4.4- Dimethyl-2-cyclohexenol

Using methods developed by Sharpless (68), Reich (69), and others, the optically active 4,4-dimethyl-2-cyclohexenol is prepared in excellent yield from the corresponding chiral selenide (eq. [19]). The (S)-4,4-dimethyl-3-p-methylphenylselenocyclohexanone, [a] 42.1° (e.e. 39%), was reduced with sodium borohydride to the (one) diastereomeric alcohol, [a] 11.0°, in quantitative yield and converted to the allylic alcohol, [a] — 17.7°, with an e.e. of 40%. 

The osmylation of l-[Af-methylphenylsulfoximinomethyl]-l-hydroxy-2-cyclopentenols and -2-cyclohexenols, obtained in turn from the corresponding 2-cycloalkenones by the addition of lithiated, V,.S -dimethyl-5-phenylsulfoximine, occurs from the same side as the sulfoximino functionality with complete Ik topicity. Subsequent thermal elimination of the sulfoximine group allows the synthesis of optically pure 2,3-dihydroxycycloalkanones. This method can, therefore, be regarded as proceeding via an auxiliary-controlled osmylation92-93. 

Another example of this type of substrate-induced diastereoselectivity is represented by the rearrangement of the S -methyl xanthate of cis-3,5-dimethyl-2-cyclohexenol 5, which takes place on heating at 140 °C for a few hours, to give 644. 

To a suspension of 23 mg (10 mmol) of sodium sand in benzene is added 1.26 g (10 mmol) of cis-3,5-dimethyl-2-cyclohexenol and the suspension refluxed with stirring. After the metal has completely reacted 0.9 g (12 mmol) of carbon disulfide is added with ice-cooling and the mixture is stirred for 2 h at r.t. and then 1.25 g (10 mmol) of CH3I is added. After stirring overnight, the mixture is filtered, washed with H20 and dried over Na,S04. The filtrate is concentrated under reduced pressure and the residue is distilled to give the pure dithiocarbonate yield 59% bp 104CC/1 Torr. 

Mn(TPP)Cl Ascorbate Cyclohexenol Styrene Styrene oxide Cyclohexene, Epoxide CIS and trans stilbenes, Epoxides CIS- and trans-2-hexenes, Epoxides 2,3-Dimethyl-2-butene, Epoxides [83]... 

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