- Water-tolerant enantioselective carbonyl-ene reactions with palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP
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Palladium(II) and platinum(II) Lewis acid catalysts bearing BINAP have been proved to be water-tolerant in enantioselective carbonyl-ene reactions, thus arylglyoxal monohydrate could be used directly as substrate achieving good to excellent enantioselectivities as high as 95.4% e.e.. The enantioselective carbonyl-ene reactions using phenylglyoxal monohydrate as substrate with four alkenes including methylenecyclohexane, 2,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene and alpha-methylstyrene, were investigated demonstrating comparable or even higher yields and enantioselectivities in comparison with the corresponding carbonyl-ene reactions using dry phenylglyoxal as substrate for both palladium(II)-BINAP catalyst and platinum(II)-BINAP catalyst. The palladium(II) and platinum(II)-BINAP catalyzed enantioselective carbonyl-ene reactions between 4-methylphenylglyoxal monohydrate and the four alkenes were also investigated affording enantioselectivities between 76.2% and 91.8% e.e.. A mechanism involving the coordination of arylglyoxal and 2,2-dihydroxy-1-phenylethanone with chiral catalyst was proposed to interpret the enantioselective carbonyl-ene reactions using arylglyoxal monohydrate as substrate.
- Luo, He-Kuan,Yang, Hai-Yan,Jie, Tan Xiang,Chiew, Ong Siong,Schumann, Herbert,Khim, Lim Bee,Lim, Christina
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- Palladium-catalyzed asymmetric arylation of 2,3-dihydrofuran with phenyl triflate. A novel asymmetric catalysis involving a kinetic resolution process
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The reaction of phenyl triflate and 2,3-dihydrofuran in benzene in the presence of a base and a palladium catalyst coordinated with (R)-BINAP gave optically active (R)-2-phenyl-2,3-dihydrofuran (1a) and a small amount of (S)-2-phenyl-2,5-dihydrofuran (2a). The two regioisomers have configurations opposite to each other. A clear correlation was observed between the enantioselectivity and the regioselectivity. Thus, the enantiomeric purity of (R)-1a increases as the ratio of (S)-2a to (R)-1a increases. A catalytic mechanism involving a kinetic resolution process is proposed to account for the relation. Factors controlling the regio- and enantioselectivities are discussed in detail using molecular models based on the X-ray structure of PdCl2{(R)-BINAP}. Crystal data for PdCl2{(R)-BINAP}: C44H32Cl2P2Pd, a = 11.751(1) ?, c = 26.538(3) ?, V = 3664.2 ?3, tetragonal, P41, Z = 4.
- Ozawa, Fumiyuki,Kubo, Akihiko,Matsumoto, Yonetatsu,Hayashi, Tamio,Nishioka, Eriko,Yanagi, Kazunori,Moriguchi, Koh-Ichi
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- Chiral separation of substituted phenylalanine analogues using chiral palladium phosphine complexes with enantioselective liquid-liquid extraction
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Chiral palladium phosphine complexes have been employed in the chiral separation of amino acids and phenylalanine analogues in particular. The use of (S)-xylyl-BINAP as a ligand for the palladium complex in enantioselective liquid-liquid extraction allowed the separation of the phenylalanine analogues with the highest operational selectivity reported to date. 31P NMR, FTIR, FIR, UV-Vis, CD and Raman spectroscopy methods have been applied to gain insight into the binding mechanism of the amino acid substrates with the chiral palladium phosphine complexes. A complexation in a bidentate fashion is proposed.
- Verkuijl, Bastiaan J.V.,Schuur, Boelo,Minnaard, Adriaan J.,De Vries, Johannes G.,Feringa, Ben L.
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- Chiral induction in the synthesis of 4,4-dimethyl-1-phenylpenta-1,2-diene (1-Ph-3-t-Bu-allene) catalyzed by chiral phosphine complexes of palladium
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4,4-Dimethyl-1-phenylpenta-1,2-diene (1-phenyl-3-t-butylallene) (2) has been prepared by a palladium-catalyzed cross-coupling reaction between either in situ prepared 4,4-dimethylpenta-1,2-dienylzinc chloride and iodobenzene (Route A) or 1-bromo-4,4-dimethylpenta-1,2-diene and phenylzinc chloride (route B).Several palladium complexes with known chiral phosphine, phosphine-amine and diphosphine ligands were used as chiral catalysts.The highest enantiomeric excess (25 percent ee) was obtained via route A with catalysis by the 1/1 complex of palladium chloride and (R,R)-2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane, .The enantiomeric excess ( 19 percent ee) when the complex Pd2 was used appeared to be independent of the temperature, the amount of catalyst, and the ratio of the reagents.However, when a magnesium or copper reagent was used instead of the zinc reagent, the configuration was reversed (3-10 percent ee).The suggested intermediate PdIPh was prepared by treating one equivalent of (R,R)-diop with PdIPh(tmeda) (tmeda = N,N,N',N',-tetramethylethanediamine) and studied by 31P NMR spectroscopy.PdIPh appeared to be present in solution as an equilibrium mixture of cis-chelating and trans-monodentate bonded species, with the ratio depending upon the concentration and the palladium/diphosphine ratio.Reaction of a slight excess of 4,4-dimethyl-1,2-pentadienyl-zinc chloride or -magnesium chloride with PdIPh gave 1-phenyl-3-t-butylallene 2 with the same configuration, though with a slightly smaller ee than that from the reactions catalyzed by PdCl2 or Pd2.The results strongly suggest that reaction of the organometallic reagent with the palladium(II) intermediate PdIPh is the enantiodifferentiating step in the catalytic cycle.
- Graaf, Wim de,Boersma, Jaap,Koten, Gerard van,Elsevier, Cornelis J.
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- Conformational flexibility of palladium BINAP complexes explored by X-ray analyses and DFT studies
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Several crystal structures and a theoretical DFT structure of the important catalyst (BINAP)PdCl2 (BINAP: 2,2′-bis(diphenylphosphino)-1, 1′-binaphthyl) have been determined. The conformational flexibilities of the BINAP backbone and of the phenyl rings do not seem to be coupled. Two novel parameter have been introduced that define the Π-Π stacking between the phenyl and biaryl rings in systems similar to the BINAP ligand, as well as the delta angle that is sensitive to the important interaction of the exchangeable ligands of the palladium with the equatorial phenyl rings of the BINAP. Furthermore, the calculated bite angle is 3° larger than the experimentally determined bite angles.
- Véron, Anna C.,Felber, Michael,Blacque, Olivier,Spingler, Bernhard
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- Enantioselective synthesis of axially chiral 3-bromo-4-alkoxy-2,6-dimethyl-5-(naphthalen-1-yl)pyridines via an asymmetric Suzuki–Miyaura cross-coupling reaction
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A simple method is reported for the synthesis of chiral mono-naphthyl substituted pyridine derivatives in good yield and with good enantiomeric excess via the asymmetric Suzuki–Miyaura cross-coupling reaction of 3,5-dibromo-4-alkoxy-2,6-dimethylpyridine and naphthalen-1-ylboronic acid. The structure and absolute stereochemistry of 3-bromo-4-methoxy-2,6-dimethyl-5-(naphthalen-1-yl)pyridine were established by single-crystal X-ray analysis.
- Pomarański, Piotr,Samanta, Sauvik,Roszkowski, Piotr,Maurin, Jan K.,Czarnocki, Zbigniew
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- Visible-Light-Induced Palladium-Catalyzed Dehydrogenative Carbonylation of Amines to Oxalamides
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The palladium-catalyzed oxidative carbonylation of amines toward the synthesis of oxalamides has been established around 30 years ago and it usually needs the presence of (over)stoichiometric amounts of oxidant. In this work, the first transformation of this type in which the oxidant was replaced by visible light is described. The new approach uses a simple robust Pd complex, which can even be partially recycled. A mechanistic reason is provided and supported by control experiments and EPR studies, showing that PdI was formed and Pd0 was the active species. Both nitrogen- and the intermediate acyl radical can be detected. Moreover, the formation of hydrogen was confirmed by gas GC.
- Meyer, Tim,Rabeah, Jabor,Brückner, Angelika,Wu, Xiao-Feng
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- Electronic behavior of calcined material obtained from 2,2-diphenylphosphino-1,1-binaphthyldichloro palladium
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The calcinations of 2,2-diphenylphosphino-1,1-binaphthyldichloro palladium under an argon atmosphere gave nano-sized Pd5P2/carbon cluster composite material. The ESR spectral examination of the material, and the reaction of either methylene blue or 2,3,5-trimethylhydroquinone in the presence of the material revealed that the calcined material has a visible light-responsive oxidation-reduction function through an electron transfer from the carbon clusters to the Pd5P2 particles.
- Yamamoto,Matsui,Okajima,Karuppuchamy,Yoshihara
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- Hydroxy complexes of palladium(II) and platinum(II) as catalysts for the acetalization of aldehydes and ketones
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The acetalization of aldehydes or ketones is a reaction of synthetic interest in organic chemistry that is commonly catalyzed by Bronsted or Lewis acids. We have found that a class of Pd(II) and Pt(II) complexes of the type [(P-P)M(μ-OH)]2+2 (P-P = a series of diphosphines; M = Pd, Pt) are effective catalysts for the acetalization of a variety of aldehydes and ketones in the presence of alcohols or glycols. The use of epoxides instead of alcohols resulted in lower rates and yields. The rate and yield of the reaction is not affected by the size of the diphosphine in the series dppe, dppp, dppb. Attempts to perform the reaction in a stereoselective fashion showed no difference depending on whether regular achiral catalysts or catalysts modified with chiral diphosphines were used.
- Cataldo, Maurizio,Nieddu, Enrico,Gavagnin, Roberta,Pinna, Francesco,Strukul, Giorgio
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- Metal-dependent reactivity of electrophilic platinum group metal lewis acid catalysts: Competitive alkene dimerization, intramolecular friedel-crafts alkylation, and carbonyl-ene reactivity
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Lewis acid complexes of the type [M{(R)-BINAP}][SbF6] 2 (M = Pt, Pd, Ni) catalyze the reaction between a-methylstyrenes and ethyl trifluoropyruvate to afford products resulting from the expected carbonyl-ene reactivity as well as tandem alkene dimerization-carbonyl-ene addition and alkene dimerization-Friedel-Crafts alkylation pathways, the distribution of which depends on the metal and the substituent attached to the aromatic ring of the styrene substrate. Kinetic studies reveal that the Lewis acid platinum complex catalyzes the dimerization of 4-chloro-α- methylstyrene much faster than its palladium counterpart and that the corresponding nickel system has platinum-like reactivity and selectivity.
- Doherty, Simon,Knight, Julian G.,Smyth, Catherine H.,Harrington, Ross W.,Clegg, William
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- MODULATORS OF GLUCOCORTICOID RECEPTOR, AP-1, AND/OR NF-kB ACTIVITY AND USE THEREOF
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Non-steroidal compounds are provided which are useful in treating diseases associated with modulation of the glucocorticoid receptor, AP-1, and/or NF-?B activity including obesity, diabetes, inflammatory and immune diseases, and have the structure of formula (I) or an enantiomer, a diastereomer, a pharmaceutically acceptable salt, or hydrate thereof, where J is selected from NR1 or C(R4)(R4a); K is selected from NR2 or C(R5)(R5a); L is selected from NR3 or C(R6)(R6a); and A, X, Y, R1, R2, R3, R4, R4a, R5, R5a, R6, R6a, R8, R10, R11, and n are defined herein. Also provided are pharmaceutical compositions and methods of treating obesity, diabetes and inflammatory or immune associated diseases comprising said compounds.
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- Effects of the electronic properties of chiral chelating diphosphines in stereoselective Diels-Alder cycloaddition reactions promoted by their transition metals complexes
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The Pd(II) and Pt(II) complexes (perchlorates and hexafluoroantimoniates, respectively) of a series of C2 symmetric biheteroaromatic diphosphines differing in their electronic properties at phosphorus have been tested as catalysts in [4 + 2]-cy
- Celentano, Giuseppe,Benincori, Tiziana,Radaelli, Stefano,Sada, Mara,Sannicolò, Franco
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p. 424 - 430
(2007/10/03)
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