Pyrrole synthesis catalyzed by AgOTf or cationic Au(I) complexes

Either silver trifluoromethanesulfonate or a mixture of gold(I) chloride, silver trifluoromethanesulfonate, and triphenylphosphine catalyze the formation of pyrroles from substituted beta-alkynyl ketones and amines. The reactions proceed by using 5 mol % of catalyst with yields of isolated pyrroles ranging from 13% to 92%. Sixteen examples are used to compare the effectiveness of each catalyst.     

Highly enantioselective nitrone cycloadditions with 2-alkenoyl pyridine N-oxides catalyzed by Cu(II)-BOX complexes

Enantioselective nitrone cycloadditions with 2-alkenoyl pyridine N-oxides as dipolarophiles have been reported. The reaction is catalyzed by Cu(II)-BOX complexes to give the expected isoxazolidine products with high diastereo- and enantioselectivity.     

Enantioselective nitrone cycloadditions of alpha,beta-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl)pyridine-cerium(IV) triflate complexes

[Structure: see text] Enantioselective nitrone cycloadditions with beta-substituted alpha,beta-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl)pyridine-cerium(IV) triflate complexes 1 have been reported. The isoxazolidine products were efficiently transformed into densely functionalized beta'-hydroxy-beta-amino acid derivatives.     

Synthesis of 2-substituted pyridines catalyzed by cobalt(I) complexes and promoted by light

A series of pyridines substituted in the 2-position were synthesized by cobalt(I)-catalyzed cotrimerization of alkynes and nitriles. The reactions are usually enhanced by light. The reaction conditions are very mild. Activity and selectivity are satisfactory with respect to formation of pyridines, but depend on the type of nitrile.     

Selenolate gold complexes with aurophilic Au(I)-Au(I) and Au(I)-Au(III) interactions

The gold(I) selenolate compound [Au(2)(SePh)(2)(mu-dppf)] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) has been prepared by reaction of [Au(2)Cl(2)(mu-dppf)] with PhSeSiMe(3) in a molar ratio 1:2. This complex reacts with gold(I) or gold(III) derivatives to give polynuclear gold(I)-gold(I) or gold(I)-gold(III) complexes of the type [Au(4)(mu-SePh)(2)(PPh(3))(2)(mu-dppf)](OTf)(2), [Au(3)(C(6)F(5))(3)(mu-SePh)(2)(mu-dppf)], or [Au(4)(C(6)F(5))(6)(mu-SePh)(2)(mu-dppf)], with bridging selenolate ligands. The reaction of [Au(2)(SePh)(2)(mu-dppf)] with 1 equiv of AgOTf leads to the formation of the insoluble Ag(SePh) and the compound [Au(2)(mu-SePh)(mu-dppf)]OTf. The complexes [Au(4)(C(6)F(5))(6)(mu-SePh)(2)(mu-dppf)] and [Au(2)(mu-SePh)(mu-dppf)]OTf (two different solvates) have been characterized by X-ray diffraction studies and show the presence of weak gold(I)-gold(III) interactions in the former and intra- and intermolecular gold(I)-gold(I) inter-actions in the later.     

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.     

Asymmetric transfer hydrogenation of ketones catalyzed by phosphine-rhodium(I) and -iridium(I) complexes

The asymmetric hydrogen transfer from propan-2-ol to prochiral ketones is effectively catalyzed by diphosphine complexes of iridium and rhodium. The influence of the reaction conditions on the activity and selectivity of the catalysts has been investigated.     

Enantioselective intramolecular amidation of sulfamate esters catalyzed by chiral manganese(III) Schiff-base complexes

Enantioselective intramolecular amidation of sulfamate esters catalyzed by chiral manganese(III) Schiff-base complexes under mild conditions (PhI(OAc)₂, Al₂O₃, C₆H₆, 5 °C) was achieved in moderate to good yields (up to 92%), substrate conversions (up to 99%), with virtually complete cis-selectivity and with ee values up to 79% ee.     

某些Au(III)、Au(I)配离子在溶液中扩散的研究

用毛细管色谱在25℃测定了AuCl4、[Au(SO3)2]、[Au(CSN2H4)2]、[Au(CN)2]等配位体离子在HCl溶液中的扩散系数及AuCl4阴离子的扩散活化能, 并与文献中其它配阴离子的D值比较, 认为扩散离子的质量和所载电荷可能是决定配阴离子扩散系数的主要因素.     

Thermodynamics of the hydrogenation of olefins catalyzed by Rh(I) and Ir(I) complexes

The homogeneous hydrogenation of cyclohexene catalyzed by Rh(I) and Ir(I) complexes of the terdentate ligands (L) HN(CH₂CH₂Aφ₂)₂ (A = P, As) was investigated in the temperature range 20 - 50°C. Thermodynamic parameters corresponding to the formation of the dihydrido complexes ML(H)₂Cl (M = Ir(I), Rh(I)) and the olefin complexes MLCl(olefin) were computed. The activation parameters corresponding to the rate constant were also calculated. An inverse relationship is found between the enthalpy of formation ΔH⁰ of the dihydrido complexes and the enthalpy of activation ΔH^≠ of the hydrogenation step. This relationship establishes the involvement of the dihydrido complexes as the active intermediates in olefin coordination and hydrogen transfer. The stereochemistry of the terdentate complexes in dihydride formation is discussed. It is concluded that the enthalpy of formation ΔH⁰ of the dihydrido complexes of terdentate ligands is very favourable, as there is no change in the configuration of the ligand in oxidative addition reaction. The significance of the steric factors in the hydrogenation step is discussed.     

Intramolecular [4 + 2] cycloadditions of 1,3-enynes or arylalkynes with alkenes with highly reactive cationic phosphine Au(I) complexes

New Au(I) complexes with bulky, biphenyl phosphines are the most reactive catalysts for the cyclizations of enynes. 1,6-Enynes with an aryl ring at the alkyne give 2,3,9,9a-tetrahydro-1H-cyclopenta[b]naphthalenes by a 5-exo-dig cyclization followed by a Nazarov-type ring expansion. 1,8-Dien-3-ynes also cyclize by a 5-exo-dig pathway to form hydrindanes.     

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.     

铜配合物催化的环状烯烃的光化学顺、反异构化反应

在大于300nm光波照射下,氯化亚铜或乙酰丙酮基铜(I)等低价铜配合物可以有效地催化中大环环状烯烃的顺、反异构化反应,对在大于250nm光波照射下,顺,顺-1,5-环辛二烯分子内环加成形成三环[3.3.0.0^2^.^6]-辛烷的反应机制,进行了讨论。     

Enantioselective intramolecular alkene hydroaminations catalyzed by yttrium complexes of axially chiral bis(thiolate) ligands

[structure: see text] A yttrium(III) complex derived from proligand 7c has been shown to be a superior catalyst for enantioselective intramolecular alkene hydroaminations that provide cyclic amines with ee's ranging from 69% to 89%.     

Investigation and mechanistic study into intramolecular hydroalkoxylation of unactivated alkenols catalyzed by cationic lanthanide complexes

Cationic lanthanide complexes of the type [Ln(CH₃CN)₉]³⁺[(AlCl₄)₃]^3–·CH₃CN (Ln = Pr, Nd, Sm, Gd, Er, Yb, Y) served as effective catalysts for the intramolecular hydroalkoxylation/cyclization of unactivated alkenols to yield the cyclic ethers with Markovnikov regioselectivity under mild conditions. Novel cationic complexes, [AlCl(CH₃CN)₅]²⁺[(AlCl₄)₂]^2–·CH₃CN and [Nd(CH₃CN)₉]³⁺[(FeCl₄)₃]^3–·CH₃CN, were synthesized and evaluated for the intramolecular hydroalkoxylation/cyclization of unactivated alkenols for comparison. The active sequence of [Nd(CH₃CN)₉]³⁺[(FeCl₄)₃]^3–·CH₃CN < [AlCl(CH₃CN)₅]²⁺[(AlCl₄)₂]^2–·CH₃CN < [Nd(CH₃CN)₉]³⁺[(AlCl₄)₃]^3–·CH₃CN observed indicated that both the cation and anion have great influence on the activity. Comparative study on the activity of AlCl₃ and its cationic complex [AlCl(CH₃CN)₅]²⁺[(AlCl₄)₂]^2–·CH₃CN revealed the formation of the cationic Al center enhanced the activity greatly. The ¹H NMR studies indicated the activation of hydroxyl and olefin by the cationic Ln³⁺ center were involved in the reaction pathways.     

A theoretical study on the trans-addition intramolecular hydroacylation of 4-alkynals catalyzed by cationic rhodium complexes

The mechanism of the intramolecular hydroacylation reaction of 4-alkynals is studied for a 4-pentynal-[Rh(PH2CH2CH2PH2)]+ model system using MP2 calculations. The endo-cyclization to form a rhodacyclohexenone intermediate is kinetically less favorable than the exo-cyclization to form a rhodacyclopentanone intermediate. The kinetic preference toward the endo-cyclization is found to be enhanced by complexation of donor ligands (H2CO, NCH, and HCCH). The formation of cyclopentenone product proceeds via reductive elimination from one of the two rhodacyclohexenone intermediates, whereas the formation of cyclobutanone product from the two rhodacyclopentanone intermediates requires high activation energy. Addition of an acetylene stabilizes the highly electron-poor rhodacyclopentanone intermediate generated from exo-cyclization and leads to an insertion to give [4 + 2] annulation product, cyclohexenone. The role of a coordinating acetone solvent in the formation of cyclopentenone product is also discussed.