Improved synthesis of phenylethylamine derivatives by Negishi cross-coupling reactions

Trifluoroacetamido-protected β-aminoalkylzinc iodides undergo Negishi cross-coupling reaction with aryl iodides in moderate to excellent yields (42-84%) based on the corresponding trifluoroacetamido-protected β-aminoalkyl iodides, employing a catalyst prepared in situ from Pd₂(dba)₃ and SPhos (1:2 M ratio). In general, meta- and para-substituted aryl iodides give good results using relatively low levels of catalyst [0.25 mol % Pd₂(dba)₃], but more hindered ortho-substituted examples require higher catalyst loadings. The preparation of trifluoroacetamido-protected β-aminoalkyl iodides is straightforward, and the intermediates are significantly more stable than the corresponding Boc-protected derivatives.     

Catalytic C-phenylation of methyl acrylate with triphenylantimony(v) dicarboxylates

Triphenylantimony dicarboxylates Ph₃Sb(OAc)₂ and Ph₃Sb(O₂CEt)₂ are efficient C-phenylating agents for methyl acrylate. In the presence of the Pd(OAc)₂, Li₂PdCl₄ or Pd₂(dba)₃(CHCl₃) catalysts in MeCN at 50 °C, methyl cinnamate forms in 70—150% yield with respect to Sb^V. Copper(ii) salts do not increase the reaction yield.     

Synthesis of poly (imino ketone)s by palladium catalysis C-N cross-coupling reaction

In this paper, taking Pd₂(dba)₃ as catalyst and 2,2??-bis-(diphenylphosphino)-1,1??-binaphtyl as ligand, six kinds of poly(imino ketone)s (PIKs) with different structures have been synthesized via palladium catalysis C-N cross-coupling reaction. The structures of polymers synthesized was characterized by means of FTIR and NMR spectroscopy, the results showed an agreement with the proposed structures. The influential disciplines of monomer concentration and catalysis system to PIKs molecular weight were discussed. Differential scanning calorimetry measurement showed that PIKs possessed high glass transition temperatures (T _g > 150°C).     

Synthesis of unsymmetric diynes by palladium and cesium fluoride catalyzed coupling of terminal bromoalkynes with alkynylstannane

The Stille reaction of unsymmetric diynes from terminal bromoalkynes with alkynylstannane in the presence of palladium catalyst and cesium fluoride was studied. The system (bromoalkyne: PhC≡CSnMe₃:Pd₂(dba)₃:PPh₃:CsF:18‐crown‐6) = (1:1:0.015:0.06:2.2:0.1) in toluene at reflux temperature was found to be the most favored. Products were obtained in 31–100% yields. Correlations between calculated electron density, dipole moments and ¹³C NMR spectral data of synthesized bromoacetylenes and diynes have been carried out. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of mesostructured silica from monoalkyl-substituted double five-ring units

A mesostructured silica-based material was synthesized by self-assembly of a novel amphiphilic molecule consisting of a well-defined siloxane head with a double five-ring (D5R) structure and a hydrophobic alkyl tail. A precursor functionalized with ethoxy groups, C₂₂H₄₅Si₁₀O₁₅(OEt)₉ (1), was hydrolyzed under an acidic condition with the retention of the D5R units, leading to the formation of two-dimensional (2D) hexagonal phase by evaporation-induced self-assembly of amphiphilic hydrolyzed molecules. Solid-state ²⁹Si MAS NMR analysis of the resulting hybrid solid confirmed that the D5R units were cross-linked to form siloxane networks. Calcination of this hybrid solid gave mesoporous silica with high BET surface area (740 m² g⁻¹). These results expand the design possibility of silica-based materials at both molecular- and meso-scales, leading to the bottom up synthesis of hierarchically ordered materials.     

Synthesis of N-aryl-aza-crown ethers via Pd-catalyzed amination reactions of aryl chlorides with aza-crown ethers

The Pd₂(dba)₃/P(i-BuNCH₂CH₂)₃N (1) catalyst system effectively catalyzes the coupling of aza-crown ethers with electronically diverse aryl chlorides, affording N-aryl-aza-crown ethers in good yields. The Pd₂(dba)₃/P(i-BuNCH₂)₃CMe (2) catalyst system containing the more constrained bicyclic triaminophosphine is useful for aryl chlorides possessing base-sensitive ester, nitro, and nitrile functional groups.     

Identification of low molecular vaporizable components in silicone resins using gas chromatography/mass spectrometry

Silicone resins can be used as polymeric precursors in the production of ceramic materials. Cohydrolysis of mixtures of trimethylchlorosilane, methyldichlorosilane, vinylmethyldichlorosilane and phenyltrichlorosilane leads to the formation of especially suitable polysiloxanes, but also low-molar mass siloxanes are formed as undesired by-products. The structures of these by-products have been elucidated. Vaporizable components of the matrix have been isolated by distillation, separated using gas chromatography and identified by mass spectrometry in EI (electron impact ionization) and CI (chemical ionization with isobutane) mode. The EI mass spectra of the siloxane oligomers with different numbers of Si-H, Si-phenyl and Si-vinyl groups show characteristic fragments like Me₃Si⁺, ViMe₂Si⁺, Vi₂MeSi⁺, PhMe₂Si⁺, and Ph₂MeSi⁺, which give a first indication to the structure, but generally do not show molecular peaks. A reliable determination of the molar mass has been possible considering the CI-ions and CI-fragments [M+1]⁺, [M−1]⁺, [M−27]⁺ and [M−77]⁺, respectively. The compounds M₂D^Ph,OH and M₃T^Ph have been identified as main components of the investigated siloxane mixture. Besides, numerous linear compounds of the type M₂(D^H)n(D^Vi)_m and M₂T^Ph(D^H)_n(D^Vi)_m M as well as cyclic ones of the structure [MT^Ph(D^H)_n(D^Vi)_m] with n, m=0–3 have been indicated. Received: 3 March 1995/Revised: 25 March 1995/Accepted: 3 April 1995     

Polycondensation of haloarylketones catalyzed by palladium compounds bearing N-heterocyclic carbene (NHC) ligands

Palladium-catalyzed α-arylation of ketones, which can efficiently give coupling products by using appropriate ligands and bases, could be applied to a polycondensation reaction. Stable N-heterocyclic carbenes (NHC) were used as favorable ligands coordinating the Pd catalysts, which were generated in situ from commercially available palladium compounds such as Pd(OAc)₂ and Pd₂(dba)₃ as suitable catalyst precursors in this polymerization. Using small amounts of binary catalysts, poly(aryl alkyl ketone)s were afforded in high yields from haloarylketones in the presence of a base. A primarily prepared palladium catalyst having an NHC ligand, [Pd(OAc)₂(NHC)], also efficiently catalyzed the polycondensation, whereas a palladium compound bearing two carbene ligands, [PdX₂(NHC)₂], did not.     

Catalytic C-phenylation of methyl acrylate with tetraphenylantimony(v) halides and carboxylates

Catalytic C-phenylation of methyl acrylate to methyl cinnamate with the Ph₄SbX complexes (X = F, Cl, Br, OH, OAc, O₂CEt) in the presence of the palladium compounds PdCl₂, Pd(OAc)₂, Pd₂(dba)₃, Pd(Ph₃P)₂Cl₂, and Pd(dppf)Cl₂ (dba is dibenzylideneacetone and dppf is bis(diphenylphosphinoferrocene)) was studied in organic solvents (MeCN, THF, DMF, MeOH, and AcOH). The highest yield of methyl cinnamate (73% based on the starting organometallic compound) was obtained for the Ph₄SbCl—PdCl₂ (1 : 0.04) system in acetonitrile.     

Rhodium and iridium complexes containing the anion of 1-phenyl-3-methyl-4-benzoyl- pyrazolone-5, a sophisticated analogue of β-diketones

Several (diolefin)M(A) complexes (M = Rh, Ir) were prepared, where AH is 1-phenyl-3-methyl- 4-benzoylpyrazolone-5, a very stable asymmetric analogue of acetylacetone. In these complexes the diolefin could be replaced by one mole of (Ph₂PCH₂CH₂)₂, two of CO or of PPh₃, or three of CNBu^t, while 1,10-phenanthroline displaced the chelating ligand to yield [(cyclooctadiene)Rh(phen)]⁺ (A)^?. Some compounds X?Y (X?Y = iodine or MeI) added oxidatively yielding the corresponding trivalent species. Using ³¹P NMR spectra the presence of the expected steric isomers was detected in (Ph₃P)(CO)Rh(A) and in (Ph₃P) (CO)Rh(A)(X)(Y).     

Chlorodiphenyltin(IV) and triphenyltin(IV) complexes of N-alkylated 2-amino-1-cyclopentene-1-carbodithioic acids: synthesis, spectroscopic characterization and X-ray studies

Four new complexes, [Ph₃Sn(isopropylACDA)] (1), [Ph₂SnCl(isopropylACDA)] (2), [Ph₃Sn(secbutylACDA)] (3), and [Ph₂SnCl(secbutylACDA)] (4), have been prepared from reaction between N-alkylated 2-amino-1-cyclopentene-1-carbodithioic acids (ACDA) with Ph₂SnCl₂ and Ph₃SnCl in 1:1 ratio. All complexes are characterized by FTIR, multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn) and mass spectrometry. In all complexes, the S–H proton has been removed and coordination takes place through the carbodithioate moiety. The ¹¹⁹Sn NMR data are consistent with five coordination of tin atom in solution. Complexes 2, 3, and 4 have also been confirmed by single X-ray crystallography. All three crystals are triclinic with space group P − 1. In complexes 2 and 4, the geometry around tin atom is distorted trigonal bipyramidal while in 3 the geometry is in between distorted tetrahedral and trigonal bipyramid. In all three structures, ligands are asymmetrically coordinated to tin atom. In addition, crystal structures are further stabilized by N–H···S hydrogen bonding.     

Catalysis of hydrosilylation by well-defined rhodium siloxide complexes immobilized on silica

Rhodium surface siloxide complexes were prepared directly by condensation of the molecular precursors ([{Rh(μ-OSiMe₃)(cod)}₂], [{Rh(μ-OSiMe₃)(tfb)}₂], [{Rh(μ-OSiMe₃)(nbd)}₂]) with silanol groups on silica surface (Aerosil 200 and SBA-15) and their structures were characterized by ¹³C and ²⁹Si CP/MAS NMR spectroscopy. Such single-site complexes were tested for their activity in hydrosilylation of carbon–carbon double bonds with triethoxysilane, heptamethyltrisiloxane and poly(hydro,methyl)(dimethyl)siloxane. The best catalyst appeared to be cyclooctadiene ligand-containing rhodium siloxide complex immobilized on Aerosil which was recycled as many as 20 times without loss of activity and selectivity in hydrosilylation of vinylheptamethyltrisiloxane with heptamethyltrisiloxane. On the ground of CP/MAS NMR measurements it was established that the mechanism of hydrosilylation catalyzed by silica-supported rhodium siloxide complexes is different from that for the complexes in the homogeneous system.     

Palladium-catalysed amination of 2-acyl-1-alkyl-5-bromopyrroles

The first intermolecular C-N bond-forming reactions between substituted 2-bromopyrroles and primary and cyclic secondary amines were performed using Pd₂(dba)₃ as catalyst with BINAP as the ligand. The aminations proceeded in the presence of NaO^tBu at 80-100 °C in 31-93% yields.     

Palladium-catalyzed cycloaddition of carbon dioxide with methoxyallene

A palladium catalyst generated from Pd₂(dba)₃·CHCl₃ and ⁿBu₂PCH₂CH₂Py (Py = 2-pyridyl) has effected novel cycloaddition of methoxyallene with CO₂ to afford (E)-5-methoxy-2-(methoxy-methylene)-4-methylene-5-pentanolide regio- and stereospecifically, where a methoxy functional group plays an important role.     

Walking Metals in d8⋅⋅⋅d8 Hetero‐bimetallic Complexes: An Original Dynamic Phenomenon

In the course of our investigations on polymetallic complexes derived from 1,3‐bis(thiophosphinoyl)indene (Ind(Ph₂P?S)₂), we observed original fluxional behavior and report herein a joint experimental/computational study of this dynamic process. Starting from the indenylidene chloropalladate species [Pd{Ind(Ph₂P?S)₂}Cl]^? ( 1 ), the new Pd^II???Rh^I hetero‐bimetallic pincer complex [PdCl{Ind(Ph₂P?S)₂}Rh(nbd)] ( 2 ; nbd=2,5‐norbornadiene) was prepared. X‐ray crystallography and DFT calculations substantiate the presence of a d⁸???d⁸ interaction. According to multinuclear variable‐temperature NMR spectroscopic experiments, the pendant {Rh(nbd)} fragment of 2 readily shifts in solution at room temperature between the two edges of the SCS tridentate ligand. To assess the role of the pincer‐based polymetallic structure on this fluxional behavior, the related monometallic Rh complex [Rh{IndH(Ph₂P?S)₂}(nbd)] ( 3 ) was prepared. No evidence for a metal shift was observed in that case, even at high temperature, thus indicating that inplane pincer coordination to the Pd center plays a crucial role. The previously described Pd^II???Ir^I bimetallic complex 4 exhibited fluxional behavior in solution, but with a significantly higher activation barrier than 2 . This finding demonstrates the generality of this metal‐shift process and the strong influence of the involved metal centers on the associated activation barrier. DFT calculations were performed to shed light onto the mechanism of such metal‐shift processes and to identify the factors that influence the associated activation barriers. Significantly different pathways were found for bimetallic complexes 2 and 4 on one hand and the monometallic complex 3 on the other hand. The corresponding activation barriers predicted computationally are in very good agreement with the experimental observations.     

Palladium-catalyzed [3 + 2] cycloaddition reaction of vinylcyclopropanes with α,β-unsaturated esters or ketones

Reaction of vinylcyclopropanes having two electron-withdrawing groups with α,β-unsaturated esters or ketones in the presence of Pd₂(dba)₃.CHC1₃-1,2- bis(diphenylphosphino)ethane (dppe) or tributylphosphine catalyst gave vinyl- cyclopentanes in good yields.     

Mechanism of the formation of palladium complexes serving as catalysts in hydrogenation reactions : I. Reactions of complexes with molecular hydrogen

The interaction of Ph₃PPD(OAc)₂₂ with molecular H₂ yields a binuclear complex of zero-valent palladium, (Ph₃P)₂Pd₂. This complex interacts reversibly with H₂ in CH₂Cl₂, yielding (Ph₃P)₂Pd₂H₂. In argon atmosphere (Ph₃P)₂Pd₂ reacts with [Ph₃PPd(OAc)₂₂ to form a binuclear complex of Pd^I with a metal—metal bond. These data, as well as the results of kinetic studies of the reactions between [Ph₃PPd(OAc)₂₂ and H₂, are in agreement with an autocatalytic mechanism for the process, including catalysis of the reduction of Pd^II complexes by the Pd⁰ compounds. It has been established that the synthesized compound of Pd^II, Pd^I and Pd⁰ with the ratio P/Pd?1, are inactive in the hydrogenation of unsaturated compounds. The catalytically active complex (PPh)₂Pd₅ is formed when palladium acetate reacts with (Ph₃P)₂Pd₂ in the presence of H₂. The same compound is formed when a solution of (Ph₃P)₂Pd₂ is treated with a mixture of H₂ and O₂ (or H₂O₂ in an atmosphere of H₂). (PPh)₂Pd₅ is an effective catalyst for the hydrogenation of olefins, dienes, acetylenes, aldehydes, organic peroxides, quinones, O₂, Schiff bases, and nitro, nitroso, and azo compounds.     

Synthesis,characterization, and reactivity studies of alkylidyne palladium cluster compounds

[Pd₄(₃-CR)(-Cl)₃(PBu ₃ ¹ )₄] (R = H, F) have been synthesized from [Pd₂(dba)₃]. PBu ₃ ¹ and CRCl₃ and characterized spectroscopically and in one case by a single crystal X-ray crystallographic analysis, These compounds undergo substitution reactions with LiBr and tertiary phosphines and are catalyst for the polymerization of ethyne. Details of these reactions are discussed for the compound [ Pd₄(₃-CR)(-Cl)₃(PBu ₃ ¹ )₄]. The cluster lbrmation reactions. have been monitored using³¹P(¹H)NMR studies.     

A novel reaction producing the rhodium(I) complexes with π-coordinated tetraphenylborate anion, (π-PhBPh3). X-ray study of [Rh(PPh3)2(π-PhBPh3)]

Treating the complexes [Rh(TFA)(PPh₃)₂], [Rh(HFA)(PPh₃)₂], and [Rh(TFA)(Cod)] (TFA - trifluoroacetylacetonate, HFA - hexafluoroacetylacetonate, Cod - 1,5 cyclooctadiene) with an excess of NaBPh₄ in acetonitrile yields the rhodium(I) complexes with coordinated [BPh₄]⁻ anion, [Rh(PPh₃)₂(π-PhBPh₃)] · 2MeCN (I) and [Rh(Cod)(π-PhBPh₃)] (II). The reactions present a new example of β-diketonate ligand replacement. The ¹H, ³¹P, and ¹¹B NMR spectra of I and II are discussed. [Rh(PPh₃)₂(π-PhBPh₃)] has been characterized by single crystal X-ray analysis.     

Synthesis of large palladium clusters. The preparation of Pd38(CO)28(PR3)12 (R = Et,Bun) and Pd34(CO)24(PEt3)12

Several methods for the synthesis of the Pd₃₈(CO)₂₈L₁₂ cluster (L = PEt₃) by treatment of Pd₁₀(CO)₁₂L₆ with CF₃COOH-Me₃NO, CF₃COOH-H₂O₂, Pd(OAc)₂-Me₃NO, and Pd₂(dba)₃ mixtures (dba is dibenzylideneacetone) were proposed. The tri-n-butylphosphine analog, Pd₃₈(CO)₂₈(PBu₃)₁₂, was synthesized by the reaction of Pd₁₀(CO)₁₄(PBu₃)₄ with Me₃NO. The reaction of Pd₄(CO)₅L₄ with Pd₂(dba)₃ yields clusters with an icosahedral packing of the metal atoms, Pd₃₄(CO)₂₄L₁₂ and Pd₁₆(CO)₁₃L₉.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 167–170, January, 1995.