Aerobic oxidative esterification

Aerobic Oxidative Esterification of Aidehydes with Aicohols The Evoiution from Pd-Pb intermetailic Catalysts to Au-NiO f Nanoparticle Catalysts for the Production of Methyl Methacrylate... 

I 13 Aerobic Oxidative Esterification of Aldehydes with Alcohols... 

Table 13.1 Catalytic activity for aerobic oxidative esterification of methacrolein (1) with methanol to form methyl methacrylate (2). i...

The Pd-Pb intermetallic catalyst and Au-NiO, nanoparticle catalyst developed and industrialized by Asahi Kasei are both unprecedented and unique aerobic oxidative esterification catalysts. We believe that three production processes - our oxidative esterification method (TEA to C4 isobutene hydrocarbon feedstock) in addition to the alpha process (C2 ethylene hydrocarbon feedstock) and the improved ACH process (C3 propene hydrocarbon to acetone feedstock see Chapter 7 in this book on the cumene-based phenol process) - will be competing for the top position in the global market as the MMA manufacturing method. 

Cinnamils (162) have surprisingly been found to evolve towards 2,3,8-triaryl vinyl fulvenes (163) and o-terphenyl derivatives (164) under NHC catalysis. The formation of these products has been rationalized via a mechanism involving a complex cascade process. Finally, a mechanistic investigation has been carried out on the NHC-catalysed aerobic oxidative esterification of aromatic aldehydes.Aryloin species have not only been identified as key intermediates of such oxidative reactions, but most importantly is that they have been shown to be the species which react with oxygen in the air and not the Breslow intermediates as previously suggested. 

It is convenient to consider the synthesis of vinyl acetate at this point, because it involves the aerobic oxidation of ethene to the unstable intermediate ethenol (H2C=CH(OH)), followed by its immediate esterification with acetic (ethanoic) acid,... 

The final oxidation step of the primary alcohol at C-l in L-Srb requires acetone protection, which is carried out in a standard textbook way in the presence of an excess of sulfuric acid. The oxidation at C-l has been accomplished in a number of ways [147] it seems that nowadays aerobic oxidation in the presence of palladium or platinum is preferred. Deprotection, requiring additional sulfuric acid, affords 2KLG, which is transformed into ASA via esterification and lac-tonization. Alternatively, the diacetone derivative of 2KLG can be converted directly into ASA by treatment with HC1 in an organic solvent. 

Palladium catalysts are widely used in liquid phase aerobic oxidations, and numerous examples have been employed for large-scale chemical production (Scheme 8.1). Several industrially important examples are the focus ofdedicated chapters in this book Wacker and Wacker-type oxidation of alkenes into aldehydes, ketones, and acetals (Scheme 8.1a Chapters 9 and 11), 1,4-diacetoxylation of 1,3-butadiene (Scheme 8.1b Chapter 10), and oxidative esterification of methacrolein to methyl methacrylate (Scheme 8.1c Chapter 13). In this introductory chapter, we survey a number of other Pd-catalyzed oxidation reactions that have industrial significance, including acetoxylation of ethylene to vinyl acetate (Scheme 8. Id), oxidative carbonylation of alcohols to dialkyl oxalates and carbonates (Scheme 8.1e), and oxidative coupling of dimethyl phthalate to 3,3, 4,4 -tetramethyl biphenylcarboxy-late (Scheme 8.1f). 

Oxidative esterification of arenes with carboxylic acids produces aryl esters, which can be used as precursors to valuable phenol derivatives (Scheme 8.6). Commercial production of phenol involves the aerobic oxidation of cumene to cumene hydroperoxide, followed by conversion to acetone and phenol under acidic conditions (Hock process) [49]. Aerobic acetoxylation of benzene to phenyl acetate provides a potential alternative route to phenol, and Pd-catalyzed methods for this transformation have been the focus of considerable effort. None ofthese methods are yet commercially viable, however. 

Isotopic-labeling experiments and evidence of a dimeric intermediate in the transition-metal-free aerobic oxidative C-C bond cleavage of a-hydroxy ketones and their esterification, on reaction with O2 as the ideal oxidant in the presence of K2CO3, have disclosed the reaction mechanism. ... 

Gorbanev, Y., Klitgaard, S., Woodley, J., et al. (2009). Gold-Catalyzed Aerobic Oxidation of 5-Hydroxymethylfurfural in Water at Ambient Temperature, Chemsuschem, 2, pp. 672-675. Casanova, O., Iborra, S. and Corma, A. (2009). Biomass into Chemicals One Pot-Base Free Oxidative Esterification of 5-Hydroxymethy 1-2-Furfural into 2,5-Dimethylfuroate with Gold on Nanoparticulated Ceria, J. Catal, 265, pp. 109-116. 

Glutamic acid is oxidized to completion by the kidney and liver cyclophorase suspensions of Green and co-workers. The oxidation proceeds by way of a-ketoglutarate, and the cyclophorase complex contains the enzymes necessary for the aerobic and anaerobic synthesis of glutamate from a-ketoglutarate and ammonia. The enzyme preparation is specific for L-glutamate D-glutamate appears to exert an inhibitory effect on the oxidation of the L-isomer. Phosphate esterification accompanies the oxidation. 

A mechanistic investigation of aerobic esterifications of aldehydes with alcohols using NHC catalysis indicates that it is the benzoin that undergoes oxidation, and not the Bres-low intermediate, nor the NHC-aldehyde tetrahedral adduct. ... 

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