Ketone functionalised complexes

Ketone functionalised carbenes were introduced by Yu et al. [220] and Ketz et aZ. [221 ]. Yu et al. used the carbene transfer method via the silver(I) carbene complex, although free carbenes with acidic methylene groups (i.e. enolisable ketones) can be isolated [222]. The respective rhodium(l) carbene complex is isostructural to the one synthesised by Herrmann et al. featuring an ester functionalised carbene (see Figure 3.76). 

Figure 5.11 Structure and luminescence spectrum of coumarin-DTPA Eu complex [61] structure of Michler ketone, functionalised dipicamide [74] and bis-pyrazolyl-triazine ligands [75-77]...

The Rh-catalysed asymmetric hydrosilylation of prochiral ketones has been studied with complexes bearing monodentate or heteroatom functionalised NHC ligands. For example, complexes of the type [RhCl(l,5-cod)(NHC)] and [RhL(l,5-cod)(NHC)][SbFg ], 70, where L = isoquinoline, 3,5-lutidine and NHC are the chiral monodentate ligands 71 (Fig. 2.11). 

Since its discovery in 1953, the reaction has been extensively studied with respect to structural variation in the phosphonium ylide, in the range of functionalised aldehydes and ketones, in the nature of the bases and the polarity of the solvents that may be used, and in the mechanism of the reaction and the factors which influence the ( /Z) ratio. Many thousands of simple and complex syntheses have been effected and the method is widely exploited in research laboratories and in the industrial processes for syntheses in the steroid and carotenoid field. 

Labande et al. tested the rhodium(I) complexes of diphenylphosphinoferrocenyl functionalised NHC ligands (Cp,Cp and Cp,Cp substitution) in the hydrosilylation of ketones finding these complexes of only moderate activity [186]. As no attempt was made for the chiral resolution of the catalysts prior to use in catalysis, the prochiral acetophenone could not be tested in asymmetric catalysis. 

Topics that have formed the subjects of reviews this year include contemporary issues in electron transport research, dynamics of bimolecular photoelectron transfer reactions, photophysical properties of functionalised fullerene derivatives, carbon-carbon bond formation via radical ions, photoinduced electron transfer processes in ketone, aldehyde, and ester synthesis, photochemical reactions between arenenitriles and benzylic donors, photo-oxidation of conjugated dienes, photoredox reactions of aromatic nitro compounds, electron transfer-mediated photochemistry of some unsaturated nitrogen-containing compounds, reactions of 02( Ag), carbon dioxide activation by aza-macrocyclic complexes, and photochromism of chalcone derivatives. ... 

Since the discovery of the Wilkinson catalyst, most of the work on hydrogenation has been carried out with functionalised alkenes as substrates and Rh(I) complexes as catalytic precursors. These hydrogenations are discussed in the next sections. There are also a few results on hydrogenation of ketones and imines, described in Section 7.2.3. 

Another magnetically recoverable catalytic silica microreactors 156 were prepared and tested in the ATH of ketones in aqueous medium [135]. Magnetite nanoparticles were coated with shells synthesised via co-polymerisation of Si(OEt)4 and the Ru-TsDPEN complex 157 functionalised with a trimethoxysilane group. The transport of the hydrophobic reactants from the water medium to an entrapped catalyst in a sol-gel matrix was ensured by the surfactant CTAC. Under these conditions, ring-substituted acetophenones were almost quantitatively reduced with HC02Na giving the corresponding alcohols in over 90 % ees within 24 h (Fig. 49). 

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