Coupling, of alcohols

Hydrolysis of epoxides Coupling of alcohols Hydroxylation of alkenes... 

Coupling of Alcohols to Ethers the Dominance of the Surface Reaction Pathway ... 

These experiments demonstrate that the surface-catalyzed 2 reaction is far more effident than either the or C pathway for the dehydrative coupling of alcohols over the solid add catalysts tested. High selectivity to configurationally inverted chiral ethers ensues, espedally in the case of the HZSM-5 catalyst, in which the minor C or C paths were further suppressed by "bottling" of 3-ethoxypentane by the narrow zeolite chaimels. 

All evidence presented herein points to the generality of the 8 2 path for the surface add-catalyzed coupling of alcohols to ethers. The prc uct composition, the flow from reactants to products, and chirality inversion demonstrate convincingly that mechanistic patterns of the reaction including otygen retention, steric hindrances due... 

Conclusive evidence has been presented that surface-catalyzed coupling of alcohols to ethers proceeds predominantly the S 2 pathway, in which product composition, oxygen retention, and chiral inversion is controlled 1 "competitive double parkir of reactant alcohols or by transition state shape selectivity. These two features afforded by the use of solid add catalysts result in selectivities that are superior to solution reactions. High resolution XPS data demonstrate that Brpnsted add centers activate the alcohols for ether synthesis over sulfonic add resins, and the reaction conditions in zeolites indicate that Brpnsted adds are active centers therein, too. Two different shape-selectivity effects on the alcohol coupling pathway were observed herein transition-state constraint in HZSM-5 and reactant approach constraint in H-mordenite. None of these effects is a molecular sieving of the reactant molecules in the main zeolite channels, as both methanol and isobutanol have dimensions smaller than the main channel diameters in ZSM-S and mordenite. 

Iridium NHC complexes have also been used to catalyse the coupling of alcohols 7 and 8. Complexes 12 [4] and 13 [5], containing chelating NHC ligands, are also effective for catalysing the same reaction. 

Compared with ketoreductases, the synthetic application of alcohol oxidases has been less explored. However, selective oxidation of primary alcohols to aldehydes is superior to the chemical methods in terms of conversion yields, selectivity, and environmental friendliness of reaction conditions. In addition, coupling of alcohol oxidase with other enzymes provides a tremendous opportunity to develop multi-enzyme processes for the production of complex molecules. Therefore, a growing impact of alcohol oxidases on synthetic organic chemistry is expected in the coming years. 

Acetals result from oxidative coupling of alcohols with electron-poor terminal olefins followed by a second, redox-neutral addition of alcohol [11-13]. Acrylonitrile (41) is converted to 3,3-dimethoxypropionitrile (42), an intermediate in the industrial synthesis of thiamin (vitamin Bl), by use of an alkyl nitrite oxidant [57]. A stereoselective acetalization was performed with methacrylates 43 to yield 44 with variable de [58]. Rare examples of intermolecular acetalization with nonactivated olefins are observed with chelating allyl and homoallyl amines and thioethers (45, give acetals 46) [46]. As opposed to intermolecular acetalizations, the intramolecular variety do not require activated olefins, but a suitable spatial relationship of hydroxy groups and the alkene[13]. Thus, Wacker oxidation of enediol 47 gave bicyclic acetal 48 as a precursor of a fluorinated analogue of the pheromone fron-talin[59]. 

Other methods that have been less regularly used are the dehydration of alcohols with dimethyl sulfoxide to form symmetrical ethers, the photochemical transformation of benzylic chlorides with fert-butyl alcohol, or radical reactions of hcxafluoroacetone with alkanes, Mercury acetate promoted couplings of alcohols with vinyl acetate or vinyl ethyl ether to form vinyl... 

Reductive coupling of alcohols, van Tamelen and Schwartz used the reagent in the reductive coupling of an alcohol to form a hydrocarbon 2 ROH— RR. The alcohol is converted by means of sodium hydride into the alkoxide (1), and this is... 

Ruthenium carbonyl catalyzes the oxidative coupling of alcohols to esters via hydrogen transfer to diphenylacetylene, chalcone, or maleic anhydride... 

When methanesulfonyl chloride was allowed to react with 2,3,4,6-tetra-O-ben-zylglucopyranose and collidine in dichloromethane, the a-glucopyranosyl chloride was isolated regardless of whether the quaternary ammonium bromide was included. Addition of methanol to the reaction mixture resulted in the formation of an anomeric mixtiue of methyl glycosides. Similar results were obtained with toluenesulfonyl chloride, although it was noted that the initial sulfonylation was somewhat slower [8,9]. The use of tosyl chloride in the dehydrative coupling of alcohols with pyranoses was later revisited by Szeja and his coworkers, with the difference that aqueous... 

EFFICIENT PRODUCTION OF DR5P FROM GLUCOSE AND ACETALDEHYDE VIA FDP BY COUPLING OF ALCOHOLIC FERMENTATION SYSTEM OF BAKER S YEAST AND DEOXYRIBOALDOLASE-EXPRESSING E. COLI... 

Nearly forty years ago, Castells et al reported the first use of NHCs in a redox process for the synthesis of esters from the oxidation of aldehydes in the presence of nitrobenzene.More recently, Rovis and Bode independently reported the catalytic coupling of alcohols and aldehydes to produce a variety of esters and a-hydrojy esters.Allqmyl aldehydes were shown to react in these conditions to provide esters via a redox process, as Zeitler disclosed in 2006. " The utility of NHCs in redox reactions was expanded by Vora and Rovis with the synthesis of amides. Thioesters can also be produced under similar conditions and other redox processes such as isomerisation of esters to aromatic aldehydes can occur. ... 

Further improvement in the reaction was possible by exclusion of the need for base. Thus, reaction of complex 7 with KO Bu resulted in the formation of the coordinatively unsaturated, 16e Ru(ll) neutral complex 8. Indeed, 8 is an excellent catalyst for the dehydrogenative coupling of alcohols to esters and the reaction proceeds with liberation of Hj under neutral conditions [llj. Table 1.2 provides a few examples. GC analysis of the reaction mixtures indicated that aldehydes were formed only in trace amounts. This catalytic reaction provided a new green pathway for the synthesis of esters directly from alcohols. Considerably less efficient methods had been reported previously for this transformation [34]. 

Table 1.2 Examples of dehydrogenative coupling of alcohols to form esters and dihydrogen catalyzed by dearomatized Ru PNN complex 8.

A nickel-catalysed coupling of alcohols and allgmes to form allylic alcohols was also reported (Scheme 14.64). The combination of Ni(COD)2 and IPr is an effective catalyst and no additives are needed. Both aliphatic and benzylic alcohols are suitable for this transformation. The reaction proceeds smoothly under mild conditions, generating allylic alcohols in good )delds. 

An iridium-mediated synthesis of pyrroles 17 was reported which was enabled by the development of Ir catalyst 18. This method allows for the smooth coupling of alcohols 16 and amino alcohols 15 through a dehy-drogenative process. Detailed mechanistic studies were conducted to identify all of the intermediates, side-products, and by-products of the reaction. It was proven that the catalytic cycle is base-promoted and hydrogen transfer shuttles are active in the system. It is important to note that this reaction can also be carried out under Ru catalysis albeit with lower reactivity (14JA4974). 

Feng J, Garza VJ, Krische MJ (2014) Redox-triggered C-C Coupling of alcohols and vinyl epoxides diastereo- and enantioseiective formation of all-carbon quaternary centers via tert-(hydroxy)-prenyiation. J Am Chem Soc 136 8911-8914... 

The cyclitol doived glycoconjugate analogue 122 has been prepared by Lewis add promoted coupling of alcohol 123 with epoxide 112 followed by dil droxylation and removal of the protecting... 

Reagent 1 has been utilized to promote the couplings of alcohols and carboxylic acids, phenols, phthalimide, thiazolidi-nedione, and sulphonamides. The compound has gained... 

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