Ethyl menthyl

The stereoisomers of ethyl menthyl (methylthio)methylphosphonate 32 were obtained from commercially available diethyl (methylthio)methylphosphonate by subjecting them to a highly diastereoselective hydroperoxide oxidation in the presence of catalytic amounts of a titanium (/ )- or (5)-BlNOL complex. The prevailing phosphorus stereoisomer was oxidized with cumene hydroperoxide in the presence of a Sharpless complex between titanium tetra(isopropoxide) and diethyl (/ ,/ )- or (S,S)-tartrate, to yield the corresponding (methylsulfinyl) methylphosphonates 33 (76-82% de). The sulfoxide 33 was obtained in a diastereo-merically pure form (>98% de, upon recrystallisation) and was shown to have an (/ P,Ss)-configuration (Scheme 11) [32]. 

TBHP = tert-butyl hydroperoxide Scheme 11 Synthesis of ethyl menthyl (methylsulfinyl)methylphosphonates 33... 

Cardellicchio C, Naso F, Annunziata M, Capozzi M (2004) A convenient route to the phosphorus and sulfur stereoisomers of ethyl menthyl (methylsulfinyl)methylphosphonate. Tetrahedron Asymmetry 15 1471-1476... 

Fig. 5a and b. H-NMR spectra in the aromatic proton region of copolymers of N-vinylcarbazole (NVC) with a (—)-ethyl menthyl fumarate (19) b (—)-dimenthyl fiimarate (20) having different compositions... 

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 —... 

Active Figure 17.20 Dehydrochlorination of menthyl and neomenthyl chlorides, (a) Neomenthyl chloride loses HCI directly from its more stable conformation, but (b) menthyl chloride must first ring-flip before HCI loss can occur. The abbreviation "Et represents an ethyl group. Sign in at www.thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

The appropriate alkyl 2-bromomethylpropenoate (l mol) TEBA-Cl (2.3 g, 10 mmol), and /-BuO,H (90%, 110 g, l.l mol) in CH2Cl2 (150 ml) are stirred at -10°C. Powdered KOH (56 mg, l. I mol) is added portionwise such that the reaction temperature does not exceed -5°C. On complete addition of the hydroxide, the mixture is stirred at -5°C for 30 min and then allowed to come to room temperature and stirred for a further I h. The mixture is filtered and evaporated under reduced pressure. n-C,H12 (200 mi) is added to the residue and the organic solution is filtered, washed with H20 (100 ml), dried (MgS04), and evaporated to yield the peroxide (ethyl ester, 92% menthyl ester, 85% /-butyl ester, 45%). 

The most important and widely used approach to chiral sulfoxides is the method developed by Andersen (5) based on the reaction between the diastereomerically pure (or strongly enriched in one dia-stereomer) menthyl arenesulfinates and Grignard reagents. The first stereospecific synthesis of optically active (+H7 )-ethyl p-tolyl sulfoxide 22 was accomplished in 1962 by Andersen (75) from (-)-(iS)-menthyl p-toluenesulfmate 45 and ethylmagnesium iodide. 

Thin layer chromatograms were obtained with silica gel as absorbent and ethyl acetate as developing solvent. The order of elution and Rf values of the major components are as follows menthyl sulfinate (0.65), menthol (0.59), sulfinyl ketal (0.30). 

The effects of polar substituents on the alkaline hydrolysis of esters are well-established. Since the rate of the reaction is determined largely by the rate of addition of hydroxide ion to the carbonyl group of the ester, any substituent which withdraws electrons from the carbonyl group will increase the reactivity of the ester. The most accessible quantitative measure of the effect is the Hammett or Taft reaction constant, and a large number of measurements are available. Taft et al.2i0 found p = 2.53 for the base-catalyzed methanolysis of meta- and para-substituted (/)-menthyl benzoates, closely similar to the known value of p = 2.37 for the alkaline hydrolysis of substituted ethyl benzoates. Jones and Sloane s value239, obtained with five esters, of p = 2.41 for the methoxyl exchange reaction of substituted methyl benzoates in methanol, is almost identical. 

Methyl-sorbate LiC4H (—) Menthyl-ethyl-ether... 

Poly-methyl-sorbate n-butyl-lithium-menthyl-ethyl-ether 1R, 3R, 4S R CHj-COOH COOH 1... 

In the case of the polymerization of methyl and butyl sorbates optical purity varies by varying the type of asymmetric complex used as catalyst. In non-systematic runs carried out with catalysts prepared from lithium-butyl and (—)-menthyl-ethyl-ether, [M]n increases... 

Section II, 1. Theoretical aspects of asymmetric polymerization have been discussed by Fueno and Furdkawa [T. Fueno, J. Furukawa J. Polymer Sci., Part A, 2, 3681 (1964)]. 1-phenyl-l,3-butadiene has been polymerized using (R)-2-methyl-butyl-lithium or butyl-lithium complexed with menthyl-ethyl-ether, yielding optically active polymers with [a] f, referred to one monomeric unit, between +0.71 and —1.79. Optical rotation dispersion between 589 m u and 365 mft is normal and the Drude equation constant is comprised between 255 raft and 280 raft [A. D. Aliev, B. A. Krenisel, T. N. Fedoiova Vysokomol. Soed. 7, 1442 (1965)]. 

Menthyl = (1/ ,2S,5/ )-2-isopropyl-5-methylcyclohexyl. Configuration of carbon atoms 1 and 2 for major isomer in parentheses. With ethyl diazoacetate the same trans.cis product ratio was obtained, and % ee s were 91(cis) and 1 l(trans). 

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