It is possible to say that zeolites are the most widely used catalysts in industry They are crystalline microporous materials which have become extremely successful as catalysts for oil refining, petrochemistry, and organic synthesis in the production of fine and speciality chemicals, particularly when dealing with molecules having kinetic diameters below 10 A The reason for their success in catalysis is related to the following specific features of these materials:1 (1) They have very high surface area and adsorption capacity (2) The adsorption properties of the zeolites can be controlled, and they can be varied from hydrophobic to hydrophilic type materials (3) Active sites, such as acid sites for instance, can be generated in the framework and their strength and concentration can be tailored for a particular application (4) The sizes of their channels and cavities are in the range typical for many molecules of interest (5-12 A), and the strong electric fields2 existing in those micropores together with an electronic confinement of the guest molecules3 are responsible for a preactivation of the reactants (5) Their intricate channel structure allows the zeolites to present different types of shape selectivity, ie, product, reactant, and transition state, which can be used to direct a given catalytic reaction toward the desired product avoiding undesired side reactions (6) All of these properties of zeolites, which are of paramount importance in catalysis and make them attractive choices for the types of processes listed above, are ultimately dependent on the thermal and hydrothermal stability of these materials In the case of zeolites, they can be activated to produce very stable materials not just resistant to heat and steam but also to chemical attacks Avelino Corma Canos was born in Moncofar, Spain, in 1951 He studied chemistry at the Universidad de Valencia (1967−1973) and received his PhD at the Universidad Complutense de Madrid in 1976 He became director of the Instituto de Tecnologia Quimica (UPV-CSIC) at the Universidad Politecnica de Valencia in 1990 His current research field is zeolites as catalysts, covering aspects of synthesis, characterization and reactivity in acid−base and redox catalysis A Corma has written about 250 articles on these subjects in international journals, three books, and a number of reviews and book chapters He is a member of the Editorial Board of Zeolites, Catalysis Review Science and Engineering, Catalysis Letters, Applied Catalysis, Journal of Molecular Catalysis, Research Trends, CaTTech, and Journal of the Chemical Society, Chemical Communications A Corma is coauthor of 20 patents, five of them being for commercial applications He has been awarded with the Dupont Award on new materials (1995), and the Spanish National Award “Leonardo Torres Quevedo” on Technology Research (1996) 2373 Chem Rev 1997, 97, 2373−2419

From Microporous to Mesoporous Molecular-Sieve Materials and Their Use in Catalysis

Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed.

In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

/pdf/palladium-ii-catalyzed-c-h-activation-c-c-cross-coupling-2546yox1wp.pdf

Palladium(II)-catalyzed C-H activation/C-C cross-coupling reactions: versatility and practicality.

Catalytic dehydrogenative cross-coupling: forming carbon-carbon bonds by oxidizing two carbon-hydrogen bonds

http://www1.udel.edu/chem/polenova/PDF/Polyoxometalates/POMs_Catalysis_NMR_ChemRev1998.pdf

Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions

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

NaBrO3 combined with NaHSO3 was found to be an excellent oxidizing reagent of alcohols, diols, and ethers under mild conditions. A variety of aliphatic and cyclic diols were selectively oxidized with satisfactory yields to the corresponding hydroxy ketones and/or diketones, which are difficult to selectively prepare due to a concomitant formation of cleaved products. For example, 2-hydroxycyclohexanone and 1,2-cyclohexanedione were selectively formed by allowing 1,2-cyclohexanediol to react with NaBrO3/NaHSO3 reagent in a selected solvent. On the other hand, an alkyl ether, such as dioctyl ether, reacted with NaBrO3/NaHSO3 in water at room temperature to give octyl octanoate in 82% yield. The same oxidation at higher temperature (60 °C) produced the α-brominated ester, octyl 2-bromooctanoate, which is considered to be formed through an alkenyl alkyl ether as the intermediate. The treatment of 1-ethoxy-1-heptene with NaBrO3/NaHSO3 afforded ethyl 2-bromoheptanoate and 2-bromoheptanoic acid as the major prod...

http://sciencemadness.org/talk/files.php?pid=123587&aid=5251

Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent

Carboxylation of anisole derivatives with CO and O2 catalyzed by Pd(OAc)2 and molybdovanadophosphates.

The radical addition of enolizable carbonyl compounds such as malonates and malononitrile to alkenes was successfully achieved through a catalytic process using the Mn(II)/Co(II)/O(2) system to afford the corresponding adducts in fair to good yields. Dimethyl malonate added to 1,5-cyclooctadiene to produce a fused bicycle compound.

Catalytic radical addition of carbonyl compounds to alkenes by Mn(II)/Co(II)/O(2) system.

Mixed addenda heteropolyoxometalate, NPV6Mo6, was found to be an efficient catalyst for the oxidative dehydrogenation of a variety of benzylic amines to the corresponding Schiff-base imines with molecular oxygen in toluene solution. Under the same reaction conditions, isochroman and indan were respectively oxidized to 3,4-dihydroisocoumarin and 1-indanone with high selectivity.

Oxidation of Benzylic Derivatives with Dioxygen Catalyzed by Mixed Addenda Metallophosphate Containing Vanadium and Molybdenum

Hydrogen iodide, HI, cleanly generated in situ from Me 3 SiCl/NaI and water in acetonitrile under mild conditions, was found to be an attractive reagent for the conversion of allylic alcohols into allylic iodides which serve as good allylic cation equivalent. Thus, treatment of allylic alcohols with Me 3 SiCl/NaI/H 2 O, followed by the substitution with N 3 − , CN − , and PhSO 2 − ions in the same flask produced the corresponding allylic compounds bearing azide, cyano, and phenyl sulfonyl functionalities in fair yields. This method provides a useful procedure for the preparation of allylic compounds from easily available allylic alcohols

Yasutaka Ishii

Papers

Oxidation of Diols and Ethers by NaBrO3/NaHSO3 Reagent

Carboxylation of anisole derivatives with CO and O2 catalyzed by Pd(OAc)2 and molybdovanadophosphates.

Catalytic radical addition of carbonyl compounds to alkenes by Mn(II)/Co(II)/O(2) system.

Oxidation of Benzylic Derivatives with Dioxygen Catalyzed by Mixed Addenda Metallophosphate Containing Vanadium and Molybdenum

Hydrogen iodide strategy for one-pot preparation of allylic azides, nitriles, and phenyl sulfones from allylic alcohols