Alcohols dehydrogenative functionalization

Processes that enable direct catalytic C-C functionalization of carbinol C-H bonds are highly uncommon. Rh-catalyzed alcohol-vinylarene C-C coupling has been described. The requirement of BF3 and trends in substrate scope suggest these processes involve alcohol dehydrogenation-reductive Prins addition [26-29]. 

Direct Dehydrogenative Functionalization of Alcohols 3.1 Facile Conversion of Alcohols into Esters and Dihydrogen... 

Oxoreductases include enzymes such as dehydrogenases, oxidases and peroxidases which catalyse transformations such as oxidation of alcohols to carbonyls and dehydrogenation of functionalized alkanes to alkenes. 

The alcoholate is either dehydrogenated via (3-CH activation to afford an M-OH function and a hydrido (olefin) metal species or, to a minor extent, converted to alcohol. The hydrido (olefin) metal species can release 1-alkenes. The route toward alcohol is regarded as reversible, and thus allows the incorporation of co-fed alcohol, causing initiation of the FT synthesis via the alcoholate and the C,O-bridging aldehyde... 

The enzyme isocitrate dehydrogenase is one of the enzymes of the Krebs or citric acid cycle, a major feature in carbohydrate metabolism (see Section 15.3). This enzyme has two functions, the major one being the dehydrogenation (oxidation) of the secondary alcohol group in isocitric acid to a ketone, forming oxalosuccinic acid. This requires the cofactor NAD+ (see Section 11.2). For convenience, we are showing non-ionized acids here, e.g. isocitric acid, rather than anions, e.g. isocitrate. 

The resulting tertiary alcohol is then dehydrated and the ketone at 11 reduced to an alcohol by means of lithium aluminium hydride to give the intermediate (22-1). The acetal is next removed by exchange with acetone in the presence of a dilute acid. The requisite 1,4-diene functionality is then put in place by dehydrogenation... 

A gold monohydride species was also suggested in the report by Ito and Sawamura et al. on the dehydrogenative silylation of alcohols by HSiEt3 and a diphosphine gold(I) complex. Reaction was selective for the silylation of hydroxy groups in the presence of alkyl halides, ketones, aldehydes, alkenes, alkynes and other functional groups [193]. 

Dehydrogenases often act primarily to reduce a carbonyl compound rather than to dehydrogenate an alcohol. These enzymes may still be called dehydrogenases. For example, in the lactic acid fermentation lactate is formed by reduction of pyruvate but we still call the enzyme lactate dehydrogenase. In our bodies this enzyme functions in both directions. However, some enzymes that act mainly in the direction of reduction are called reductases. An example is aldose reductase, a member of a family of aldo-keto reductases71 73 which have (a / P)8-barrel structures.74 76... 

In A, a Raney copper catalyst would be able to hydro-dehydrogenate alcoholic functions (-H, +H) on metallic copper sites. About 10 to 15% of the copper would be hydroxylated copper able to catalyze the degradation reactions DOH, RC, RM. These sites would be more reactive than Cu towards Mn + in the oxido-reduction modification of the initial Raney copper, so that, beeing first exchanged, the rates of DOH, RC, RM decrease. 

Interpretation of the optimum metal content for these reactions. As already mentioned an optimum Pt content was found for dehydrogenation of liquid alcohols and cyclopentane-deuterium exchange in gas phase. Also, with Pt/Ti02 samples which had not been preoxidized and which were accordingly non-stoichiometric according to conductivity measurements, the same optimum content was found for the initial rate of OIE, whereas this rate decreased as a function of Pt content for preoxidized samples (44). 

Lack of congruence of function and structure A common reaction catalyzed by two enzymes does not imply a common structure or sequence Dehydrogenation is the reaction common to alcohol DH from horse liver (HLADH) and alcohol DH from yeast (YADH), but they have neither a common structure nor a common sequence. 

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