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Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
supporting information

(2020/02/15)

Photorelease of Pyridines Using a Metal-Free Photoremovable Protecting Group
The photorelease of bioactive molecules has emerged as a valuable tool in biochemistry. Nevertheless, many important bioactive molecules, such as pyridine derivatives, cannot benefit from currently available organic photoremovable protecting groups (PPGs). We found that the inefficient photorelease of pyridines is attributed to intramolecular photoinduced electron transfer (PET) from PPGs to pyridinium ions. To alleviate PET, we rationally designed a strategy to drive the excited state of PPG from S1 to T1 with a heavy atom, and synthesized a new PPG by substitution of the H atom at the 3-position of 7-dietheylamino-coumarin-4-methyl (DEACM) with Br or I. This resulted in an improved photolytic efficiency of the pyridinium ion by hundreds-fold in aqueous solution. The PPG can be applied to various pyridine derivatives. The successful photorelease of a microtubule inhibitor, indibulin, in living cells was demonstrated for the potential application of this strategy in biochemical research.
Dong, Zaizai,Fang, Xiaohong,Kou, Xiaolong,Tan, Weihong,Tang, Xiao-Jun,Wu, Yayun,Zhang, Zhen,Zhao, Rong,Zhou, Wei
supporting information
p. 18386 - 18389
(2020/08/24)

Synthesis method of 3-bromopyridine
The invention belongs to the field of organic synthesis, and particularly relates to a synthesis method of 3-bromopyridine. The synthesis method comprises the following steps: (1) dropwise adding bromine into pyridine and 80-95% sulfuric acid at 0 DEG C, and reacting at 130-140 DEG C for 7-8 hours; (2) after the reaction is finished, cooling, pouring into ice water, and regulating the pH value to8 by using 6N sodium hydroxide; and (3) extracting with an organic solvent, layering, drying, filtering, concentrating and distilling. The method has the beneficial effects of high yield, mild reaction conditions, simple reaction steps and simple and easily available raw materials, and is suitable for industrial production.
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Paragraph 0017-0024

(2020/05/05)

Base-catalyzed aryl halide isomerization enables the 4-selective substitution of 3-bromopyridines
The base-catalyzed isomerization of simple aryl halides is presented and utilized to achieve the 4-selective etherification, hydroxylation and amination of 3-bromopyridines. Mechanistic studies support isomerization of 3-bromopyridines to 4-bromopyridines proceedsviapyridyne intermediates and that 4-substitution selectivity is driven by a facile aromatic substitution reaction. Useful features of a tandem aryl halide isomerization/selective interception approach to aromatic functionalization are demonstrated. Example benefits include the use of readily available and stable 3-bromopyridines in place of less available and stable 4-halogenated congeners and the ability to converge mixtures of 3- and 5-bromopyridines to a single 4-substituted product.
Bandar, Jeffrey S.,Puleo, Thomas R.
p. 10517 - 10522
(2020/10/18)

Implementing Hydrogen Atom Transfer (HAT) Catalysis for Rapid and Selective Reductive Photoredox Transformations in Continuous Flow
The reductive transformation of aryl halides and carbonyl compounds is a key step in many photoredox transformations. By combining a highly reducing organic photocatalyst with a thiol hydrogen atom transfer (HAT) catalyst, we showcase rapid and highly selective reactions of these synthetically important starting materials in continuous flow. The fast reduction of aryl iodides, bromides and chlorides has been demonstrated with residence times in some cases below one minute. Selectivity between mono- and di-dehalogenation could also be achieved in some cases. Aryl ketones, aldehydes and imines were shown to undergo facile pinacol couplings, and the coupling of an aryl chloride with a styrene was also successful.
Steiner, Alexander,Williams, Jason D.,Rincón, Juan A,de Frutos, Oscar,Mateos, Carlos,Kappe, C. Oliver
supporting information
p. 5807 - 5811
(2019/08/01)

Axial coordination reactions with nitrogenous bases and determination of equilibrium constants for zinc tetraarylporphyrins containing four β, β ′-fused butano and benzo groups in nonaqueous media
The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four β,β′-fused butano or benzo groups and the equilibrium constants (logK) determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano-And benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4-22 nm red-shift of the Soret and Q bands. The logK values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and β-substituents of the porphyrin and the conjugate acid dissociation constants (pKa) of the nitrogenous base.
Ye, Lina,Fang, Yuanyuan,Ou, Zhongping,Wang, Liping,Xue, Songlin,Lu, Yang,Kadish, Karl M.
p. 196 - 206
(2019/02/19)

A Practical and Robust Multistep Continuous Process for Manufacturing 5-Bromo-N-(tert-butyl)pyridine-3-sulfonamide
A multistep continuous flow process involving (1) magnesium-halogen exchange, (2) sulfonylation with sulfuryl chloride, and (3) reaction with tert-butylamine was developed for the synthesis of an arylsulfonamide pharmaceutical intermediate in the synthesis of BMS-919373. The process was successfully implemented, including a robust control strategy to manage the levels of several process impurities, to produce 76 kg of 5-bromo-N-(tert-butyl)pyridine-3-sulfonamide (2). As the instability of the reactive intermediates and existence of strong exotherms made a batch process unsuitable for production beyond a 1 kg scale, the alternative continuous process led to a practical and robust manufacturing route to the active pharmaceutical ingredient.
Yu, Miao,Strotman, Neil A.,Savage, Scott A.,Leung, Simon,Ramirez, Antonio
p. 2088 - 2095
(2019/10/08)

Synthesis method of 3-bromopyridine
The invention belongs to the field of organic synthesis, and particularly relates to a synthesis method of 3-bromopyridine. The invention includes following steps: (1), dropwise adding bromine into pyridine and sulfuric acid of 80-95% at 0 DEG C, and allowing reaction at 130-140 DEG C for 7-8h; (2), cooling after reaction is finished, pouring into ice water, and using 6N sodium hydroxide to adjustPH to 8; (3), using an organic solvent for extraction, layering, drying, filtering, concentrating, and distilling. The synthesis method has the advantages of being high in yield, mild in reaction condition, simple in reaction step, simple and easy-to-obtain in raw material and suitable for industrial production.
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Paragraph 0017-0024

(2019/05/28)

Synthesis of bromocyclopropylpyridines via the Sandmeyer reaction
The reactions of 2-amino-5-cyclopropylpyridine with organic nitrites in the presence of copper(II) halides in various organic solvents were investigated. Optimal reaction conditions for the Sandmeyer reaction were developed and successfully applied to the synthesis of useful building blocks, bromo and chlorocyclopropylpyridines. Aminocyclopropylpyridines were synthesized in high yields from the corresponding aminobromopyridines under standard Suzuki coupling conditions.
Striela, Romualdas,Urbelis, Gintaras,Sūd?ius, Jurgis,Ston?ius, Sigitas,Sadzevi?ien?, Rita,Labanauskas, Linas
supporting information
p. 1681 - 1683
(2017/04/06)

Molybdenum-Catalyzed Deoxygenation of Heteroaromatic N-Oxides and Hydroxides using Pinacol as Reducing Agent
A molybdenum-catalyzed deoxygenation of pyridine N-oxides and N-hydroxybenzotriazoles, as well as other azole N-oxides, has been developed using pinacol as an environmentally friendly oxo-acceptor. The only by-products are acetone and water making the process a convenient alternative to established protocols in terms of waste generation. The reaction is highly chemoselective and a variety of functional groups are tolerated. The processes are usually very clean allowing the isolation of the pure deoxygenated products after a simple extraction in most cases. (Figure presented.).
Rubio-Presa, Rubén,Fernández-Rodríguez, Manuel A.,Pedrosa, María R.,Arnáiz, Francisco J.,Sanz, Roberto
supporting information
p. 1752 - 1757
(2017/05/22)

Development of a Continuous-Flow Sonogashira Cross-Coupling Protocol using Propyne Gas under Process Intensified Conditions
The development of a continuous-flow Sonogashira cross-coupling protocol using propyne gas for the synthesis of a key intermediate in the manufacturing of a β-amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitor, currently undergoing late stage clinical trials for a disease-modifying therapy of Alzheimer's disease, is described. Instead of the currently used batch manufacturing process for this intermediate that utilizes TMS-propyne as reagent, we herein demonstrate the safe utilization of propyne gas, as a cheaper and more atom efficient reagent, using an intensified continuous-flow protocol under homogeneous conditions. The flow process afforded the target intermediate with a desired product selectivity of ～91% (vs the bis adduct) after a residence time of 10 min at 160 °C. The continuous-flow process compares favorably with the batch process, which uses TMS-propyne and requires overnight processing, TBAF as an additive, and a significantly higher loading of Cu co-catalyst.
Znidar, Desiree,Hone, Christopher A.,Inglesby, Phillip,Boyd, Alistair,Kappe, C. Oliver
p. 878 - 884
(2017/06/23)

Dehalogenation degradation method for halogenated pyridine compound
The invention provides a dehalogenation degradation method for a halogenated pyridine compound. The halogenated pyridine compound is adopted as a raw material, alcohol is adopted as a hydrogen source, water is adopted as a solvent, reacting is carried out for 3-10 h under normal pressure at the temperature of 20 DEG C to 120 DEG C under the action of a supported catalyst, and the halogenated pyridine compound is subjected to dehalogenation degradation in situ through water phase hydrogen production. A pyridine ring of the halogenated pyridine compound at least contains an F or Cl or Br or I substituent group. The supported catalyst is composed of an active component and a carrier, the active component is composed of a mixture of transition metal and other metal, the transition metal is one of Rh, Pd, Pt and Ni, and other metal is one of Se, Ca, Ba, La and Ce. The carrier is one of activated carbon, kieselguhr, zeolite, gamma-Al2O3, AlF3 and MgO. H2 is not directly used as a reduction agent, activated hydrogen is prepared through in-situ catalysis to directly participate in reacting, the advantages of being high in reaction activity, high in selectivity, high in safety, environmentally friendly and the like are achieved, and good application prospects are achieved.
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Paragraph 0021; 0022

(2016/12/16)

CONDENSED-CYCLIC COMPOUND AND ORGANIC LIGHT-EMITTING DIODE INCLUDING THE CONDENSED-CYCLIC COMPOUND
A condensed-cyclic compound and an organic light-emitting diode including the condensed-cyclic compound.
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(2014/04/03)

Synthesis of asymmetrically substituted terpyridines by palladium-catalyzed direct C - H arylation of pyridine N-oxides
The synthesis of asymmetrically substituted 2,2′:6′, 2′′-terpyridines is reported. First, palladium-catalyzed C - H arylation of pyridine N-oxides with substituted bromopyridines gave 2,2′-bipyridine N-oxides, which were further arylated in a second step to form 2,2′:6′,2′′-terpyridine N-oxides. Yields of up to 77 % were obtained with N-oxides bearing an electron-withdrawing ethoxycarbonyl substituent in the 4-position. Pd(OAc)2 with either P(tBu) 3 or P(o-tolyl)3 was used as the catalyst. Cyclometalated complexes derived from Pd(OAc)2 and these phosphines were also effective. K3PO4 as the base gave better results than K2CO3. Subsequent deoxygenation with H2 and Pd/C as the catalyst gave the asymmetrically substituted 2,2′:6′, 2′′-terpyridines in near quantitative yield. This reaction sequence significantly reduces the number of steps required in comparison with known cross-coupling methods and therefore allows convenient and scalable access to substituted terpyridines.
Duric, Sasa,Sypaseuth, Fanni D.,Hoof, Santina,Svensson, Emma,Tzschucke, C. Christoph
supporting information
p. 17456 - 17463
(2014/01/06)

Efficient indium-mediated dehalogenation of aromatics in ionic liquid media
An efficient indium-mediated dehalogenation reaction of haloaromatics and haloheteroaromatics in ionic liquids has been studied. This method is simple and effective in the presence of [bmim]Br. Furthermore, this methodology is environmentally friendly compared with conventional ones.
Canete, Alvaro F.,Salas, Cristian O.,Zacconi, Flavia C.
p. 398 - 407
(2013/03/13)

Functional polypyridine ligands from copper-mediated room temperature coupling of 4-chloro-2-trimethylsilylpyridine
A range of functional polypyridine ligands (bipyridines and terpyridine) has been synthesized by copper-mediated oxidative homocoupling of 4-chloro-2-trimethylsilylpyridine or cross-coupling with functional bromopyridines. The reaction proceeded smoothly at room temperature.
Lou?rat, Frédéric,Gros, Philippe C.
supporting information; experimental part
p. 3558 - 3560
(2010/08/07)

Bromine-lithium exchange under non-cryogenic conditions: TMSCH 2Li-LiDMAE promoted C-2 lithiation of 2,3-dibromopyridine
The first C-2 selective bromine-lithium exchange in 2,3-dibromopyridine was performed at 0°C in toluene using the TMSCH2Li-LiDMAE reagent. The Royal Society of Chemistry.
Gros, Philippe C.,Elaachbouni, Fatima
scheme or table
p. 4813 - 4815
(2009/03/12)

Deoxygenation of pyridine N-oxides with dimethylthiocarbamoyl chloride
(Chemical Equation Presented) Treatment of pyridine N-oxides with dimethylthiocarbamoyl chloride in boiling acetonitrile effects chemoselective deoxygenation to pyridines.
Ponaras, Anthony A.,Zaim, Oemer
p. 487 - 489
(2008/03/29)

TMSCH2Li and TMSCH2Li-LiDMAE: Efficient reagents for noncryogenic halogen-lithium exchange in bromopyridines
(Chemical Equation Presented) TMSCH2Li and TMSCH 2Li-LiDMAE have been used efficiently for bromine-lithium exchange in 2-bromo-, 3-bromo-, and 2,5-dibromopyridines under noncryogenic conditions, while low temperatures (-78 to -100°C) are always needed with n-BuLi. The aminoalkoxide LiDMAE induced a remarkable C-2 selectivity with 2,5-dibromopyridines in toluene at 0°C, which was unprecedented at such a temperature. The lithiopyridines were successfully reacted witb electrophiles also under noncryogenic conditions giving the expected adducts in good yields.
Doudouh, Abdelatif,Woltermann, Christopher,Gros, Philippe C.
p. 4978 - 4980
(2008/02/07)

Preparation of novel substituted haloarene compounds
This invention relates to a new process for the preparation of novel substituted haloarene compounds of the formula I or IV: respectively, wherein R1, R2, R3, R4, R5, X, and Y are as defined herein, that comprises a novel and efficient selective mono-lithiation of a dihaloarene of the formula II or V: respectively, by an organo-lithium compound in the presence of a carbonyl reactant of the formula III: wherein R1 and R2 are as defined herein. In the process of the instant invention, the newly formed lithiated haloarene is sequentially quenched in situ by the carbonyl reactant to form said substituted haloarene. The process is suitable for batch or continuous flow systems. The substituted haloarenes produced by the process of the present invention are useful intermediates in the preparation of N-aryl or N-heteroaryl substituted pharmaceutically active compounds that include selective antagonists, inverse agonists and partial agonists of serotonin 1 (5-HT1) receptors useful in treating or preventing depression, anxiety, obsessive compulsive disorder (OCD) and other disorders for which a 5-HT1 agonist or antagonist is indicated.
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(2008/06/13)

N-octylquinolinium tribromide: A task specific quinoline based ionic liquid as a new brominating agent
The N-octylquinolinium tribromide has been synthesized and explored as a new efficient brominating agent. It has high active bromine content per molecule and shows a remarkable reactivity towards various substrates. No organic solvent has been used during any stage of the reaction. The N-octylquinolinium tribromide is stable for months and acts as a safe source of bromine for complete bromination of phenols, aromatic amines, alkenes and alkynes.
Kaushik,Polshettiwar, Vivek
p. 2542 - 2545
(2007/10/03)

Selective monolithiation of 2,5-dibromopyridine with butyllithium
Selective monolithiation of 2,5-dibromopyridine at either the 2-position or the 5-position is reported. Solvent and concentration strongly influence the selectivity. Coordinating solvents and higher concentration favor the 5- position while non-coordinati
Wang, Xin,Rabbat, Philippe,O'Shea, Paul,Tillyer, Richard,Grabowski,Reider, Paul J.
p. 4335 - 4338
(2007/10/03)

Chiral phosphorus(III) triflates. On the nature of the phosphorus-oxygen interaction
Reaction of chiral phosphorodiamidites with trimethylsilyltriflate affords chiral phophorus(III) triflate species, such as 1-trifluoromethylsulfonato-2,9-(dibenzyl)diaza-1-phospha[4.0.3]bicyclononane 4, which has been examined by a combination of solution and solid state analytical techniques. Arguably the most important feature of this molecule is the nature of the interaction between phosphorus and triflate oxygen atoms. Single crystal X-ray diffraction analysis reveals that the phosphorus atom interacts principally with two oxygen atoms from two different triflate groups in the solid state, implying overall four-coordination at phosphorus. At distances of 2.841 and 2.755 A, these interactions are well within the van der Waals distance for a phosphorus-oxygen [P-O] interaction (ca. 3.35 A) but are nevertheless over 1 A longer than expected for a single [P-O] covalent bond. Investigations in solution via a combination of 31P, 19F, 13C, variable concentration, variable temperature NMR spectroscopy and solution conductivity provide support for a phosphorus-oxygen interaction which is intermediate between 'ionic' (two-coordinate phosphorus) and 'covalent' (three-coordinate phosphorus) and which possesses dynamic character in solution. Indeed, it has proved possible to calculate a relative equilibrium constant between 'ionic' and 'covalent' forms of 4 using empirical NMR data (13C and 19F; CH2Cl2 solvent; 300 K). These calculations return an equilibrium constant of ca. 3 (2.8 using 13C-NMR data and 3.3 using 19F-NMR data) in favour of the ionic form, a result commensurate with those suggested from variable temperature 19F-NMR and solution conductivity studies. Indeed, that the triflate group in 4 is capable of being displaced readily has been demonstrated by reaction with two-electron nitrogen, oxygen and phosphorus donor molecules. We have found 13C{1H}-NMR spectroscopy to be an extremely valuable probe of the ionic character of the triflate group in such systems providing a quantitative measure of the relative strength of interaction (relative basicity Br) between donor molecule and phosphorus atom of 4; the stronger the interaction, the more ionic the character of the triflate group and the lower the value of Br. Indeed, Br values for various ligands correlate well with steric and electronic properties of the latter and 31P-NMR resonances of the adducts themselves. As expected, the relative basicity of a given ligand correlates to the equilibrium constants K for adduct formation, which range from 39 M-1 for the weakest binding ligand studied (1,4-dioxane) to 5.4×104 M-1 for the strongest binding ligand (4-Me2N-NC5H4).
Jones, Victoria A.,Sriprang, Sarin,Thornton-Pett, Mark,Kee, Terence P.
p. 199 - 218
(2007/10/03)

SIMPLE AND CONVENIENT DEOXYGENATION OF HETEROAROMATIC N-OXIDES WITH SODIUM HYPOPHOSPHITE
Sodium hypophosphite catalytic transfer hydrogenation in the presence of 10percent palladium on carbon constitutes a simple and excellent deoxygenation method for heteroaromatic N-oxides in acetic acid medium.
Balicki, Roman,Kaczmarek, Lukasz
p. 385 - 386
(2007/10/02)

ORGANIC SYNTHESIS USING ORGANOSULFUR-NITRITES AND -NITRATES
Thionitrites or thionitrates have been considered to be unstable.However, bulky groups' thio-NOn such as t-butylthio-nitrites and -nitrates have been readily synthesized and found to be stable enough for the use of the useful organic syntheses as an excellent nitrosation and diazotization reagents under mild conditions.Direct conversion of amines to the corresponding halides in the presence of copper halides (II), fluorination of heterocyclic amines in the presence of sodium tetrafluoroborate, α- oximation of methylene groups in ketones, facile cleavage of C=N bond to ketones, and desulfurization of thioacetals and thioketals, and other useful organic syntheses are described.
Kim, Yong Hae
p. 249 - 260
(2007/10/02)

Hydrolysis of glycosylpyridinium ions by anomeric-configuration-inverting glycosidases
The hydrolyses of five β-D-xylopyranosylpyridinium ions by the β-D-xylosidase of Bacillus pumilus proceed with kcat values 108-109-fold larger than the rates of spontaneous hydrolysis of the same compounds.Log(kcat) values correlate well with aglycon pKa 1g(V) = -0.52, r = 0.99>, whereas the correlation of log(kcat/Km) is poor 1g(V/K) = ca. -0.6>.The (13)-β-D-glucanase of Sporotrichum dimorphosporum hydrolyses 4-bromo-2-(β-D-glucopyranosyl)isoquinolinium ion with a rate enhancement of 108.The amyloglucosidase II of Aspergillus niger hydrolyses three α-D-glucopyranosylpyridinium ions with rate enhancements of 105-108.The efficient hydrolysis of glycosylpyridinium ions by these three inverting glycosidases, the catalytic mechanism of which is unlikely to involve a nucleophile from the enzyme, makes it improbable that the hydrolysis of glycosylpyridinium ions by retaining glycosidases, discovered some years ago, is initiated by addition of a catalytic nucleophilic carboxylate group of the enzyme to the pyridinium ring.
Padmaperuma, Bimali,Sinnott, Michael L.
p. 79 - 86
(2007/10/02)

POTENTIOMETRIC STUDIES ON THE REACTION OF PICRIC ACID WITH SOME AROMATIC AMINES IN METHYL ISOBUTYL KETONE
The reaction between picric acid and some aniline and pyridine derivatives has been investigated in methyl isobutyl ketone by the potentiometric method.Overall picrate formation constants KBHA, ammonium cationic acid dissociation constants KBH+ and apparent ion-pair formation Ki* and dissociation Kd* constants have been determined.
Smagowski, Henryk,Bartnicka, Halina
p. 201 - 209
(2007/10/02)

SPECTROPHOTOMETRIC INVESTIGATION ON THE REACTION OF IONIZATION OF SOME DERIVATIVES OF ANILINE AND PYRIDINE IN MEDIA OF ACETIC ACID
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Lasinska, Ewa,Korewa, Ryszard,Nesterowicz, Marianna
p. 613 - 620
(2007/10/02)

HOMOTRANSMETALLATION DES HALOGENO-3 PYRIDINES BROMEES EN -2 OU -4 PAR LE N-BUTYLLITHIUM. PROPOSITION D'UN NOUVEAU MECANISME DE TELESUBSTITUTION DU BROME.
These are new examples of the homotransmetallation reaction.Instead of the ordinary bromo-metal exchange it is possible to obtain selectively from the 2-bromo 3-fluoro or 2-bromo 3-chloro pyridines the 2-bromo 3-halogeno 4-lithio pyridines, which is very interesting for synthetic utility.From the 4-bromo 3-halogeno pyridines, we can see an isomerization with an halogen dance mechanism and we obtain the 5-bromo 3-halogeno 4-lithio pyridines.In the case of the 2-bromo 3-fluoro pyridine we explain a telesubstitution of bromine from 2 to 4 by a transitory homotransmetallation reaction during the Li-Br exchange.
Mallet, M.,Queguiner, G.
p. 2253 - 2262
(2007/10/02)

HYDRODEHALOGENATION OF BROMO- AND CHLOROPYRIDINES OVER PALLADIUM COMPLEX AND PALLADIUM METAL CATALYSTS
The hydrodehalogenation of 2-chloro-, 2-bromo-, 3-bromo, and 3,5-dibromopyridine has been studied in the presence of a palladium complex catalyst immobilized on silica gel, and a Pd/C catalyst.Cleavage of bromine from bromopyridines over the Pd complex is significantly faster than from the bromo-substituted furanes and thiophenes previously studied.Debromination over Pd/C is faster than over the complex catalyst.Over both catalysts 3-bromopyridine debrominates faster than the 2-isomer.When molecular deuterium is used, the respective deuterated pyridines can be obtained.
Gurovets, A. S.,Sharf, V. Z.,Belen'kii, L. I.
p. 1023 - 1025
(2007/10/02)

ANOMALOUS ORIENTATION EFFECTS DURING BENZOYLOXYLATIONS BY "SILVER BROMIDE DIBENZOATE"
The solid complex formed from bromine and silver benzoate reacts with both arenes and alkenes to form aryl and alkyl benzoates, respectively.Highly unusual substituent effects are observed in the benzoyloxylations of arenes.Electron-withdrawing groups (e.g. -NO2, -CN,-CO-) on the aromatic ring facilitate reaction though directing the attacking reagent exclusively to the meta position.In alkanes, tertiary positions are most prone to attack.
Bryce-Smith, Derek,Isaacs, Neil S.,Tumi, Seddeg O.
p. 1471 - 1472
(2007/10/02)

Decarboxylative Ipso Halogenation of Mercury(II) Pyridinecarboxylates. Facile Formation of 3-Iodo- and 3-Bromopyridines
Treatment of mercury(II) nicotinate with iodine and bromine in nitrobenzene at 180-185 deg C for 2 h afforded 3-iodo- and 3-bromopyridines in 44percent and 27percent yields, respectively, without any regioisomers and dihalopyridines.From mercury(II) picolinate only 2-3percent of 2-bromopyridine was obtained under similar reaction conditions, while the reaction using mercury(II) isonicotinate did not give any products.When a mixture of nicotinic acid and HgO was used in place of mercury(II) nicotinate, the halodecarboxylation occurred with similar ease.An ionic pathway involving the initial attack of electrophilic Hg(II) species on the ring-C bearing carboxyl group to afford a 3-pyridylmercury(II) compound and the subsequent replacement of the Hg(II) moiety by electrophilic iodine and bromine was proposed for this reaction.
Uemura, Sakae,Tanaka, Sakuya,Okano, Masaya,Hamana, Masatomo
p. 3297 - 3301
(2007/10/02)

Synthese de xanthones et thioxanthones a deux noyaux heteroatomiques
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Trecourt, Francois,Queguiner, Guy
p. 912 - 942
(2007/10/02)

Reaction of halogen with metal salts of pyridinecarboxylic acid - decarboxylative ipso-substitution
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Uemura, Sakae,Tanaka, Sakuya,Okano, Masaya,Hamana, Masatomo
p. 132
(2007/10/02)

BROMINATION OF PYRIDINE IN THE PRESENCE OF SOME LEWIS ACIDS
The bromination of pyridine in the form of complexes with some Lewis acids and in the presence of catalytic amounts of the latter was studied.It is shown that bromination takes place readily at ca. 100 deg C in the presence of catalysts such as AlCl3, ZnCl2, SbCl3, InCl3, TeCl4, and HgCl2.The principal bromination products are 3-bromopyridine and 3,5-dibromopyridine.The problem of the possibility of so-called ? back-bonding in the case of elements of the higher periods (particurarly In, Te, and Sb) is discussed.
Lokhov, R. E.,Lokhova, S. S.,Gaidarova, N. M.,Belen'kii, L. I.
p. 923 - 926
(2007/10/02)

Chlorierung und Bromierung von Pyridin-Palladium(II)-chlorid-Komplex
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Paraskewas, Spyridon
p. 378 - 379
(2007/10/02)

Electronic Effects on the Menschutkin Reaction. A Complete Kinetic and Thermodynamic Dissection of Alkyl Transfer to 3- and 4-Substituted Pyridines
The relationship between kinetic and thermodynamic parameters is explored for quaternization of a series of pyridines (mostly 3- and 4-substituted) with several methylating and ethylating reagents in several solvents.The reaction with methyl iodide in acetonitrile is reversible at temperatures in the neighborhood of 100 deg C so that the effect of substituents on free energy, enthalpy, and entropy for activation of the forward and reverse reactions and for the overall quaternization can be determined.A variety of experimental techniques was used to obtain rates over a range of 1013 and to determine enthalpies and entropies of reaction.The results are self-consistent and agree generally with isolated published values for similar systems.The relationship between thermodynamic and activation parameters is examined, and a gross disparity is found between free energy and enthalpy behavior compared with that of the entropies.A consistent picture of the quaternization reaction emerges, based on many studies using a variety of mechanistic probes.The transition state is "early" as far as bond formation to the base in concerned but "late" in terms of bond rupture between the transferring alkyl group and the leaving group with solvent reorganization nearly complete.Quaternization of the 3- and 4-substituted pyridines does not follow the reactivity-selectivity principle, but that of 2-substituted pyridines does.The current practice of assigning detailed bimolecular structures to transition states for substitution, addition, or elimination reactions by application of the Hammond postulate is criticized in view of its inability to handle the dominating role of solvation dynamics and because of the considerable difference in potential energy content (and therefore structure) between the transition states and the reactants or products.
Arnett, Edward M.,Reich, Ronald
p. 5892 - 5902
(2007/10/02)

STUDIES ON A GENERAL METHOD FOR THE DEMETHYLATION OF QUATERNIZED NITROGEN HETEROCYCLES
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Deady, Leslie W.,Finlayson, Wayne L.
p. 947 - 950
(2007/10/02)

Process for the preparation of carboxylic acid amides from organic halides
Carboxylic acid amides are obtained from aryl, heterocyclic, and vinylic halides and substituted derivates thereof, by reacting same with a primary or secondary amine and carbon monoxide, in the presence of a palladium catalyst and if necessry a tertiary amine at about 20°-150° C and from at least a half atmosphere pressure.
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(2008/06/13)

Process for the preparation of carboxylic acid esters from organic halides
Carboxylic acid esters or amides are obtained from aryl, heterocyclic, vinylic, ethynylic, and benzylic halides and substituted derivates thereof, by reacting same with an alcohol or primary or secondary amine and carbon monoxide, in the presence of a palladium catalyst and if necessary a tertiary amine at about 20°-150° C and from about a half to about 100 atmospheres pressure. A typical example is the conversion of bromobenzene into n-butyl benzoate at 100° C and one atmosphere of carbon monoxide in the presence of tri-n-butyl-amine and a catalytic amount of PdBr2 [P(C6 H5)3 ]2.
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(2008/06/13)