Transition metal catalysts synthesis

Asao N, Nogami T, Takahashi K, Yamamoto Y (2002) Pd(U) Acts simultaneously as a Lewis acid and as a transition-metal catalyst synthesis of cyclic alkenyl ethers liom acetylenic aldehydes. J Am Chem Soc 124 764—765... 

Addition of HCN to unsaturated compounds is often the easiest and most economical method of making organonitnles. An early synthesis of acrylonitrile involved the addition of HCN to acetylene. The addition of HCN to aldehydes and ketones is readily accompHshed with simple base catalysis, as is the addition of HCN to activated olefins (Michael addition). However, the addition of HCN to unactivated olefins and the regioselective addition to dienes is best accompHshed with a transition-metal catalyst, as illustrated by DuPont s adiponitrile process (6—9). 

Studies of the synthesis of quiaolines usiag transition-metal catalysts and nonacidic conditions (55) have determined that mthenium(III) chloride is the most effective of a wide range of catalysts. The reaction between nitrobenzene and 1-propanol or 1-butanol gives 65 and 70% yields of 2-ethyl-3-methylquiQoline [27356-52-1] and 3-ethyl-2-propylquiQoline, respectively. 

One of the most exciting discoveries related to quinone/hydroquinone chemistry is thek synthesis by biosynthetic routes (12,13). Using bacterial enzymes to convert D-glucose [50-99-7] (7) to either 1,2- or l,4-ben2enediol allows the use of renewable raw material to replace traditional petrochemicals. The promise of reduced dependence on caustic solutions and the use of transition-metal catalysts for thek synthesis are attractive in spite of the scientific and economic problems still to be solved. 

Synthesis of N-heterocycles with C—N bond formation catalyzed by transition metal catalysts 97SL749. 

L. Brandsma, S. E. Vasilevsky, and H. D. Verkiuijsse, in Application of Transition Metal Catalysts in Organic Synthesis. Springer-Verlag, Heidelberg, 1998. 

Perhaps the most successful industrial process for the synthesis of menthol is employed by the Takasago Corporation in Japan.4 The elegant Takasago Process uses a most effective catalytic asymmetric reaction - the (S)-BINAP-Rh(i)-catalyzed asymmetric isomerization of an allylic amine to an enamine - and furnishes approximately 30% of the annual world supply of menthol. The asymmetric isomerization of an allylic amine is one of a large and growing number of catalytic asymmetric processes. Collectively, these catalytic asymmetric reactions have dramatically increased the power and scope of organic synthesis. Indeed, the discovery that certain chiral transition metal catalysts can dictate the stereo-... 

Chiral epoxides and their corresponding vicinal diols are very important intermediates in asymmetric synthesis [163]. Chiral nonracemic epoxides can be obtained through asymmetric epoxidation using either chemical catalysts [164] or enzymes [165-167]. Biocatalytic epoxidations require sophisticated techniques and have thus far found limited application. An alternative approach is the asymmetric hydrolysis of racemic or meso-epoxides using transition-metal catalysts [168] or biocatalysts [169-174]. Epoxide hydrolases (EHs) (EC 3.3.2.3) catalyze the conversion of epoxides to their corresponding vicinal diols. EHs are cofactor-independent enzymes that are almost ubiquitous in nature. They are usually employed as whole cells or crude... 

Organosilicon compounds are widely used in our daily life as oil, grease, rubbers, cosmetics, medicinal chemicals, etc. However, these compounds are not naturally occurring substances but artificially produced ones (for reviews of organosilicon chemistry, see [59-64]). Hydrosilylation reactions catalyzed by a transition-metal catalyst are one of the most powerful tools for the synthesis of organosilicon compounds. Reaction of an unsaturated C-C bond such as alkynes or alkenes with hydrosilane affords a vinyl- or alkylsilane, respectively (Scheme 16). 

C-C and C-E (E = heteroatom) bond formations are valuable reactions in organic synthesis, thus these reactions have been achieved to date by considerable efforts of a large number of chemists using a precious-metal catalysts (e.g., Ru, Rh, and Pd). Recently, the apphcation range of iron catalysts as an alternative for rare and expensive transition-metal catalysts has been rapidly expanded (for recent selected examples, see [12-20, 90-103]). In these reactions, a Fe-H species might act as a reactive key intermediate but also represent a deactivated species, which is prepared by p-H elimination. 

Besides supported (transition) metal catalysts, structure sensitivity can also be observed with bare (oxidic) support materials, too. In 2003, Hinrichsen et al. [39] investigated methanol synthesis at 30 bar and 300 °C over differently prepared zinc oxides, namely by precipitation, coprecipitation with alumina, and thermolysis of zinc siloxide precursor. Particle sizes, as determined by N2 physisorpt-ion and XRD, varied from 261 nm for a commercial material to 7.0 nm for the thermolytically obtained material. Plotting the areal rates against BET surface areas (Figure 3) reveals enhanced activity for the low surface area zinc... 

Logadottir A, Rod TH, N0rskov JK, Hammer B, Dahl S, Jacobsen CJH. 2001. The Br0nsted-Evans-Polanyi relation and the volcano plot for ammonia synthesis over transition metal catalysts. J Catal 197 229. 

Brandsma, L., in Preparative Acetylenic Chemistry, Heus-Kloos, Y. A., Van Der Heiden, R., Verkruijsse, H. D., eds., 2nd ed. Elsevier, New York, 1988 Brandsma, L., Vasilevsky, S. F., Verkruijsse, H. D., Application of Transition Metal Catalysts in Organic Synthesis. Springer-Verlag New York, 1999. 

The other direction concerns the use of immobilized transition metal catalysts in the synthesis of libraries of organic compounds of interest in therapeutic drug discovery. One such strategy uses immobilized catalysts (e.g., scandium complexes), leading to efficient library syntheses of quinolines, amino ketones, and amino acid esters.72,73... 

The recent progress surveyed in this review shows the promise that late transition metal catalysts can provide in the production of new materials. We will continue our exploration of new catalyst design for the synthesis of new functional materials with unconventional topologies. Given the unique features of late transition-metal polymerization catalysts and further improvement in catalyst stability and activity for copolymerization with polar comonomers, the future of designing novel functional polymeric materials with late-transition-metal catalysts is very promising. 

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. 

The isomerization of allyl ethers and allyl acetals to vinyl ethers or vinyl acetals, respectively, has found many applications in organic synthesis (Equation (17)). Various transition metal catalysts have been reported in the literature for the isomerization of allyl ethers and allyl acetals. 

In contrast to the palladium-catalyzed reactions, little attention has been paid to other transition-metal catalysts. Recently some efficient reactions using copper(i or 11), gold(m), platinum(n), and tungsten(O) have been developed for the synthesis of nitrogen-heterocycles. The copper-catalyzed cyclizations of 2-alkynylaniline derivatives into... 

Brunner, H., Enantioselective Synthesis of Organic Compounds with Optically Active Transition Metal Catalysts in Substoichiometric Quantities, 18, 129. 

One of the very few examples of a practical application of a transition-metal catalyst in total synthesis is shown in Scheme 20.22 [107]. The chloroiridic acid catalyst (HjIrCfs) (6) reduces 71 to androsterone (72) by selective attack of the sterically less hindered ketone in the 3-position of 71. 

In contrast to the maturity of asymmetric synthesis utilizing chiral transition metal catalysts, asymmetric phase transfer catalysis is still behind it and covers organic reactions to lesser extent. Thus, it is further necessary in wide range to explore efficient asymmetric phase transfer catalysis keeping its superiority of easy operation, mild reaction conditions, and environmental binignancy. 

This chapter has discussed the transition metal-catalyzed synthesis of allenes. Because allenes have attracted considerable attention as useful synthons for synthetic organic chemistry, effective synthetic methods for their preparation are desirable. Some recent reports have demonstrated the potential usefulness of optically active axially chiral allenes as chiral synthons however, methods for supplying the enantiomerically enriched allenes are still limited. Apparently, transition metal-catalyzed reactions can provide solutions to these problems. From the economics point of view, the enantioselective synthesis of axially chiral allenes from achiral precursors using catalytic amounts of chiral transition metal catalysts is especially attractive. Considering these facts, further novel metal-catalyzed reactions for the preparation of allenes will certainly be developed in the future. 

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