Methylcyclohexene oxide, reduction

Reduction of epoxides. The reaction of diborane alone with epoxides is complicated. Thus 1,2-butylene oxide requires 48 hrs. and gives a mixture of butanols (96% 2-butanol and 4% 1-butanol) in only 48% yield. The reaction with trisub-stituted epoxides is even more complicated and only trace amounts of simple alcohols are formed. Brown and Yoon1 found that the presence of trace amounts of sodium or lithium borohydride greatly enhances the rate of reaction and modifies the course to give predominantly anti-Markownikov opening of the epoxide ring. Thus 1-methylcyclohexene oxide is reduced mainly to m-2-methylcydohexanol ... 

Pre-cooled 1-methylcyclohexene oxide added to a stirred 0.76 M soln. of KBHPh3 in THF containing 0.76 Af Ph3B-THF at 0°, the mixture stirred for 0.5 h, and hydrolyzed with HjO at room temp, for 0.5 h c/5-2-methylcyclohexanol. Y 90%. Ph3B as Lewis acid dramatically accelerates the rate of reduction and directs attack of hydride exclusively at the most congested C-atom of trisubst. epoxides tetra-subst. epoxides failed to react. F.e.s. N.M. Yoon, K.E. Kim, J. Org. Chem. 52, 5564-70 (1987). 

In this synthesis the geometry of the acyclic double bonds is controlled through their formation as part of the thiane ring. Thiacyclohexanone (711) was converted to 4-thia-l-methylcyclohexene by reaction with methylmagnesium iodide and subsequent dehydration. Metallation of (712) with s-butyllithium and alkylation of the anion with the epoxide (713) gave a tertiary alcohol which was dehydrated to yield (714). A second alkylation of (714) with trails-4-chloro-3-methyl-2-butene 1-oxide (715) completed the carbon skeleton of the Cis juvenile hormone. Reduction of (716) with lithium in ethylamine and then desulfurization with Raney nickel led to trienol (717), a product converted previously to (718). 

Some other catalytic events prompted by rhodium or ruthenium porphyrins are the following 1. Activation and catalytic aldol condensation of ketones with Rh(OEP)C104 under neutral and mild conditions [372], 2. Anti-Markovnikov hydration of olefins with NaBH4 and 02 in THF, a catalytic modification of hydroboration-oxidation of olefins, as exemplified by the one-pot conversion of 1-methylcyclohexene to ( )-2-methylcycIohexanol with 100% regioselectivity and up to 90% stereoselectivity [373]. 3. Photocatalytic liquid-phase dehydrogenation of cyclohexanol in the presence of RhCl(TPP) [374]. 4. Catalysis of the water gas shift reaction in water at 100 °C and 1 atm CO by [RuCO(TPPS4)H20]4 [375]. 5. Oxygen reduction catalyzed by carbon supported iridium chelates [376]. - Certainly these notes can only be hints of what can be expected from new noble metal porphyrin catalysts in the near future. 

Both cis- and tram-isomers were formed from 1-methylcyclohexene in trichloroethylene, as deduced from the complexity of the H-NMR spectrum of the isolated product (21 %)31. Different physical properties and stereochemistry were assigned to the adduct prepared from 1-phenylcyclohexene in the same conditions by different authors31,32, but the possibility that different dimers were isolated by homospecific and heterospecific dimerization should be considered, syn Addition was claimed in one of these reports, since the presumed cis adduct was converted to m-2-phenylcyclohexanamine by reduction with lithium aluminum hydride31. However, oxidation of the tram-adduct afforded the corresponding nitro derivative, whose dipole moment agreed with the value calculated for the tram-product32. 

The stereospecific conversion of cyclohexene into the corresponding amido selenide 54 is illustrated in Scheme 8. These amidoselenenylation reactions are commonly employed for the preparation of allylic and saturated amides by oxidative or reductive deselenenylation. Propionitrile, butyronitrile, benzonitrile and ethyl cyanoacetate may be used in place of acetonitrile. Styrene gave poor results and other electron-rich olefins such as 1-methylcyclohexene or 2,3-di-methylbut-2-ene did not give the amidoselenenylation products. The reaction can also be effected starting from the hydroxy- or methoxyselenenylation products of alkenes, in the presence of water and trifluoromethanesulfonic acid in this case the nitriles are used in stoichiometric amounts [48c]. This methodology was employed to prepare the amidoselenenylation products of styrene, 55, and of electron-rich olefins. It was necessary, however, to replace the phenyl-... 

Scheme 6.31. A representation of the pathway for hydroboration of 1-methylcyclohexene with the dimer of 9-borabicyclo[3.3.1]nonane (9-BBN) (i.e., [9-BBN]2), which yields (a)(E)-or (frani)-2-methylcyclohexanol oxidatively (hydrogen peroxide anion, HO2 ), or (b) meth-ylcyclohexane, reductively (acetic acid, CH3CO2H). The kinetics of hydroboration are in accord with rapid, reversible formation of 9-BBN monomer from the dimer prior to the ratedetermining step. (See Brown, H.C. Chandrasekharan, X Wang, K. K. Pure Appl. Chem., 1983,55,1387.)...

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