Phosphorylation of oxyethylated resorcinol and calix[4]resorcinarene with P(III) acid amides

Abstract

Phosphorylation of 1,3-bis(2-hydroxyethoxy)benzene and octa(2-hydroxyethyl) calix[4]-resorcinarenes with P(III) acid amides and chloramides has been studied. It has been determined that the nature of phosphorous acid amides affects significantly the synthetic result of the reaction.     

General Catalytic Methylation of Amines with Formic Acid under Mild Reaction Conditions

A general catalytic protocol for the methylation of amines has been developed applying, for the first time, formic acid as the C₁ building block and silanes as reducing agents. A broad range of aromatic and aliphatic, both primary and secondary, amines has been converted to the corresponding tertiary amines including [N‐¹³C]‐labelled drugs in good to excellent yields under mild conditions.     

Manganese(III) Porphyrin-Catalyzed Dehydrogenation of Alcohols to form Imines,Tertiary Amines and Quinolines

Manganese(III) porphyrin chloride complexes have been developed for the first time as catalysts for the acceptorless dehydrogenative coupling of alcohols and amines. The reaction has been applied to the direct synthesis of imines, tertiary amines and quinolines where only hydrogen gas and/or water are formed as the by-product(s). The mechanism is believed to involve the formation of a manganese(III) alkoxide complex which degrades into the aldehyde and a manganese(III) hydride species. The latter reacts with the alcohol to form hydrogen gas and thereby regenerates the alkoxide complex.     

绿色催化二氧化碳、炔丙醇和亲核试剂的三组分反应

近些年来,将CO₂转化为高附加值化学品受到广泛关注。其中,CO₂、炔丙醇和亲核试剂的三组分反应可用于制备用途广泛的羰基化合物,该方法具有步骤经济性、原子经济性等优点。由于CO₂分子具有热力学稳定性和动力学惰性,多数CO₂参与的化学反应在热力学上不支持。然而,CO₂、炔丙醇和双亲核试剂三组分反应是热力学有利的CO₂转化反应,实现了邻二醇或氨基醇和CO₂到环状碳酸酯以及2-噁唑啉酮的高效转化。本综述旨在于总结并讨论近年来CO₂、炔丙醇和亲核试剂三组分反应制备多种羰基化学物的主要进展。     

Synthesis, Characterization, and Catalytic Activity of Rh(I) Complexes with (S)-BINAPO, an Axially Chiral Inducer Capable of Hemilabile P,O-Heterobidentate Coordination

Summary.  The reaction of dinuclear rhodium(I) derivatives of the formula [Rh(DIOL)X]₂ with the axially chiral phosphinyl phosphane 2-(diphenylphosphinyl)-2′-(diphenylphosphanyl)-1,1′-binaphthalene ((S)-BINAPO, 1) leads to the formation of cationic complexes [(BINAPO)Rh(DIOL)]⁺ where the ligand (S)-BINAPO consistently displays a P,O-chelate coordination which is mantained even in solvents of fair polarity. The mononuclear rhodium(I) complexes (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,5-cyclooctadiene) rhodium tetrafluoroborate (3b) and (S)-2-diphenylphosphanyl-2′-diphenylphosphinyl-1,1′-binaphthalene-(1,4-norbornadiene) rhodium tetrafluoroborate (3c) with 1,5-cyclooctadiene (COD) and 2,5-norbornadiene (NBD) as the diolefin were isolated and characterized. Both show a fluxional behaviour in solution which is due to the mobility of the diolefin rather than to a displacement-recombination of the oxygenated arm of the ligand. The mobility of the 1,4-norbornadiene ligand in 3c is extremely pronounced and the coordinated diolefin flexibility could be frozen only at about 200 K. These complexes are active but poorly stereoselective catalysts for the hydrogenation, hydroboration, and hydroformylation of alkenes. Received June 16, 2000. Accepted (revised) July 24, 2000     

Catalytic Intramolecular Aminofluorination,Oxyfluorination, and Carbofluorination with a Stable and Versatile Hypervalent Fluoroiodine Reagent

Application of a fluoroiodine analogue of the Togni reagent was studied in fluorocyclization reactions. In the presence of a transition‐metal catalyst the applied fluoroiodine reagent can be used for aminofluorination, oxyfluorination, and carbofluorination reactions. The described procedure has a very broad synthetic scope for preparation of functionalized hetero‐ and isocyclic compounds having a tertiary fluorine substituent.     

Heteroleptic and Homoleptic Iron(III) Complexes with a Tris(N-Heterocyclic Carbene) Borate Ligand: Synthesis,Characterization, and Catalytic Application

Heteroleptic and homoleptic iron(III) complexes supported by a tris(N-heterocyclic carbene) borate ligand have been prepared and crystallographically characterized. The strong electron-donating character of the tris(carbene) donor was revealed by UV-vis absorption spectroscopy and electrochemical measurements combined with quantum chemical calculations. The catalytic activity of each complex was evaluated in cyclohexane oxidation reaction using meta-chloroperoxybenzoic acid (=mCPBA) as an oxidant, and both complexes show high catalytic activity and selectivity with TON=∼350 and A/(K+L)=8–10. Mechanistic studies suggested that radical-chain processes are involved in the reaction due to mCPBA acting as a one-electron oxidant, concomitant with the pathway of metal-based reactive species. Moreover, it was found that the homoleptic and heteroleptic complexes differed significantly in the involvement of metal-based active species, with the homoleptic complex exhibiting more metal-based reactions.     

Phosphorylation of Dialkylaminomethylated Calix[4]-Resorcinarenes with Some P(III) and P(IV) Derivatives

Abstract

The phosphorylation of dialkylaminomethylated calix[4]resorcinarenes with P(m)-amides and P(TV)chlorides under various conditions results in the formation of different structures with phosphorus containing fragments fixed on the cavity rim. Hydrophosphoryl compounds based on dialkylaminomethylated calix[4]resorcinarenes have been synthesized and some of their properties investigated.     

Extraction of Ce(III), Gd(III) and Yb(III) from Citrate Medium by High Molecular Weight Amines

Abstract

High molecular weight amines have been used for the extraction of citrate complexes of Ce(III), Gd(III) and Yb(III). The effect of different variables on extraction has been studied. The citrate species extracted in the organic phase have been proposed as [(RNH₃ ⁺)₃] [M(Cit)₂]^3-.     

Cationic complexes of dirhodium(II) with 1,8-naphthyridine: Catalysis of reactions involving silanes

The synthesis of cationic dirhodium(II) complexes by partial or total substitution of the acetate groups of [Rh₂(OAc)₄] with different homoleptic neutral bidentate ligands has been attempted. The ligand 1,8-naphthyridine gave the best results: substitution of one as well as of all four acetate ligands is possible, giving rise to mono-, di- and tetra-cationic complexes. One of the resulting tetrasubstituted complexes has been structurally characterised and found to exhibit the expected lantern-shaped structure. All cationic complexes have been investigated as catalysts in different reactions involving silanes: promising results have been obtained, particularly in the silylformylation of alkynes.     

Heterobimetallic Catalysis: Platinum‐Gold‐Catalyzed Tandem Cyclization/C−X Coupling Reaction of (Hetero)Arylallenes with Nucleophiles

Heterobimetallic catalysis offers new opportunities for reactivity and selectivity but still presents challenges, and only a few metal combinations have been explored so far. Reported here is a Pt‐Au heterobimetallic catalyst system for the synthesis of a family of multi‐heteroaromatic structures through tandem cyclization/C?X coupling reaction. Au‐catalyzed 6‐endo‐cyclization takes place as the first fast step. Pt‐Au clusters are proposed to be responsible for the increased reactivity in the second step, that is, the intermolecular nucleophilic addition which occurs through an outer‐sphere mechanism by hybrid homogeneous‐heterogeneous catalysis.     

Polymer Supported Schiff Base Complexes of Iron(III), Cobalt(II) and Nickel(II) Ions and their Catalytic Activity in Oxidation of Phenol and Cyclohexene

The polymer supported transition metal complexes of N,N′‐bis (o‐hydroxy acetophenone) hydrazine (HPHZ) Schiff base were prepared by immobilization of N,N′‐bis(4‐amino‐o‐hydroxyacetophenone)hydrazine (AHPHZ) Schiff base on chloromethylated polystyrene beads of a constant degree of crosslinking and then loading iron(III), cobalt(II) and nickel(II) ions in methanol. The complexation of polymer anchored HPHZ Schiff base with iron(III), cobalt(II) and nickel(II) ions was 83.30%, 84.20% and 87.80%, respectively, whereas with unsupported HPHZ Schiff base, the complexation of these metal ions was 80.3%, 79.90% and 85.63%. The unsupported and polymer supported metal complexes were characterized for their structures using I.R, UV and elemental analysis. The iron(III) complexes of HPHZ Schiff base were octahedral in geometry, whereas cobalt(II) and nickel(II) complexes showed square planar structures as supported by UV and magnetic measurements. The thermogravimetric analysis (TGA) of HPHZ Schiff base and its metal complexes was used to analyze the variation in thermal stability of HPHZ Schiff base on complexation with metal ions. The HPHZ Schiff base showed a weight loss of 58% at 500°C, but its iron(III), cobalt(II) and nickel(II) ions complexes have shown a weight loss of 30%, 52% and 45% at same temperature. The catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in presence of hydrogen peroxide as an oxidant. The supported HPHZ Schiff base complexes of iron(III) ions showed 64.0% conversion for phenol and 81.3% conversion for cyclohexene at a molar ratio of 1∶1∶1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 55.5% conversion for phenol and 66.4% conversion for cyclohexene at 1∶1∶1 molar ratio of substrate to catalyst and hydrogen peroxide. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 90.5% and 96.5% with supported HPHZ Schiff base complexes of iron(III) ions, but was found to be low with cobalt(II) and nickel(II) ions complexes of Schiff base. The selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was different with studied metal ions and varied with molar ratio of metal ions in the reaction mixture. The selectivity was constant on varying the molar ratio of hydrogen peroxide and substrate. The energy of activation for epoxidation of cyclohexene and phenol conversion in presence of polymer supported HPHZ Schiff base complexes of iron(III) ions was 8.9 kJ mol^?1 and 22.8 kJ mol^?1, respectively, but was high with Schiff base complexes of cobalt(II) and nickel(II) ions and with unsupported Schiff base complexes.     

Fluorocyclisation of Oximes to Isoxazolines Through I(I)/I(III) Catalysis

A regioselective fluorocyclisation of β,γ-unsaturated oximes through I(I)/I(III) catalysis is disclosed to generate 5-fluoromethylated isoxazolines. The transformation leverages p-iodotoluene as an inexpensive catalyst, Selectfluor® as the terminal oxidant and an amine⋅HF complex (1 : 7.5) as both the fluoride and Brønsted acid source. The λ³-iodane p-TolIF₂, which is generated in situ, engages the pendant alkene of the substrate to facilitate a cyclisation/fluorination sequence. A range of 5-fluoromethyl isoxazolines can be generated using this method, including aliphatic and aromatic systems (up to 56 % yield). Single crystal X-ray analysis of a representative example reveals a conformation that is consistent with the stereoelectronic gauche effect between the exocyclic C(sp³)−F bond and the C(sp³)−O of the isoxazoline (ϕ_OCCF=−62.0°).     

P(III) Ligands in Homogeneous Catalysis : Good Deeds and Misdeeds

Abstract

The use of P(III) compounds as ancillary ligands on transition metal species active in homogeneous catalysis often provides dramatic or subtle modifications of their activity and/or selectivity in the conversion of unsaturated substrates.¹ The versatile behaviour of P(III) ligands has been assessed to steric and electronic control on the co-ordination sphere of the metal centre.² This can be extended by the use of functionalized phosphanes.     

Cobalt Nanoparticles Formed upon Reaction of Cp*Co(III) Metallacycles with Na[BHEt3] Show Catalytic Activity in the Hydrosilylation of Aryl Ketones,Aldehydes and Nitriles

The reactivity of the 2-phenylpyridine-derived [Cp*CoI(phpy-κ^C,N)] metallacycle towards Et₃SiH and hydrides was evaluated. The treatment of the same Co(III) complex with Na[BHEt₃] resulted in its decomposition into cobalt nanoparticles. The hydride-promoted decomposition of the metallacycle involves the transient formation of an elusive hydrido-cobalt(III) intermediate, the traces of which were detected by ¹H NMR spectroscopy at sub-ambient temperature. The Co nanoparticles produced from a 5 mol% and 10 mol% load of cobaltacycle and Na[BHEt₃] respectively contain Co(0) that is responsible for the hydrosilylation by Et₃SiH of arylketones into silylalkyl ethers. To minimize the residual side reduction of carbonyls by Na[BHEt₃], a mixture of 5 mol% of the latter with 5 mol% of BEt₃ was found to produce optimal hydrosilylation yields at 40 °C in 2 h. Under similar conditions, several arylnitriles were mono-hydrosilylated into N-silyl-imines in yields ranging from 68 to 100 %.     

Dual Hypervalent Iodine(III) Reagents and Photoredox Catalysis Enable Decarboxylative Ynonylation under Mild Conditions

A combination of hypervalent iodine(III) reagents (HIR) and photoredox catalysis with visible light has enabled chemoselective decarboxylative ynonylation to construct ynones, ynamides, and ynoates. This ynonylation occurs effectively under mild reaction conditions at room temperature and on substrates with various sensitive and reactive functional groups. The reaction represents the first HIR/photoredox dual catalysis to form acyl radicals from α‐ketoacids, followed by an unprecedented acyl radical addition to HIR‐bound alkynes. Its efficient construction of an mGlu5 receptor inhibitor under neutral aqueous conditions suggests future visible‐light‐induced biological applications.