PALLADIUM CATALYZED TANDEM CYCLIZATION-ANION CAPTURE PROCESSES .1. BACKGROUND AND HYDRIDE ION CAPTURE BY ALKYL-PALLADIUM AND PI-ALLYL-PALLADIUM SPECIES

A new, wide ranging, synthetically powerful, catalytic tandem cyclisation-anion capture process is proposed which depends on the rate of cyclisation of an organopalladium specifies (RPdX) onto a proximate alkene or diene being significantly faster than anion exchange and reductive elimination in the sequence RPdX --> RPdY --> RY + Pd(0). The catalytic cyclisation - anion capture sequence is illustrated for hydride capture by a wide variety of substrates giving rise to fused- and spiro-, carbo- and hetero-cyclic systems, regio- and stereo-specifically.

Synthèse d’un inhibiteur de la rénine, l’aliskiren et développement de méthodes catalytiques d’alkylation asymétrique

Une nouvelle approche pour la synthèse de l’aliskiren, un puissant inhibiteur de la rénine pour le traitement de l’hypertension chez l’homme, a été développée. De cette approche, des étapes clés tels qu’une allylation avec un des catalyseurs de MacMillan, une cyclisation par métathèse (RCM) pour la préparation d’une lactone à neuf membres et une séquence de réactions d’aziridination diastéréosélective/réarrangement de cycle par une catalyse acide donnant un produit aminohydroxylé ont permis de compléter la synthèse de l’aliskiren en 11 étapes. Durant l’élaboration de la séquence de réactions pour la préparation de l’aliksiren, il a été noté que la lactone à neuf membres avait une facilité à se réarranger via des intermédiaires quinonoïdaux et les produits issus de cette tendance ont été analysés. De plus, une étude sur la réaction de RCM, donnant la lactone à neuf membres, a montré une dépendance envers la nature diastéréomérique du substrat de départ. Une méthodologie d’alpha-allylation asymétrique de cétones catalysée au palladium, tirant avantage d’un ligand chiral PHOX, a été explorée et utilisée en vue de la synthèse de l’aliskiren. De cette méthode, une étude pour la synthèse de produits alpha-allylcétones acycliques a été démontrée et un effet d’additif sur la sélectivité et la vitesse de réaction a été découvert. De plus, la production d’un intermédiaire avancé d’un produit d’intérêts a été accomplie et la nature de la contribution de l’additif a été investiguée. Les produits obtenus depuis la méthodologie d’allylation catalysée au palladium et la formation d’intermédiaire cationique des certains dérivés de la synthèse de l’aliskiren ont inspirés une nouvelle approche faisant appel à des techniques d’alkylation en catalyse acide pour la formation de produits diaryliques. Il a été trouvé que le catalyseur de chlorure d’or(III) et de triflate de bismuth(III) étaient particulièrement efficaces, démontrant une différence de cinétique pour la réactivité d’un mélange diastéréoisomériques d’alcools alpha-substitués de départ.

Regioselective Bis-Selenation of Allenes Catalyzed by Palladium Complexes: A Theoretical Study

The reaction mechanism of Pd(O)-catalyzed allene bis-selenation reactions is investigated by using density functional methods. The overall reaction mechanism has been examined. It is found that with the bulkier PMe3 ligand, the rate-determining step is the reductive elimination process, while allene insertion and reductive elimination processes are competitive for the rate-determining step with the PH3 ligand, indicating the importance of the ligand effect. For both cis and trans palladium complexes, allene insertion into the Pd-Se bond of the trans palladium complex using the internal carbon atom attached to the selenyl group is prefer-red among the four pathways of allene insertion processes. The formation of sigma-allyl and pi-allyl palladium complexes is favored over that of the sigma-vinyl palladium species. By using methylallene, the regioselectivity of monosubstituted allene insertion into the Pd-Se bond is analyzed.

Carbon dioxide pressure induced heterogeneous and homogeneous Heck and Sonogashira coupling reactions using fluorinated palladium complex catalysts

The Heck reaction of iodobenzene and methyl acrylate was investigated with CO2-philic Pd complex catalysts having fluorous ponytails and the organic base triethylamine (Et3N) in the presence of CO2 under solventless conditions at 80 degrees C. The catalysts are not soluble in the organic phase in the absence Of CO2 and the reaction occurs in a solid-liquid biphasic system. When the organic liquid mixture is pressurized by CO2, CO2 is dissolved into the organic phase and this promotes the dissolution of the I'd complex catalysts. As a result, the Heck reaction occurs homogeneously in the organic phase, which enhances the rate of reaction. This positive effect Of CO2 pressurization competes with the negative effect that the reacting species are diluted by an increasing amount of CO2 molecules dissolved. Thus, the maximum conversion appears at a CO2 pressure of around 4 MPa under the present reaction conditions. The catalysts are separated in the solid granules by depressurization and are recyclable without loss of activity after washing with n-hexane and/or water.

Enantiospecific assembly of a homochiral, hexanuclear palladium complex

The linking of orthopalladated ferrocenylene units by parabanato(2-) ligands results in enantiospecific assembly of a hexanuclear complex in which (i) the steric bulk of the ferrocenylene moiety, (ii) the folded configuration dictated by the imidato(2-) bridging ligand, and (iii) the strong preference for a trans arrangement of the carbonyl oxygen and ferrocenyl carbon atoms, combine to ensure that only ferrocenylene-palladium units with the same chirality can be located at adjacent positions in the assembled complex. The resulting tris-parabanato(2-)-bridged, hexapalladium complex is thus homochiral (R,R,R,R,R,R or S,S,S,S,S,S), as demonstrated by H-1 NMR spectroscopy and by X-ray analysis of a racemic crystal which shows the complex to possess a tapering, twisted, trigonal-prismatic skeleton of palladium atoms with threefold crystallographic symmetry. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)-deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2]. 13C NMR, 1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1. © 2005 NRC Canada.

Organometallic chemistry of chiral diphosphazane ligands: Synthesis and structural characterisation

The diphosphazane ligands of the type, (C20H12O2)PN(R)P(E)Y2 (R = CHMe2 or (S)-*CHMePh; E = lone pair or S; Y2 = O2C20H12 or Y = OC6H5 or OC6H4Me-4 or OC6H4OMe-4 or OC6H4But-4 or C6H5) bearing axially chiral 1,1'-binaphthyl-2,2′-dioxy moiety have been synthesised. The structure and absolute configuration of a diastereomeric palladium complex, [PdCl2{ηsu2}-((O2C20H12)PN((S)-*CHMePh)PPh2] has been determined by X-ray crystallography. The reactions of [CpRu(PPh3)2Cl] with various symmetrical and unsymmetrical diphosphazanes of the type, X2PN(R)PYY′ (R = CHMe2 or (S)-*CHMePh; X = C6H5 or X2 = O2C20H12; Y=Y′= C6H5 or Y = C6H5, Y′ = OC6H4Me-4 or OC6H3Me2-3,5 or N2C3HMe2-3,5) yield several diastereomeric neutral or cationic half-sandwich ruthenium complexes which contain a stereogenic metal center. In one case, the absolute configuration of a trichiral ruthenium complex, viz. [Cp*Ruη2-Ph2PN((S)-*CHMePh)*PPh (N2C3HMe2-3,5)Cl] is established by X-ray diffraction. The reactions of Ru3(CO)12 with the diphosphazanes (C20H12O2)PN(R)PY2 (R = CHMe2orMe; Y2=O2C20H12or Y= OC6H5 or OC6H4Me-4 or OC6H4OMe-4 or OC6H4But-4 or C6H5) yield the triruthenium clusters [Ru3(CO)10{η-(O2C20H12)PN(R)PY2}], in which the diphosphazane ligand bridges two metal centres. Palladium allyl chemistry of some of these chiral ligands has been investigated. The structures of isomeric η3-allyl palladium complexes, [Pd(η3-l,3-R′2-C3H3){η2-(rac)-(02C20H12)PN(CHMe2)PY2}](PF6) (R′ = Me or Ph; Y = C6H5 or OC6H5) have been elucidated by high field two-dimensional NMR spectroscopic and X-ray crystallographic studies.

Immobilization of dipyridyl complex to magnetic nanoparticle via click chemistry as a recyclable catalyst for Suzuki cross-coupling reactions

A magnetic nanoparticle (MNP)-supported di(2-pyridyl)methanol palladium dichloride complex was prepared via click chemistry. The MNP-supported catalyst was evaluated in Suzuki coupling reaction in term of activity and recyclability in DMF. It was found to be highly efficient for Suzuki coupling reaction using aryl bromides as substrates and could be easily separated by an external magnet and reused in five consecutive runs without obvious loss of activity.

Double cyclometalation via carbon-silicon bond cleavage by palladium(II) acetate. X-ray structure of a cationic 1,4-dipalladated benzene ring and selective synthesis of heterobimetallic 1,4-phenylene-bridged platinum(II)-palladium(II) complexes

The disilylated compound 1,4-bis(trimethylsilyl)-2,3,5,6-tetrakis((dimethylamino)methyl)benzene, (Me(3)Si)(2)C2N4, 4, can be electrophilically palladated selectively at the C-Si bonds to afford the neutral 1,4-bis(palladium) complex [(AcOPd)(2)(C2N4)], from which the dicationic [(LPd)(2)(C2N4)](2+) (L = MeCN) organometallic species are accessible. The monosilylated species (Me(3)Si)(H)C2N4, 5, can be used for the preparation of the dicationic heterodinuclear platinum(II)-palladium(II) species [(LPd)(LPt)(C2N4)](2+) (L = MeCN) via a sequence of transmetalation of the organolithium derivative of 5 with [PtCl2(SEt(2))(2)], followed by a C-Si bond palladation reaction.

A single-step procedure for the preparation of palladium nanoparticles and a phosphine-functionalized support as catalyst for Suzuki cross-coupling reactions

We here report the preparation of supported palladium nanoparticles (NPs) stabilized by pendant phosphine groups by reacting a palladium complex containing the ligand 2-(diphenylphosphino)benzaldehyde with an amino-functionalized silica surface The Pd nanocatalyst is active for Suzuki cross-coupling reaction avoiding any addition of other sources of phosphine ligands The Pd intermediates and Pd NPs were characterized by solid-state nuclear magnetic resonance and transmission electron microscopy techniques The synthetic method was also applied to prepare magnetically recoverable Pd NPs leading to a catalyst that could be reused for up to 10 recycles In summary we gathered the advantages of heterogeneous catalysis magnetic separation and enhanced catalytic activity of palladium promoted by phosphine ligands to synthesize a new catalyst for Suzuki cross-coupling reactions The Pd NP catalyst prepared on the phosphine-functionalized support was more active and selective than a similar Pd NP catalyst prepared on an amino-functionalized support (C) 2010 Elsevier Inc All rights reserved

Biscarboxy-Functionalized Imidazole and Palladium as Highly Active Catalytic System in Protic Solvents: Methanol and Water

The coupling reaction between aryl bromides and boron reagents is efficiently catalyzed by an in situ generated palladium complex obtained from palladium(II) acetate (0.1 mol%) and 1,3-bis(carboxymethyl)imidazole (0.2 mol%). The catalytic system is very active in protic solvents, especially in methanol. Biaryl derivatives have been prepared in good isolated yields (up to >99%), and additionally styrene and stilbene derivatives have also been prepared by means of this protocol.

Remarkably large captodative stabilisation in radical ions

Palladium complex-catalyzed carbonylation of arylsulfonyl chlorides in the presence of metal alkoxides M(OR)n (M=B, Al, and Ti) gives the corresponding esters along with diaryl disulfides. With metal carboxylates M(OCOR)n (M=Na, K, Ca, Mg, and Zn), the free acids are also obtained

Short-bite chiral diphosphazanes derived from (S)-?-methyl benzyl amine and their Pd, Pt and Rh metal complexes

New chiral diphosphazane ligands of the type Ph(2)PN(S-*CHMePh)PYY' {YY'= Ph(2) (2), O2C6H4 (3); Y= Ph, Y'= Cl {4a (SS), 4b (SR)}, N(2)C(3)HMe(2)-3,5 {5a (SR), 5b (SS)} are synthesised starting from a chiral aminophosphine, Ph(2)PNH(S-*CHMePh) (1). The structure of one of the diastereomer 5a has been confirmed by single crystal X-ray diffraction {Orthorhombic system, P2(1)2(1)2(1); a=10.456 (4), b=15.362 (7), c=17.379 (6) Angstrom, Z=4}. Transition metal mononuclear complexes [Rh{eta(2)-(Ph(2)P)(2)N- (S-*CHMePh)}(2)](+)(BF4)(-) (6), [PdCl2{eta(2)-(Ph(2)P)(2)N(S-*CHMePh)}] (7) and [PtCl2{eta(2)-(Ph(2)P)(2)N- (S-*CHMePh)}] (8) have also been synthesised. The structure of the palladium complex 7 is solved by X-ray crystallography {Orthorhombic system, P2(1)2(1)2(1); a=8.746 (2), b=18.086 (2), c=20.811 (3) Angstrom, Z=4}. All these compounds are characterised by micro analyses, IR and NMR spectroscopic data.

Luminescent properties of Langmuir-Blodgett films of europium bisphthalocyanine

Eu(III)-octa-4-(tetrahydrofurfuroxy) phthalocyanine (EuPc2') was synthesied and characterized by elementary analysis, IR, MS, UV-vis spectra. EuPc2' has good film-forming ability from determination of isotherm of pi-A. The complex LB film was formed by depositing of EuPc2' on a quartz slide with the LB techniques of the Z-type, The luminescent properties of pure and doped LS films were determined. The results showed that pure films have good luminescent properties, the thicker the LB films, the stronger the fluorescent intensity. The films doped with o-phenanthroline (abbreviated as phen) made the relative intensity of fluorescent emission behavior enhance in comparison to that of pure LB film, But the amount of phen may be not too much. Our results showed that EuPc2':phen = 1: 10 (molar ratio) has the best fluorescent behavior. The electronic spectroscopic characterization of the LB films is also given.