- Heterogeneous Suzuki-Miyaura coupling of heteroaryl ester: Via chemoselective C(acyl)-O bond activation
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A site-selective supported palladium nanoparticle catalyzed Suzuki-Miyaura cross-coupling reaction with heteroaryl esters and arylboronic acids as coupling partners was developed. This methodology provides a heterogeneous catalytic route for aryl ketone formation via C(acyl)-O bond activation of esters by successful suppression of the undesired decarbonylation phenomenon. The catalyst can be reused and shows high activity after eight cycles. The XPS analysis of the catalyst before and after the reaction suggested that the reaction might be performed via a Pd0/PdII catalytic cycle that began with Pd0.
- Ma, Hongpeng,Bai, Chaolumen,Bao, Yong-Sheng
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p. 17266 - 17272
(2019/06/24)
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- Selective Monoacylation of Diols and Asymmetric Desymmetrization of Dialkyl meso-Tartrates Using 2-Pyridyl Esters as Acylating Agents and Metal Carboxylates as Catalysts
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With 2-pyridyl benzoates as acylating agents and Zn(OAc)2 as a catalyst, 1,2-diols, 1,3-diols, and catechol were selectively monoacylated. Furthermore, the highly enantioselective desymmetrization of meso-tartrates was achieved for the first time, utilizing 2-pyridyl esters and NiBr2/AgOPiv/Ph-BOX in CH3CN or CuCl2/AgOPiv/Ph-BOX in EtOAc catalyst systems (up to 96% ee). The latter catalyst system was also effective for the kinetic resolution of dibenzyl dl-tartrate.
- Hashimoto, Yuki,Michimuko, Chiaki,Yamaguchi, Koki,Nakajima, Makoto,Sugiura, Masaharu
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p. 9313 - 9321
(2019/08/12)
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- Access to N-Substituted 2-Pyridones by Catalytic Intermolecular Dearomatization and 1,4-Acyl Transfer
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A novel rhodium-catalyzed dearomatization of O-substituted pyridines to access N-substituted 2-pyridones has been developed. A computational study suggests a mechanism involving the formation of a pyridinium ylide followed by an unprecedented 1,4-acyl migratory rearrangement from O to C. Furthermore, the chiral dirhodium complexes serve as the catalyst for the asymmetric transformation with excellent enantioselective control. DFT calculations indicate the chirality is transferred from axial chirality to the central stereogenic centre. The stronger π–π interaction and CH–π interaction account for the high enantioselectivity.
- Xu, Guangyang,Chen, Ping,Liu, Pei,Tang, Shengbiao,Zhang, Xinhao,Sun, Jiangtao
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supporting information
p. 1980 - 1984
(2019/01/04)
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- Transesterification of (hetero)aryl esters with phenols by an Earth-abundant metal catalyst
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Readily available and inexpensive Earth-abundant alkali metal species are used as efficient catalysts for the transesterification of aryl or heteroaryl esters with phenols which is a challenging and underdeveloped transformation. The simple conditions and the use of heterogeneous alkali metal catalyst make this protocol very environmentally friendly and practical. This reaction fills in the missing part in transesterification reaction of phenols and provides an efficient approach to aryl esters, which are widely used in the synthetic and pharmaceutical industry.
- Chen, Jianxia,Namila,Bai, Chaolumen,Baiyin, Menghe,Agula, Bao,Bao, Yong-Sheng
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p. 25168 - 25176
(2018/07/29)
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- 4-(N,N -dimethylamino)pyridine hydrochloride as a recyclable catalyst for acylation of inert alcohols: Substrate scope and reaction mechanism
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4-(N,N-Dimethylamino)pyridine hydrochloride (DMAP·HCl), a DMAP salt with the simplest structure, was used as a recyclable catalyst for the acylation of inert alcohols and phenols under base-free conditions. The reaction mechanism was investigated in detail for the first time; DMAP·HCl and the acylating reagent directly formed N-acyl-4-(N′,N′-dimethylamino) pyridine chloride, which was attacked by the nucleophilic substrate to form a transient intermediate that released the acylation product and regenerated the DMAP·HCl catalyst.
- Liu, Zhihui,Ma, Qiaoqiao,Liu, Yuxiu,Wang, Qingmin
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supporting information
p. 236 - 239
(2014/01/23)
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- Comparison of aminolysis of 2-pyridyl and 4-pyridyl x-substituted benzoates in acetonitrile: Evidence for a concerted mechanism involving a cyclic transition state
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A kinetic study on reactions of 2-pyridyl X-substituted benzoates (6a-i) with a series of cyclic secondary amines in MeCN is reported. The Hammett plot for the reaction of 6a-i with piperidine consists of two intersecting straight lines while the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρX = 1.28 and r = 0.63, indicating that the nonlinear Hammett plot is not caused by a change in the rate-determining step but rather by resonance stabilization of substrates possessing an electron-donating group (EDG) in the benzoyl moiety. The Bronsted-type plots are linear with βnuc = 0.59 ± 0.02, which is typical of reactions reported to proceed through a concerted mechanism. A cyclic transition state (TS), which forces the reaction to proceed through a concerted mechanism, is proposed. The deuterium kinetic isotope effect of 1.3 ± 0.1 is consistent with the proposed mechanism. Analysis of activation parameters reveals that ΔH? increases linearly as the substituent X changes from an electron-withdrawing group (EWG) to an EDG, while TΔS ? remains nearly constant with a large negative value. The constant TΔS? value further supports the proposal that the reaction proceeds through a concerted mechanism with a cyclic TS.
- Um, Ik-Hwan,Bae, Ae-Ri,Um, Tae-Il
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p. 1206 - 1212
(2014/03/21)
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- Light-induced enantiospecific 4π ring closure of axially chiral 2-pyridones: Enthalpic and entropic effects promoted by H-bonding
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Nonbiaryl axially chiral 2-pyridones were synthesized and employed for light-induced electrocyclic 4π ring closure leading to bicyclo-β-lactam photoproducts in solution. The enantioselectivity in the photoproducts varied from 22 to 95% depending on the reaction temperature and the ability of the axially chiral chromophore to form intramolecular and/or intermolecular H-bonds with the solvent. On the basis of the differential activation parameters, entropic control of the enantiospecificity was observed for 2-pyridones lacking the ability to form H-bonds. Conversely, enthalpy played a significant role for 2-pyridones having the ability to form H-bonds.
- Kumarasamy, Elango,Jesuraj, Josepha L.,Omlid, Joseph N.,Ugrinov, Angel,Sivaguru, Jayaraman
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supporting information; experimental part
p. 17106 - 17109
(2011/12/13)
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- Selective deprotection and amidation of 2-pyridyl esters via N-methylation
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The 2-pyridyl residue serves as a protecting group for various carboxylic acids. The protecting group is selectively cleaved under mild conditions via N-methylation of the pyridyl group. During the deprotection process, the various functional groups as we
- Yamada, Shinji,Abe, Misato
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experimental part
p. 8667 - 8671
(2011/01/04)
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- A kinetic study on aminolysis of 2-pyridyl X-substituted benzoates: Effect of changing leaving group from 4-nitrophenolate to 2-pyridinolate on reactivity and mechanism
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Second-order rate constants (kN) have been measured spectrophotometrically for nucleophilic substitution reactions of 2-pyridyl X-substituted benzoates 8a-e with a series of alicyclic secondary amines in H2O at 25.0 ± 0.1 °C. The kN values for the reactions of 8a-e are slightly smaller than the corresponding reactions of 4-nitrophenyl X-substituted benzoates 1a-e (e.g., kN 1a-e/kN8a-e = 1.1 3.1), although 2-pyridinolate in 8a-e is ca. 4.5 pKa units more basic than 4-nitrophenolate in 1a-e. The Bronsted-type plot for the aminolysis of 8c (X = H) is linear with βnuc = 0.77 and R2 = 0.991 (Figure 1), which is typical for reactions reported previously to proceed through a stepwise mechanism with breakdown of a zwitterionic tetrahedral intermediate T± being the rate-determining step (RDS), e.g., aminolysis of 4-nitrophenyl benzoate 1c. The Hammett plot for the reactions of 8a-e with piperidine consists of two intersecting straight lines (Figure 2), i.e., ρ = 1.71 for substrates possessing an electron-donating group (EDG) while ρ = 0.86 for those bearing an electron-withdrawing group (EWG). Traditionally, such a nonlinear Hammett plot has been interpreted as a change in RDS upon changing substituent X in the benzoyl moiety. However, it has been proposed that the nonlinear Hammett is not due to a change in RDS since the corresponding Yukawa-Tsuno plot exhibits excellent linear correlation with ρ = 0.85 and r = 0.62 (R2 = 0.995, Figure 3). Stabilization of substrates 8a-e in the ground state has been concluded to be responsible for the nonlinear Hammett plot.
- Lee, Jong Pal,Bae, Ae Ri,Im, Li-Ra,Um, Ik-Hwan
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experimental part
p. 3588 - 3592
(2011/10/02)
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- Effect of alkali metal ions on alkaline ethanolysis of 2-pyridyl and 4-pyridyl benzoates in anhydrous ethanol
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Pseudo-first-order rate constants (kobsd) have been measured for nucleophilic substitution reactions of 2-pyridyl benzoate 5 with alkali metal ethoxides (EtOM, M = Li, Na, K) in anhydrous ethanol. The plots of k obsd vs. [EtOM]o are curved upwardly but linear in the excess presence of 18-crown-6-ether (18C6) with significant decreased k obsd values in the reaction with EtOK. The kobsd value for the reaction of 5 with a given EtONa concentration decreases steeply upon addition of 15-crown-5-ether (15C5) to the reaction medium up to ca. [15C5]/[EtONa]o = 1, and remains nearly constant thereafter, indicating that M+ ions catalyze the reaction in the absence of the complexing agents. Dissection kobsd into kEtO- and k EtOM, i.e., the second-order rate constants for the reaction with the dissociated EtO. and the ion-paired EtOM, respectively has revealed that ion-paired EtOM is 3.2-4.6 times more reactive than dissociated EtO. It has been concluded that M+ ions increase the electrophilicity of the reaction center through a 6-membered cyclic transition state. This idea has been examined from the corresponding reactions of 4-pyridyl benzoate 6, which cannot form such a 6-membered cyclic transition state.
- Lee, Jae-In,Kang, Ji-Sun,Kim, Song-I,Um, Ik-Hwan
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experimental part
p. 2929 - 2933
(2012/05/05)
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- A facile synthesis of carboxamides by dehydration condensation between free carboxylic acids and amines using O,O′-DI(2-pyridyl) thiocarbonate as a coupling reagent
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Carboxamides are prepared in high yields by dehydration condensation between nearly equimolar amounts of free carboxylic acids and amines both of which involve secondary or tertiary alkyl substituted ones with O,O′-di(2-pyridyl) thiocarbonate, a coupling reagent, in the presence of a catalytic amount of 4-(dimethylamino)pyridine.
- Shiina, Isamu,Saitoh, Katsuyuki,Nakano, Masakazu,Suenaga, Yoshihito,Mukaiyama, Teruaki
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p. 621 - 630
(2007/10/03)
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- A New Method for the Preparation of Active Esters Using Di-2-pyridyl Carbonate
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The use of di-2-pyridyl carbonate in the presence of a catalytic amount of 4-dimethylaminopyridine is found to be very effective in the preparation of various active esters.
- Kim, Sunggak,Ko, Young Kwan
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- DI-2-PYRIDYL CARBONATE: A NEW EFFICIENT COUPLING AGENT FOR THE DIRECT ESTERIFICATION OF CARBOXYLIC ACIDS
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Reaction of carboxylic acids with equimolar amounts of di-2-pyridyl carbonate and alcohols or thiols in the presence of 4-dimethylaminopyridine as a catalyst in methylene chloride at room temperature affords the corresponding esters in high yields under mild conditions.
- Kim, Sunggak,Lee, Jae In,Ko, Young Kwan
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p. 4943 - 4946
(2007/10/02)
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- O-Acylation using organothallium compounds
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Thallous salts of β-dicarbonyl compounds, prepared by reaction of the β-dicarbonyl compounds with a thallous alkoxide, are treated with alkyl halides to give C-alkyl products in high yield, with acyl halides at room temperature to give C-acyl products, and with acyl halides at low temperatures to give O-acyl products. Thallous phenolates are esterified with acyl or aroyl halides. Anhydrides are also prepared, as are biaryls and bi-sec-alkyls. N-Heterocyclics, including purines and pyrimidines, are N-alkylated. Lactams are O-acylated or N-alkylated.
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