- Synthesis, structure and oxo-transfer properties of dioxotungsten(VI) complexes with pyridine-based NO- and NS-bidentate ligands
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Treatment of [WO2Cl2(DME)] with 2-pyridylalkoxo NO-bidentate ligands [HLn (n = 1-5)] in the presence of n-BuLi or 2-pyridylthiolato NS-bidentate ligands [LiLn (n = 6, 7)] gave the corresponding dioxotungsten(VI)
- Wong,Yang,Zhou,Lee,Mak,Ng
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- Synthesis of pyridine-alkoxide ligands for formation of polynuclear complexes
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We have prepared and characterized a series of novel polydentate N,O-donor ligands derived from our well-studied ligand 2-(2-pyridinyl)-2-propanol (pyalkH), having the general formula Me{C(OH)(2-py)CH2}nH, where n = 2 or 3. Like pyalkH, these analogues bind via N and O with deprotonation at the latter, thus extending the strongly donor pyridine-alkoxide chelation power of pyalkH to polydentate forms. The greater denticity allows for more effective binding and polynuclear cluster formation with first-row transition metals. Several stable alkoxo-bridged polynuclear clusters of these ligands with Mn, Cu, Co and Ni have been prepared; all reported ligands and complexes have been characterized, including by X-ray crystallography. We report a one-step synthesis of these ligands, alongside pyalkH, on a multi-gram scale from inexpensive starting materials. We have also developed a new scalable procedure for the isolation of pyalkH that avoids the need for chromatography, making large-scale production of this ligand commercially viable.
- Shopov, Dimitar Y.,Sharninghausen, Liam S.,Sinha, Shashi Bhushan,Borowski, Julia E.,Mercado, Brandon Q.,Brudvig, Gary W.,Crabtree, Robert H.
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- Mechanism of Oxidative Dehydrogenation of Alcohols co-ordinated to Ruthenium
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The oxidative dehydrogenation of the complexes 2+, 2+ and >2+ to the corresponding carbonyl species has been studied in aqueous solution by kinetic and electrochemical techniques.The mechanistic scheme was found to involve the intermediacy of a ruthenium(IV)-alkoxide species, formed by disproportionation of the ruthenium(III) complex produced in the initial step of the oxidation process.The rate-determining removal of the proton from the α-carbon atom of the chelate ring is general-base catalysed.
- Ridd, Michael J.,Gakowski, David J.,Sneddon, Graeme E.,Keene, F. Richard
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- Light-Driven Water Oxidation with the Ir-blue Catalyst and the Ru(bpy)32+/S2O82- Cycle: Photogeneration of Active Dimers, Electron-Transfer Kinetics, and Light Synchronization for Oxygen Evolution with High Quantum Efficiency
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Light-driven water oxidation is achieved with the Ru(bpy)32+/S2O82- cycle employing the highly active Ir-blue water oxidation catalyst, namely, an IrIV,IV2(pyalc)2 μ-oxo-dimer [pyalc = 2-(2′-pyridyl)-2-propanoate]. Ir-blue is readily formed by stepwise oxidation of the monomeric Ir(III) precursor 1 by the photogenerated Ru(bpy)33+, with a quantum yield φ of up to 0.10. Transient absorption spectroscopy and kinetic evidence point to a stepwise mechanism, where the primary event occurs via a fast photoinduced electron transfer from 1 to Ru(bpy)33+, leading to the Ir(IV) monomer I1 (k1 ～108 M-1 s-1). The competent Ir-blue catalyst is then obtained from I1 upon photooxidative loss of the Cp? ligand and dimerization. The Ir-blue catalyst is active in the Ru(bpy)32+/S2O82- light-driven water oxidation cycle, where it undergoes two fast photoinduced electron transfers to Ru(bpy)33+ [with kIr-blue = (3.00 ± 0.02) × 108 M-1 s-1 for the primary event, outperforming iridium oxide nanoparticles by ca. 2 orders of magnitude], leading to a IrV,V2 steady-state intermediate involved in O-O bond formation. The quantum yield for oxygen evolution depends on the photon flux, showing a saturation regime and reaching an impressive value of φ(O2) = 0.32 ± 0.01 (corresponding to a quantum efficiency of 64 ± 2%) at low irradiation intensity. This result highlights the key requirement of orchestrating the rate of the photochemical events with dark catalytic turnover.
- Volpe, Andrea,Tubaro, Cristina,Natali, Mirco,Sartorel, Andrea,Brudvig, Gary W.,Bonchio, Marcella
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- Electrochemical properties and C-H bond oxidation activity of [Ru(tpy)(pyalk)Cl]+ and [Ru(tpy)(pyalk)(OH)]+
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[Ru(tpy)(pyalk)Cl]Cl (pyalk = 2-(2′-pyridyl)-2-propanol) was synthesized and characterized crystallographically and electrochemically. Upon dissolution in water and acetonitrile, [Ru(tpy)(pyalk)Cl]Cl was found to form [Ru(tpy)(pyalk)Cl]+ and [Ru(tpy)(pyalk)(OH)]+, respectively. The Ru(ii/iii) couple of [Ru(tpy)(pyalk)Cl]+ was found to be relatively low compared to that of other Ru complexes in acetonitrile, but the Ru(iii/iv) couple was not significantly different than other Ru complexes bearing anionic ligands. Pourbaix diagrams were generated for [Ru(tpy)(phpy)(OH2)]+ (phpy = 2-phenylpyridine) and [Ru(tpy)(pyalk)(OH)]+ in water, and it was found that [Ru(tpy)(pyalk)(OH)]+ has a lower Ru(ii/iii) potential than [Ru(tpy)(phpy)(OH2)]+ under neutral to alkaline pH. [Ru(tpy)(pyalk)(OH)]+ was found to catalyze C-H bond hydroxylation of secondary alkanes and epoxidation of alkenes using cerium(iv) ammonium nitrate as the primary oxidant.
- Nilles, Christian K.,Herath, Hashini N. K.,Fanous, Hanna,Ugrinov, Angel,Parent, Alexander R.
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p. 9701 - 9708
(2018/08/06)
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- Oxidation of Tertiary Aromatic Alcohols to Ketones in Water
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A new rosin-based amphiphile enables the oxidation of tertiary aromatic alcohols in water under mild conditions. The oxidation process is mediated by β-scission of alkoxy radicals. Our catalyst system including the surfactant, catalysts, and water can be easily recycled within the same reaction vial. (Figure presented.).
- Chen, Dengfeng,Zhang, Yuchen,Pan, Xingyu,Wang, Fei,Huang, Shenlin
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supporting information
p. 3607 - 3612
(2018/09/18)
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- Ligand Tuning in Pyridine-Alkoxide Ligated Cp?IrIII Oxidation Catalysts
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Six novel derivatives of pyridine-alkoxide ligated Cp?IrIII complexes, potent precursors for homogeneous water and C-H oxidation catalysts, have been synthesized, characterized, and analyzed spectroscopically and kinetically for ligand effects. Variation of alkoxide and pyridine substituents was found to affect their solution speciation, activation behavior, and oxidation kinetics. Application of these precursors to catalytic C-H oxidation of ethyl benzenesulfonate with aqueous sodium periodate showed that the ligand substitution pattern, solution pH, and solvent all have pronounced influences on initial rates and final conversion values. Correlation with O2 evolution profiles during C-H oxidation catalysis showed these competing reactions to occur sequentially, and demonstrates how it is possible to tune the activity and selectivity of the active species through the NO ligand structure.
- Sackville, Emma V.,Kociok-K?hn, Gabriele,Hintermair, Ulrich
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supporting information
p. 3578 - 3588
(2017/10/03)
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- HETEROCYCLIC COMPOUNDS AND USES THEREOF
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Heterocyclic compounds of formula (I), methods for their preparation, pharmaceutical compositions containing such a compound and their therapeutic uses.
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Paragraph 0337
(2014/09/29)
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- METALLOINSERTOR COMPLEXES TARGETED TO DNA MISMATCHES
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A composition including a Rh or Ru metailoinsertor complex specifically targets mismatch repair (MMR)~deficient cells. Selective cytotoxicity is induced in MMR-deficient cells upon uptake of the inventive metailoinsertor complexes.
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Paragraph 00151
(2015/01/09)
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- An unusual ligand coordination gives rise to a new family of rhodium metalloinsertors with improved selectivity and potency
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Rhodium metalloinsertors are octahedral complexes that bind DNA mismatches with high affinity and specificity and exhibit unique cell-selective cytotoxicity, targeting mismatch repair (MMR)-deficient cells over MMR-proficient cells. Here we describe a new generation of metalloinsertors with enhanced biological potency and selectivity, in which the complexes show Rh-O coordination. In particular, it has been found that both δ- and -[Rh(chrysi)(phen)(DPE)]2+ (where chrysi =5,6 chrysenequinone diimmine, phen =1,10-phenanthroline, and DPE = 1,1-di(pyridine-2-yl)ethan-1-ol) bind to DNA containing a single CC mismatch with similar affinities and without racemization. This is in direct contrast with previous metalloinsertors and suggests a possible different binding disposition for these complexes in the mismatch site. We ascribe this difference to the higher pKa of the coordinated immine of the chrysi ligand in these complexes, so that the complexes must insert into the DNA helix with the inserting ligand in a buckled orientation; spectroscopic studies in the presence and absence of DNA along with the crystal structure of the complex without DNA support this assignment. Remarkably, all members of this new family of compounds have significantly increased potency in a range of cellular assays; indeed, all are more potent than cisplatin and N-methyl-N'-nitro-nitrosoguanidine (MNNG, a common DNA-alkylating chemotherapeutic agent). Moreover, the activities of the new metalloinsertors are coupled with high levels of selective cytotoxicity for MMR-deficient versus proficient colorectal cancer cells.
- Komor, Alexis C.,Barton, Jacqueline K.
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p. 14160 - 14172
(2015/01/09)
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- Access to "friedel-Crafts-Restricted" tert -alkyl aromatics by activation/methylation of tertiary benzylic alcohols
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Herein we describe a two-step protocol to prepare m-tert-alkylbenzenes. The appropriate tertiary benzylic alcohols are activated with SOCl2 or concentrated HCl and then treated with trimethylaluminum, affording the desired products in 68-97% yields (22 examples). This reaction sequence is successful in the presence of a variety of functional groups, including acid-sensitive and Lewis-basic groups. In addition to t-Bu groups, 1,1-dimethylpropyl and 1-ethyl-1-methylpropyl groups can also be installed using this method.
- Hartsel, Joshua A.,Craft, Derek T.,Chen, Qiao-Hong,Ma, Ming,Carlier, Paul R.
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experimental part
p. 3127 - 3133
(2012/05/20)
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- Proton NMR and IR study of self-association in pyridylalkanols: Open or cyclic dimers? Higher polymers?
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1H NMR measurements indicate that (X-pyridyl)alkanols of the general formula (C5H4N)(CH2)nOH, where n = 1, 2 or 3, self-associate as open dimers, cyclic dimers, trimers and tetramers, with considerable variations depending on the position of the alkyl chain and its length. (X-Pyridyl)propan-2-ols behave like the corresponding pyridylmethanols with, however, somewhat lower association constants. The IR spectra of 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X = 3 or 4) in carbon tetrachloride suggest weak association, while the 2-pyridyl derivative occurs mainly as the intramolecularly hydrogen-bonded rotamer. The OH NMR shifts for the 3- and 4-pyridyl derivatives in benzene are concentration-dependent, but neither the equilibrium constants nor the degree of association can be evaluated. Benzyl alcohol in benzene associates as an open dimer and a cyclic tetramer, as does 2phenylpropan-2-ol, only more weakly. Rotation barriers for 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X = 2, 3 or 4) in DMSO or nitrobenzene are 20-21 kcal mol-1. Copyright
- Lomas, John S.,Adenier, Alain,Cordier, Christine
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p. 295 - 307
(2007/10/03)
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- New syntheses of substituted pyridines via bromine-magnesium exchange
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Bromine-magnesium exchange using iPrMgCl in THF at room temperature on 2-, 3- and 4-bromopyridines allowed the synthesis of various functionalized pyridines. The methodology was successfully used for the synthesis of 4- azaxanthone. Moreover, single exchange reactions observed on 2,6-, 3,5-, 2,3- and 2,5-dibromopyridines, with complete regioselectivity in the case of 2,3- and 2,5-dibromopyridines, afforded substituted bromopyridines, which were then involved in a second exchange step to provide difunctionalized pyridines. (C) 2000 Elsevier Science Ltd.
- Trécourt, Fran?ois,Breton, Gilles,Bonnet, Véronique,Mongin, Florence,Marsais, Francis,Quéguiner, Guy
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p. 1349 - 1360
(2007/10/03)
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- Pyridylmagnesium chlorides from bromo and dibromopyridines by bromine- magnesium exchange: A convenient access to functionalized pyridines
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Various bromopyridines were converted to the corresponding pyridylmagnesium chlorides at room temperature by treatment with iPrMgCl. The resulting Grignard reagents were quenched by various electrophiles to afford functionalized pyridines. The bromine-magnesium exchange of some dibromopyridines was also studied.
- Trecourt, Francois,Breton, Gilles,Bonnet, Veronique,Mongin, Florence,Marsais, Francis,Queguiner, Guy
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p. 4339 - 4342
(2007/10/03)
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- Aggregative activation in heterocyclic chemistry. Part 5. Lithiation of pyridine and quinoline with the complex base BuLi·Me2N(CH2)2OLi (BuLi·LiDMAE)
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It is shown that the complex base BuLi·LiDMAE reacts with pyridine to give metallated species which, after trapping by electrophiles, lead to 2-substituted pyridines in good to excellent yields. The same reactions have been less successfully performed with quinoline.
- Gros, Philippe,Fort, Yves,Caubere, Paul
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p. 3597 - 3600
(2007/10/03)
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- Organomolybdenum and Organotungsten Reagents, V. - On the Additive, Reductive Carbonyl Dimerization (ARCD Reaction)
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Reagents of the type R4(PrO)4(μ-PrO)2W2 (3; R = Me, Et, Pr, Bu, sBu, iBu, Hex, Me3SiCH2, Ph) prepared in situ by the action of organolithium or Grignard compounds on (PrO)4(μ-PrO)2W2Cl4 (2), react with aromatic aldehydes or ketones and with the α,β-unsaturated ketone benzylidene acetone in a novel reaction, called the ARCD reaction, to give products 4 of the type RR'R''C-CRR'R'' with mostly good yields.In the case of benzylidene acetone and furfural besides the ARCD products the rearranged products 27 and 29 are formed.With the reagent Ph4(PrO)4(μ-PrO)2W2 (3b) ARCD reactions are also possible in moderate yields with aliphatic aldehydes and ketones.The more closely investigated reagent Me4(PrO)4(μ-PrO)2W2 (3a; decomposition at about -45 deg C) tolerates the aromatic bound functional groups Cl, F, OH, OMe, and NMe2 in the substrates, but not the NO2 and CO2Et substituents.It reacts with PhCOX (X = OEt, Cl, OCOPh) via acetophenone to give PhCMe2-CMe2Ph. - For the ARCD reactions a radical mechanism (Scheme 7) is postulated. - Key Words: Tungsten complexes/ Carbonyl dimerization
- Kauffmann, Thomas,Jordan, Jan,Voss, Karl-Uwe,Wilde, Heinz-Wilhelm
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p. 2083 - 2092
(2007/10/02)
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- Smoking compositions containing an oxalate flavorant-release additive
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In one embodiment this invention provides smoking compositions which contain a novel oxalate ester flavorant-release additive. Under cigarette smoking conditions, a combustible filler additive such as methyl 2-pyrazinyl-2-propanyl oxalate or di(2-pyrazinyl-2-propanyl) oxalate pyrolyzes and releases 2-isopropenylpyrazine flavorant as a volatile component of the cigarette smoke. STR1
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- Compounds with Bridgehead Nitrogen. Part 58. Configurational Assignments to 1-methyl-1-isopropylperhydro-oxazolopyridines
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Protonation of the diastereomeric 1-methyl-1-isopropylperhydro-oxazolopyridines by treatment of ether solutions with dry hydrogen chloride gas gave markedly different proportions of the trans-fused and O-outside cis-fused hydrochlorides.On this basis and from a consideration of the ease of protonation of the conformers of the free bases C-1 configurational assignments were made.
- Crabb, Trevor A.,Trethewey, Andrew N.
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p. 818 - 834
(2007/10/02)
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- Applications of Organolithium and Related Reagents in Synthesis. Part 3. A General Study of the Reaction of Lithium Alkyls with Pyridine Ketones
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The reaction of MeLi and PhLi with acetylpyridines (1a-c) and their annelated derivatives (2a), (2b), (3), and (4) has been examined.The 3- and 4-pyridyl ketones (1b), (1c), (3), and (4) gave similar results to acetophenone and 3,4-dihydronaphthalen-1(2H)-one.In the case of the 2-pyridyl ketones (1a), (2a), and (2b) unexpectedly low yields of products resulted from the addition of RLi to the carbonyl group; the reaction was efficiently enhanced by initially adding an additional amount of LiBr.These results were accounted for by the chelation of RLi or LiBr by the 2-pyridyl ketones.
- Epsztajn, Jan,Bieniek, Adam
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p. 213 - 220
(2007/10/02)
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- Nitrogen- and sulfur-containing models for metallo-enzymes. Part I. Synthesis and physical studies of 2(2-pyridyl)-1,3-dithioalkyl-2-propanols, 2(2-pyridyl)- and 2(2-imidazolyl)-1,3-dimercapto-2-propanols
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Several compounds of the title class have been synthesized as small-molecule analogues for the metal-binding sites in such biochemical systems as ADH.The ligands containing pyridine and two thioethers do not bind divalent metals Co(2+), Zn(2+), Cu(2+), N
- Curtis, N. J.,Brown, R. S.
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