Formation by oxidation

CV of solutions of lithium bis[ salicy-lato(2-)]borate in PC shows mainly the same oxidation behavior as with lithium bis[2,2 biphenyldiolato(2-)-0,0 ] borate, i.e., electrode (stainless steel or Au) passivation. The anodic oxidation limit is the highest of all borates investigated by us so far, namely 4.5 V versus Li. However, in contrast to lithium bis[2,2 -biphenyl-diolato(2-)-0,0 Jborate based solutions, lithium deposition and dissolution without previous protective film formation by oxidation of the anion is not possible, as the anion itself is probably reduced at potentials of 620-670 mV versus Li, where a... 

The acid 19 has been dimerized, although in low yield, in the course of a perhydro-phenanthrene synthesis [141]. When the oxidation potential of the double bond is sufficiently lowered by alkyl substituents, lactone formation by oxidation of the couble bond rather than of the carboxyl group occurs (Eq. 7) [142] (see also chap. 15). 

The individual steps of the multistep chemical reduction of COj with the aid of NADPHj require an energy supply. This supply is secured by participation of ATP molecules in these steps. The chloroplasts of plants contain few mitochondria. Hence, the ATP molecules are formed in plants not by oxidative phosphorylation of ADP but by a phosphorylation reaction coupled with the individual steps of the photosynthesis reaction, particularly with the steps in the transition from PSII to PSI. The mechanism of ATP synthesis evidently is similar to the electrochemical mechanism involved in their formation by oxidative phosphorylation owing to concentration gradients of the hydrogen ions between the two sides of internal chloroplast membranes, a certain membrane potential develops on account of which the ATP can be synthesized from ADP. Three molecules of ATP are involved in the reaction per molecule of COj. 

Irradiation of at longer wavelengths (>280 nm) provided phenyl formate (6) as a major volatile product, together with minor amounts of phenol and phenoxyacetone (4), as well as other products. A possible pathway for formation of phenyl formate by oxidation and subsequent cleavage is provided in Scheme III. Phenoxyacetic acid (7) was also identified as a minor product by mass-gc analysis. Photolysis of phenoxyacetone ( ) and phenoxyacetic acid (7)12 yields phenol together with photo-Fries products (also shown in Scheme III). 

Scheme 2.1-1. Hydropolyborate formation by oxidation of NaBH4. Anions in parentheses are possible intermediates.

Brown RC, Cascio C, Papadopoulos V. 2000. Pathways of neurosteroid biosynthesis in cell lines from human brain regulation of dehydroepiandrosterone formation by oxidative stress and beta-amyloid peptide. J Neurochem 74 ... 

Plate 16.1 a) Soil profile coloured by goethite (Ochrept, France), b) Soil profile coloured by hematite (Ultisol, Brazil), c) Soil profile coloured by lepidocrocite (Aquept, South Africa), d) Ferrihydrite formation by oxidation of Fe " in water seeping out of a Cley. 

The old method of SS bond formation by oxidative cyclization of the A-thioacyl thioureas (133) still remains in use (Scheme 31). At 20°C the sulfur atoms in (133) are substituted by Cl <81JGU1720, 82JIC663). The oxidation is also effected by metabolically in the mycelia of Pithium ultimum Trow <88MI413-01>. 

Much recent research (7-5) has been devoted to converting methane to products that are more easily transported and more valuable. Such more valuable products include higher hydrocarbons and the partial oxidation products of methane which are formed by either direct routes such as oxidative coupling reactions or indirect methods via synthesis gas as an intermediate. The topic of syngas formation by oxidation of CH4 has been considered primarily from an engineering perspective (7-5). Most fundamental studies of the direct oxidation of CH4 have dealt with the CH4 + O2 reaction system in excess O2 and at lower temperatures (6-10). 

N—O bond formation by oxidative procedures has found less application. However, the 1,2,4-oxadiazole system (450) can be prepared by the action of sodium hypochlorite on N-acylamidines (449) (76S268). 

Other Oxidations. Glycol formation by oxidation of styrene [75], as well as oxidation of prochiral phosphines to the optically active phosphine oxides [76] by chiral PTC, gave only low asymmetric inductions. 

Conditions of recovery of the polymer from the latex must be controlled strictly to avoid modifying the copolymer structure (mainly crosslinking and consequent gel formation by oxidation). A partially soluble polymer can be studied by selective extraction, but experience shows that extraction conditions favor crosslinking and/or degradation. Thus results obtained by extraction must be accepted very cautiously. 

The rather unstable D-t/ reo-2,5-hexodiulosonic acid was obtained by the oxidation of D-glucose with Acetobacter melanogenum.280 2,3-Diulosonic acids are formed by oxidation of L-ascorbic acids (see Section II.5), and their formation by oxidation with hydrogen peroxide is discussed in the following chapter. 

In a general sense, the Reformatsky reaction can be taken as subsuming all enolate formations by oxidative addition of a metal or a low-valent metal salt into a carbon-halogen bond activated by a vicinal carbonyl group, followed by reaction of the enolates thus formed with an appropriate electrophile (Scheme 14.1).1-3 The insertion of metallic zinc into a-haloesters is the historically first and still most widely used form of this process,4 to which this chapter is confined. It is the mode of enolate formation that distinguishes the Reformatsky reaction from other fields of metal enolate chemistry. 

Scheme 1. The essentials of biaryl formation by oxidative coupling of arenes.

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