Showing papers on "Pyridine published in 2012"
TL;DR: Stereoselective Addition to N-Activated Pyridines James A. Bull, Guillaume Pelletier,† and Andre ́ B. Charette are credited for this work.
Abstract: Stereoselective Addition to N-Activated Pyridines James A. Bull,‡ James J. Mousseau, Guillaume Pelletier,† and Andre ́ B. Charette*,† †Department of Chemistry, Universite ́ de Montreál, P.O. Box 6128, Station Downtown, Montreál, Queb́ec, Canada H3C 3J7 ‡Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ, U.K. Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
679 citations
TL;DR: A nitrogen-doped porous carbon monolith was synthesized as a pseudo-capacitive electrode for use in alkaline supercapacitors and possible redox reaction pathways based on the calculated redox affinity of different groups and surface analysis were proposed.
Abstract: A nitrogen-doped porous carbon monolith was synthesized as a pseudo-capacitive electrode for use in alkaline supercapacitors. Ammonia-assisted carbonization was used to dope the surface with nitrogen heteroatoms in a way that replaced carbon atoms but kept the oxygen content constant. Ammonia treatment expanded the micropore size-distributions and increased the specific surface area from 383 m2?g-1 to 679 m2?g-1. The nitrogen-containing porous carbon material showed a higher capacitance (246 F?g-1) in comparison with the nitrogen-free one (186 F?g-1). Ex situ electrochemical spectroscopy was used to investigate the evolution of the nitrogen-containing functional groups on the surface of the N-doped carbon electrodes in a three-electrode cell. In addition, first-principles calculations were explored regarding the electronic structures of different nitrogen groups to determine their relative redox potentials. We proposed possible redox reaction pathways based on the calculated redox affinity of different groups and surface analysis, which involved the reversible attachment/detachment of hydroxy groups between pyridone and pyridine. The oxidation of nitrogen atoms in pyridine was also suggested as a possible reaction pathway.
355 citations
TL;DR: In this article, the absorption coefficients of pyridine for acidic sites and nitrobenzene for basic sites, estimated for various metal oxides by IR coupled with mass spectrometry, were within ±10% of the average value, which indicates that the integrated molar extinction coefficients could be used for semiquantification of acid/base sites of various oxides samples.
Abstract: Acid/base properties (type, strength, number) of a wide range of metal oxides were studied by IR (infra-red) spectroscopy. Ammonia, pyridine and CD3CN were used as probe molecules for acidity measurement. CO2, CHCl3, benzaldehyde and nitrobenzene were used for basicity measurement. Pyridine for the nature and number of acid sites, CD3CN for the strength of acid sites, CHCl3 for the strength of basic sites and nitrobenzene for the number of basic sites were found to be suitable probes. The absorption coefficients of pyridine for acidic sites and nitrobenzene for basic sites, estimated for various metal oxides by IR coupled with mass spectrometry, were within ±10% of the average value, which indicates that the integrated molar extinction coefficients could be used for semi-quantification of acid/base sites of various oxides samples. The comprehensive IR results in this study will be available to characterize properties of Lewis and Bronsted acid sites and basic sites on metal oxides by a simple IR experiment.
270 citations
TL;DR: Enantiopure C(1)-symmetric bis(imino)pyridine cobalt chloride, methyl, hydride, and cyclometalated complexes are active as catalysts for the enantioselective hydrogenation of geminal-disubstituted olefins.
Abstract: Enantiopure C1-symmetric bis(imino)pyridine cobalt chloride, methyl, hydride, and cyclometalated complexes have been synthesized and characterized. These complexes are active as catalysts for the enantioselective hydrogenation of geminal-disubstituted olefins.
264 citations
TL;DR: In this paper, high purity aligned nitrogen doped multi walled carbon nanotubes were synthesized by the catalytic chemical vapor deposition method using pyridine and Fe/Co (2:1 volume ratio) as the single C/N pre...
248 citations
TL;DR: Preliminary mechanistic investigations show that an iron-catalyzed hydrometalation is followed by transmetalation and reaction with the electrophile (CO(2)).
Abstract: The iron-catalyzed hydrocarboxylation of aryl alkenes has been developed using a highly active bench-stable iron(II) precatalyst to give α-aryl carboxylic acids in excellent yields and with near-perfect regioselectivity. Using just 1 mol % FeCl2, bis(imino)pyridine 6 (1 mol %), CO2 (atmospheric pressure), and a hydride source (EtMgBr, 1.2 equiv), a range of sterically and electronically differentiated aryl alkenes were transformed to the corresponding α-aryl carboxylic acids (up to 96% isolated yield). The catalyst was found to be equally active with a loading of 0.1 mol %. Preliminary mechanistic investigations show that an iron-catalyzed hydrometalation is followed by transmetalation and reaction with the electrophile (CO2).
223 citations
TL;DR: Establishment of this structure-activity relationship has produced base metal catalysts that exhibit high turnover frequencies for the hydrogenation of unfunctionalized, tri- and tetrasubstituted alkenes, one of the most challenging substrate classes for homogenous hydrogenation catalysts.
Abstract: The activity of aryl-substituted bis(imino)pyridine and bis(arylimidazol-2-ylidene)pyridine iron dinitrogen complexes has been evaluated in a series of catalytic olefin hydrogenation reactions. In general, more electron donating chelates with smaller 2,6-aryl substituents produce more active iron hydrogenation catalysts. Establishment of this structure-activity relationship has produced base metal catalysts that exhibit high turnover frequencies for the hydrogenation of unfunctionalized, tri- and tetrasubstituted alkenes, one of the most challenging substrate classes for homogenous hydrogenation catalysts.
192 citations
TL;DR: Preliminary mechanistic studies revealed that pyridine played a crucial role for the high yields and selectivities of iron for C-H functionalization/C-S bond formation under mild conditions.
191 citations
TL;DR: The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-mETHoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature and supporting the need for an electronically enriched ortho-iodo substituent in catalyst 4f.
Abstract: The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. ...
180 citations
TL;DR: The transition-metal-catalyzed cyclo-trimerization reaction is a powerful methodology to synthesize polycyclic molecules in a single step with optimal atom efficiency.
Abstract: Transition-metal-catalyzed [2+2+2] cyclo(co)trimerization reactions are a powerful methodology to synthesize various complex multi-substituted (poly)cyclic molecules in a single step with optimal atom efficiency. Ever since the discovery, the reaction has been plagued by issues concerning regio- and chemoselectivity. Over the last decades many advances have been made to overcome these issues by, for example, employing regio-directing groups or tethering the reaction partners together in an intramolecular approach. These solutions, however, have certain limitations. Nowadays, it is also possible to synthesize chiral molecules by performing an asymmetric transition-metal-catalyzed [2+2+2]-cyclo(co)trimerization reaction. This review focuses on the recent advances in mechanistic insight, solving the regioselectivity issue, synthesis of chiral molecules and alternative approaches for the synthesis of substituted benzenes, pyridines and 2-pyridones. In addition, recent applications in areas such as total synthesis of natural products are also described, demonstrating that the transition-metal-catalyzed [2+2+2]-cyclo(co)trimerization reaction is a powerful tool and a welcome addition to the chemist’s ‘synthetic toolbox’. 1 Introduction 2 Synthesis of Benzene Derivatives 2.1 Mechanistic Insight 2.2 Regioselectivity 2.3 Synthesis of Chiral Systems 2.4 Other [2+2+2] Approaches 2.5 Synthesis of (Iso)quinolines 3 Synthesis of Pyridine Derivatives 3.1 Mechanistic Insight 3.2 Regioselectivity 3.3 Synthesis of Chiral Systems 4 Synthesis of Pyridone Derivatives 4.1 Mechanistic Insight 4.2 Regioselectivity 4.3 Synthesis of Chiral Systems 5 Applications 6 Future Directions 7 Conclusion
166 citations
TL;DR: This work reproduced the loss of picolinate and acetylacetonate ancillary ligands in solution by the addition of Brønsted or Lewis acids and advantageously used this degradation reaction for the efficient synthesis of tris-heteroleptic cyclometalated iridium(III) complexes.
Abstract: Investigations of blue phosphorescent organic light emitting diodes (OLEDs) based on [Ir(2-(2,4-difluorophenyl)pyridine)(2)(picolinate)] (FIrPic) have pointed to the cleavage of the picolinate as a possible reason for device instability. We reproduced the loss of picolinate and acetylacetonate ancillary ligands in solution by the addition of Bronsted or Lewis acids. When hydrochloric acid is added to a solution of a [Ir(C(∧)N)(2)(X(∧)O)] complex (C(∧)N = 2-phenylpyridine (ppy) or 2-(2,4-difluorophenyl)pyridine (diFppy) and X(∧)O = picolinate (pic) or acetylacetonate (acac)), the cleavage of the ancillary ligand results in the direct formation of the chloro-bridged iridium(III) dimer [{Ir(C(∧)N)(2)(μ-Cl)}(2)]. When triflic acid or boron trifluoride are used, a source of chloride (here tetrabutylammonium chloride) is added to obtain the same chloro-bridged iridium(III) dimer. Then, we advantageously used this degradation reaction for the efficient synthesis of tris-heteroleptic cyclometalated iridium(III) complexes [Ir(C(∧)N(1))(C(∧)N(2))(L)], a family of cyclometalated complexes otherwise challenging to prepare. We used an iridium(I) complex, [{Ir(COD)(μ-Cl)}(2)], and a stoichiometric amount of two different C(∧)N ligands (C(∧)N(1) = ppy; C(∧)N(2) = diFppy) as starting materials for the swift preparation of the chloro-bridged iridium(III) dimers. After reacting the mixture with acetylacetonate and subsequent purification, the tris-heteroleptic complex [Ir(ppy)(diFppy)(acac)] could be isolated with good yield from the crude containing as well the bis-heteroleptic complexes [Ir(ppy)(2)(acac)] and [Ir(diFppy)(2)(acac)]. Reaction of the tris-heteroleptic acac complex with hydrochloric acid gives pure heteroleptic chloro-bridged iridium dimer [{Ir(ppy)(diFppy)(μ-Cl)}(2)], which can be used as starting material for the preparation of a new tris-heteroleptic iridium(III) complex based on these two C(∧)N ligands. Finally, we use DFT/LR-TDDFT to rationalize the impact of the two different C(∧)N ligands on the observed photophysical and electrochemical properties.
TL;DR: A ring-opening copolymerization of cyclohexene oxide with alicyclic anhydrides containing different ring strain was performed applying metal salen chloride complexes, (salen)MCl (M = Al, Cr, Co; salen = N,N-bis(3,5-di-tert-butylsalicylidene)diimine) with different metals and ligand-diimines backbones.
Abstract: Ring-opening copolymerization of cyclohexene oxide with alicyclic anhydrides containing different ring strain (succinic anhydride, cyclopropane-1,2-dicarboxylic acid anhydride, and phthalic anhydride) was performed applying metal salen chloride complexes, (salen)MCl (M = Al, Cr, Co; salen = N,N-bis(3,5-di-tert-butylsalicylidene)diimine) with different metals and ligand–diimine backbones. While some of the bulk copolymerizations afforded poly(ester-co-ether)s, all solution polymerizations produced perfect alternating copolymers. The chromium catalysts performed best while the aluminum catalysts were the least active ones. For each metal, the salophen complexes yielded the best performing catalyst. A variety of cocatalysts have been employed: bis(triphenylphosphoranylidene)ammonium chloride, N-heterocyclic nucleophiles including 4-(dimethylamino)pyridine, N-methylimidazole, and 1,5,7-triazabicyclododecene and the phosphines trimesitylphosphine, tris(2,4,6-trimethoxyphenyl)phosphine, tricyclohexylphosphine t...
TL;DR: This work represents the first general process for C-3 arylation of substituted imidazo[1,2-a]pyridine by Cu(I) catalysis to construct various functionalized imidaz[ 1,2,a] pyridine core π-systems.
TL;DR: The synthesis of the first isolatable oxygen-bridged bis(silylenes) D and pincer-type bis( silylene) E is described, which underlines that silylene are no longer laboratory curiosities and may provide access to new silicon(II)based functional groups in coordination chemistry toward transition metals.
Abstract: The chemistry of stable silylenes has received wide interest since the first isolation of Nheterocyclic silylenes (NHSis) by Denk and West et al. While stable silylenes have received a lot of attention, the chemistry of bis(silylenes), compounds with two divalent silicon sites in a single molecule, is much less developed. To date, bis(silylenes) have been limited to two types of compounds, which can be defined as follows: 1) “interconnected bis(silylenes)” in which the two divalent silicon atoms are adjacent to each other and connected by a central single bond (I–III), and 2) “spacer-separated bis(silylenes)” in which the divalent silicon atoms are separated by a spacer (A–E; Scheme 1). Recently, interconnected bis(silylenes) I–III have been the subject of active research because of their distinct reactivity in comparison to isoelectronic disilynes. For example, compounds I, which bear amidinate ligands, were independently synthesized by Roesky and co-workers, and Jones et al. Furthermore, bis(silylenes) of type II and III, which are stabilized by an intramolecular phosphine donor and an N-heterocyclic carbene (NHC), respectively, were also reported. On the other hand, spacer-separated bis(silylenes) are intriguing as novel bidentate s-donor ligands for transition metals because of their unique structure and their coordination ability. The first spacer-separated bis(silylene) A was reported by Lappert and co-workers in 2005. Bis(silylene) B was synthesized by the reduction of dichlorosilaimine NHC·Cl2Si = NR (NHC = 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene, R = 2,6-bis(2,4,6-triisopropylphenyl)-phenyl) through initial formation of the elusive silaisocyanide intermediate. In addition, compound C was prepared by the reaction of bis(silylene) I (R = tBu, R = Ph) with phenylacetylene PhC CH. Very recently, we described the synthesis of the first isolatable oxygen-bridged bis(silylene) D and pincer-type bis(silylene) E. 11] This development underlines that silylenes are no longer laboratory curiosities and may provide access to new silicon(II)based functional groups in coordination chemistry toward transition metals. In general, complexes of silylenes and transition metals have received much attention because they can play a key role as intermediates in transition-metalcatalyzed transformation of silicon compounds. Very recently, bis(silylenes) D and E have been employed as new silicon(II)-based donor ligands to stabilize unusually electron-rich complexes of silylenes and Group 10 metals. In order to gain access to other new bis(silylenes) as potential bidentate s-donor ligands, we set out to investigate a novel Scheme 1. Bis(silylenes) I–III and spacer-separated bis(silylenes) A–E.
TL;DR: DFT calculations support a plausible reaction pathway where migratory insertion of the alkyne into the rhodium-thiolate bond is the rate-determining step.
Abstract: Rh–N-heterocyclic carbene compounds [Rh(μ-Cl)(IPr)(η2-olefin)]2 and RhCl(IPr)(py)(η2-olefin) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, py = pyridine, olefin = cyclooctene or ethylene) are highly active catalysts for alkyne hydrothiolation under mild conditions. A regioselectivity switch from linear to 1-substituted vinyl sulfides was observed when mononuclear RhCl(IPr)(py)(η2-olefin) catalysts were used instead of dinuclear precursors. A complex interplay between electronic and steric effects exerted by IPr, pyridine, and hydride ligands accounts for the observed regioselectivity. Both IPr and pyridine ligands stabilize formation of square-pyramidal thiolate–hydride active species in which the encumbered and powerful electron-donor IPr ligand directs coordination of pyridine trans to it, consequently blocking access of the incoming alkyne in this position. Simultaneously, the higher trans director hydride ligand paves the way to a cis thiolate–alkyne disposition, favoring formation of 2,2-d...
TL;DR: The use of a 1:1 ratio of Pd/pyridine proved critical to maximize reaction rates and yields inFujiwara-Moritani C-H olefination reactions.
TL;DR: Not only does the rhodium(I)-catalyzed extrusion of carbon monoxide from biaryl ketones and alkyl/alkenyl aryl ketones provide an alternative pathway to construct useful scaffolds, but also offers a new strategy for C-C bond activation.
Abstract: Snipping tool: the rhodium(I)-catalyzed extrusion of carbon monoxide from biaryl ketones and alkyl/alkenyl aryl ketones was developed to produce biaryls and alkyl/alkenyl arenes, respectively, in high yields. A wide range of functionalities are tolerated. Not only does this method provide an alternative pathway to construct useful scaffolds, but also offers a new strategy for C-C bond activation.
TL;DR: In this article, a pyridine-thermal strategy for successive exfoliation and reduction of graphite oxide with the use of Pyridine as the intercalating agent and dispersant is reported, and the obtained graphene exhibits a good performance in capacitive deionization.
Abstract: A novel pyridine–thermal strategy for successive exfoliation and reduction of graphite oxide with the use of pyridine as the intercalating agent and dispersant is reported, and the obtained graphene exhibits a good performance in capacitive deionization.
TL;DR: A new method for the catalytic aerobic oxygenation of unactivated sp(3)-C-H bonds is described, which utilizes Pd(OAc)(2) as a catalyst in conjunction with NaNO(3) as an redox co-catalyst.
Abstract: This paper describes a new method for the catalytic aerobic oxygenation of unactivated sp3-C–H bonds. This transformation utilizes Pd(OAc)2 as a catalyst in conjunction with NaNO3 as a redox co-catalyst. Both oxime ether and pyridine derivatives are effective directing groups for these reactions. The oxygen incorporated into the product derives from the solvent (acetic acid). Preliminary results show that the addition of simple NaCl to the reaction mixture results in aerobic chlorination under analogous conditions.
TL;DR: A silver-catalyzed dehydrogenative cross-coupling reaction of substituted furans, thiophene, thioazole, and pyrrole 1a-e with dialkyl phosphites 2 was first developed to afford corresponding phosphonated products 3a-h with up to 89% yield and good regioselectivities.
Abstract: A silver-catalyzed dehydrogenative cross-coupling reaction of substituted furans, thiophene, thioazole, and pyrrole 1a–e with dialkyl phosphites 2 was first developed to afford corresponding phosphonated products 3a–h with up to 89% yield and good regioselectivities. Moreover, an unprecedented coupling of various substituted pyridines 1f–k with dialkyl phosphites 2 using AgNO3 as a catalyst and K2S2O8 as an oxidant, followed by reduction with Na2S2O3, was also realized to furnish desired pyridine phosphonates 3i–q in satisfactory yields with good regioselectivities.
TL;DR: In this paper, the infrared spectra of MIL-100(Al) have been recorded after evacuation from room temperature up to 623 K. The results show the presence of impurities like carboxylic acid and nitrates resulting from the synthesis step, explaining the low amount of Al-OH groups detected.
Abstract: Infrared spectra of MIL-100(Al) have been recorded after evacuation from room temperature up to 623 K. In addition to adsorbed water molecules characterized by specific (ν+δ)H2O combination bands at about 5300 cm–1, spectra analysis shows the presence of impurities like carboxylic acid and nitrates resulting from the synthesis step, explaining the low amount of Al–OH groups detected. The Lewis acidity has been characterized by CO [ν(CO) at 2183 cm–1], pyridine [ν8a band estimated at 1618 cm–1], and CD3CN [ν(CN) at 2326 cm–1] adsorption on the activated sample. The acidity is strong as revealed by the ν(CN) wavenumber. Interestingly, CO gives rise to an interaction weaker than that expected from pyridine and CD3CN results. Quantitative results relative to the number of Al3+5c sites are in full agreement with those reported elsewhere from 27Al NMR experiments. The Bronsted acidity mainly results from the presence of coordinated water species in the nonfully dehydrated sample and not from the structural Al–O...
TL;DR: Pd(IV)-fluoride complexes, some of which are remarkably insensitive to water, have been synthesized and used in the title reaction, which proceeds with high selectivity to give the product of the C(sp(3))-F coupling.
Abstract: Pd(IV)-fluoride complexes, some of which are remarkably insensitive to water, have been synthesized and used in the title reaction, which proceeds with high selectivity to give the product of the C(sp(3))-F coupling. Preliminary mechanistic studies implicate a pathway involving dissociation of pyridine followed by direct C-F coupling at the Pd center.
TL;DR: In this article, the authors investigated the acid strength and steam stability of nanocrystalline MFI zeolites with different crystallite size (2-300nm), which were obtained using gemini-surfactants having different alkyl chain lengths.
TL;DR: In this paper, three transition metal complexes of the type ML2 (where M = Ni, Co, or Cu(II); HL = N′-[phenyl(pyridin-2-yl)methylidene] furoic acid hydrazide and 2-benzoyl pyridine] have been prepared by treating [NiCl2(PPh3)2], [CoCl2 (PPh 3)2] or [CuCl2[PPh4] with N′]-phenyl-pyrin-two-ylmethyl
TL;DR: In this article, three different classes of tridentate, nitrogen-based, terpyridine, and pyridine bis(oxazoline) ligands have been synthesized and evaluated in the catalytic hydrosilylation of olefins with tertiary silanes.
TL;DR: The experimental data, in combination with broken-symmetry density functional theory calculations, established spin crossover (low to intermediate spin) ferric compounds antiferromagnetically coupled to bis(imino)pyridine radical anions.
Abstract: Addition of biphenylene to the bis(imino)pyridine iron dinitrogen complexes, (iPrPDI)Fe(N2)2 and [(MePDI)Fe(N2)]2(μ2-N2) (RPDI = 2,6-(2,6-R2—C6H3—N═CMe)2C5H3N; R = Me, iPr), resulted in oxidative addition of a C—C bond at ambient temperature to yield the corresponding iron biphenyl compounds, (RPDI)Fe(biphenyl). The molecular structures of the resulting bis(imino)pyridine iron metallacycles were established by X-ray diffraction and revealed idealized square pyramidal geometries. The electronic structures of the compounds were studied by Mossbauer spectroscopy, NMR spectroscopy, magnetochemistry, and X-ray absorption and X-ray emission spectroscopies. The experimental data, in combination with broken-symmetry density functional theory calculations, established spin crossover (low to intermediate spin) ferric compounds antiferromagnetically coupled to bis(imino)pyridine radical anions. Thus, the overall oxidation reaction involves cooperative electron loss from both the iron center and the redox-active bis(...
TL;DR: Two series of new tetracyclic pyrazolo[3,4-b]pyridine-based coumarin chromophores synthesized through a facile reaction between 3-aldehyde-7-diethylaminocoumarin and 5-aminopyrazole derivatives exhibited high fluorescence quantum yields and good electrochemical, thermal, and photochemical stabilities.
Abstract: Two series of new tetracyclic pyrazolo[3,4-b]pyridine-based coumarin chromophores were synthesized through a facile reaction between 3-aldehyde-7-diethylaminocoumarin (5) or 3-acetyl-7-diethylaminocoumarin (6) and 5-aminopyrazole derivatives (7) in a one-pot procedure. Different condensed products were obtained from compounds 5 and 6, and the potential reaction mechanism was studied using the reaction of 5 with 5-amino-1-phenylpyrazole (7a). The molecular structures were characterized by NMR and HRMS and confirmed by X-ray diffraction. The photophysical, electrochemical, and thermal properties of these compounds were investigated by absorption spectroscopy, fluorescence spectroscopy, single photon counting technique, cyclic voltammetry, thermogravimetric analysis, etc. Results show that the compounds exhibited high fluorescence quantum yields and good electrochemical, thermal, and photochemical stabilities. In addition, the application of these highly fluorescent compounds in living cell imaging was also ...
TL;DR: The weakly coordinated triflate complex [(P^P)Pd(OTf)](+)(OTf)(-) (1) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate and provides an entry to mechanistic observations including intermediates reactive toward methanol.
Abstract: The weakly coordinated triflate complex [(P∧P)Pd(OTf)]+(OTf)− (1) (P∧P = 1,3-bis(di-tert-butylphosphino)propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH3OH or CD3OD to 1 forms the hydride species [(P∧P)PdH(CH3OH)]+(OTf)− (2-CH3OH) or the deuteride [(P∧P)PdD(CD3OD)]+(OTf)− (2D-CD3OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P∧P)PdH(pyridine)]+(OTf)− (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF3·OEt2, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2D-CD3OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and <0.2% of terminal olefin. Reaction of 2-pyr/BF3·OEt2 with a stoichiometric amount of 1-13C-labeled 1-octene at −80 °C yields a ...
TL;DR: Tertiary amine formation via polyalkylation does not occur, making this ruthenium system an excellent catalyst for the synthesis of sec-amines.
TL;DR: A novel iron-mediated direct C-H arylation of quinones and pyridine analogues with arylboronic acids has been developed using dichloromethane and water as solvents at ambient temperature.