Di-/-menthol

Resolution methods using nonoptically active agents are also used by taking advantage of the fact that certain benzoic acid derivatives of (di)-menthol can be inoculated with crystals of one enantiomer to induce immediate crystallization of that enantiomer. Although repeated crystallizations and separations must be done, the technique has been successful for (—)-menthol (157). 

IR Melting Range (/-menthol)—41° to 44° (Appendix IIB) Nonvol. Res.—0.05% (M-16) Readily Ox. Subs, (di-menthol)—pass (M-13) Specific Rotation (/-menthol)— between -45° and -51° (Appendix IIB) Specific Rotation (il menthol)—between —2° and +2° (Appendix IIB)... 

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. 

Cervinka has employed these reagents in the asymmetric reduction of im-monium salts (49,50) and imines (51). The reduction of 2-substituted jV-methyl-A -tetrahydropyridinium perchlorates (10) with (— )-menthol-LAH in ether or THF led to optically active piperidine derivatives (eq. [10]). The optical purity obtained for the Pr" derivative was 12%. In the case of R = Me and Pr" the configuration of the predominant enantiomer was shown to be S. The (-)-menthol-LAH reagent was similarly shown to reduce l-methyl-2-alkyl-A -di-hydropyrrolinium perchlorates (11) to optically active pyrrolidine derivatives (eq. [11]). The optical yield could be calculated only for R = CH2Ph, and was only 6% (/ enantiomer) obtained with a 1 1 (— )-menthoi-LAH reagent. With 2 1 or 3 1 molar ratios of menthol LAH, the optical yield decreased. The... 

Other ingredients Di- -propyi isocinchomerate, A-Octyi bicycioheptene- dicarboxamide Eucalyptol, Menthol, Methyl salicylate, thymol ... 

To our knowledge, the first examples of asymmetrically substituted monocyclic phosphoranes are 60 and 61, described by Moriarty et al.135 and involving the reaction of a substituted o-benzoquinone136,137 (Scheme 6) on an aminophosphine (59), itself obtained by alcoholysis of 58 with l-( — )-menthol. In contrast to the amino phosphine 53 (Scheme 5), 59 is a mixture of the diastereoisomers 59a and b, and its reaction with 3,5-di-tert-butyl-l,2-benzoquinone yields two diastereoisomeric phosphoranes, 60a and b. Finally, alcoholysis of the P(V)—NR2 bond138 in 60a and b leads to 61a and b or 62. 

Dichlorodimethyltitanium, 216 Intramolecular alkylation 9-Bromo-9-phenylfluorene, 48 Chloromethyl ethyl ether, 75 Di-p-carbonylhexacarbonyldicobalt, 99 l-Hydroxy-3-trimethylsilylmethyl-3-butene, 147 Menthol, 172 Potassium t-butoxide, 252 Miscellaneous alkylations at active hydrogens... 

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... 

The cationic BINAP-Rh complexes catalyze asymmetric 1,3-hydrogen shifts of certain alkenes. Diethylgeranylamine can be quantitatively isomerized in THF or acetone to citronellal di-ethylenamine in 96-99% ee (eq 17). This process is the key step in the industrial production of (-)-menthol. In the presence of a cationic (R)-BINAP-Rh complex, (5)-4-hydroxy-2-cyclopentenone is isomerized five times faster than the (R) enantiomer, giving a chiral intermediate of prostaglandin synthesis. ... 

Pure meto-cresol has been used for manufacture of synthetic musk— musk ambrette, used as a fixative to perfumes, for manufacture of synthetic Thymol and Menthol amd also leather preservative p-chloro-meto-cresol, synthetic pyre-throids, and lastly for manufacture of 2,3,6-trimethylphe-nol—an intermediate for vitamin E. o-Cresol has been used for manufacture of Coumarin and some derivatives which are employed in perfumery as fixative. o-Cresol has also been used for making Novolac and epoxy resins and also for the herbicides based on di-nitro-oAt/io-cresol, etc. In sum, individual cresols have been very successfully converted to important intermediates in the organic chemical synthesis. It is expected that further development work will lead to synthesis of many more organic chemicals of vital importance. While new chemicals using individual cresols are in the pipeline... 

In 1979, Koga and coworkers disclosed the first practical example of a catalytic enantioselective Diels-Alder reaction [44] promoted by a Lewis acidic complex, presumed to be menthoxyaluminum dichloride (1), derived from menthol and ethylaluminum di chloride, whose structure remains undefined [45]. This complex catalyzed the cycloaddition of cyclopentadiene with acrolein, methyl acrylate, and methacrolein with enantioselectivities as high as 72% ee. Oxidation of 2 (predominantly exo) followed by recrystallization actually lowered the ee ... 

Butadiene and secondary amines, with a catalyst formed from nickel(II) acetylacetonate and triethylaluminum in the presence of chiral phosphonite ligands derived from menthol, 1,2 5.6-di-O-isopropylideneglucose or cholesterol, give linear and branched telomers along with simple addition products and cyclic dimers6. The linear telomers are the major products. An optical yield of 37 % was obtained for the branched morpholine telomer 2. which was obtained in 30 % yield when bis(menthoxy)(2-methylpropyl)phosphane was employed. 

Chiral alkoxy-l,3-cyclohexadienes 1 add to 1,4-naphthoquinone (2) yielding 3 with moderate to very high diastereomcric ratios. The best results (d.r. 97.5 2.5) are achieved for dienes le and lf(l,2 5,6 -di-O-isopropylidene-a-D-glucopyranoside as an auxiliary). Diene Id (2.3,4,6-tetra-0-methyl-/(-D-glucopyranoside as auxiliary) gives a d.r. of only 58.5 41.5. Terpene derivatives as auxiliary alcohols do not work much better d.r. 63 27, 53 47, 64 36 are obtained for la [(-)-borneol], lb [( — )-menthol] and lc [(—)isopinocampheol], respectively18. 

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