A New Catalyst System for the Heck Reaction of Unreactive Aryl Halides

A simple solution to the age-old problem of the Heck reaction of cheap but unreactive chloro- and bromoarenes [for example, reaction (1)] has been found in the catalyst [Pd(CH₃CN)₂Cl₂]⋅6 Ph₄PCl in the presence of N,N-dimethylglycine as additive. The reaction then proceeds with exceptionally high efficiency.     

N-isocyaniminotriphenylphosphorane (Ph3PNNC) as an efficient reagent for the synthesis of ferrocene-containing 1,3,4-oxadiazole derivatives

Reaction of N-isocyaniminotriphenylphosphorane (Ph₃PNNC) with an aromatic aldehyde in the presence of ferrocene carboxylic acid and a secondary amine proceeds smoothly at room temperature under neutral conditions to afford sterically congested ferrocene-containing 1,3,4-oxadiazole derivatives in high yields. The reaction progresses smoothly and clearly under mild conditions and no side reactions were observed.     

Four-component synthesis of ferrocene-containing 1,3,4-oxadiazoles from N-isocyaniminotriphenylphosphorane (Ph3PNNC), a primary amine,a cyclic ketone and ferrocene carboxylic acid

The 1:1 imine intermediate created by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane (Ph₃PNNC) in the presence of ferrocene carboxylic acid and the corresponding iminophosphorane intermediate was formed. Afterwards, ferrocene containing 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reaction proceeded under mild conditions at room temperature.     

Synthesis and reactivity of N-hydroxy-2-aminoindoles

Catalytic hydrogenation of (2-nitrophenyl)acetonitriles bearing an electron-withdrawing substituent α to the nitrile, using Pd/C and (Ph₃P)₄Pd, affords N-hydroxy-2-aminoindoles in good to excellent yields. (Ph₃P)₄Pd decreases the reduction rate of the intermediate hydroxylamine and acts as a catalyst during the cyclization onto the nitrile.     

A novel imido-transfer reaction of aldehydes with Ph3PNTs using RuCl2(PPh3)3 as catalyst

(N-Tosylimino)triphenylphosphorane (Ph₃PNTs) was found to be an efficient imido-transfer reagent for the imidation of a variety of aldehydes using RuCl₂(PPh₃)₃ as the catalyst.     

First examples of neutral rhenium(V) complexes with a novel semi-rigid ligand containing a P,N,N,S donor atom set: Synthesis,characterisation and crystal structure

A new PN₂S ligand, N-[2-(diphenylphosphino)phenyl]-2-[(S-trityl)acetylamino]ethanamide [Ph-P(Ph₂)N₂S(Trt)], was synthesised and reacted with Re^V precursors. The reaction of both tritylated and detritylated ligands with ReOCl₃(PPh₃)₂ gave the same expected neutral complex [ReO{Ph-P(Ph₂)N₂S}] (4) in good yield. An unexpected neutral and diamagnetic species, [ReN{Ph-P(Ph₂)N₂S(Trt)}] (5), has been isolated during the complexation of the tritylated ligand with ReNCl₂(PPh₃)₂. The complexes, characterized by classical spectroscopic methods and X-ray analysis for 4, are the first examples of neutral semi-rigid-PN₂S rhenium(V) complexes.     

N-Isocyaniminotriphenylphosphorane (Ph3PNNC) as an Efficient Reagent for the Synthesis of Fully Substituted 1,3,4-Oxadiazoles from 3-Phenyl-2-Propynoic Acid,Secondary Amines and Aromatic Bis-Aldehydes

Abstract

Reactions of N-isocyaniminotriphenylphosphorane (Ph₃PNNC) with aromatic bis-aldehydes (isophthalaldehyde and terphthalaldehyde) in the presence of 3-phenyl-2-propynoic acid and secondary amines proceed smoothly at room temperature and in neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions and no side reactions were observed.     

Effects of substituent and catalyst on the intramolecular Povarov reaction—synthesis of chromenonaphthyridines

2-(N-Alkenyl-N-aryl)aminochromone-3-carbaldehyde undergoes intramolecular Povarov reaction with aromatic amines in the presence of Ph₃P·HClO₄ to produce chromenonaphthyridine. The effects of substituent and catalyst have been studied. The substituent on the alkenyl part of aminochromone controls the mode of reaction as well as the stereochemistry of the product.     

An efficient and green protocol for synthesis of novel [1,3]oxazino[5,6-c]quinolin-5-one derivatives using [Et3NH]HSO4 as a reusable catalyst

A simple, efficient, and eco-friendly procedure has been developed using acidic ionic liquid [Et₃NH]HSO₄ as catalyst for the synthesis of novel [1,3]oxazino[5,6-c]quinolin-5-one derivatives via one-pot three-component condensation reaction of 4-hydroxyquinolin-2(1H)-one, amine and formaldehyde in aqueous ethanol at room temperature. Mild and environmentally benign reaction conditions, short reaction time, good to excellent yields, nontoxic, cheap and easily available catalyst, reusability of catalyst and reaction media, and easy work-up are the key features of this method.     

Kinetic studies on the hydrosilylation of phenylacetylene with R3SiH (R3 = PhMe2, Ph2Me,Ph3, Et3) using bis(1,2‐diphenylphosphinoethane)norbornadiene rhodium(I) hexafluorophosphate as catalyst

Product distribution and kinetic studies on the hydrosilylation of phenylacetylene by Ph₃SiH, Ph₂MeSiH, PhMe₂SiH and Et₃SiH were performed using bis‐[1,2‐diphenylphosphinoethane]norbornadienerhodium(I) hexafluorophosphate, 1, as catalyst. Pre‐equilibration of the catalyst with the acetylene produced hydrosilylations, pre‐equilibration with the silane did not. The catalyst showed a pronounced selectivity for cis‐addition to form β‐products, t‐PhCH­CHSiR₃, unlike most hydrosilylation catalysts. The kinetic studies showed a hydrosilylation reaction that is zero order with respect to both acetylene and the silane, with a dependency upon catalyst concentration. The k_obs value is directly influenced by the substituents on the silane: k(PhMe₂SiH) > k (Et₃SiH > k (Ph₂MeSiH) > k (Ph₃SiH). Intercalation of the catalyst in hectorite was not useful, since either no reaction occurred in non‐polar solvents, or extraction of the catalyst occurred in polar solvents to produce the same product distributions. Copyright © 2000 John Wiley & Sons, Ltd.     

One‐Pot Synthesis of 3‐Acetyl‐2‐aryl‐3,4‐dihydroquinazolines from N‐[2‐(Azidomethyl)phenyl]benzamides Utilizing Intramolecular Aza‐Wittig Reaction

A new and convenient method for the preparation of 3,4‐dihydroquinazolines 5 with aryl and Ac groups at C(2) and N(3), respectively, has been developed. The key sequence is the formation of aza‐phosphorane intermediates by the reaction of N‐[2‐(azidomethyl)phenyl]benzamides 1 with Ph₃P, followed by intramolecular aza‐Wittig reaction and 3‐acetylation, which can be conducted in one‐pot.     

Catalytic olefin hydrogenation with the application of a new water soluble rhodium catalyst

The catalyst precursor preparedin situ from rhodium dimer [Rh(cod)Cl]₂ and a new water-soluble phosphine Ph₂PCH₂CH₂CONHC(CH₃)₂CH₂SO₃H (in Li⁺ salt form) has been found to act as an effective olefin hydrogenation catalyst. Catalytic hydrogenation reactions have been tested in either two phase: aqueous catalyst/insoluble olefin or methanolic catalyst/olefin systems. The observed reaction rates were higher for terminal than for internal olefins. 1-Hexene in methanolic solution has been hydrogenated with a turnover frequency of about 8000 h^–1. This system has also been applied in the form of a supported aqueous phase catalyst.     

Bis(triphenylphosphine)palladium(II)succinimide as a precatalyst for Suzuki cross-coupling—subtle effects exerted by the succinimide ligand

A new palladium(II) precatalyst for Suzuki cross-coupling of aryl halides and organoboronic acids has been identified, namely bis(triphenylphosphine)palladium(II)succinimide [(Ph₃P)₂Pd(N-Succ)₂] 2. The precatalyst is easily prepared from palladium(0) precursors, such as (Ph₃P)₄Pd or Pd₂dba₃·CHCl₃/Ph₃P and succinimide, is air, light and moisture stable, and may be employed with a variety of substrates to give the cross-coupled products, in good yields and in reasonable time, at relatively low catalyst loadings.     

Trishomoaromatic (B3N3Ph6) Dianion: Characterization and Two-Electron Reduction

Benzene, a common aromatic compound, can be converted into an unstable antiaromatic 8π-electron intermediate through two-electron reduction. However, as an isoelectronic equivalent of benzene, borazine (B₃N₃Ph₆), having weak aromaticity, undergoes a totally different two-electron reduction to afford (B₃N₃R₆)²⁻ homoaromatic compounds. Reported here is the synthesis of homoaromatic (B₃N₃Ph₆)²⁻ by the reduction of B₃N₃Ph₆ with either potassium or rubidium in the presence of 18-crown-6 ether. Theoretical investigations illustrate that two electrons delocalize over the three boron atoms in (B₃N₃Ph₆)²⁻, which is formed by the geometric and orbital reorganization and exhibits (π,σ)-mixed homoaromaticity. Moreover, (B₃N₃Ph₆)²⁻ can act as a robust 2e reductant for unsaturated compounds, such as anthracene, chalcone, and tanshinones. This 2e reduction is of high efficiency and selectivity, proceeds under mild reaction conditions, and can regenerate neutral borazine.     

Hydrosilylation of alkenes catalyzed by Fe powder

A novel iron-catalyzed hydrosilylation of alkenes process under solvent-free conditions has been reported. The influence of the amount of Fe catalyst, reaction temperature and various alkenes and silanes on the hydrosilylation were investigated. High yields of adduct were obtained in the hydrosilylation of octene with MeCl₂H, Me₂ClSiH and Ph₂SiH₂ by using 10?mol% iron powder as a signal catalyst.     

Facile synthesis of fluorinated α-imino alkynes by the coupling reaction of imidoyl iodides with terminal alkynes

A series of N-arylbromodifluoroacetimidoyl iodides and 1-alkynes were converted into α-imino alkynes by using Pd(Ph₃)₂Cl₂/CuI as the catalyst under mild conditions. The reaction proceeded smoothly to give the coupling products in good to excellent yields.     

Dinuclear Zinc Hydride Supported by an Anionic Bis(N‐Heterocyclic Carbene) Ligand

Methylene‐linked bis(N,N′‐di‐tert‐butylimidazol‐2‐ylidene) 1 reacted with diethylzinc to give dinuclear zinc ethyl compound 2 , which contains a formally anionic bis(carbene) ligand as a result of deprotonation of the methylene bridge. The reaction of 2 with PhSiH₃ gave the phenylsilyl compound 3 . The zinc hydride 4 was obtained by the reaction of 2 with LiAlH₄ or Ph₃SiOH followed by treatment with PhSiH₃. X‐ray diffraction studies show that compounds 2 , 3 , and 4 all have a similar dimeric structure with D_2h symmetry. The reaction of hydride 4 with carbon dioxide and N,N′‐diisopropylcarbodiimide gave formato ( 5 ) and formamidinato ( 7 ) derivatives as a result of the insertion of the heterocumulene into both Zn? H bonds. Reaction with Ph₂CO gave the diphenylmethoxy compound 6 . Hydride 4 shows catalytic activity in the hydrosilylation of 1,1‐diphenylethylene and methanolysis of silanes.     

Cyclic sulfur nitrogen compounds and phosphorus reagents: Part XII. Reactions of S4N4 with (2-pyridylamino) phosphines [1]

Tetrasulfurtetranitride, S₄N₄ reacts with (2-pyridylamino)-diphenylphosphine in MeCN at room temperature to form the cyclotrithiazene (NC₅H₄NH)-Ph₂PN S₃N₃ ( 1 ) in good yield. By contrast, the cyclophosphathiazenes Ph₂PS₂N₃ ( 2 ) and 1,5(Ph₂P)₂S₂N₄ ( 3 ) are isolated from the same reaction mixture under reflux conditions. In solution, compound 1 is found to be transformed into 2 . The reaction of S₄N₄ with (2-pyridylamino)phenyl(dicyclohexylamino)phosphine in MeCN at room temperature affords Ph(DCA)PS₂N₃ ( 4 ) (DCA = dicylohexylamino) as the only reaction product. This on treatment with norbornadiene produces the addition product Ph(DCA)PS₂N₃·C₇H₈ ( 5 ). The structure of 4 has been established by X-ray diffraction. Its PSN ring adopts a skew boat conformation with S N bond lengths varying from 1.574(4) to 1.606(4) Å. The mean value of the endocyclic P N bonds amounts to 1.618(3) Å.     

Polymerization of cyclohexene oxide with aluminum complex-silanol catalyst. IV. Photopolymerization with Ph3SiCOPh-Al complex-alcohol catalyst system

A new catalyst system (Ph₃SiCOPh-aluminum complex-alcohol) was investigated for photopolymerization of cyclohexene oxide. Polymer conversion and molecular weight increased with polymerization time. When a Ph₃SiCOPh-Al (n-Praa)₃-alcohol catalyst system was used the catalyst activity decreased, depending on the alcohol: i-PrOH > n-PrOH > i-BuOH > MeOH > t-BuOH > H₂O. When the Ph₃SiCOPh-Al complex-i-PrOH catalyst system was used the catalyst activity decreased, depending on the ligand of the Al complex: ß-ketoester > orthocarbonyl phenol > ß-diketone. Benzophenone derivatives were effective for catalyst activation as a photosensitizer.     

Multicomponent one pot synthesis of C-glucosides of 1-azaindolizines

Abstract

A protocol based on Groebke-Blackburn-Bienayame (GBB) multicomponent reaction has been developed for efficient and atom economical synthesis of C-glucosides of 1-azaindolizine, i.e. 2-(β-D-glucopyranosyl)-3-N-alkylamino-1-azaindolizine. Thus, a series of fourteen novel 2-(β-D-glucopyranosyl)-3-N-alkylamino-1-azaindolizines have been synthesized in moderate to good yields by reaction of a perbenzylated β-C-glucopyranosyl aldehyde with differently substituted 2-aminopyridines and alkyl isocyanides using InCl₃ as acid catalyst. All synthesized β-C-glucosides were unambiguously characterized with the help of spectroscopic (IR, ¹H-NMR, ¹³C-NMR and mass spectra) data analysis.