Catalytic reactions involving alcohols

Strictly related to catalytic reactions involving CO and H20 are reactions in which CO and alcohols, ROH, or CO and amines, R2NH, are used as building blocks. The catalytic addition of carbon monoxide and an alcohol to an olefin yields carboxylic esters (hydroesterification). Thus, the synthesis of methyl propionate from ethylene, CO, and methanol using a catalytic system composed of Ru3(CO)u and [PPh4]I (190°C, 20 bar C2H4, 45 bar CO, 2.5 hr, yield 74%, CT 1000) has been reported (323) ... 

Catalytic reactions involving secondary alcohols on metal oxides are thought to proceed through mechanisms involving a cooperative action of acidic and basic sites. For the studied zeolites, a quasi-linear correlation was established between the alkene selectivities and the ratio of basic to acidic sites, as determined by adsorption calorimetry (Figure 13 see also Figure 6). 

The TT-allyl complex thus generated is of prime interest since its reactivity toward nucleophiles can provide a catalytic route to a whole class of molecules. This feature was essential for the discovery of catalytic reactions involving the acylpalladation of allenes as a key step. First, y-allenyl alcohols react with aryl halides under carbonylative conditions at 65 °C to form furans in a 24-89% yield range, typically 50-89% yields (Scheme... 

The majority of catalytic enantioselective allylation reactions involve the chiral Lewis-acid-catalysed additions of allylsilanes or allylstannanes to carbonyl compounds. Monothiobinaphthol has been used by Woodward et al. as a chiral promoter in the enantioselective catalytic allylation of aryl ketones with impure Sn(allyl)4, prepared from allyl chloride, air-oxidised magnesium and SnCl4. Therefore, the allylation of arylketones in these conditions was achieved very efficiently, since the corresponding allylic alcohols were formed in... 

Oxidations Using Oxoammonium Ions. Another oxidation procedure uses an oxoammonium ion, usually derived from the stable nitroxide tetramethylpiperidine nitroxide, TEMPO, as the active reagent.31 It is regenerated in a catalytic cycle using hypochlorite ion32 or NCS33 as the stoichiometric oxidant. These reactions involve an intermediate adduct of the alcohol and the oxoammonium ion. 

The original medicinal chemistry synthesis of ether 18 involved reaction of alcohol 10 with racemic imidate 17 in the presence of a catalytic amount of TfOH and furnished an approximately 1.1 1 mixture of 18 19 (Scheme 7.3) [1], We thought it worthwhile to reinvestigate this reaction with chiral imidate 67 in an effort to explore the diastereoselectivity of the etherification. 

The applications of polyoxometalates in catalytic dehalogenation of halocar-bons have been succinctly reviewed by Hill and coworkers [188]. This reaction involves the photocatalytic transformation of organic halides coupled with the oxidation of sacrificial organic reductants (secondary alcohols or tertiary amides) (Eq. (9)) [189, 190] ... 

Finally, we note that all transfers to alcohol-water mixtures or additions of alcohol to crystal mother liquor involve changes in the proton activity of the solution. Care must be taken to ensure that the pH does not change too much, or the crystal may be disrupted. Worse still, the enzymatic activity may be abolished. Control of proton activity in mixed solvents is discussed in Section III,D. If dielectric effects are controlled and pH is properly adjusted, the microenvironment of a crystalline protein will correspond closely to that of aqueous solution at room temperature. Such correspondence is essential for temporal resolution of individual steps in a catalytic reaction. 

In this volume the editors are presenting a set of what they believe are recent outstanding developments which concentrate heavily on mechanisms involved in several different classes of catalytic reactions Isomerization of olefins (M. Orchin), dehydration of alcohols (H. Pines and J. Manassen), hydrogen exchange (J. L. Garnett and W. A. Sollich-Baumgartner), and hydrogenation of unsaturated hy-... 

The involvement of transition-metal allenylidene complexes in homogeneous catalysis was reported for the first time by B. M. Trost and co-workers in 1992 (Scheme 35) [293-295]. The catalytic reactions allowed the preparation of a wide variety of tetrahydropyranyl and furanyl p,y-unsaturated ketones starting from hydroxy-functionalized alkynols and allylic alcohols, the key step in the catalytic... 

Metal-catalyzed substitution reactions involving propargylic derivatives have not been studied in much detail until recently [311, 312]. In this context, the ability shown by transition-metal allenylidenes to undergo nucleophilic additions at the Cy atom of the cumulenic chain has allowed the development of efficient catalytic processes for the direct substitution of the hydroxyl group in propargylic alcohols [313]. These transformations represent an appealing alternative to the well-known and extensively investigated Nicholas reaction, in which stoichiometric amounts of [Co2(CO)g] are employed [314-317]. 

In another example, a catalytic amount of cerium triflate hydrate was dispersed and isolated in [BMIMJPFg for the direct formation of tetrahydropyranol derivatives. The reaction involves a simple homoallyl alcohol and an aldehyde. When an organic solvent such as chloroform was employed, an undesired ether derivative formed as the major product. In the ionic liquid, however, the desired tetrahydropyranol was exclusive. Although the yield was moderate, this example constitutes the first relatively facile and direct formation of the synthetically useful pyranol derivative the only effective catalyst reported is the ionic liquid (168). 

Trust s group has shown that another selective reaction involving C—O bond formation followed by rearrangement and C—C bond formation occurred when Cp-containing ruthenium complexes were used as catalytic precursors. With RuCl(Cp)(PPh3)2 in the presence of NH4PF6, an additive known to facilitate chloride abstraction from the metal center, the addition of allylic alcohols to terminal alkynes afforded unsaturated ketones [46, 47]. It has been shown that the key steps are the... 

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