Other Hydrogen Transfer Reactions

A few remarkable, but rather uncommon, transfer hydrogenations also deserve mention within the context of this chapter namely, the reduction of alkynes to alkenes using a chromium catalyst, and the reduction of double bonds using diimines. 

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Ru(II), Ru(I) and Ir(I) in an aqueous medium (90). Data for the different complexes are shown in Table II. The highest conversion is observed with the ruthenium(II) complexes, which correlates with the facility of Ru complexes to catalyze other hydrogen transfer reactions. The complex PdCl2(TPPMS)2 has been used as a two-phase aqueous-organic catalyst for the carbonylation of allylic chlorides (Eq. 30) 91). The reaction pro-... 

Other hydrogen transfer reactions of glycine derivatives have been used to introduce functional groups at the a-position. For example, reactions with bromine or A -bromosuccinimide, fert-butyl perbenzoate in the presence of a copper catalyst, and tert-butyl hydroperoxide and formate, have been used to produce a-bromo-, benzoyloxy- and carboxy-substituted glycine derivatives, respectively (Scheme 2) [12-14]. 

For other hydrogen-transfer reactions, satisfactory ab initio potential energy surfaces [115, 116] and approximate quantum trajectory calculations of isotope effects [136] are also available in a few instances, but for the most part experimental measurements have been compared with values calculated on the basis of empirical or semi-empirical potential surfaces, making use of transition-state theory, and discussion has centred on the pros and cons of the surface used and the type of tunnelling correction made [3, 19]. 

Cracking, isomerization, and hydrogen transfer reactions account for the majority of cat cracking reactions. Other reactions play an important role in unit operation. Two prominent reactions are dehydrogenation and coking. 

The hydrogen-transfer reaction (c) from one ligand X to the other ligand Y is often utilized when chelating ligands have to be bonded to tin. The leaving group HY... 

For the hydrogen transfer reactions, the substrate (0.100 g, 0.64 mmol) was dissolved in anhydrous n-heptane (8 mL) and the solution transferred under N2 into a glass reaction vessel where the catalyst (0.100 g) had been previously treated. Catalytic tests were carried out with magnetic stirring under N2 at boiling point temperature with 2-propanol and 90°C or 140°C with other donor alcohols. 

Other than hydrogen transfer reactions, catalytic applications of Cp lr complexes for the deuteration of organic molecules [81-84], asymmetric Diels-Alder reactions [85, 86],... 

Molecular hydrogen is not the only source of hydrogen since other molecules such as alcohols can also be used as a hydrogen source. In that case, one refers to hydrogen-transfer reactions. In the hydrogen-transfer processes, a donor species DH2 transfers two hydrogen molecules to an acceptor species A (Scheme 3). 

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