Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy. As of 2005, over 3% of the total energy consumption in the United States was supplied by biomass, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy. Similarly, the European Union received 66.1% of its renewable energy from biomass, which thus surpassed the total combined contribution from hydropower, wind power, geothermal energy, and solar power. In addition to energy, the production of chemicals from biomass is also essential; indeed, the only renewable source of liquid transportation fuels is currently obtained from biomass.

The Catalytic Valorization of Lignin for the Production of Renewable Chemicals

s, or keywords if they used Heck-type chemistry in their syntheses, because it became one of basic tools of organic preparations, a natural way to

http://aether.cmi.ua.ac.be/artikels/Artikels%20Gitte/Artikels/Reviews/Heck%20reactie%20Beletskaya%20%20Chem.%20Rev.%20003009.pdf

The heck reaction as a sharpening stone of palladium catalysis.

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Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

ion. The oxidative addition mechanism was originally proposed22i because of the lack of a strong rate dependence on polar factors and on the acidity of the medium. Later, however, the electrophilic substitution mechanism also was proposed. Recently, the oxidative addition mechanism was confirmed by investigations into the decomposition and protonolysis of alkylplatinum complexes, which are the reverse of alkane activation. There are two routes which operate in the decomposition of the dimethylplatinum(IV) complex Cs2Pt(CH3)2Cl4. The first route leads to chloride-induced reductive elimination and produces methyl chloride and methane. The second route leads to the formation of ethane. There is strong kinetic evidence that the ethane is produced by the decomposition of an ethylhydridoplatinum(IV) complex formed from the initial dimethylplatinum(IV) complex. In D2O-DCl, the ethane which is formed contains several D atoms and has practically the same multiple exchange parameter and distribution as does an ethane which has undergone platinum(II)-catalyzed H-D exchange with D2O. Moreover, ethyl chloride is formed competitively with H-D exchange in the presence of platinum(IV). From the principle of microscopic reversibility it follows that the same ethylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II). Important results were obtained by Labinger and Bercaw62c in the investigation of the protonolysis mechanism of several alkylplatinum(II) complexes at low temperatures. These reactions are important because they could model the microscopic reverse of C-H activation by platinum(II) complexes. Alkylhydridoplatinum(IV) complexes were observed as intermediates in certain cases, such as when the complex (tmeda)Pt(CH2Ph)Cl or (tmeda)PtMe2 (tmeda ) N,N,N′,N′-tetramethylenediamine) was treated with HCl in CD2Cl2 or CD3OD, respectively. In some cases H-D exchange took place between the methyl groups on platinum and the, CD3OD prior to methane loss. On the basis of the kinetic results, a common mechanism was proposed to operate in all the reactions: (1) protonation of Pt(II) to generate an alkylhydridoplatinum(IV) intermediate, (2) dissociation of solvent or chloride to generate a cationic, fivecoordinate platinum(IV) species, (3) reductive C-H bond formation, producing a platinum(II) alkane σ-complex, and (4) loss of the alkane either through an associative or dissociative substitution pathway. These results implicate the presence of both alkane σ-complexes and alkylhydridoplatinum(IV) complexes as intermediates in the Pt(II)-induced C-H activation reactions. Thus, the first step in the alkane activation reaction is formation of a σ-complex with the alkane, which then undergoes oxidative addition to produce an alkylhydrido complex. Reversible interconversion of these intermediates, together with reversible deprotonation of the alkylhydridoplatinum(IV) complexes, leads to multiple H-D exchange

Activation of c-h bonds by metal complexes

Asymmetric Transfer Hydrogenation Catalyzed by Chiral Ruthenium Complexes

Transformations of Chloroarenes, Catalyzed by Transition-Metal Complexes

A method for homogenizing heterogeneous catalyst is described. The method is based on growing polyaminoamido (PAMAM) dendrons on silica-coated magnetic nanoparticles. After the dendronizing process, the silica-coated magnetic nanoparticles are more stable and more soluble in organic solvents. The dendronized particles are phosphonated, complexed with [Rh(COD)Cl]2, and applied in catalytic hydroformylation reactions. These new catalysts are proven to be highly selective and reactive.

/pdf/metal-supported-on-dendronized-magnetic-nanoparticles-highly-1v5ands8n3.pdf

Metal supported on dendronized magnetic nanoparticles: highly selective hydroformylation catalysts.

Asymmetric synthesis of acids by the palladium-catalyzed hydrocarboxylation of olefins in the presence of (R)-(-)- or (S)-(+)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate

Alkali-induced disproportionation of palladium(II) tertiary phosphine complexes, [L2PdCl2], to LO and palladium(O). Key intermediates in the biphasic carbonylation of ArX catalyzed by [L2PdCl2]

of aryl olefins and vinyl esters. 5 However, the thirdand fourthgeneration catalysts displayed low activity compared to the lower generations. This was believed to be due to incomplete phosphonation reactions arising from steric crowding and ultimately resulting in the threshold of dendrimer growth being reached. 6 It was perceived that extending the chain length of each generation would relieve the steric crowding and allow for increased catalyst loading at higher generations. To extend the chain length, the ethylenediamine linker was substituted by 1,4-diaminobutane, 1,6diaminohexane, and 1,12-diaminododecane. The lengthening of the monomeric unit of the dendrimer should decrease the congestion at the surface. This can easily be observed by comparing the theoretical amine content (Table 1 in the Supporting Information) for the various chain lengths and generations. For example, the C12 G-4 (1.84 mmol of NH 2/g of SiO2) dendrimer has approximately half the amine content of the C2 G-4 (3.55 mmol NH2/g SiO2) dendrimer. Polyamidoamino (PAMAM) dendrimers up to generation 4 ( 14) were constructed on the surface of aminopropylsilica employing a standard divergent growth strategy. 7,8 The isolation of the dendrimers under construction proved to be extremely timeconsuming, as the filters generally became clogged with precipitated diamine. In the case of the diaminedodecane linkers, filtration and washing took up to 3 days. Figures 1 -3 (see Supporting Information for Figures 2 and 3) show the gradual (1) (a) Annis, D. A.; Jacobsen, E. N. J Am. Chem. Soc. 1999, 121, 707714. (b) Shuttleworth, S. J.; Allin, M.; Sharma, P. K. Synthesis1997, 12171239. (c) Nozaki, K.; Itoi, Y.; Shibahara, F.; Shirakawa, E.; Ohta, T.; Takaya, H.; Hiyama, T.J. Am. Chem. Soc . 1998, 120, 4051-4052. (d) Chen, J.; Alper, H. J. Am. Chem. Soc . 1997, 119, 893-895. (e) Nait Ajjou, A.; Alper H.J. Am. Chem. Soc. 1998, 120, 1466-1468. (2) (a) Matthews, O. A.; Shipway, A. N.; Stoddart, J. F. Prog. Polym. Sci. 1998, 23, 1-56. (b) Frechet, J. M. J.; Hawker, C. J.; Gitsov, I.; Leon, J. W. Pure Appl. Chem. 1996, 10, 1399-1425. (c) Ardin, N.; Astruc, D. Bull. Soc. Chim. Fr. 1995, 132, 875-909. (d) Caminade, A. M.; Laurent, R.; Chaudret, B.; Majoal, J. P.Coord. Chem. Re V. 1998, 178-180, 793-821. (e) Bianchini, C.; Burnaby, D. G.; Evans, J.; Fredani, P.; Meli, A.; Oberhauser, W.; Psaro, R.; Sordelli, L.; Vizza, F.J. Am. Chem. Soc. 1999, 121, 5961-5971. (3) (a) Knapen, J. W. J.; van der Made, A. W.; de Wilde, J. C.; van Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; van Koten, G. Nature 1994, 372, 659-663. (b) Reetz, M. T.; Lohmer, G.; Schwickardi, R. Angew. Chem., Int. Ed. Engl. 1997, 36, 1526-1529. (c) Reetz, M. T. Topics Catal. 1997, 4, 187-200. (4) (a) Ungvary, F.Coord. Chem. Re V. 1999, 188, 263-296. (b) Ungvary, F. Coord. Chem. Re V. 1997, 167, 233-260. (c) Dickson, R. S. Homogeneous Catalysis with Compounds of Rhodium and Iridium ; D. Reidel: Boston, 1985; Chapter 4. (d) Herrmann, W. A.; Cornils, B. Angew. Chem., Int. Ed. Engl. 1997, 36, 1048-1067. (5) Bourque, S. C.; Maltais, F.; Xiao, W.-J., Tardif, O.; Alper, H.; Arya, P.; Manzer, L. E.J. Am. Chem. Soc . 1999, 121, 3035-3038. (6) A communication, which was received following submission of the manuscript, concerns the synthesis of phosphine-functionalized carbosilane dendrimers (G0 -G2) and the use of their palladium complexes for allylic alkylation. The authors note that, “The dendrimer with seventy-two phosphine groups could not be prepared, probably because of surface congestion.” See: de Groot, D.; Eggeling, E. B.; de Wilde, J. C.; Kooijman, H.; van Haaren, R. J.; van der Made, A. W.; Spek, A. L.; Voget, D.; Reek, J. N. H.; Kanier, P. C. J.; van Leeuwen, P. W. N. M. J Chem. Soc., Chem. Commun . 1999, 16231624. (7) (a) Tomalia, D. A.; Baker, H.; Dewald, J.; Hall, M.; Kallos, G.; Martin, S.; Roeck, J.; Ryder, J.; Smith, P. olym. J. 1995, 17, 117-132. (b) Tomalia, D. A.; Baker, H.; Dewald, J.; Hall, M.; Kallos, G.; Martin, S.; Roeck, J.; Ryder, J.; Smith, P. Macromolecules1986, 19, 2466-2468. (c) Tomalia, D. A.; Hall, M.; Hedstrand, D.J. Am. Chem. Soc . 1987, 109, 1061-1063. (d) Tomalia, D. A.; Berry, V.; Hall, M.; Hedstrand, D. Macromolecules1987, 20, 1164-1167. (e) Tsubokawa, N.; Ichioka, H.; Satoh, T.; Hayashi, S.; Fujiki, K. React. Funct. Polym. 1998, 37, 75-82. (8) See Supporting Information for procedure, Figure 2, and the hydroformylation results of vinyl acetate. Table 1. Hydroformylation of Styrene with Rh-PPh2-PAMAM-SiO2 Catalystsa

Howard Alper

Papers

Transformations of Chloroarenes, Catalyzed by Transition-Metal Complexes

Metal supported on dendronized magnetic nanoparticles: highly selective hydroformylation catalysts.

Asymmetric synthesis of acids by the palladium-catalyzed hydrocarboxylation of olefins in the presence of (R)-(-)- or (S)-(+)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate

Alkali-induced disproportionation of palladium(II) tertiary phosphine complexes, [L2PdCl2], to LO and palladium(O). Key intermediates in the biphasic carbonylation of ArX catalyzed by [L2PdCl2]

Hydroformylation Reactions Using Recyclable Rhodium-Complexed Dendrimers on Silica