Promotion of acetophenone formation from methyl(phenyl)rhodium carbonyl complexes by organic halides

[C₅Me₅RhPh(CO)CH₃] reacted thermally to give acetophenone (27%) and toluene (9%); acetophenone formation was substantially increased in the presence of halobenzenes PhX (the order of effectiveness being X = I> Br> Cl) or methyl iodide, but 1-electron oxidisers promoted C---C coupling (toluene formation).     

Palladium(0)-catalyzed direct cross-coupling reaction of allylic alcohols with aryl- and alkenylboronic acids

Allylic alcohols can be used directly for the palladium(0)-catalyzed allylation of aryl- and alkenylboronic acids with a wide variety of functional groups. A triphenylphosphine-ligated palladium catalyst turns out to be most effective for the cross-coupling reaction and its low loading (less than 1 mol%) leads to formation of the coupling product in high yield. The Lewis acidity of the organoboron reagents and poor leaving ability (high basicity) of the hydroxyl group are essential for the cross-coupling reaction. The reaction process is atom-economical and environmentally benign, because it needs neither preparation of allyl halides and esters nor addition of stoichiometric amounts of a base. Furthermore, allylic alcohols containing another unsaturated carbon-carbon bond undergo arylative cyclization reactions leading to cyclopentane formation.     

Reduction of ketones and alkyl iodides by SmI(2) and Sm(II)-HMPA complexes. Rate and mechanistic studies

The effect of HMPA on the electron transfer (ET) rate of samarium diiodide reduction reactions in THF was analyzed for a series of ketones (2-butanone, methyl acetoacetate, and N,N-dimethylacetoacetamide) and alkyl iodides (1-iodobutane and 2-iodobutane) with stopped flow spectrophotometric studies. Activation parameters for the ET processes were determined by temperature-dependence studies over a range of 30-50 degrees C. The ET rate constants and the activation parameters obtained for the above systems in the presence of different equivalents of HMPA were compared to understand the mechanism of action of HMPA on various substrates. The results obtained from these studies indicate that coordination or chelation is possible in the transition state geometry for SmI(2)/ketone systems even in the presence of the sterically demanding ligand HMPA. After the addition of 4 equiv of HMPA the ET rate and activation parameters for ketone reduction by Sm is unaffected by further HMPA addition while a linear dependence of ET rate on the equivalents of HMPA was found in the SmI(2)/alkyl iodide system. The results of these studies are consistent with an inner-sphere-type ET for the reduction of ketones by SmI(2) (and SmI(2)[bond]HMPA complexes) and an outer-sphere-type ET for the reduction of alkyl iodides by SmI(2) or SmI(2)[bond]HMPA complexes.     

The formation of cobalt acetylides by direct reaction at cobalt(III)

A new method is described for the preparation of cobalt(III) acetylides, in which monosubstituted alkynes are treated directly with cobalt(III) forms of quadridentate Schiff base compounds in methanol.     

Direct asymmetric aldol-Tishchenko reaction of aliphatic ketones catalyzed by syn-aminoalcohol-Yb(III) complexes

The asymmetric direct aldol condensation of aldehydes with ethyl- and propylketones is catalyzed by syn-alpha-aminoalcohol-Yb(OTf)3 complexes, yielding the anti-1,3-diol monoesters with high diastereocontrol and good enantioselectivity. Three adjacent stereogenic centers are created in a simultaneous aldol condensation and Evans-Tishchenko reduction in an acyclic system.     

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.     

Palladium(0) nanoparticle-catalyzed sp C-H activation: a convenient route to alkyl-aryl ketones by direct acylation of aryl bromides and iodides with aldehydes

Palladium(0) nanoparticles efficiently catalyze aliphatic aldehyde C-H functionalization by aryl halides to produce alkyl-aryl ketones in good yields. A wide range of substituted aryl and hetero-aryl bromides/iodides and open-chain aldehydes of varied chain length participated in this reaction.     

Synthesis and crystal structure of (dibenzo-18-crown-6)(iodo)(trichlorometane)potassium

A new complex compound (dibenzo-18-crown-6)(iodo)(trichlorometane)potassium was obtained. Its crystal structure was studied by X-ray structural analysis. The complex molecule is built by the “guest-host” type: its K⁺ cation is in the crown ligand hollow and is coordinated via its all six O atoms, and also via the iodine ligand I and one Cl atom of the ligand CHCl₃ molecule. The coordination polyhedron of this K⁺ cation is a slightly distorted hexagonal bipyramid. In the crystal structure the complex molecules are connected in infinite chains by intercomplex hydrogen bonds Cl₃C-H?I ⁱ between the ligand molecule CHCl₃ and the iodine ligand of a neighboring complex molecule.     

The cross-aldol reaction of hexafluoroacetone (HFA) with ketones catalyzed by an acid

The cross-aldol reactions of hexafluoroacetone (HFA) and ketones using an acid catalyst are reported. When concentrated sulfuric acid was employed as the catalyst, HFA reacted regioselectively with various ketones at 50-100 °C to give the aldol adducts (6) in good yields. The reaction is initiated by an acid-catalyzed transformation of the ketone into the corresponding enol that reacts with HFA. The obtained adducts (6) can be reduced with hydrogen under a Ru/C catalyst to lead to the corresponding fluorine-containing diols (13).     

Rhodium carbonyl complexes of thetrans-[RhCl(CO)(PR3)2] type with pyridylphosphines

Summary Trans-[RhCl(CO)(PR₃)₂] complexes [PR₃=tris-(2-pyridyl)phosphine {P(2-pyl)₃}, phenylbis(2-pyridyl)phosphine {PPh(2-pyl)₂} or tris(3-pyridyl)phosphine {P(3-pyl)₃}] have been synthesized and examined by spectroscopic methods (i.r., u.v.-vis,³¹P{¹H} n.m.r.,¹H n.m.r.). In solution the P(2-pyl)₃ and PPh(2-pyl)₂ complexes exhibit equilibrium between the pentacoordinate state, with one of the phosphine molecules coordinated via nitrogen and phosphorus, and complexes with the phosphine coordinated only through nitrogens.     

A radical mechanism of the reaction of molybdenum carbonyl complexes with bis(triethylgermyl)mercury

The reaction of [Cp(CO)₃Mo]₂ with (Et₃Ge)₂Hg occurs in toluene and THF by a radical mechanism. The interaction between [Cp(CO)₃Mo]₂Hg and (Et₃Ge)₂Hg has a radical character only in THF. The formation of Cp(CO)₃MoH at the first stage of these reactions substantially affects the further course of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1648–1650, September, 1993.     

Reactivities of novel [hydroxy(tosyloxy)iodo]arenes and [hydroxy(phosphoryloxy)iodo]arenes for alpha-tosyloxylation and alpha-phosphoryloxylation of ketones

Novel [hydroxy(tosyloxy)iodo]arenes bearing 2-thienyl, 3-thienyl, N-tosyl-4-pyrazolyl, 3-trifluoromethylphenyl, and 3,5-bis(trifluoromethy)phenyl as an aromatic group, and [hydroxy(phosphoryloxy)iodo]arenes bearing N-tosyl-4-pyrazolyl, 3-trifluoromethylphenyl, and 3,5-bis(trifluoromethy)phenyl as an aromatic group, were prepared. alpha-Tosyloxylation and alpha-phosphoryloxylation of ketones with these compounds were carried out, respectively. Their reactivities were compared with that of the parent [hydroxy(tosyloxy)iodo]benzene and [hydroxy(phosphoryloxy)iodo]benzene, respectively, and consequently [hydroxy(tosyloxy)iodo]arenes and [hydroxy(phosphoryloxy)iodo]arenes bearing 3-trifluoromethylphenyl and 3,5-bis(trifluoromethy)phenyl as an aromatic group showed the best reactivity. These new compounds can be used as powerful alpha-tosyloxylation and alpha-phosphoryloxylation reagents, instead of the parent [hydroxy(tosyloxy)iodo]benzene and [hydroxy(phosphoryloxy)iodo]benzene.     

Mizoroki-Heck reaction of (1-fluorovinyl)methyldiphenylsilane with aryl iodides

The Mizoroki-Heck reaction of (1-fluorovinyl)methyldiphenylsilane with a variety of aryl iodides was accomplished under the conditions composing Pd(OAc)(2), Ag(2)CO(3) and MS 4 ? in 1,4-dioxane to give the corresponding (E)-β-aryl-(α-fluorovinyl)methyldiphenylsilanes with excellent stereoselectivity.     

Rhodium(I) carbonyl complexes of quinoline carboxaldehyde ligands and their catalytic carbonylation reaction

The dimeric rhodium precursor [Rh(CO)₂Cl]₂ reacts with quinoline (a) and its three isomeric carboxaldehyde ligands [quinoline-2-carboxaldehyde (b), quinoline-3-carboxaldehyde (c), and quinoline-4-carboxaldehyde (d)] in 1:2 mole ratio to afford complexes of the type cis-[Rh(CO)₂Cl(L)] (1a-1d), where L = a-d. The complexes 1a-1d have been characterised by elemental analyses, mass spectrometry, IR and NMR (¹H, ¹³C) spectroscopy together with a single crystal X-ray structure determination of 1c. The X-ray crystal structure of 1c reveals square planar geometry with a weak intermolecular pseudo dimeric structure (Rh?Rh = 3.573 Å). 1a-1d undergo oxidative addition (OA) with different electrophiles such as CH₃I, C₂H₅I and I₂ to give Rh(III) complexes of the type [Rh(CO)(COR)Cl(L)I] {R = -CH₃ (2a-2d), R = -C₂H₅ (3a-3d)} and [Rh(CO)Cl(L)I₂] (4a-4d) respectively. 1b exhibits facile reactivity with different electrophiles at room temperature (25 °C), while 1a, 1c and 1d show very slow reactivity under similar condition, however, significant reactivity was observed at a temperature ∼40 °C. The complexes 1a-1d show higher catalytic activity for carbonylation of methanol to acetic acid and methyl acetate [Turn Over Frequency (TOF) = 1551-1735 h⁻¹] compared to that of the well known Monsanto’s species [Rh(CO)₂I₂]⁻ (TOF = 1000 h⁻¹) under the reaction conditions: temperature 130 ± 2 °C, pressure 33 ± 2 bar, 450 rpm and time 1 h. The organometallic residue of 1a-1d was also isolated after the catalytic reaction and found to be active for further run without significant loss of activity.     

Ruthenium(II) porphyrin catalyzed tandem carbonyl ylide formation and 1,3-dipolar cycloaddition reactions of alpha-diazo ketones

[reaction: see text] The ruthenium porphyrin-catalyzed reactions of diazo ketones with pi-unsaturated compounds via carbonyl ylide formation/cycloaddition cascade exhibit product yields and selectivities comparable to the analogous reactions with dirhodium carboxylates as catalysts. By grafting a ruthenium porphyrin on poly(ethylene glycol) (Zhang, J.-L.; Che, C.-M. Org. Lett. 2002, 4, 1911), a recyclable catalytic system is developed with over 5700 product turnovers attained for the reaction of 1-diazo-2,5-hexanedione with dimethyl acetylenedicarboxylate.     

Amination and amidation of aryl iodides catalyzed by copper(I)-phenanthroline complexes

Four kinds of copper(I)-phenanthroline complexes ([Cu^I(phen)₂]Cl, [Cu^I(phen)Cl]₂, [Cu^I(phen)₂]BF₄, and Cu^I(phen)PPh₃Cl) were prepared and used as catalysts for amination and amidation of aryl iodide to investigate the influence on the yields of products due to differences of the structures. These complexes were found to work as catalysts on these reactions and showed that the differences of structures of copper(I) complexes significantly influenced the yield of aryl-nitrogen bond forming processes.     

Preparation of ketones by direct reaction of grignard reagents with acid chlorides in tetrahydrofuran

Grignard reagents react with acid chlorides in tetrahydrofuran at low temperature to produce ketones in excellent yields. The results reported here strongly indicate the importance of the solvent in Grignard reagent chemistry.