Oxidation cycloalkanols

Tertiary alcohols are usually degraded unselectively by strong oxidants. Anhydrous chromium trioxide leads to oxidative ring opening of tertiary cycloalkanols (L.F. Fieser, 1948). 

The derivatives 24 were synthesised by the acylation of trans-2-aminocy-clopentanol (n=l) or frans-2-aminocyclohexanol (n=2) with 3,3-ethylene-dioxydodecanoic acid in the presence of EDC, DMAP and DIPEA followed by acidolysis with THF in DCM. The cycloalkanone analogues 25 were obtained by Swern oxidation of the corresponding cycloalkanols 24 (Scheme 10). 

Recently, Corma et al. have patented a process of oxidizing cycloalkane with molecular oxygen to produce cycloalkanol and/or cycloalkanone in the presence of hydrotalcite-intercalated heteropoly anion [Co MnCo (H20)039] (M = W or Mo), which comprised one cobalt as a central atom and another as a substitute of a W=0 fragment in the Keggin structure [98]. At 130 °C and 0.5 MPa, 64 and 24% selectivity to cyclohexanone and cyclohexanol, respectively, was achieved at cyclohexane conversion about 5%. This catalytic system could be of practical importance provided a true heterogeneous nature of catalysis and good catalyst recyclability had been proved. Unfortunately, this information was lacking in [98]. 

The kinetics of the potassium hexacyanoferrate(III)-catalysed oxidation of glucose with ammonium peroxodisulfate have been studied.82 The kinetics and mechanism of oxidation of some cycloalkanols by alkaline Fe(CN) have been reported.83 The same group has also studied the oxidation of cycloalkanones under comparable conditions and determined the order of reactivity as cyclohexanone > cyclopentanone > cyclo-octanone > cycloheptanone.84 Palladium(II) has been found to catalyse the oxidation of formaldehyde, thiourea, and thioacetamide by alkaline Fe(CN)g, whereas no effect is observed in the oxidation of acetaldehyde.85 The orders of reaction have been determined and a mechanism was proposed. 

The reagent oxidizes benzyl and allyl alcohols to carbonyl compounds in high yield. Yields are low for primary alkanols and cycloalkanols ( 30%).1... 

The electrolysis of 2-amino- 1-cycloalkanol 15 in an MeCN/H20—NaCl—(Pt) system at pH 4 (buffered) yields keto nitrile 16 in 62% yield (Scheme 3-5)52). The formation of 16 can be explained by fragmentation of the intermediate 6e/a-hydroxy-,V-chloroamine and the subsequent further oxidation with [Cl]+. 

Greater preparative importance attaches to oxidative ring opening of cycloalkanols and cycloalkanones, which then afford alkanedioic acids containing an unchanged number of carbon atoms. Thus, for instance, adipic acid is obtained in up to 90% yield from cyclohexanol or cyclohexanone by means of about 60% nitric acid containing vanadium and copper salts as catalyst 125... 

An oxidizing reagent based on potassium ferrate(Vl) has been described [78], This potassium ferrate, when used in conjunction with an appropriate heterogeneous catalyst such as KIO montmorillonite clay, is a strong oxidant which produces cycloalkanols and cycloaUcanones from cycloalkanes, and benzyl alcohol and benzaldehyde from toluene. 

During research into the oxidation of cycloalkanols, Ishihara and coworkers also found that the selective oxidation of 4-ferf-butylcyclohexanol (101) to 4-tert-butyl-2-cyclohexenone (102) can be achieved in excellent yield in the presence of a catalytic amount of sodium 2-iodobenzenesulfonate and two equivalents of Oxone (Scheme 4.51) [80], Using this procedure, five- and six-membered cycloalkanols can be transformed into the corresponding enones 103-107 in good yields [80],... 

Chromic acid oxidation of 1-substituted cycloalkanols (434 m = 0,1,..n = 1,2, 3. ..) proceeds with ring-cleavage, giving keto-acids. Lead tetra-acetate oxidation of the cyclobutanol (435) has been reported to take an unusual course, giving in addition to the expected y-hydroxy-ketone (436) the new compound (437), whose structure was confirmed by X-ray analysis. 

Closely related to the above reaction is the base-induced elimination from a,a-dibora-y-chloropropane and co-sulfonyloxy derivatives, which produce cy-cloalkylboranes. Oxidation of these leads to the corresponding cycloalkanols (Chart 16.2) [6, 7]. 

Scheme 22.1 Oxidation of cycloalkane to cycloalkanol and cycloalkanone catalyzed by lris(pyrazol-l-yl)inethane Re, V, Fe, or Cu complexes.

Cyclopropanol (Schaafsma et al., 1966) and cyclobutanol (Meyer and Rocek, 1972) undergo rapid oxidative cleavage, due to the release of the strain energy of the aliphatic ring. Chain opening is a typical reaction of strained cycloalkanols in presence of one-electron oxidants. A mixture of reaction products is formed, and the actual composition of the reaction... 

---