The Palladium-Catalyzed Cross-Coupling Reaction of Phenylboronic Acid with Haloarenes in the Presence of Bases

Suzuki–Miyaura cross-coupling reaction catalyzed by Pd/MgLa mixed oxide

A new, reusable Pd/MgLa mixed oxide catalyst has been applied successfully in the Suzuki-Miyaura carbon-carbon cross-coupling reaction of aryl halides as well as benzylic bromide with boronic acids in ethanol. The catalyst is air stable, can be stored and handled under an ambient atmosphere and after the reaction it can be recovered by simple filtration and reused without significant loss of activity.

Self-organization of mesomeric–ionic hybrid heterocycles into liquid crystal phases: a new class of polar mesogens

The first mesoionic nematic and smectic A mesogens derived from sydnones that are characterized by both covalent and ionic features have been synthesized and evidenced by optical, calorimetric and X-ray diffraction studies.

Efficient batch and continuous flow Suzuki cross-coupling reactions under mild conditions, catalysed by polyurea-encapsulated palladium (ii) acetate and tetra-n-butylammonium salts

Suzuki cross-coupling reactions are effected in both conventional organic solvents, under continuous flow conditions at 70 degree C, and in batch mode in supercritical carbon dioxide (scCO2), at temperatures as low as 40 degrees C in the presence of palladium(II) acetate microencapsulated in polyurea [PdEnCat] and tetra-n-butylammonium salts.

α2-Adrenoreceptors Profile Modulation. 2. Biphenyline Analogues as Tools for Selective Activation of the α2C-Subtype

A series of derivatives structurally related to biphenyline (3) was designed with the aim to modulate selectivity toward the alpha(2)-AR subtypes. The results obtained demonstrated that the presence of a correctly oriented function with positive electronic effect (+sigma) in portion X of the ligands is an important factor for significant alpha(2C)-subtype selectivity (imidazolines 5, 13, 16, and 19). Homology modeling and docking studies support experimental data and highlight the crucial role for the hydrogen bond between the pyridine nitrogen in position 3 of 5 and the NH-indole ring of Trp6.48, which is favorably oriented in the alpha(2C)-subtype, only.

Oligomers of Hexa-peri-hexabenzocoronenes as “Super-oligophenylenes”: Synthesis, Electronic Properties, and Self-assembly

Hexa-peri-hexabenzocoronene (HBC) is a remarkable polycyclic aromatic hydrocarbon and is often called "superbenzene" because of its similarity to benzene. In this article we present the facile synthesis of oligomers of HBC, up to trimers (3, 4, 5a-c) with different modes of connection. UV-vis and fluorescence spectroscopy studies reveal that the oligomers are electronically decoupled. This arises from the small atomic orbital coefficients of the bridge-head carbon atoms, the large torsion angle between the HBC units, and the large distance of interacting transition dipoles due to the size of the HBC chromophore. For comparison, a methylene-bridged HBC dimer 6, so-called "superfluorene", was prepared. The induced planarity improves pi-conjugation and suppresses the geometrical relaxation of the backbone upon electronic excitation, leading to a prominent 0-0 transition band in the fluorescence spectra. The self-assembly of the oligomers and of superfluorene 6 was studied by wide-angle X-ray diffraction (WAXD) in the bulk state, and ordered columnar stacking occurs in the HBC dimer 3, p-HBC trimer 4, and superfluorene 6. Measurements of shear-aligned samples show that, despite increasing aspects ratio by linear entrainment of disks, the anitropic element that is subject to alignment by shear is the supramolecular columns.

Mass spectrometric studies on the coupling model reaction towards alkenyl-aryl ketones

The palladium catalysed coupling reactions of 1-iodo-cyclohexene have been investigated with the aim of the synthesis of model compounds towards unsaturated aryl-alkenyl ketones of practical interest in carbonylative Suzuki reaction. In addition to the target compounds, the formation of 1-aryl-cyclohexene derivatives, 1,1'-bi(cyclohex-1-en-1-yl), 1,2-dicyclohex-1-en-1-yl-ethane-1,2-dione, dicyclohex-1-en-1-yl-ketone and 1-aryl-2-cyclohexenyl-cyclohexene derivatives, as well as their isomerization products, have been observed in parallel and consecutive reactions, respectively. The complex reaction mixtures have been analysed with GC-MS providing valuable information to the investigation of the homogeneous catalytic reaction.

Intramolecular formal oxa-[3 + 3] cycloaddition approach to the ABD system of phomactin A

The ABD-ring of phomactin A was synthesized using an intramolecular formal oxa-[3 + 3] cycloaddion of an alpha,beta-unsaturated iminium salt tethered to a 1,3-diketone. This represents the first time that the 12-membered ring has been formed simultaneously with the 1-oxadecalin and should afford a facile route to the challenging structure of phomactin A. [reaction: see text]

Design, Synthesis, and Antiviral Activity of Certain 3-Substituted 2,5,6-Trichloroindole Nucleosides

A series of trichlorinated indole nucleosides has been synthesized and tested for activity against human cytomegalovirus (HCMV) and herpes simplex virus type-1 (HSV-1) and for cytotoxicity. Modifications of the previously reported 2,5,6-trichloro-1-(beta-d-ribofuranosyl)indole at the 3-position of the heterocycle were designed in part to test our hypothesis that hydrogen bonding is required at that position for antiviral activity. Analogues were synthesized using electrophilic addition at the 3-position or by synthesis of modified indole heterocycles followed by glycosylation and modification of the sugar. Among the modifications at the 3-position, only those analogues with hydrogen-bond-accepting character were active against HCMV (e.g., 3-formyl-2,5,6-trichloro-1-(beta-D-ribofuranosyl)indole, FTCRI, IC50 = 0.23 microM). Conversely, analogues with non-hydrogen-bonding substituents at the 3-position (e.g., 3-methyl-2,5,6-trichloro-1-(beta-D-ribofuranosyl)indole) were much less active (IC50 = 32 microM) than those with the requisite hydrogen-bonding capacity. The 5'-O-acyl analogue of FTCRI was obtained as an intermediate and also found to be a potent inhibitor of HCMV (IC50 < 0.1 microM). The synthesis of some additional 5'-O-acylated analogues did not provide a compound with increased antiviral activity. None of the indole nucleosides had significant activity against HSV-1, and none were cytotoxic to uninfected cells in their antiviral dose range. Results obtained from the antiviral evaluations have validated our hypothesis that hydrogen bonding at the 3-position is required for antiviral activity in this series of chlorinated indole nucleosides.

Comparative studies of potential cancer biomarkers carbon-11 labeled MMP inhibitors (S)-2-(4'-[11C]methoxybiphenyl-4-sulfonylamino)-3-methylbutyric acid and N-hydroxy-(R)-2-[[(4'-[11C]methoxyphenyl)sulfonyl]benzylamino]-3-methylbutanamide

(S)-2-(4'-[11C]methoxybiphenyl-4-sulfonylamino)-3-methylbutyric acid ([11C]MSMA) and N-hydroxy-(R)-2-[[(4'-[11C]methoxyphenyl)sulfonyl]benzylamino]-3-methylbutanamide ([11C]CGS 25966), carbon-11 labeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer biomarkers. [11C]MSMA was prepared by appropriate precursor (S)-2-(4'-hydroxybiphenyl-4-sulfonylamino)-3-methylbutyric acid tert-butyl ester, which was synthesized in eight steps from amino acid (L)-valine in 39.4% chemical yield. This precursor was labeled by [11C]methyl triflate through O-[11C]methylation method at the hydroxyl position of biphenol under basic conditions, followed by a quick acid hydrolysis and isolated by solid-phase extraction (SPE) purification to produce pure target compound [11C]MSMA in 35-55% radiochemical yield, based on 11CO2, decay corrected to end of bombardment (EOB), and 20-25 min synthesis time. [11C]CGS 25966 was prepared in our previous work starting from amino acid (D)-valine. The biodistribution of [11C]MSMA and [11C]CGS 25966 were determined at 45 min post iv injection in breast cancer animal models MCF-7's transfected with IL-1alpha implanted athymic mice and MDA-MB-435 implanted athymic mice. The results showed the uptakes of [11C]MSMA and [11C]CGS 25966 in these tumors were 0.95 and 0.42%dose/g in MCF-7's transfected with IL-1alpha implanted mice, 0.98 and 1.53%dose/g in MDA-MB-435 implanted mice, respectively; the ratios of tumor/muscle (T/M) and tumor/blood (T/B) were 1.21 and 1.09 (T/M, MCF-7's), 0.99 and 0.84 (T/B, MCF-7's), 1.38 and 1.27 (T/M, MDA-MB-435), 1.27 and 1.95 (T/B, MDA-MB-435), respectively. The micro-PET images of [11C]MSMA and [11C]CGS 25966 in both breast cancer athymic mice were acquired for 15 min from a MCF-7's transfected with IL-1alpha and/or MDA-MB-435 implanted mouse at 45 min post iv injection of 1 mCi of the tracer using a dedicated high resolution (<3 mm full-width at half-maximum) small FOV (field-of-view) PET imaging system, Indy-PET II scanner, developed in our laboratory, which showed both tumors were invisible with both tracers. The results were compared. From our results, we concluded that both [11C]MSMA and [11C]CGS 25966 might be unsuitable as PET tracers for cancer imaging.

Liquid Crystalline Bolaamphiphiles with Semiperfluorinated Lateral Chains: Competition between Layerlike and Honeycomb-Like Organization

Novel bolaamphiphilic triblockmolecules consisting of a rigid biphenyl unit, with a polar 2,3-dihydroxypropyloxy group and a phenolic OH group at opposite ends, as well as a semiperfluorinated chain in a lateral position have been synthesized via palladium catalyzed cross coupling reactions as the key steps. The thermotropic liquid crystalline behavior of these compounds was investigated by polarized light microscopy, DSC and X-ray scattering, and the influence of the length of the lateral chain on the mesomorphic properties was studied. The compound with the shortest chain as well as the long chain derivatives form lamellar mesophases composed of segregated layers of the bolaamphiphilic moieties and sublayers comprising the fluid lateral chains. The layers within the lamellar phases of the short chain compound adopt a positional correlation, leading to a 2D lattice (Col(r)/p2mm), whereas the layers of the lamellar phases of the long chain derivatives are noncorrelated (Lam). Compounds with a medium chain length organize into columnar phases, where the nonpolar lateral chains segregate into columns, which are embedded in networks of regular (Col(h)) or stretched (Col(r)/c2mm) hexagonal cylinder shells consisting of the bolaamphiphilic units. In total, an unusual phase sequence was found, where, with respect to the chain length, columnar mesophases occur between two mesophases with layer organization.

Ring-Closing Olefin Metathesis of 2,2‘-Divinylbiphenyls: A Novel and General Approach to Phenanthrenes

[reaction: see text] The ring-closing olefin metathesis (RCM) of 2,2'-divinylbiphenyls, using a second-generation RCM ruthenium-based catalyst, leads to differently substituted phenanthrenes in quantitative yield under very mild reaction conditions, independent of both nature and position of the groups present on the biphenyl moiety.

Theoretical Study of Trans-metalation Process in Palladium-Catalyzed Borylation of Iodobenzene with Diboron

Trans-metalation process in the palladium-catalyzed borylation of iodobenzene with diboron was theoretically investigated with the DFT method. Palladium(II) hydroxo phenyl complex, Pd(OH)(Ph)(PH(3))(2), and the fluoro analogue easily undergo the trans-metalation with diboron, B(2)(eg)(2) (eg = -OCH(2)CH(2)O-), to afford Pd(Ph)(Beg)(PH(3))(HO-Beg) and Pd(Ph)(Beg)(PH(3))(F-Beg), respectively, where B(2)(eg)(2) is adopted as a model of bis(pinacolato)diboron used experimentally. The electron re-distribution in the trans-metalation clearly indicates that the B-B bond scission occurs in a heterolytic manner. In the chloro analogue, PdCl(Ph)(PH(3))(2), however, the trans-metalation occurs in a homolytic manner with much difficulty, which is consistent with the experimental result. The significant differences between the chloro complex and the other hydroxo and fluoro complexes are easily interpreted in terms that hydroxo and fluoro ligands can form strongly bonding interaction with B(2)(eg)(2) but the chloro ligand cannot.

Biphenyl-based analogues of thiolactomycin, active against Mycobacterium tuberculosis mtFabH fatty acid condensing enzyme

Analogues of the antibiotic thiolactomycin, with biphenyl-based 5-substituents, were found to have excellent in vitro inhibitory activity against the recombinant Mycobacterium tuberculosis beta-ketoacyl-ACP synthase mtFabH condensing enzyme. In particular, 5-(4'-benzyloxy-biphen-4-ylmethyl)-4-hydroxy-3,5-dimethyl-5H-thiophen-2-one exhibited approximately a 4-fold increased potency against this key condensing enzyme involved in M. tuberculosis mycolic acid biosynthesis, compared to thiolactomycin.

Synthesis, structure, theoretical studies, and Ligand exchange reactions of monomeric, T-shaped arylpalladium(II) halide complexes with an additional, weak agostic interaction

A series of monomeric arylpalladium(II) complexes LPd(Ph)X (L = 1-AdPtBu2, PtBu3, or Ph5FcPtBu2 (Q-phos); X = Br, I, OTf) containing a single phosphine ligand have been prepared. Oxidative addition of aryl bromide or aryl iodide to bis-ligated palladium(0) complexes of bulky, trialkylphosphines or to Pd(dba)2 (dba = dibenzylidene acetone) in the presence of 1 equiv of phosphine produced the corresponding arylpalladium(II) complexes in good yields. In contrast, oxidative addition of phenyl chloride to the bis-ligated palladium(0) complexes did not produce arylpalladium(II) complexes. The oxidative addition of phenyl triflate to PdL2 (L = 1-AdPtBu2, PtBu3, or Q-phos) also did not form arylpalladium(II) complexes. The reaction of silver triflate with (1-AdPtBu2)Pd(Ph)Br furnished the corresponding arylpalladium(II) triflate in good yield. The oxidative addition of phenyl bromide and iodide to Pd(Q-phos)2 was faster than oxidative addition to Pd(1-AdPtBu2)2 or Pd(PtBu3)2. Several of the arylpalladium complexes were characterized by X-ray diffraction. All of the arylpalladium(II) complexes are T-shaped monomers. The phenyl ligand, which has the largest trans influence, is located trans to the open coordination site. The complexes appear to be stabilized by a weak agostic interaction of the metal with a ligand C-H bond positioned at the fourth-coordination site of the palladium center. The strength of the Pd.H bond, as assessed by tools of density functional theory, depended upon the donating properties of the ancillary ligands on palladium.

Palladium-catalyzed cross-coupling of stereospecific potassium cyclopropyl trifluoroborates with aryl bromides

[reaction: see text] Stereospecific cyclopropanation of alkenylboronic esters of pinacol followed by in situ treatment with excess KHF(2) afforded the corresponding potassium cyclopropyl trifluoroborates in high yields, which then underwent Suzuki-Miyaura cross-coupling reactions with aryl bromides to give cyclopropyl-substituted arenes in good yields with retention of configuration. This promises to be a useful method for the synthesis of enantiomerically pure cyclopropanes.

2,3-Diarylpyran-4-ones: a new series of selective cyclooxygenase-2 inhibitors

A new series of cyclooxygenase-2 (COX-2) inhibitors with gamma-pyrone as central scaffold unit has been synthesized and their biological activities were evaluated against cyclooxygenase inhibitory activity. The changes of physical properties of the molecules were performed according to the medicinal chemistry principles and moderate oral anti-inflammatory activity was obtained with this series of inhibitors.

NiCl2(dppe)-Catalyzed Cross-Coupling of Aryl Mesylates, Arenesulfonates, and Halides with Arylboronic Acids

An investigation of the NiCl(2)(dppe)-, NiCl(2)(dppb)-, NiCl(2)(dppf)-, NiCl(2)(PCy(3))(2)-, and NiCl(2)(PPh(3))(2)-catalyzed cross-coupling of the previously unreported aryl mesylates, and of aryl arenesulfonates, chlorides, bromides, and iodides containing electron-withdrawing and electron-donating substituents with aryl boronic acids, in the absence of a reducing agent, is reported. NiCl(2)(dppe) was the only catalyst that exhibited high and solvent-independent activity in the two solvents investigated, toluene and dioxane. NiCl(2)(dppe) with an excess of dppe, NiCl(2)(dppe)/dppe, was reactive in the cross-coupling of electron-poor aryl mesylates, tosylates, chlorides, bromides, and iodides. This catalyst was also efficient in the cross-coupling of aryl bromides and iodides containing electron-donating substituents. Most surprisingly, the replacement of the excess dppe from NiCl(2)(dppe)/dppe with excess PPh(3) generated NiCl(2)(dppe)/PPh(3), which was found to be reactive for the cross-coupling of both electron-rich and electron-poor aryl mesylates and chlorides. Therefore, the solvent-independent reactivity of NiCl(2)(dppe) provides an inexpensive and general nickel catalyst for the cross-coupling of aryl mesylates, tosylates, chlorides, bromides, and iodides with aryl boronic acids.

In vitro structure-activity relationship and in vivo studies for a novel class of cyclooxygenase-2 inhibitors: 5-aryl-2,2-dialkyl-4-phenyl-3(2H)furanone derivatives

5-Aryl-2,2-dialkyl-4-phenyl-3(2H)furanone derivatives were studied as a novel class of selective cyclooxygenase-2 inhibitors with regard to synthesis, in vitro SAR, antiinflammatory activities, pharmacokinetic considerations, and gastric safety. 1f, a representative compound for methyl sulfone derivatives, showed a COX-2 IC(50) comparable to that of rofecoxib. In case of 20b, a representative compound for sulfonamide derivatives, a potent antiinflammatory ED(50) of 0.1 mg kg(-1) day(-1) was observed against adjuvant-induced arthritis by a preventive model, positioning 20b as one of the most potent COX-2 inhibitors ever reported. Furthermore, 20b showed strong analgesic activity as indicated by its ED(50) of 0.25 mg/kg against carrageenan-induced thermal hyperalgesia in the Sprague-Dawley rat. 3(2H)Furanone derivatives showed due gastric safety profiles as selective COX-2 inhibitors upon 7-day repeat dosing. A highly potent COX-2 inhibitor of the 3(2H)furanone scaffold could be considered suitable for a future generation COX-2 selective arthritis medication with improved safety profiles.

SSR182289A, a selective and potent orally active thrombin inhibitor

SSR182289A 1 is the result of a rational optimisation process leading to an orally active thrombin inhibitor. The structure incorporates an original 2-(acetylamino)-[1,1'-biphenyl]-3-sulfonyl N-terminal motif, a central l-Arg surrogate carrying a weakly basic 3-amino-pyridine, and an unusual 4-difluoropiperidine at the C-terminus. Its synthesis is convergent and palladium catalysis has been employed for the construction of the key C-C bonds: Suzuki coupling for the bis-aryl fragment and Sonogashira reaction for the delta- bond of the central amino-acid chain. The compound is a potent inhibitor of thrombin's activities in vitro and demonstrates potent oral anti-thrombotic potencies in three rat models of thrombosis. The observed in vitro potency could be rationalized through the examination of the interactions within the SSR182289A 1 - thrombin crystal structure. SSR182289A 1, has been therefore selected for further development.

Discovery, Modeling, and Human Pharmacokinetics ofN-(2-Acetyl-4,6-dimethylphenyl)-3-(3,4-dimethylisoxazol-5-ylsulfamoyl)thiophene-2-carboxamide (TBC3711), a Second Generation, ETASelective, and Orally Bioavailable Endothelin Antagonist1

Sitaxsentan (1) (Wu et al. J. Med. Chem. 1997, 40, 1690) is our first endothelin antagonist being evaluated in clinical trials. It has demonstrated biological effects in an acute hemodynamic study in CHF (Givertz et al. Circulation 2000, 101, 2922), an open-label 20-patient pulmonary hypertension trial (Barst et al. Chest 2002, 121, 1860-1868), and a 31-patient trial in essential hypertension (Calhoun et al. AHA Scientific Sessions 2000). In a phase 2b/3 pulmonary arterial hypertension trial, once a day treatment of 100 mg of sitaxsentan statistically significantly improved 6-min walk distance and NYHA class at 12 weeks (Barst et al. Am. J. Respir. Crit. Care Med. 2004, 169, 441). We have since reported on our efforts in generating follow-up compounds (Wu et al. J. Med. Chem. 1999, 42, 4485) and recently communicated that an ortho acyl group on the anilino ring enhanced oral absorption in this category of compounds (Wu et al. J. Med. Chem. 2001, 44, 1211). Here we report an expansion of this work by substituting a variety of electron-withdrawing groups at the ortho position and evaluating their effects on oral bioavailability as well as structure-activity relationships. As a result, TBC3711 (7z) was identified as our second endothelin antagonist to enter the clinic due to its good oral bioavailability (approximately 100%) in rats, high potency (ET(A) IC(50) = 0.08 nM), and optimal ET(A)/ET(B) selectivity (441 000-fold). Compound 7z has completed phase-I clinical development and was well tolerated with desirable pharmacokinetics in humans (t(1/2) = 6-7 h, oral availability > 80%).

Synthesis and structure-activity relationship of novel, highly potent metharyl and methcycloalkyl cyclooxygenase-2 (COX-2) selective inhibitors

A novel series of benzo-1,3-dioxolane metharyl derivatives was synthesized and evaluated for cyclooxygenase-2 (COX-2) and cyclooxygenase-1 (COX-1) inhibition in human whole blood (HWB). In the present study, structure-activity relationships (SAR) in the metharyl analogues were investigated. The spacer group and substitutions in the spacer group were found to be quite important for potent COX-2 inhibition. Compounds in which a methylene group (8a-c), carbonyl group (12a-c), or methylidene group (7a-c) connected cycloalkyl groups to the central benzo-1,3-dioxolane template were found to be potent and selective COX-2 inhibitors. Aryl-substituted compounds linked to the central ring by either a methylene or a carbonyl spacer resulted in potent, highly selective COX-2 inhibitors. In this series of substituted-(2H-benzo[3,4-d]1,3-dioxolan-5-yl))-1-(methylsulfonyl)benzene compounds, SAR studies demonstrated that substitution at the 3-position of the aryl group optimized COX-2 selectivity and potency, whereas substitution at the 4-position attenuated COX-2 inhibition. Mono- or difluoro substitution at meta position(s), as in 22c and 22h, was advantageous for both in vitro COX-2 potency and selectivity (e.g., COX-2 IC(50) for 22c = 1 microM and COX-1 IC(50) for 22c = 20 microM in HWB assay). Several novel compounds in the (2H-benzo[3,4-d]1,3-dioxolan-5-yl))-1-(methylsulfonyl)benzene series, as shown in structures 7c, 8a, 12a, 21c, 22c, 22e, and 22h, selectively inhibited COX-2 activity by 40-50% at a test concentration of 1 microM in an in vitro HWB assay.