Co-operative catalysis

Scheme 3 Co-operative catalysis leads to increased catalytic efficiency and enantioselectivity.

Wang and co-workers reported an enantioselective metal-organic catalyzed aerobic oxidative aza-Morita-Baylis-Hilman reaction between N-aiyl THIQs and electron-deficient olefins such as acrolein and acrylonitrile (Scheme 7.7). Under co-operative catalysis with Cu(OTf)2 and quinine, sp C-H olefination at the benzylic position of THIQs occurred to afford the... 

Scheme 7.7 A mmetric CDC alkenylation of Af-aiyl THIQs under metal-organic co-operative catalysis. MS4A = 4 A molecular sieve, EWG eleetron withdrawing group.

When the initial LA concentration is large, the quantity of substrate transferred to the aqueous phase allows the lipoxygenation to progress. This reaction consumes LA and produces HP, which favor the transfer of residual substrate between the two phases. Then catalysis and transfer have a reciprocal influence on each other. We demonstrated that the use of a non-allosteric enzyme in a compartmentalized medium permits the simulation of a co-operativity phenomenon. The optimal reaction rate in the two-phase system is reached for a high initial LA concentration 14 mM. Inhibition by substrate excess is observed in two-phase medium. 

Last but not the least we would like to thank Professor Delmon Advisory Editor, Studies in Surface Science and Catalysis Series, and Elsevier Publishing Company for their help and co-operation in bringing out this volume. 

G. G. Stanley, Bimetallic Hydroformylation Catalysis The Uses of Homobimetallic Co-operativity in Organic Synthesis , in M. G. Scaros, M. L. Prunier (editors). Catalysis of Organic Reactions, Marcel Dekker, New York, 1995, p. 363. 

The general emphasis in this work is to compare the reactivity and selectivity of function-bearing micelles in catalysis with their simple counterparts. TThe pattern of research has been guided by the analogy of enzymic catalysis, and surfactants carrying the common prosthetic groups of protease enzymes have been synthesized. Most studies have been concerned with acyl transfer from reactive esters, and several authors have sought to demonstrate co-operativity between different catalytic sites. 

Over the anode, the hydrogen and CO produced via reactions (1) and (2) are then oxidized at the anode by reacting with the oxygen species transported from the cathode. The catalysis of the fuel such as methane at the anode and oxygen at the cathode becomes increasingly important with demanding catalytic activity as the SOFC operation temperature decreases, which is the aim under intensive research efforts. 

Various other biphasic solutions to the separation problem are considered in other chapters of this book, but an especially attractive alternative was introduced by Horvath and co-workers in 1994.[1] He coined the term catalysis in the fluorous biphase and the process uses the temperature dependent miscibility of fluorinated solvents (organic solvents in which most or all of the hydrogen atoms have been replaced by fluorine atoms) with normal organic solvents, to provide a possible answer to the biphasic hydroformylation of long-chain alkenes. At temperatures close to the operating temperature of many catalytic reactions (60-120°C), the fluorous and organic solvents mix, but at temperatures near ambient they phase separate cleanly. Since that time, many other reactions have been demonstrated under fluorous biphasic conditions and these form the basis of this chapter. The subject has been comprehensively reviewed, [2-6] so this chapter gives an overview and finishes with some process considerations. 

Although suggested to operate by a mechanism analogous to Scheme 14, the case of the catalysis by the mononuclear complex Fe(CO)5 was proposed to be more limited.86,88 Relative to the Ru catalyst, the equilibrium constant for formation of the metallocarboxylic acid adduct, Fe(C0)4(C02H)-, was found to be several orders... 

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