Hydrogenation of cyclohexene catalyzed by polymer- bound rhodium(I) and iridium(I) complexes

The catalytic hydrogenation of cyclohexene using Rh^I and Ir^I polymer-bound cationic complexes as catalysts is reported, and the solvent effect in these reductions has been investigated. In most case the reaction is characterized by the presence of a solvent-dependent induction period which has been investigated and is discussed. In several cases ESR-active Rh^II species have been detected at the end of the catalytic reaction. Recycling of the catalysts led to higher catalytic activity.     

Hydroformylation of olefins catalyzed by rhodium complex anchored on clay matrices

Investigations on the catalytic activity of a transient Rh(I) triphenylphosphine complex1 anchored on montmorillonite clay have been carried out with respect to hydroformylation of olefins at 70°C and 60 atm of CO+H₂ (1:1). The analysis has shown that aldehydes and hydrocarbons of the corresponding olefins result under hydroformylation conditions. In limonene, reaction proceeds with double hydroformylation and hydrogenation to give the respective oxo products. The catalytic activities of1 are compared with Wilkinson's Rh^I (H) (CO) (PPh₃)₂ (6) complex in solution under the same hydroformylation conditions.     

Hydrogenation of olefins using water and zinc metal catalyzed by a rhodium complex

The hydrogenation of olefins using H₂O or D₂O as a hydrogen source and zinc metal as a reducing agent has been found to be catalyzed by a rhodium complex. α,β-Unsaturated ketones also underwent hydrogenation, affording the corresponding saturated ketones selectively.     

Preparation of poly(oxybutyleneoxymaleoyl) catalyzed by a proton exchanged montmorillonite clay

The polycondensation of tetrahydrofuran with maleic anhydride catalyzed by Maghnite-H+ (Mag-H) was investigated. Maghnite is a montmorillonite sheet silicate clay that is exchanged with protons to produce Maghnite-H [1]. It was found that the polymerization in bulk is initiated by Mag-H in the presence of acetic anhydride at 40 degrees C.The effects of the amounts of Mag-H and acetic anhydride were studied. The polymerization yield increased as the proportions of catalyst and acetic anhydride were increased.     

Highly enantioselective spiro cyclization of 1,6-enynes catalyzed by cationic skewphos rhodium(I) complex

A cationic rhodium(I) complex having a skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers of spiro-rings.     

Enantioselective spiro ene-carbocyclization of 1,6-enynes catalyzed by tropos rhodium(I) complex with skewphos ligand

A tropos rhodium(I) complex having skewphos ligand is shown to be a highly enantioselective catalyst for asymmetric ene-type carbocyclization of 1,6-enynes with tri-substituted olefins to control quaternary stereogenic centers or spiro-rings.     

Hydrogenation of alkenes catalyzed by supported Ziegler catalysts

Supported Ziegler catalysts prepared by the reaction of a Ni(II) 1-butylsalicylaldiminate or Ni(II) 2-ethylhexanoate with Al₂O₃/SiO₂ treated with AlEt₃ or NaAlH₂ (OCH₂CH₂OCH₃)₂ are efficient catalysts for hydrogenation of simple alkenes. The factors influencing their activity are reported.

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, qp - Ni(II) - Ni(II) 2- Al₂O₃/SiO₂, AlEt₃ NaAlH₂ (OCH₂CH₂OCH₃)₂, . , .

     

Hydrogenation of aldehydes catalyzed by kieselguhr‐supported carboxymethylcellulose‐nickel complex

A new kieselguhr‐supported carboxymethylcellulose‐nickel complex (Kie‐CMC‐Ni) has been prepared by a simple method, which has been found to catalyze the hydrogenation of benzaldehyde, valeraldehyde and isobutyraldehyde to the corresponding alcohols in high yield (100, 92 and 86% respectively). The catalyst could be reused without obvious loss of its catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.     

Amination of aryl- and vinylacetylenic compounds catalyzed by rhodium(I) complexes

New rhodium-catalyzed amination reactions of arylacetylenes and cyclohexen-1-ylacetylene in the presence of strong bases with the use of carbon dioxide as an auxiliary are described. Secondary amines attack the terminal carbon atom of the triple bond followed by protonation of the adjacent carbon atom. Alternatively, the reaction can proceed further with the addition of the second alkyne molecule. The conditions for the selective synthesis of enamines (up to 87% yield) or α-substituted propynylamines (up to 86% yield) are reported. Dipartimento di Chimica Organica e Industriale dell'Università, Viale delle Scienze, I-43100 Parma, Italia. Dipartimento di Chimica, Università della Calabria, Arcavacata di Rende, I-80036 Cosenza, Italia. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 966–970, May, 1998.     

Hydrogen transfer reactions catalyzed by neutral rhodium(I) Schiff base complexes

Summary Hydrogen transfer reactions from 2-propanol to acetophenone or cyclohexene are catalyzed by neutral rhodium(I) complexes of the type [Rh(COD)L] and [Rh₂(COD)₂L] (where L and L are Schiff base ligands and COD=cycloocta-1,5-diene). Some dependency of the catalytic activity on the electronic and steric properties of the ligands are discussed.     

Chelation-assisted hydroesterification of alkenes catalyzed by rhodium complex

[reaction: see text] The hydroesterification of alkenes with 2-pyridylmethanol (1) catalyzed by Rh(4)(CO)(12) is described. The reaction is accelerated by the presence of a pyridine ring in the alcohol 1. The reaction is applicable to various alkenes, both terminal and internal alkenes.     

Enantioselective rhodium(I)-triethylamine catalyzed addition of potassium isopropenyl trifluoroborate to enones

A general process is reported for the highly enantioselective 1,4-addition of isopropenyl trifluoroborate to cyclic enones under catalysis by a chiral Rh(I) complex and triethylamine at room temperature.     

Regiocontrolled synthesis of allylsilanes by means of rhodium(I) or iridium(I) catalyzed isomerization of olefins

Rhodium(I) or iridium(I) catalyzed migration of double-bond has been successfully applied to the regiocontrolled synthesis of allylsilane from olefin silylated at a remote sp carbon.     

Synthesis of quinazolines from (2-aminoaryl)methanols and arylmethanamines catalyzed by rhodium complex

Russian Journal of General Chemistry - Efficient synthesis of quinazoline derivatives via rhodium-catalyzed dehydrogenation and ring-closing method was developed with moderate to high yields.     

Hydrogenation of nitroarenes catalyzed by a dipalladium complex

A dipalladium complex [Pd₂( L )Cl₂](PF₆)₂ ( 2 ), via the substitution of (PhCN)₂PdCl₂ with 5‐phenyl‐2,8‐bis(6′‐bipyridinyl)‐1,9,10‐anthyridine ( L ) followed by the anion exchange, was found to be a good pre‐catalyst for the reduction of nitroarenes to yield the corresponding anilines under atmospheric pressure of hydrogen in methanol. This method provides a straightforward access to a diverse array of functionalized anilines, exhibiting a possible application in synthetic chemistry. The catalytic activity of this complex is enhanced by the di‐metallic system via the synergistic effect.     

Spontaneous disproportionation of rhodium(I) bisoxazolinates to rhodium(II)

[RhI(t-Bu2-boxate)(C2H4)2] spontaneously disproportionates to the mononuclear [RhII(t-Bu2-boxate)2], whereas [RhI(Ph2-boxate)(C2H4)2] is stable against disproportionation.     

Kinetic studies of cyclohexane hydrogenation catalyzed by the Rh(I) compounds with 2-aminopyridine

The kinetics of homogeneous hydrogenation of cyclohexene in the presence of the catalytic Rh₂Cl₂(C₈H₁₄)₄ + 2-aminopyridine has been investigated (C₈H₁₄ = cyclooctene). The rate of reaction may be expressed as

At 30 °C the equilibrium constants are: K₁ = 862 mol⁻¹ l, K₂ = 4.9 mol⁻¹ l and rate constant k = 14.0 mol⁻¹ l s⁻¹. The activation parameters are: E_a = 26.9 kJ mol⁻¹, ΔH^≠ = 24.4 kJ mol⁻¹, ΔS^≠ = − 135.9 J K⁻¹ mol⁻¹. The catalyst is about 10 times more active in the hydrogenation of cyclohexene than RhCl (PPh₃)₃.