniol was reported to give enantiomerically pure (R)-(+)-citronellol. ... 

Several natural products (Scheme 60) have been synthesized in vitro via singlet oxygen ene reactions. For example, clavukerin C was prepared in racemic form, in a biomimetic synthesis by Kim and Pak, whereas a-farnesene hydroperoxide was obtained starting from geraniol. 

Azides [e.g. (+)-neomenthyl azide no physical data reported] are formed efficiently by inversion, from the corresponding alcohols and diphenylphosphoryl azide, in the presence of triphenylphosphine and diethyl azodicarboxylate [which has also been used for esterification with inversion (Vol. 5, p. 334) for a related esterification of (—)-menthol see ref. 119] a conceptually similar synthesis also yields (+)-neomenthyl azide. Cyanoselenenylation of aldehydes and of alcohols has been reported thus treatment of geraniol with o-nitrophenyl seleno-cyanide-Bu sP-THF yields the selenide (19) which can be converted into the... 

There has been considerable activity in this area of monoterpenoid synthesis. Syntheses of [7- C]-, [7, 8- C]-, and [7, 8- H]-geraniol have been reported. The ocimene (42 X=H) has been synthesized again by Vig et ai, this time from trans-6,6-ethylenedioxy-2-methylhept-2-en-l-ol via Wittig reactions. Both (4iE )- and (4Z)-(6S)-2,6-dimethyloct-4-ene have been synthesized by known routes from 5-3-methylpent-l-yne. The addition of organohomocuprates (e.g. F. J. McQuillin, Chem. and Ind., 1976, 941. 

Another related synthesis made use of the intramolecular cycloaddition of co-nitroalkene 243, also derived from geraniol epoxide 237. Generation of the expected nitrile oxide dipole using p-chlorophenyl isocyanate and triethylamine quantitatively gave the annulated isoxazoline 244 as a 2 1 mixture of diastereo-isomers (Scheme 6.94). Reductive hydrolysis of the cycloadduct to the aldol product followed by dehydration provided enone 245, which was used to prepare the sesquiterpene nanaimoal 246 (242). 

Synthesis from Linalool. A 96% pure synthetic geraniol prepared by isomerization of linalool has become commercially available. Orthovanadates are used as catalysts, to give a >90% yield of a geraniol nerol mixture [31]. Geraniol of high purity is finally obtained by fractional distillation. 

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. 

Synthesis from Geraniol. Currently, the most important synthetic procedures are vapor-phase dehydrogenation and oxidation of geraniol or geraniol-nerol mixtures. Catalytic dehydrogenation under reduced pressure using copper catalysts is preferred [54]. 

Synthesis from Geraniol or Nerol. ( )-Citronellal can be obtained by vapor-phase rearrangement of geraniol or nerol in the presence of, e.g., a barium-containing copper-chromium oxide catalyst [63]. 

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