Olefin hydrogenation imines

Scheme 15. Ir-Catalysed hydrogenation of unfunctionalized olefins and imines using PHOX-ligands.

Reduction of amides without hydride reagents Asymmetric hydrogenation of un functionalized olefins/enamines/imines... 

The formation of small amounts of the hydrogen abstracdon products, amines (128) and (130) from the thermolysis in the absence of solvent of azides (127) and (129) also lends some support to the dew that a free alkylnitrene is formed . However, routes to the amines other than hydrogen abstracdon may be envisaged. For example, 1,3-dipolar addidons (of the type described for azide 119) to olefins and imines formed in the thermolysis of the azide, followed decomposition of the adducts and hydrolysis could give 128 and 130. 

The titanium complexes bearing <9-phosphinophenoxo ligands shown in Scheme 380 are prepared by metallation of the corresponding phenol followed by reaction with CpTiCl3. The complexes were found to be fluxional by H NMR analysis at low temperature. The X-ray structure shows that in the solid state the molecule is chiral at the metal center. These complexes are effective catalysts for olefin hydrogenation and imine hydrosilylation.911... 

Scheme 8.12 Hydrogenations of olefins with BINOL-derived A -phosphino sulfox-imine ligands.

Scheme 8.14 Hydrogenation of olefin with P/N-sulfinyl imine ligands.

This chapter discusses the development of scaleable and robust manufacturing processes for rhodium and rathenium containing precatalysts that are used for the asymmetric hydrogenation of a diverse range of olefins, ketones and imines. The application of these precatalysts to the preparation of a variety of pharmacentical intermediates, many of which have been operated on commercial scale, is also discussed. 

It is of interest that antibacterial activity can be retained even when the imine carbon-nitrogen bond is replaced by a carbon to carbon double bond. Base-catalyzed condensation of 5-nitrofurfuraldehyde (24) with 2,6-dimethylpyridine (38) affords olefin 39. Treatment of this compound with hydrogen peroxide gives the corresponding N-oxide (40). Heating of... 

The development of chiral phosphorus ligands has made undoubtedly significant impact on the asymmetric hydrogenation. Transition metal catalysts with efficient chiral phosphorus ligands have enabled the synthesis of a variety of chiral products from prochiral olefins, ketones, and imines in a very efficient manner, and many practical hydrogenation processes have been exploited in industry for the synthesis of chiral drugs and fine chemicals. 

As illustrated in the hydrogenation of cyclic imines, the system is compatible with a wide range of functional groups, such as olefins, protected or unpro-... 

Kaneda et al. reported substrate-specific hydrogenation of olefins using the tri-ethoxybenzamide-terminated polypropylene imine) dendrimers (PPI) as nanoreactors encapsulating Pd nanoparticles (mean diameter 2-3 nm) [59]. The catalytic tests were performed in toluene at 30 °C under dihydrogen at atmospheric pressure (Table 9.3). The hydrogenation rates were seen to decrease with increasing generation of dendrimers, from G3 to G5. 

In this chapter, we review the growing family of phospholane-based chiral ligands, and specifically examine their applications in the field of enantioselective hydrogenation. In general, this ligand class has found its broadest applicability in the reduction of prochiral olefins and, to a significantly lesser extent, ketones and imines this is reflected in the composition of the chapter. Several analogous phosphacycle systems have also been included, where appropriate. 

Secondary phosphine oxides are known to be excellent ligands in palladium-catalyzed coupling reactions and platinum-catalyzed nitrile hydrolysis. A series of chiral enantiopure secondary phosphine oxides 49 and 50 has been prepared and studied in the iridium-catalyzed enantioselective hydrogenation of imines [48] and in the rhodium- and iridium-catalyzed hydrogenation functionalized olefins [86]. Especially in benzyl substituted imine-hydrogenation, 49a ranks among the best ligands available in terms of ex. 

Asymmetric catalytic reduction reactions represent one of the most efficient and convenient methods to prepare a wide range of enantiomerically pure compounds (i.e. a-amino acids can be prepared from a-enamides, alcohols from ketones and amines from oximes or imines). The chirality transfer can be accomplished by different types of chiral catalysts metallic catalysts are very efficient for the hydrogenation of olefins, some ketones and oximes, while nonmetallic catalysts provide a complementary method for ketone and oxime hydrogenation. 

Secondary and tertiary amines can be obtained if the hydroformylation of olefins is conducted in the presence of primary and secondary amines under elevated hydrogen partial pressures. Here the rhodium catalyst is involved in both steps, the hydroformylation of an olefin as well as the hydrogenation of the imine or enamine resulting from a condensation of the oxo-aldehyde with the amine (Scheme 14). This combination of hydroformylation and reductive amination is also known as hydroaminomethylation and has been applied to the synthesis of various substrates of pharmaceutical interest [55-57] as well as to the synthesis of macrocycles [60-63] and dendrimers [64,65]. 

Hydroaminomethylation is a simple, efficient and atom-economic method to synthesize various amines. This one-pot reaction consists of three consecutive steps in the first step a hydroformylation of an olefin is performed followed by the reaction of the resulting aldehyde with a primary or secondary amine to give the corresponding enamine or imine. Lastly, this intermediate is hydrogenated to the desired secondary or tertiary amine (Fig. 11) [33-39]. In most cases rhodium salts or complexes are used as the homogeneous catalyst in the hydroaminomethylation. 

Iridium-Catalyzed Asymmetric Hydrogenation of Olefins with Chiral N,P and C,N Ligands 73 Table 19 Asymmetric hydrogenation of imines... 

Aqueous organometalHc catalysis allows the use of NH3-solutions in water for the direct synthesis of amines from olefins in a combined hydroformylation/reductive amination procedure (Scheme 4.19). The hydroformylation step was catalyzed by the proven Rh/TPPTS or Rh/BINAS (44) catalysts, while the iridium complexes formed from the same phosphine ligands and [ IrCl(COD) 2] were found suitable for the hydrogenation of the intermediate imines. With sufficiently high NH3/olefin ratios (8/1) high selectivity towards the formation of primary amines (up to 90 %) could be achieved, while in an excess of olefin the corresponding... 

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