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Transition-metal catalysis reduction

The model can also be extended to three-way catalysis as far the active site is a cation of transition metal, the reductant being CO and the feed CO/NO/HC being very near stoichiometry [10,11],... [Pg.172]

As shown in Figure 1.26, a chiral Sm(III) complex catalyzes asymmetric reduction of aromatic ketones in 2-propanol with high enantioselectivity. Unlike other late-transition-metal catalysis, the hydrogen at C2 of 2-propanol directly migrates onto the carbonyl carbon of substrate via a six-membered transition state 26A, as seen in the Meerwein-Ponndorf-Verley reduction. ... [Pg.22]

Ojima and co-workers first reported the RhCl(PPh2)3-catalyzed hydrosilylation of carbonyl-containing compounds to silyl ethers in 1972.164 Since that time, a number of transition metal complexes have been investigated for activity in the system, and transition metal catalysis is now a well-established route for the reduction of ketones and aldehydes.9 Some of the advances in this area include the development of manganese,165 molybdenum,166 and ruthenium167 complex catalysts, and work by the Buchwald and Cutler groups toward extension of the system to hydrosilylations of ester substrates.168... [Pg.250]

Our synthetic method for CO2 fixation was based on the use of transition-metal catalysis combined with electrochemical techniques [10]. Within this methodology, the electrochemical CO2 fixation into some alkenes has been reported to afford carbo lic acids in a reductive hydrocarboxylation-tjqje reaction catalyzed by nickel complexes, under mild conditions [11]. The electrocarboxylation of organic halides to the corresponding carboxylic acids has also been reported [12], yields and efficiency of the reaction being strongly dependent on the reaction conditions. [Pg.214]

Silylenes can be generated by photolysis, thermal decomposition of a suitable precursor molecule, by reduction of silylhalides, and by transition metal catalysis. Ever more unique and ingenious methods have been used to prepare such intermediates. Since this section is devoted to reactions at a Si(II) center, the means by which that center is created are not discussed in detail. However, a brief overview of the most common methods for generating such species follows. [Pg.304]

In our previous book on domino reactions [4h], we have classified domino reactions according to the mechanism of the different steps. This organizing principal will also be used in this book, and you will find chapters about transition metal catalysis including carbonylation, metathesis and CH-activation, nucleophiHc substitutions, radical reactions, pericyclic reactions, Michael reactions, aldol reactions, oxidations, and reductions. [Pg.2]

Turning to non-transition-metal catalysis, transition-state structures for the reduction of 2-methyl- and 2-isopropyl-cyclohexanone by LAH have been identified by DFT, and LUMO maps and NBO analysis have been used to examine the uneven distribution of the molecular orbital about the carbonyl r-plane, in order to explain the product ratio " substituent effects, the conformational ratio in the reactant, and... [Pg.48]

The possibilities for the formation of carbon-carbon bonds involving arenes have been dramatically increased in recent years by the use of transition metal catalysis. Copper-mediated reactions to couple aryl halides in Ulknann-type reactions [12, 13] have been known for many years, and copper still remains an important catalyst [14, 15]. However, the use of metals such as palladium [16,17] to effect substitution has led to such an explosion of research that in 2011 transition metal-catalyzed processes comprised more than half of the reactions classified as aromatic substitutions in Organic Reaction Mechanisms [18]. The reactions often involve a sequence outlined in Scheme 6.6 where Ln represents ligand(s) for the palladium. Oxidative addition of the aryl halide to the paiiadium catalyst is followed by transmetalation with an aryl or alkyl derivative and by reductive elimination to give the coupled product and legeuCTate the catalyst. Part 6 of this book elaborates these and related processes. [Pg.135]

The same effect has been observed in the case of an encapsulated organogold catalyst of cycloi-somerization of enyne 441 by Scheme 5.23, and it has been attributed [22] to the hydrophobic environment within the coordination capsule 575, preventing carbenium-ionic intermediates of the catalytic process from their side reactions with water. The same caging catalyst has been used in [23] to perform the combined enzymatic and transition metal catalysis of tandem reactions by Scheme 5.24. The authors of this work also developed a tandem olefin isomerization-reduction reaction by Scheme 5.25 with the encapsulated organoruthenium cation as a catalyst on its... [Pg.434]


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See also in sourсe #XX -- [ Pg.152 , Pg.153 ]




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