Search

Asymmetrical oxidation was performed of menthone dithiolane obtained in 95–98% yield by condensation of menthone with 1,2-ethanedithiol in the presence of boron trifluoride etherate. 6-Isopropyl-9-methyl-1,4-dithiaspiro[4,5]decane-1,4-dioxide (yield 5–55%) and 6-isopropyl-9-methyl-1,4-dithiaspiro[4,5]-decane-1,1,4-trioxide (yield 65–70%) were synthesized. Chemical structures of compounds obtained were proved by XRD analysis, NMR and IR spectroscopy.

The two diastereomers of spirocyclic 5,6-dimethyl-4H-1,3-dioxin-4-one (5,6) have been synthesized by acetalization of tert-butyl 2-methyl-3-oxobutanoate (2) with (-)-menthone (4). Their structures have been determined by NMR analysis.

The titled compound was prepared by the Beckmann rearrangement of (−)-menthone oxime in polyphosphoric acid, and the value of its optical rotation was revised.

Three (6a – c) of the four conceivable diastereomeric 1-ferrocenylalkylamines can be synthesized from I-(−)-menthone and ferrocene in high enantiomeric purity. The many potential applications of such compounds, including their use as chiral templates in diastereoselective four component condensations (4CC, Ugi Reaction) are examined. Furthermore, NMR evidence for the first example of up-down-isomerism, a new type of conformational stereoisomerism of ferrocene derivatives, is discussed.

1,3-Dioxan-4-ones 6and 7 derived from (–)-menthone can be utilized in resolution of 3-hydroxycarboxylic acids and asymmetric synthesis of 2-substituted 3-hydroxycarboxylic acids.

Two chiral auxiliaries and the role they play in the preparation of chiral carbonyl compounds and heterocyclic compounds are presented. Key reactions include SN2′ displacements, Mitsunobu with hydrazoic acid, and 3,3-sigmatropic rearrangements. One of the auxiliaries serves many functions and is removed either by oxidative cleavage or RCM reaction.

Asymmetric desymmetrization of prochiral 2,2′,6,6′-biphenyltetrol by acetalization with l -menthone affords isomenthonide 5b of S -axial chirality. A variety of ( S )-6,6′-dialkoxy-2,2′-biphenyldiols of high enantiomeric purities are synthesized by using 5b as an intermediate. Thus, etherification of the hydroxy groups of 5b followed by hydrolysis of the isomenthonide moiety give the corresponding 6,6′-dialkoxy-2,2′-biphenyldiols ( 12 ). Intermolecular cyclization of 5b with 1,ω-dibromoalkanes followed by hydrolysis yields 2,2′-biphenyldiols 13 with alkylenedioxy bridges at the 6 and 6′ positions. Regioselective functionalization of 13 leading to 3,3′-dimethyl, -diphenyl, and -bis(TBS) derivatives is achieved either via directed lithiation of a carbamate derivative or via regioselective bromination reaction of 13 . Origin of the stereoselectivity in acetalization reaction as well as thermal stability of the axial chirality of 2,2′-biphenyldiols is also discussed.

Enantiodifferentiating functionalization of meso -1,3-diols is realized by the utilization of titanium tetrachloride-promoted selective ring-cleavage reaction of spiroacetals derived from l-menthone