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Redox neutral

Redox initiation, in aqueous dispersion polymerization, 11 197—198 Redox neutral atmosphere, 14 84 Redox potentials, of plutonium in acid,... [Pg.793]

Hence, in a broader-sense TT may be utilized in a number of reactions with greater efficacy, for instance complexation, precipitation, redox, neutralization. Further, TT can be used to titrate gases against other gases devoid of a liquid-phase and to titrate liquid solutions with gaseous reagents. [Pg.200]

In analogy with acid-base neutrality at pH = 7, we can also define redox neutrality through the molecular dissociation process ... [Pg.545]

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]. [Pg.296]

A second basic interaction pathway between transition metal complexes and organic substrates is SET (Path B). The overall processes can involve one individual or several sequential SET steps. For the latter, timing and direction of SET steps determine the reaction outcome significantly. The catalyzed reaction can proceed either as redox-neutral processes, in which oxidative and reductive SET steps are involved in the catalytic cycle, or as overall oxidative or reductive catalytic reactions, where two oxidative or reductive SET steps occur consecutively in the catalytic cycle. The third pathway (Path C) consists of a direct atom or group abstraction by the metal complex, which is possible for a weak R-X bond. [Pg.123]

Heck reaction (Redox-neutral radical addition) 1 Ti(II) 3.2... [Pg.181]

Radical cyclization (Redox-neutral, Heck-type) 1 Mn(0) 9.2... [Pg.182]

Abstract This review summarizes the current status of transition metal catalyzed reactions involving radical intermediates in organic chemistry. This part focuses on radical-based methods catalyzed by group 8 and group 9 metal complexes. Reductive and redox-neutral coupling methods catalyzed by low-valent metal complexes as well as catalytic oxidative C-C bond formations are reviewed. [Pg.191]

Ethanol production is essentially redox neutral however metabolism associated with biomass production generates nett NADH, which is oxidised largely by glycerol production. Other important NADH oxidising reactions with flavour implications are the production of 2,3-butanediol, L-malic acid and succinic add. When glycerol production is stimulated by non-growth associated reactions (i.e. osmotic stress) NAD+ reduction occurs by other reactions including the oxidation of acetaldehyde to acetic acid... [Pg.324]

Stability and multitude/diversity of metal-ligand bonds which can be formed by some metal ion in redox-neutral to oxidizing aqueous media and its biocatalytic feasibility and thus possible essentiality are linked to each other. [Pg.150]

The products of bioreactions can be reduced or oxidized, and all feasible pathways have to be redox neutral. There are several cofactors that transfer redox power in a pathway or between pathways, each equivalent to the reducing power of a molecule of H2, e.g., nicotinamide adenine dinucleotide (NADH), and these have to be included in the stoichiometric balances as H equivalents through redox balancing. For instance, for the reaction of glucose to glycerol (CHs/30), j NADH equivalent is consumed ... [Pg.31]

Scheme 1 Reaction of methylcobalamin in aqueous media (a) and (b) reduction of cobalt, (c) redox-neutral reaction (CH transfer Co(lll) —> Hg(ll)). Scheme 1 Reaction of methylcobalamin in aqueous media (a) and (b) reduction of cobalt, (c) redox-neutral reaction (CH transfer Co(lll) —> Hg(ll)).
Abstract Progress in the field of metal-catalyzed redox-neutral additions of oxygen nucleophiles (water, alcohols, carboxylic acids, and others) to alkenes, alkynes, and allenes between 2001 and 2009 is critically reviewed. Major advances in reaction chemistry include development of chiral Lewis acid catalyzed asymmetric oxa-Michael additions and Lewis-acid catalyzed hydro-alkoxylations of nonacti-vated olefins, as well as further development of Markovnikov-selective cationic gold complex-catalyzed additions of alcohols or water to alkynes and allenes. [Pg.123]

The synthesis of oxygen-frmctionalized products by conceptually simple redox-neutral heterofunctionalizations from simple and abrmdant precursors is a challenge for catalysis development. [Pg.151]

Causey, T.B, Zhou, S., Shanmugam, K.T., and Ingram, L.O. (2003) Engineering the metabolism of Escherichia coli W3110 for the conversion of sugar to redox-neutral and oxidized products homoacetate production. Proc. Nad. Acad. Sci. USA., 100, 825-832. [Pg.174]

Figure 2. Redox cofactor requirement in L-arjabinose catabolism. L-Arabinose conversion to equimolar amounts of CO2 and ethanol is redox neutral, i- -anaerobic fermentation to ethanol should be possible. However, the conversion of L-arabinose to D-xylulose requires NADPH and NAD and produces NADH and NADP. NADPH is mainly regenerated in the oxidative part of the pentose phosphate pathway, where the reduction ofNADP is coupled to C02 production. The abbreviations are G6p, glucose 6-phosphate F6P, fructose 6-phosphate X5P, D-Xylulose 5-phosphate GAP, D-glyceraldehyde 3-phosphate. (Reproduced from Ref. 165 with permission from Elsevier Science)... Figure 2. Redox cofactor requirement in L-arjabinose catabolism. L-Arabinose conversion to equimolar amounts of CO2 and ethanol is redox neutral, i- -anaerobic fermentation to ethanol should be possible. However, the conversion of L-arabinose to D-xylulose requires NADPH and NAD and produces NADH and NADP. NADPH is mainly regenerated in the oxidative part of the pentose phosphate pathway, where the reduction ofNADP is coupled to C02 production. The abbreviations are G6p, glucose 6-phosphate F6P, fructose 6-phosphate X5P, D-Xylulose 5-phosphate GAP, D-glyceraldehyde 3-phosphate. (Reproduced from Ref. 165 with permission from Elsevier Science)...
Fig. 5 Redox-neutral cleavage of model p-aryl ethers... Fig. 5 Redox-neutral cleavage of model p-aryl ethers...
The general process of a C(sp )—H bond functionalization through [l,5]-hydride transfer is illustrated by a model reaction shown in Scheme 4.1. The typical substrate 1 in this type of reaction usually has both a hydride donor moiety and a hydride acceptor moiety. A [l,5]-hydride transfer process generates a zwitterionic intermediate which undergoes subsequent cycliza-tion readily, yielding the desired C—C or C—X bond-forming product. The key features of the reaction include (1) the reaction is redox neutral, thus no external oxidant is required (2) the reaction is waste minimized in that all atoms in the starting material are present in the final product. In this context,... [Pg.126]

This chapter highlights the recent advances in the area of catalytic asymmetric [l,5]-hydride transfer reactions which have recently emerged as an alternative mediod for the direct functionalization of the C(sp )—H bonds. The intramolecular hydride transfer nature renders the reaction to be a redox-neutral process, thus preventing the use of an external oxidant. The readily occurrence of... [Pg.138]

The Bode group documented detailed research on the asymmetric NHC-catalyzed annulation reaction of ynals and stable enols (kojic acid) to afford enantioenriched dihydropyranone products in excellent yields. Mechanistically, the key a,p-unsaturated acyl azolium intermediate was accessible via an NHC-catalyzed redox neutral reaction of ynals. The annulation occurs via... [Pg.337]

The redox-neutral approach to sp C—H functionalization 13CEJ13274. Regioselective Suzuki—Miyaura reactions of (hetero) aromatic bis-triflates Electronic versus steric effects 13SL412. [Pg.203]

An enantioselectlve redox-neutral domino reaction catalysed by gold(I) occurs allowing functionalization of unreactive sp C—H bonds and furan-fused azepines with high enantioselectivities (Scheme 124). ... [Pg.521]

Transaminases (also termed amino transferases [EC 2.6.l.X]) catalyze the redox-neutral amino-transfer reaction between an amine donor and a carbonyl group serving as acceptor (Scheme 2.225) [94, 1707-1712]. These enzymes require an activated benzaldehyde (pyridoxal-5 -phosphate, PLP, vitamin Bg) as cofactor, which functions as a molecular shuttle for the transfer of the NHa-moiety. In a first step, PLP forms a ketimine Schiff base with the amine-donor. Tautomerization of the C=N bond yields an aldimine, which is hydrolyzed to yield the cofactor in its aminated form (pyridoxamine, PMP). The latter reacts through the same order of events with the carbonyl group of the substrate to form the amine product and... [Pg.254]


See other pages where Redox neutral is mentioned: [Pg.36]    [Pg.545]    [Pg.119]    [Pg.448]    [Pg.181]    [Pg.211]    [Pg.176]    [Pg.35]    [Pg.136]    [Pg.310]    [Pg.125]    [Pg.151]    [Pg.241]    [Pg.423]    [Pg.111]    [Pg.175]    [Pg.183]    [Pg.632]    [Pg.646]    [Pg.424]    [Pg.372]   


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