Mechanistic Insight

4 Effects of Chemical Doping Upon Physical Properties of 

2 BSCCO Films by CVD Using Fluorinated Metal-Organic Precursors. . 115 

1 CVD of TBCCO Thin Films on Single Crystal Substrates.121 

There are several possible mechanisms that have been proposed since the first report of nickel-catalyzed coupling of alkynes and a,P-unsaturated carbonyls. This section will briefly cover the metallacycle-based mechanism as it is generally considered in both the alkylative and reductive coupling manifolds. However, it should be emphasized that different variants may proceed via differing pathways. 

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Fukuzumi S. Catalysis on Electron Transfer and the Mechanistic Insight into Redox Reactions Bull. Chem. Soc. Jpn. 1997 70 1-28... 

NEW MECHANISTIC INSIGHT INTO THE ELECTROPHILIC BROMINATION OF OLEFINS... 

Site-Directed Mutagenesis Provides Mechanistic Insights... 

Although the mechanistic insights for the model complex of [FeFe] hydrogenase became clearer little by little, those for the [NiFe] hydrogenase are still challenging topics. 

Mechanistic Insight into the Decomposition of Oxygen-Rich Molecular Precursors... 

Reduction of Ketones and Enones. Although the method has been supplanted for synthetic purposes by hydride donors, the reduction of ketones to alcohols in ammonia or alcohols provides mechanistic insight into dissolving-metal reductions. The outcome of the reaction of ketones with metal reductants is determined by the fate of the initial ketyl radical formed by a single-electron transfer. The radical intermediate, depending on its structure and the reaction medium, may be protonated, disproportionate, or dimerize.209 In hydroxylic solvents such as liquid ammonia or in the presence of an alcohol, the protonation process dominates over dimerization. Net reduction can also occur by a disproportionation process. As is discussed in Section 5.6.3, dimerization can become the dominant process under conditions in which protonation does not occur rapidly. 

Mechanistic insight is a key to both discovery of new reactions and to their successful utilization in specific applications. Use of reactions in a synthetic context often entails optimization of reaction conditions based on mechanistic interpretations. Part A of this text provides fundamental information about the reactions discussed here. Although these mechanistic concepts may be recapitulated briefly in Part B, the details may not be included where appropriate, reference is made to relevant sections in Part A. In addition to experimental mechanistic studies, many reactions of... 

To gain mechanistic insight into the reduction of allylic alcohol 46, the reaction was monitored by measuring the hydrogen evolution and ReactIR3). The addition of 0.5 equiv of Red-Al resulted in the evolution of 2 mol of H2 and the formation of the dimeric intermediate 83 (Scheme 7.26) [19b, 30], Figure 7.2 shows the cumulative evolution of hydrogen (mmol) and the cumulative amount of Red-Al ... 

This work was supported by the National Science Foundation. J. J. S. thanks the Cornell Graduate School, Department of Education, and Franz Roessler Foundation for fellowships. The authors have benefited greatly from the detailed mechanistic insight provided through numerous discussions with Professor Paul Chirik. 

More recent studies, particularly with slower hafnium complexes, have provided more detailed mechanistic insight As a step polymerization, the reaction is "nonideal" in that inequivalent reactivities for different Si-H functional groups in the system are observed. For exaniple, disilanes tend to be more reactive than monosilanes. Beyond disilane formation, the preferred dehydrocoupling reaction appears to involve addition of one silicon at a time to the growing chain, via M-S1H2R intermediates (n = 1 above). The Si-Si bond-forming reactions are also reversible. 

Reactions of tc-excessive heteroaromatic compounds such as pyrroles, thiophenes and furans with carbenoids have been known for several years 6-10>u>. Recent activities were directed towards further synthetic applications of already known reactions, evaluation of the efficacy of novel catalysts and towards mechanistic insights. 

Fraser, C. S., and Doudna, J. A. (2006). Structural and mechanistic insights into hepatitis C viral translation initiation. Nat. Rev. Microbiol. 5(1), 29-38. 

Further mechanistic insights into hydrogenations catalyzed by HRuCl(PPh3)3 (7, p. 83) have been obtained indirectly, from studies on hydrogenation of some ruthenium(III) phosphine complexes (83). A frequently considered mechanism for hydrogen reduction of metal salts involves slow formation of an intermediate monohydride, followed by a faster reaction between the hydride and starting complex (/, p. 72), Eqs. (2) and (3) ... 

The results of studies employing CpFe(C0)2 complexes within Scheme 4 offer more mechanistic insight into the reaction chemistry of a,3-dialkoxyethyl complexes. One equivalent of LiHBEt3 thus reduced the a-ethoxy-6-methoxyethylidene salt 14a in THF (-80°), but the product corresponded to addition of one hydride— an a-ethoxy-6-methoxyethyl CpFe(C0)2 complex (16a). After pre-... 

More mechanistic insight into the C-H functionalization process of arenes is provided by theoretical and experimental studies. Multifluorinated, electron poor, aromatic substrates readily undergo CH activation with coordina-tively unsaturated rhenium complexes, attributed to the stronger C-Re bond in the product, whereas with monofluorinated analogs, the if -complex predominates (Equation (60)).61... 

Additional mechanistic insight into the reductive nitrosylation of ferri-heme proteins was obtained from kinetic studies carried out on aqueous solutions of Cytm, metMb, and metHb at various pH values (67). For example, Cytm undergoes reduction by NO to Cyt11 in aqueous solutions at pH values > 6.5. A hypothetical reaction mechanism is shown in Scheme 2 which would predict the rate law presented in Eq. (31) (67). 

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