Menthyl alcohol

Menthol—Menthyl alcohol—C,oHa,0—156—exists in essential oil of peppermint. It crystallizes in colorless prisms fusible at 36° (90°.8 F.) sparingly soluble in water readily soluble in alcohol, ether, carbon disulfid, and in acids. Corresponding to it are a series of menthyl ethers. 

Methyl-2-butanol Menthyl alcohol 2-Octanol 1-Phenylethanol a-Methyl-4-nitrobenzylamine... 

Menthyl alcohol reacts with dichlorocarbene under phase transfer conditions to yield predominantly /-menthyl chloride, a fact which suggests that an SNi pathway is important although not unique. A significant amount of leakage into the sequential or carbonium ion pathway probably accounts for the production of almost equal amounts of exo and e small amounts of formate esters are isolated in these reactions, suggesting that hydrolysis of II occurs but is not a major process. Several examples are recorded in Table 3.2. 

Standnikow has prepared several of the esters of menthol by heating magnesium iodo-mentholate with the esters of ethyl alcohol. For example, with ethyl acetate, propionate, and benzoate the corresponding menthyl esters were obtained. These bodies have the following boiling-points —... 

In these estimations it -is necessary to calculate all the esters and all the alcohols to one formula, expressing the result, for instance, as menthyl acetate, although as a matter of fact small quantities of the corresponding propionate and butyrate may also be present, which it is impossible to estimate separately. 

Although menthyl esters, especially 19, are most often used to prepare sulfoxides, esters derived from optically active alcohols other than menthol have been prepared . Ridley and Smal prepared arenesulfmic esters of 1,2 5,6-di-O-cyclohexylidene-a-D-glucofuranose. Unfortunately, these diastereomers were oils, except for the mesityl derivative, with the major epimer having configuration R at sulfur and so they offered no advantage over the menthyl esters. Separation of the epimers by chromatography failed. 

Another enantiospecific synthesis of longifolene shown in Scheme 13.32 used an intramolecular Diels-Alder reaction as a key step. An alcohol intermediate was resolved in sequence B by formation and separation of a menthyl carbonate. After oxidation, the dihydropyrone ring was introduced by 7-addition of the ester enolate of methyl 3-methylbutenoate, followed by cyclization. 

Menthone and camphor undergo asymmetric hydrosilylation to give alkoxysilanes with up to 82% optical purity using neutral rhodium(I) catalysts containing DIOP or neomenthyl- or menthyl-diphenylphos-phine even triphenylphosphine gave about 65% ee (300). Hydrolysis to alcohols was not reported. The ferrocenyl ligands (28, 29) are similarly effective for asymmetric hydrosilylation (255), and could be used for production of the optically active alcohols. 

Methyl isobutyl ketone was reduced with (- )-menthol-LAH in ether to give the (+ )-(S)-carbinol (53) in low optical yield. Methyl neopentyl ketone was similarly reduced to the (-I- )-carbinol, although pinacolone was reduced to only racemic alcohol. Maximum stereoselectivity in the reduction of both ketones and alkenynols was obtained with a 2 1 (-)-menthol-LAH reagent. The observed low stereoselectivity was attributed mainly to insufficient interaction of the remote isopropyl substituent on the menthyl group with the substituents on... 

The first indication of the chirality of sulfuranes was provided by the X-ray analysis of spirosulfurane 176 (192). This work clearly demonstrated the presence of enantiomeric pairs of 176 in the crystal lattice. In 1975, the optically active chlorosulfurane 177, the first example of an optically active tetracoordinate sulfurane, was synthesized by Martin and Balthazor (194,195) by the route indicated in Scheme 15. Reaction of (-)-(5)-menthyl benzenesulfinate 178 with the protected Grignard reagent 179 gave the corresponding sulfoxide alcohol (-)-(5>180 which was cyclized to the chlorosul-... 

Mandelic acid with a 13 - 20 % enantiomeric excess of the (R)-isomer has been obtained from reduction of phenylglycolic acid in aqueous alcohol buffers containing strychnine in low concentration. The optical yield depends upon pH and is highest (20 - 24 %) at pH 0 or 9.2 and at low current density. In the pH range 2-4, the optical yield drops to 2-8% [42]. The higher result compares well with the maximum value of 20% excess R-isomer found from reduction of (-)-menthyl phenylglycolate in aqueous buffers where the (-)-menthyl ester is the only chiral reagent present [43 ]. 

TRANSESTERIFICATION OF METHYL ESTERS OF AROMATIC AND o,p-UNSATURATED ACIDS WITH BULKY ALCOHOLS (-)-MENTHYL CINNAMATE AND (-)-MENTHYL NICOTINATE... 

TRANSESTERIFICATION OF METHYL ESTERS OF AROMATIC AND a,B-UNSATURATED ACIDS WITH BULKY ALCOHOLS (-)-NENTHYL CINNAHATE AND (-)-MENTHYL NICOTINATE (2-Propeno1c acid, 3-pheity1, 5-BethyI-2-(l- ethyIethyl)cyclohevl ester, [lR-(la,2B.Sa)-) and... 

Glazer, J., and E. E. Turner The Mutarotation of laevo menthyl benzoyl-formate in alcoholic solutions. J. chem. Soc. [London] 1949 Suppl., 169. 

Ketcnc equivalents, such as ketene acetals and thioacetals, can be used in cycloadditions to electron-deficient alkenes (see Sections 1.3.2.1. and 1.3.2.2.). In an example of a fumaric acid diester fitted with two chiral alcohol auxiliary groups, the aluminum(III)-catalyzed cycloaddition of 1,1-dimethoxyethene with di-(—)-menthyl fumarate (9) proceeds with > 99% diastereomeric excess. Intermediate 10 can be readily converted to cyclobutanone derivatives.17, 18... 

Frankland and Price 17 were the first to attempt the resolution of alcohols (and acids) by fractional crystallization of their solid esters. The isomeric solid esters formed from Z-s-butylcarbinol and di-dibenzoyl-glyceric acid failed to separate on crystallization the corresponding di-alcohol-i-acid ester was liquid. Marckwald and McKenzie 18-19 effected partial resolutions of dl-mandelic acid and related acids with 1-menthol and d-bomeol, and of di-2-octanol with d-tartaric acid, but did not develop a satisfactory method for resolving alcohols. Later investigators, however, have employed the following resolving agents in several more or less successful resolutions of certain alcohols (a) i-menthyl isocyanate, (6) d-camphoric acid, (c) d- or i-mandelic acid, (d) d- or... 

Z-Menthyl Isocyanate. Pickard and Littlebury 20-21 found that Z-menthyl isocyanate forms crystalline esters (urethanes) with many alcohols and phenols. The two diastereoisomeric urethanes from cZZ-l-phenyl-1-p-hydroxyphenylethane and from dZ-oc-tetrahydro-/3-naphthol were separated readily.2 The method has not been applied widely. Z-Men-thyl isocyanate is the most readily available resolving agent of this type but is difficult to prepare. The urethanes are not easily hydrolyzed, and the isocyanate is not recovered in the hydrolysis but is converted to the amine. 

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