By metal catalyzed

Dyrks, T., Dyrks, E., Hartmann, T., Masters, C.L. and Beyreuther, K. (1992). Amyloidogenicity of d A4 and /3 A4-bearing amyloid protein precursor fragments by metal-catalyzed oxidation. J. Biol. Chem. 267, 18210-18217. 

Synthetically important substitutions of aromatic compounds can also be done by nucleophilic reagents. There are several general mechanism for substitution by nucleophiles. Unlike nucleophilic substitution at saturated carbon, aromatic nucleophilic substitution does not occur by a single-step mechanism. The broad mechanistic classes that can be recognized include addition-elimination, elimination-addition, and metal-catalyzed processes. (See Section 9.5 of Part A to review these mechanisms.) We first discuss diazonium ions, which can react by several mechanisms. Depending on the substitution pattern, aryl halides can react by either addition-elimination or elimination-addition. Aryl halides and sulfonates also react with nucleophiles by metal-catalyzed mechanisms and these are discussed in Section 11.3. 

Interaction of an electrophilic carbene or carbenoid with R—S—R compounds often results in the formation of sulfonium ylides. If the carbene substituents are suited to effectively stabilize a negative charge, these ylides are likely to be isolable otherwiese, their intermediary occurence may become evident from products of further transformation. Ando 152 b) has given an informative review on sulfonium ylide chemistry, including their formation by photochemical or copper-catalyzed decomposition of diazocarbonyl compounds. More recent examples, including the generation and reactions of ylides obtained by metal-catalyzed decomposition of diazo compounds in the presence of thiophenes (Sect. 4.2), allyl sulfides and allyl dithioketals (Sect. 2.3.4) have already been presented. 

Figure 19.19 shows a plot of the results of such an assay done to determine the maleimide content of activated BSA. This particular assay used 2-mercaptoethanol which is relatively unaffected by metal-catalyzed oxidation. For the use of cysteine or cysteine-containing peptides in the assay, however, the addition of EDTA is required to prevent disulfide formation. Without the presence of EDTA at 0.1 M, the metal contamination of some proteins (especially serum proteins such as BSA) is so great that disulfide formation proceeds preferential to maleimide coupling. Figure 19.20 shows a similar assay for maleimide-activated BSA using the more innocuous cysteine as the sulfhydryl-containing compound. 

Schematic representation of carbon filaments of different structure produced by metal-catalyzed decomposition of methane, (a) Platelet structure, (b) "herringbone" structure, and (c) ribbon structure. MP denotes a nanosized metal particle.

Indoles can be formed by metal-catalyzed cyclizations of azobenzenes on disubstituted alkynes (Equation (106)). 

The synthesis of alcohols, ethers, and ketones by metal-catalyzed addition of water or alcohols to alkenes and alkynes is a well-established reaction in organic chemistry. Many regio- and stereoselective modifications of these reactions are known. In contrast, the analogous addition of ammonia or primary and secondary amines to nonactivated alkenes and alkynes has not had a comparable development, in spite of extensive efforts. In this section, we summarize the recent results of amination to unsaturated compounds. 

Synthesis of Phosphonium Salts by Metal-Catalyzed Addition Reaction... 

H. J. Dai, A. G. Rinzler, P. Nikolaev, A. Thess, D. T. Colbert, and R. E. Smalley, Single-wall nanotubes produced by metal-catalyzed disproportionation of carbon monoxide, Chem. Phys. Lett. 260, 471 75 (1996). 

The use of ethylene adduct lb is particularly important when the species added to activate catalyst la is incompatible with one of the reaction components. Iridium-catalyzed monoallylation of ammonia requires high concentrations of ammonia, but these conditions are not compatible with the additive [Ir(COD)Cl]2 because this complex reacts with ammonia [102]. Thus, a reaction between ammonia and ethyl ciimamyl carbonate catalyzed by ethylene adduct lb produces the monoallylation product in higher yield than the same reaction catalyzed by la and [Ir(COD)Cl]2 (Scheme 27). Ammonia reacts with a range of allylic carbonates in the presence of lb to form branched primary allylic amines in good yield and high enantioselectivity (Scheme 28). Quenching these reactions with acyl chlorides or anhydrides leads to a one-pot synthesis of branched allylic amides that are not yet directly accessible by metal-catalyzed allylation of amides. 

Besides a variety of other methods, phenols can be prepared by metal-catalyzed oxidation of aromatic compounds with hydrogen peroxide. Often, however, the selectivity of this reaction is rather poor since phenol is more reactive toward oxidation than benzene itself, and substantial overoxidation occurs. In 1990/91 Kumar and coworkers reported on the hydroxylation of some aromatic compounds using titanium silicate TS-2 as catalyst and hydrogen peroxide as oxygen donor (equation 72) . Conversions ranged from 54% to 81% with substituted aromatic compounds being mainly transformed into the ortho-and para-products. With benzene as substrate, phenol as the monohydroxylated product... 

The electrodeposition of cadmium sulfide thin films was carried out by the electroreduction of the aqueous thiocyanate complex of Cd(II). Formation of CdS is supposed to proceed by metal-catalyzed ligand reduction [179]. 

Li, S., T.H. Nguyen, C. Schoneich, and R.T. Borchardt, Aggregation and precipitation of human relaxin induced by metal-catalyzed oxidation. Biochemistry, 1995. 34(17) 5762-72. 

This paper presents the results of an investigation of the oxidation of substituted olefins in the presence of hydrocarbon-soluble transition metal complexes. Results indicate that the initial interaction of oxygen with the olefin probably does not occur within the coordination sphere of the metal. The best interpretation appears to be autoxidation of the olefin, initiated either by the metal or by metal catalyzed decomposition of peroxidic impurities. The initial product of an olefin having allylic hydrogens is an allylic hydroperoxide species this is usually the case in radical initiated autoxidations. Nonetheless, with some metal complexes the product profile differs markedly from that observed when radical initiators are used. In the presence of several complexes, oxidation is... 

Since the title compounds can be stereoselectively functionalized in the 1-position by metal-catalyzed nucleophilic substitutions of the acetoxy group, a great number of 1,4-disubstituted 2-cyclohexenes with defined 1,4-relative stereochemistry are available. 

Alper reaction. The Alper reaction corresponds to the ring expansion of azir-idines by metal-catalyzed CO insertion (Scheme 3). 

It has been suggested that D-arabino-hexos-2-ulose (205) is formed by metal-catalyzed autooxidation of glucose.410... 

Epoxide Formation from Ylides Prepared by Metal-catalyzed Carbene Formation... 

Fig. 11 Transition metal catalyzed in radical reactions based on the involved electron transfer steps, (a) Redox chain reactions by metal-catalyzed single electron transfer, (b) Coordinative radical reactions by metal-catalyzed single electron transfer...

The G-B bond of boronic esters is inert for functionalization of remote sites other than the B-G bond by metal-catalyzed reactions (Equations (98)-(100)). Gross-coupling reactions of 320478 and 321,479 and titanium-Wittig reaction on polymer resin 323480 have been studied. 

A9. Amici, A., Levine, R. L., Tsai, L., and Stadtman, E. R., Conversion of amino acid residues in proteins and amino acid homopolymers to carbonyl derivatives by metal-catalyzed oxidation reactions. J. Biol. Chem. 264, 3341-3346 (1989). 

Stadtman, E. R., Oxidation of free amino acids and amino acid residues in proteins by radiolysis and by metal-catalyzed reactions. Ann. Rev. Biochem. 62, 979-821 (1993). 

Marek I (2004) In de Meijere A, Diederich F (eds) Modern C-C and C-X bond formations by metal-catalyzed cross-coupling reactions. Wiley-VCH,Weinheim (in press)... 

Olefin alkylation, long carried out in solution with Bronsted acids, is now beginning to turn to the use of zeolites or other solid acid reagents under mild conditions. The main problem is removal of both the heat generated by the reaction and the carbon deposits. While the former problem can be solved by slurry reactor techniques, the latter requires a chemical treatment which is best carried out by metal-catalyzed hydrogenation at high temperature. 

Hydroxymethylation of organic halides can bt effected by metal-catalyzed cross-coupling with the Grignard reagent (diisopropoxymcthylsilyl)methylmagnesium chloride (1) followed by oxidation. This two-step process i- particularly useful for regio- and ster-eocontrolled conversion of vinyl halides into al.ylic alcohols and of allylic halides into homoallylic alcohols. ... 

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