Stoichiometric relations

Mori has reported the nickel-catalyzed cyclization/hydrosilylation of dienals to form protected alkenylcycloalk-anols." For example, reaction of 4-benzyloxymethyl-5,7-octadienal 48a and triethylsilane catalyzed by a 1 2 mixture of Ni(GOD)2 and PPhs in toluene at room temperature gave the silyloxycyclopentane 49a in 70% yield with exclusive formation of the m,//7 //i -diastereomer (Scheme 14). In a similar manner, the 6,8-nonadienal 48b underwent nickel-catalyzed reaction to form silyloxycyclohexane 49b in 71% yield with exclusive formation of the // /i ,// /i -diastereomer, and the 7,9-decadienal 48c underwent reaction to form silyloxycycloheptane 49c in 66% yield with undetermined stereochemistry (Scheme 14). On the basis of related stoichiometric experiments, Mori proposed a mechanism for the nickel-catalyzed cyclization/hydrosilylation of dienals involving initial insertion of the diene moiety into the Ni-H bond of a silylnickel hydride complex to form the (7r-allyl)nickel silyl complex li (Scheme 15). Intramolecular carbometallation followed by O-Si reductive elimination and H-Si oxidative addition would release the silyloxycycloalkane with regeneration of the active silylnickel hydride catalyst. 

Product Formation It is important to check that the product formed is growth associated. Some products are formed after cell mass reaches the stationary phase of the growth cycle and, therefore, are not growth associated. The evolution of carbon dioxide can be measured and related stoichiometrically to the cell growth. One product that is quite general to many fermentations is the hydrogen ion. The amount of alkali added to the fermentation broth to maintain the pH may be proportional to the growth. 

A related stoichiometric cycloaromatization of enediyne involving a ruthenium vinylidene intermediate takes place in the presence of RuCl(Cp)(PMe3)2/ NH4PF6 but a radical process has been proposed [45]. 

Intermediate 2 can coordinate an additional alkyne (or olefin) to give 5 after insertion into the Ni-C bond (Scheme 7). Reductive elimination affords the corresponding cyclodecatriene derivative. Several related stoichiometric reactions with certain Ni complexes and alkynes or allene have been observed, thus confirming the proposed catalytic cycle (route ( )) [48] (eqs. (17) and (18)). 

Principle mechanisms of pyrone formation are summarized in Scheme 2. The probable pathway via Structures 10-11-12 is based on related stoichiometric reactions with model complexes [19] and X-ray structural investigations on precatalysts, and is consistent with the experimental details. In 11, the sp center next to nickel is suitable for the insertion of further alkynes, yielding the intermediate 12. Reductive elimination of the product 9 and addition of a further alkyne molecule closes the cycle. Analogous complexes to the intermediate 11 were shown to be versatile stoichiometric reagents for transformations to unsaturated acids and esters, by the groups of Hoberg, Dinjus, and Walther [20]. 

We first describe the standard heat of formation (AH/) and then the standard heat of combustion (AH ). The units of both quantities are usually tabulated as energy per mole, such as J/g mol, kJ/g mol, kcal/g mol, or Btu/lb mol. The per mole refers to the specified reference substance in the related stoichiometric equation. 

Aphotic zone oxygen consumption rates that, when vertically integrated, provide a net water column oxygen demand that can then be related stoichiometrically to a carbon export flux. 

While the scope is somewhat limited and the yields are only moderate, this process provides a very direct and convenient route to 2,3-disubstituted indenones that would be quite hard to prepare by most other procedures. Mechanistically, it is not clear if this reaction proceeds by addition of the vinylic palladium intermediate across the aldehyde moiety and subsequent p-hydride elimination, or whether the aldehyde C-H bond undergoes oxidative addition to the vinylic palladium intermediate and two subsequent reductive eliminations generate the final indenone product. Related stoichiometric arylpalladium compounds have been reported to react with alkynes to afford both indenones and indenols [109,130]. 

A similar complex could be isolated by the reaction of palladiumbis-(acetylacetonate) with two moles of triisopropyl phosphine and two moles of 6-lactone (Equation 7). By ring opening of the lactone a palladium complex with two long-chain carboxylate substituents was formed. It is remarkable that the same ring opening reaction which is discussed in the catalytic cycle could be observed in a related stoichiometric experiment. 

In contrast to each of the above variations, alkyl iodides may also be utihzed directly in nickel-catalyzed conjugate additions. The mechanism of this class of reactions is not well defined however, the related stoichiometric coupling of enals (e.g., 79) with alkyl halides (e.g., 78) has been demonstrated to proceed through nickel-Jt-aUyl intermediates.l The most widely used variant employs nickel(II) chloride hexahydrate in either catal)hic or stoichiometric quantities with activated zinc as a stoichiometric reductant (Scheme g2) [144-148] pjjg organic hahde may be either sp or sp hybridized, and alkene geometry in the final product (e.g., 80) is maintained with alkenyl iodides. 

Additionally, a rhodium-catalyzed silicon-assisted activation of a C-CN and C-Cl bond was reported in 2008. Under these catalytic conditions, carbon-cyano bonds in aryl, alkenyl, allyl, and benzyl cyanides bearing a variety of functional groups can be silylated. The observation of an enamine side product in the silylation of benzyl cyanides and related stoichiometric... 

The quantity of heat released or absorbed in a reaction is related stoichiometrically to the amounts (mol) of reactants and products. (Section 6.4)... 

Relating stoichiometric to site constants. Derive the relationship between stoichiometric-model binding constants Kj and Kz with site-model binding constants Ka... 

The main focus of this chapter is homogeneous catalysis which involves the cleavage of C-C=0 and C-CN bonds. Catalytic reactions are categorized in the following order (i) type of bond cleaved (ii) mechanism (oxidative addition, others, and unclear) and (iii) strategy (directed, non-directed, and others). Related stoichiometric reactions are also given when necessary. For catalytic reactions via decarboxylation of a-keto carboxylic acids, refer to Chapter 4. 

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