Rearrangement of geraniol

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]. 

Rearrangement of geraniol. Treatment of geraniol (1), or the cw-isomer nerol, with this superacid in SO -CSj at -78° followed by careful quenching... 

S)-(-)-CITRONELLOL from geraniol. An asymmetrically catalyzed Diels-Alder reaction is used to prepare (1 R)-1,3,4-TRIMETHYL-3-C YCLOHEXENE-1 -CARBOXALDEHYDE with an (acyloxy)borane complex derived from L-(+)-tartaric acid as the catalyst. A high-yield procedure for the rearrangement of epoxides to carbonyl compounds catalyzed by METHYLALUMINUM BIS(4-BROMO-2,6-DI-tert-BUTYLPHENOXIDE) is demonstrated with a preparation of DIPHENYL-ACETALDEHYDE from stilbene oxide. A palladium/copper catalyst system is used to prepare (Z)-2-BROMO-5-(TRIMETHYLSILYL)-2-PENTEN-4-YNOIC ACID ETHYL ESTER. The coupling of vinyl and aryl halides with acetylenes is a powerful carbon-carbon bond-forming reaction, particularly valuable for the construction of such enyne systems. 

Methods for oxidative transformations continue to receive attention. Nickel peroxide on graphite oxidizes geraniol to citral in 89% yield. Three groups report " the oxidative rearrangement of tertiary vinyl carbinols. Linalool is con-... 

C. A. Hachey, D. Rearrangement of linalool, geraniol, and nerol and their derivatives. 

The 1,8-terpins 9 and 10, which are monoterpenes of high flavor threshold, were observed in the acid hydrolysates of each variety. These diols are derivable as thermodynamically stable end-products of acid catalyzed rearrangement of monoterpenes v iich are at the oxidation state of geraniol. However, few conpounds at this oxidation state were seen among the aglycons, and the precursors of the terpins 9 and 10 in these varieties have yet to be discovered. 

The reagent is recommended for conversion of allylic alcohols into allylic chlorides without rearrangement. Thus geraniol (I) can be converted into geranyl chloride (2) in 75 81 % yield. ... 

The exceptional bulkiness of 2,6-di-tert-butyl-4-broniophenoxy ligands in MABR is essential here for the smooth rearrangement of epoxy silyl ethers, and the less bulky methylaluminum bis(4-bromo-2,6-diisopropylphenoxide) (MAIP) was found to be totally ineffective in the rearrangement of the tert-butyldimethylsilyl ether of epoxy-geraniol (139). BF3-OEt2 as an ordinary Lewis acid gave fluorohydrin 140 as sole isol-able product (Sch. 114). 

It was previously noted that enolates of a-allyloxy ketones were capable of either 2,3- or 3,3-rear-rangement, depending upon counterion, reaction conditions and substituents. Ester enolates show a greater propensity for the 2,3-pathway, as illustrated by the geraniol-derived alkoxyacetate (198) which afforded hydroxy ester (200) as the sole product upon treatment with LDA in THF at -78 to 0 C. The 3,3-product (201) could be obtained by addition of TBDMS-Cl and HMPA to the enolate at -78 °C and thermal rearrangement of the TBS enol ether (199b Scheme 14). ... 

Thermal and mercury(ii)-catalysed [3,3]sigmatropic rearangement of allylic trichloroacetimidates and allylic pseudo-ureas" e.g. geraniol, linalool) are useful for the 1,3-transposition of hydroxy- and amino-groups the former is synthetically preferred. The [2,3]sigmatropic rearrangement of allylic sulphoxides has been used to effect an alkylative 1,3-carbonyl transposition of enones (e.g. carvone). ... 

K. Takabe, T. Katagiri, and J. Tanaka, Chem. Letters, 1977, 1025. For related work where rearrangement occurs, see Vol. 4, p. 17. For the reverse conversion of geraniol to geranyl chloride without rearrangement, see Vol. 3, p. 38, ref. 186. 

As mentioned previously, the Chugaev elimination has found particular use in the field of terpenoid chemistry, not only in structural studies, but also in synthesis. For example, a tandem Claisen rearrangement-ene reaction of geraniol derivative 23 gave... 

This method was used in a highly stereoselective synthesis of a pheromone diol (6) of the queen butterfly. The key step involved rearrangement of the acetate (4), obtained in several steps from geraniol, to the acid (5). Lithium aluminum hydride reduction of (5) gave the diol (6). 

Nerol and linalool underwent considerably more elimination than did geraniol, to give the same hydrocarbons. The major products and their relative proportions were consistent with those for carbocationic rearrangement of derivatives of linalool, nerol, and geraniol under acidic conditions. 

An additional ethinylation (C2) of 6-methyl-5-hepten-2-one (Cg) leads to dehydro-linalool (Cio) as a monoterpene which is partially hydrogenated to linalool. The acid-catalyzed allyl rearrangement of linalool affords geraniol. 

---