Diols 1,3-, catalyses oxidation

Ishii, Y., Yamawaki, K., Ura, T., et al. (1988). Hydrogen Peroxide Oxidation Catalyzed by Heteropoly Acids Combined with Cetylpyridinium Chloride. Epoxidation of Olefins And Allylic Alcohols, Ketonization of Alcohols and Diols, and Oxidative Cleavage of 1,2-Diols and Olefins, J. Org. Chem., 53, pp. 3587-3593 Sato, K., Aoki, M., Ogawa, M., et al. (1997). A Halide-Free Method for Olefin Epoxidation with 30% Hydrogen Peroxide, Bull. Chem. Soc. Jpn., 70, pp. 905-915 Xi, Z. W., Zhou, N., Sun, Y., et al. (2001). Reaction-Controlled Phase-Transfer Catalysis for Propylene Epoxidation to Propylene Oxide, Science, 292, pp. 1139-1141 Neumann, R. 

Silver carbonate, alone or on CeHte, has been used as a catalyst for the oxidation of methyl esters of D-fmctose (63), ethylene (64), propylene (65), trioses (66), and a-diols (67). The mechanism of the catalysis of alcohol oxidation by silver carbonate on CeHte has been studied (68). 

Acidification with trichloracetic acid catalyses oxidation , the fractional increase in the rate coefficient per mole of acid added, viz. Ak/ko)/[sicid], being of the order of two. Strong catalysis by alkali metal acetates has been observed for several oxidations, e.g. of m-cyclohexane-l,2-diol °, formic acid , methyl mannoside and galactoside and several a-hydroxycarboxylic acids °. 

Heteropoly acids can be synergistically combined with phase-transfer catalysis in the so-called Ishii-Venturello chemistry for oxidation reactions such as oxidation of alcohols, allyl alcohols, alkenes, alkynes, P-unsaturated acids, vic-diols, phenol, and amines with hydrogen peroxide (Mizuno et al., 1994). Recent examples include the epoxidations of alkyl undecylenates (Yadav and Satoskar, 1997) and. styrene (Yadav and Pujari, 2000). 

Hydrogenolysis of epoxides to alcohols by catalytic hydrogenation over platinum requires acid catalysis. 1-Methylcyclohexene oxide was reduced to a mixture of cis- and /ranj-2-methylcyclohexanol [652]. Steroidal epoxides usually gave axial alcohols stereospecifically 4,5-epoxycoprostan-3a-ol afforded cholestan-3a,4/J-diol [652 ]. 

The class of 3-silyl-substituted reagents provides, upon addition with aldehydes, allylic silanes that offer many options for further derivatization. Oxidative processes are described in previous sections (see the sections on Preparation of 1,2-Diols and 1,4-Diols). If the appropriate silicon substituents are chosen, formal [3+2] cycloadditions with aldehydes can be promoted under Lewis acid catalysis. For example, the mismatched addition of the Z-3-propyl-3-benzhydryldimethyl allylsilane 183 to an a-benzyloxy aldehyde proceeds with low diastereofacial selectivity in favor of product 184 however, after protection of the secondary alcohol, an efficient [3+2] annulation provides the polysubsubstituted furan 185 in good yield and acceptable stereoselectivity (Scheme 24). ° The latter is brought forward to a tricyclic unit found in the antitumor natural product angelmicin B. 

Phase-transfer catalysis has been developed by the combination of Keggin-type heteropolyanions and quaternary countercations such as tetrahexyl-ammonium or cetylpyridinium ion. The oxidations of alcohols (306), allyl alcohols (307), olefins (308), alkynes (309), /J-unsaturated acids (310), v/ c-diols (311), phenol (312), and amines (313) are the examples. 

A major development in this area was brought about by the invention of crosslinked polystyrene-supported 9-(/)-chlorobenzoy 1 )quinine ligands 17 [54] and 18 [55], The salient feature of this invention is the connection of the quinine unit to the polymer backbone through a sterically undemanding spacer. Thereby, the quinuclidine, which in catalysis coordinates to osmium, is free of steric interaction with the polymeric side chain. Dihydroxylation of trans-stilbene in the presence of 17 and NMO as co-oxidant gave stilbene diol with 87% ee. However, changing the terminal oxidant to K3[Fe(CN6)] led to full inhibition of the reaction. This result was explained by a possible collapse of the polymer in the required protic solvent, which prevented substrate penetration. 

MeO-PEG-modified DPP and PYR ligands 23 and 24 were introduced by Bolm [68]. Whereas 23 showed the expected excellent enantioselectivities in the oxidation of various aromatic olefins (eemax = 99%), the catalysis of 24 gave an efficient conversion of terminal aliphatic olefins into their respective diols (eemax = 90% for 3,3-dimethyl-1-butene). As with the corresponding silica gel-bound ligand 21, sequential use of 23a led to a slight decrease in enantioselectivity in consecutive runs. This result was again attributed to partial hydrolysis of the ester moiety. After replacement of the ester by an ether function, the enantiomeric excess of the product remained constant over a period of several runs [69]. 

Iodoxybenzene (PI1IO2) has been briefly explored in the oxidation of benzylic alcohols to benzaldehydes, giving best results with an acetic acid catalysis.120 The guanidinium salt of m-iodoxybenzoic acid is soluble in CH2C12 and able to carry out oxidative breakages of 1,2-diols.120... 

Oxidation of organic compounds by ruthenium tetraoxide has been reviewed. The oxidation of various types of organic compounds such as alkanes, alkenes, allenes, aromatic rings, alcohols, amines, and sulfides has been discussed The cyclic oxoruthe-nium(VI) diesters that are formed in the initial step of the oxidation of alkenes are considered to be intermediates in the formation of 1,2-diols.70 The development of new and selective oxidative transformations under ruthenium tetroxide catalysis during the past 10 years has been reviewed. The state of research in this field is summarized and a systematic overview of the reactivity and the reaction mode of ruthenium tetroxide is given.71... 

A widely applied strategy for the synthesis of various difunctionalized organic molecules, e.g. diols, dialdehydes, etc., relies on the oxidative cleavage of olelinic double bonds. Besides transition metal catalysis for asymmetric synthesis, periodate oxidation and ozonolysis are the standard tools for oxidative bond cleaving reactions. For economic and safety reasons, technically applicable alternatives to osmium-based chemistry and ozonolysis are of great interest. 

In Wang et al. s synthesis of asimilobin (Scheme 10-23), the key diol 123 was also prepared by Sharpless AD in high enantioselectivity. Oxidation of 123 furnished the trans-threo-tram fow-THF intermediate 124 in catalysis of Co(modp)2. The C2 symmetrical diol 124 was desymmetralized and converted... 

Ruthenium catalysis allows dihydroxylation providing an easy access to syn-diols, but over-oxidation is a common side reaction. The improved protocol for the Ru-catalyzed syn-dihydroxylation uses only 0.5 mol% catalyst under acidic conditions that gave products in high yields with only minor formation of side products. ... 

Applications of POMs to catalysis have been periodically reviewed [33 0]. Several industrial processes were developed and commercialized, mainly in Japan. Examples include liquid-phase hydration ofpropene to isopropanol in 1972, vapor-phase oxidation of methacrolein to methacrylic acid in 1982, liquid-phase hydration of isobutene for its separation from butane-butene fractions in 1984, biphasic polymerization of THE to polymeric diol in 1985 and hydration of -butene to 2-butanol in 1989. In 1997 direct oxidation of ethylene to acetic acid was industrialized by Showa Denko and in 2001 production of ethyl acetate by BP Amoco. 

Two types of kinetics have been observed in the oxidation of 1,2-diols by periodate. The first of these, exemplified by ethane-1,2-diol, is of a mixed-order type, and is consistent with the reversible formation of the cyclic diester as an intermediate. The second type, exemplified by pinacol, is second-order kinetics, the reaction showing general acid-base catalysis and a complex dependence of rate on pH. 

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