- Reductive amination of aldehydes and ketones by a Hantzsch dihydropyridine using scandium triflate as a catalyst
-
Direct reductive amination of aldehydes and ketones was carried out using a Hantzsch dihydropyridine as a reducing agent in the presence of a catalytic amount of a Lewis acid.
- Itoh, Takashi,Nagata, Kazuhiro,Kurihara, Ayako,Miyazaki, Michiko,Ohsawa, Akio
-
-
Read Online
- Oxidative-aromatization of hantzsch ester 1,4-dihydropyridines by KBrO 3/Cocl2.6H2O under mild condition
-
KBrO3/CoCl2.6H2O system was used as an effective oxidizing agent for the oxidation of 1,4-dihydropyridines to the corresponding pyridine derivatives in refluxing CH3CN. The products were obtained in high to exce
- Dilmaghani, Karim Akbari,Zeynizadeh, Behzad,Mirzaei, Mansoor
-
-
Read Online
- Photoinduced Aromatization of Dihydropyridines
-
The combination of tris(bipyridine)ruthenium(II)/visible light/air is found to be effective for the aromatization of many dihydropyridines. A low catalyst loading of just 0.02 mol% is required.
- Lu, Zheng,Yang, Yong-Qing,Li, Hong-Xia
-
-
Read Online
- A novel, facile, simple and convenient oxidative aromatization of Hantzsch 1,4-dihydropyridines to pyridines using polymeric iodosobenzene with KBr
-
An easy, safe, effective and handy method for oxidative aromatization of Hantzsch 1,4-dihydropyridines catalyzed by hypervalent iodine (iodosobenzene) and potassium bromide to corresponding pyridine derivatives in high-yields and within short span of time was described. Dealkylation in case of 4-n-alkyl substituted 1,4-dihydropyridines was not obtained.
- Kumar, Parvin
-
-
Read Online
- Histidine-Specific Peptide Modification via Visible-Light-Promoted C-H Alkylation
-
Histidine (His) carries a unique heteroaromatic imidazole side chain and plays irreplaceable functional roles in peptides and proteins. Existing strategies for site-selective histidine modification predominantly rely on the N-substitution reactions of the moderately nucleophilic imidazole group, which inherently suffers from the interferences from lysine and cysteine residues. Chemoselective modification of histidine remains one of the most difficult challenges in peptide chemistry. Herein, we report peptide modification via radical-mediated chemoselective C-H alkylation of histidine using C4-alkyl-1,4-dihydropyridine (DHP) reagents under visible-light-promoted conditions. The method exploits the electrophilic reactivity of the imidazole ring via a Minisci-type reaction pathway. This method exhibits an exceptionally broad scope for both peptides and DHP alkylation reagents. Its utility has been demonstrated in a series of important peptide drugs, complex natural products, and a small protein. Distinct from N-substitution reactions, the unsubstituted nitrogen groups of the modified imidazole ring are conserved in the C-H alkylated products.
- Chen, Xiaoping,Ye, Farong,Luo, Xiaosheng,Liu, Xueyi,Zhao, Jie,Wang, Siyao,Zhou, Qingqing,Chen, Gong,Wang, Ping
-
-
Read Online
- Formation of pyridines from N-methylpyrimidinium iodide and enaminoesters
-
The reaction of N-methylpyrimidinium iodide with enaminoesters yiels a mixture of 3-ethoxycarbonyl-2-methylpyridine and 3,5-diethoxycarbonyl-2,6-dimethylpyridine.Mechanisms of the transformations of the pyrimidine ring found are suggested. - Keywords: N-methylpyridinium iodide; enaminoesters; ring transformation; pyridines; β-substituted.
- Gromov, S. P.,Razinkin, M. A.
-
-
Read Online
- The Aromatization of Hantzsch Dihydropyridines with Nitric Oxide (NO)
-
Hantzsch dihydropyridines were readily oxidized by nitric oxide to give corresponding pyridines in quantitative yields.This reaction system required no work-up procedure.In the presence of oxygen, it was possible to reduce nitric oxide to less than an equ
- Itoh, Takashi,Nagata, Kazuhiro,Okada, Mamiko,Ohsawa, Akio
-
-
Read Online
- Additive-controlled synthesis of 1- and 2-dexoysugars from thioglycosides
-
Two photoreactions for the synthesis of 1- and 2-deoxysugars from thioglycosides were developed. In the presence of Hantzsch ester as an additive, a wide range of 1-deoxysugars were synthesized in moderate to excellent yields under irradiation with UV light without an exogenous photosensitizer. On the other hand, the utilization of 2,4,6-tri-tert-butylpyrimidine (TTBP) as the additive furnished a variety of 2-deoxysugars as the main products from their corresponding thioglycosides. The reported methodology has a broad substrate scope and high functional group tolerance and is scalable to gram-scale reaction.
- Gao, Chen-Fei,Wu, Biao,Wu, Xia,Xiong, De-Cai,Ye, Xin-Shan
-
-
- Dealkenylative Ni-Catalyzed Cross-Coupling Enabled by Tetrazine and Photoexcitation
-
A new and general method to functionalize the C(sp3)-C(sp2) bond of alkyl and alkene linkages has been developed, leading to the dealkenylative generation of carbon-centered radicals that can be intercepted to undergo Ni-catalyzed C(sp3)-C(sp2) cross-coupling. This one-pot protocol leverages the easily procured alkene feedstocks for organic synthesis with excellent functional group compatibility without the need for a photoredox catalyst.
- Cao, Yuhui,Che, Jinteng,Chen, Han,Chen, Si-Cong,Fang, Xianhe,Guo, Yinliang,Guo, Zhixian,Kong, Lingran,Li, Chen,Lu, Jia-Tian,Luo, Tuoping,Zhang, Nan,Zhu, Qi
-
supporting information
p. 14046 - 14052
(2021/09/13)
-
- The photoredox-catalyzed hydrosulfamoylation of styrenes and its application in the novel synthesis of naratriptan
-
The hydrosulfamoylation of diverse aryl olefins provides facile access to alkylsulfonamides. Here we report a novel protocol utilizing radical-mediated addition and a thiol-assisted strategy to achieve the hydrosulfamoylation of diverse styrenes in modest to excellent yields under mild and economic reaction conditions. The methodology was found to provide an efficient and convenient approach for the synthesis of the anti-migraine drug naratriptan and it also can be used for the late-stage functionalization of natural products or medicines.
- Zhang, Mingjun,Chen, Miaomiao,Ding, Xin,Kang, Jin,Gao, Yongyue,He, Xingxing,Wang, Ziwen,Lu, Aidang,Wang, Qingmin
-
supporting information
p. 9140 - 9143
(2021/09/14)
-
- Anti-Markovnikov hydroarylation of alkenes via polysulfide anion photocatalysis
-
A protocol for anti-Markovnikov hydroarylation of alkenes with aryl halides has been developed using polysulfide anions as photocatalysts in the presence of the Hantzsch ester and water under irradiation with visible light.
- Chiba, Shunsuke,Li, Haoyu,Liu, Yuliang
-
supporting information
p. 6264 - 6267
(2021/07/02)
-
- Visible-light-driven external-photocatalyst-free alkylative carboxylation of alkenes with CO2
-
Herein, we report a novel protocol for visible-light-driven alkylative carboxylation of alkenes with CO2 in the absence of external photocatalyst. Under the irradiation of visible light, a variety of 4-alkyl-1,4-dihydropyridines (alkyl-DHPs) serve as not only alkyl radical precursors but also photoexcited reductants probably with the potential to reduce benzyl radicals. Several styrenes and acrylates are applicable in this reaction to give structurally diverse carboxylic acids in good to excellent yields. These reactions feature mild reaction conditions (1 atm of CO2, room temperature, visible light, photocatalyst- and transition metal-free), good functional group tolerance, easy scalability, as well as high regio-, and chemo-selectivity. Mechanistic investigations provide evidence that alkyl radical, benzyl radical and carbanion might be involved in this reaction, providing a novel strategy for CO2 utilization.[Figure not available: see fulltext.]
- Niu, Ya-Nan,Jin, Xing-Hao,Liao, Li-Li,Huang, He,Yu, Bo,Yu, Yu-Ming,Yu, Da-Gang
-
p. 1164 - 1169
(2021/06/17)
-
- Photoactive electron donor-acceptor complex platform for Ni-mediated C(sp3)-C(sp2) bond formation
-
A dual photochemical/nickel-mediated decarboxylative strategy for the assembly of C(sp3)-C(sp2) linkages is disclosed. Under light irradiation at 390 nm, commercially available and inexpensive Hantzsch ester (HE) functions as a potent organic photoreductant to deliver catalytically active Ni(0) species through single-electron transfer (SET) manifolds. As part of its dual role, the Hantzsch ester effects a decarboxylative-based radical generation through electron donor-acceptor (EDA) complex activation. This homogeneous, net-reductive platform bypasses the need for exogenous photocatalysts, stoichiometric metal reductants, and additives. Under this cross-electrophile paradigm, the coupling of diverse C(sp3)-centered radical architectures (including primary, secondary, stabilized benzylic, α-oxy, and α-amino systems) with (hetero)aryl bromides has been accomplished. The protocol proceeds under mild reaction conditions in the presence of sensitive functional groups and pharmaceutically relevant cores.
- Kammer, Lisa Marie,Badir, Shorouk O.,Hu, Ren-Ming,Molander, Gary A.
-
p. 5450 - 5457
(2021/05/05)
-
- Diastereoselective Synthesis of Aryl C-Glycosides from Glycosyl Esters via C?O Bond Homolysis
-
C-aryl glycosyl compounds offer better in vivo stability relative to O- and N-glycoside analogues. C-aryl glycosides are extensively investigated as drug candidates and applied to chemical biology studies. Previously, C-aryl glycosides were derived from lactones, glycals, glycosyl stannanes, and halides, via methods displaying various limitations with respect to the scope, functional-group compatibility, and practicality. Challenges remain in the synthesis of C-aryl nucleosides and 2-deoxysugars from easily accessible carbohydrate precursors. Herein, we report a cross-coupling method to prepare C-aryl and heteroaryl glycosides, including nucleosides and 2-deoxysugars, from glycosyl esters and bromoarenes. Activation of the carbohydrate substrates leverages dihydropyridine (DHP) as an activating group followed by decarboxylation to generate a glycosyl radical via C?O bond homolysis. This strategy represents a new means to activate alcohols as a cross-coupling partner. The convenient preparation of glycosyl esters and their stability exemplifies the potential of this method in medicinal chemistry.
- Wei, Yongliang,Ben-zvi, Benjamin,Diao, Tianning
-
supporting information
p. 9433 - 9438
(2021/03/16)
-
- Visible-Light-Promoted Photocatalyst-Free Hydroacylation and Diacylation of Alkenes Tuned by NiCl2·DME
-
Herein, we describe a visible light-promoted hydroacylation strategy that facilitates the preparation of ketones from alkenes and 4-acyl-1,4-dihydropyridines via an acyl radical addition and hydrogen atom transfer pathway under photocatalyst-free conditions. The efficiency was highlighted by wide substrate scope, good to high yields, successful scale-up experiments, and expedient preparation of highly functionalized ketone derivatives. In addition, this protocol allows for the synthesis of 1,4-dicarbonyl compounds through alkene diacylation in the presence of NiCl2·DME.
- Zhao, Xinxin,Li, Bing,Xia, Wujiong
-
supporting information
p. 1056 - 1061
(2020/02/15)
-
- Cross-Coupling Reactions of Alkenyl Halides with 4-Benzyl-1,4- Dihydropyridines Associated with E to Z Isomerization under Nickel and Photoredox Catalysis
-
Cross-coupling reactions of alkenyl halides with 4-alkyl-1,4-dihydropyridines as alkylation reagents have been achieved by combination of nickel and photoredox catalysts. Alkenyl halides bearing alkyl and aryl substituents are available. Particularly, in
- Nakajima, Kazunari,Guo, Xifeng,Nishibayashi, Yoshiaki
-
supporting information
p. 3653 - 3657
(2018/11/10)
-
- Ligand-Controlled Regioselective Hydrocarboxylation of Styrenes with CO2 by Combining Visible Light and Nickel Catalysis
-
The ligand-controlled Markovnikov and anti-Markovnikov hydrocarboxylation of styrenes with atmospheric pressure of CO2 at room temperature using dual visible-light-nickel catalysis has been developed. In the presence of neocuproine as ligand, the Markovnikov product is obtained exclusively, while employing 1,4-bis(diphenylphosphino)butane (dppb) as the ligand favors the formation of the anti-Markovnikov product. A range of functional groups and electron-poor, -neutral, as well as electron-rich styrene derivatives are tolerated by the reaction, providing the desired products in moderate to good yields. Preliminary mechanistic investigations indicate the generation of a nickel hydride (H-NiII) intermediate, which subsequently adds irreversibly to styrenes.
- Meng, Qing-Yuan,Wang, Shun,Huff, Gregory S.,Konig, Burkhard
-
supporting information
p. 3198 - 3201
(2018/03/13)
-
- Photochromic coenzyme Q derivatives: Switching redox potentials with light
-
Coenzyme Q is an important redox cofactor involved in a variety of cellular processes, and is thus found in several cell compartments. We report a photochromic derivative of coenzyme Q that combines the molecular structures of the redox active cofactor and a photochromic dye. Light irradiation triggers an electronic rearrangement reversibly changing the redox potential. We used this effect to control the intermolecular redox reaction of the photochromic coenzyme Q derivative with dihydropyridine in solution by light irradiation. On mitochondria, the altered redox properties showed an effect on the respiratory chain. The experiments demonstrate that the redox reactions can be initiated inside the system of interest through irradiation with light and the accompanied photoisomerization.
- Simeth, Nadja A.,Kneuttinger, Andrea C.,Sterner, Reinhard,K?nig, Burkhard
-
p. 6474 - 6483
(2017/08/29)
-
- Visible-Light-Mediated Aromatic Substitution Reactions of Cyanoarenes with 4-Alkyl-1,4-dihydropyridines through Double Carbon-Carbon Bond Cleavage
-
Novel aromatic substitution reactions of cyanoarenes with 4-alkyl-1,4-dihydropyridines as alkylating reagents in the presence of a catalytic amount of a photoredox catalyst proceed smoothly to give the corresponding alkyl-substituted arenes in good to high yields. The present reaction system realizes a novel C-C bond-forming reaction between two fragments generated from the C-C bond-cleavage reactions of two independent substrates.
- Nakajima, Kazunari,Nojima, Sunao,Sakata, Ken,Nishibayashi, Yoshiaki
-
p. 1028 - 1032
(2016/04/05)
-
- One-Pot Synthesis of Hantzsch Pyridines via NH4I Promoted Condensation of 1,3-Dicarbonyl Compounds with DMSO and NH4OAc
-
A one-pot synthesis of Hantzsch pyridines was achieved through NH4I-promoted condensation of 1,3-dicarbonyl compounds with DMSO and NH4OAc, in which the C4 of the pyridine rings was derived from DMSO and the nitrogen atom resulted from NH4OAc and NH4I. The target product could be obtained in moderate to excellent yields.
- Chang, Liming,Lai, Junyi,Yuan, Gaoqing
-
p. 887 - 894
(2016/09/20)
-
- 9-Phenyl-10-methylacridinium: A highly efficient and reusable organocatalyst for mild aromatization of 1,4-dihydropyridines by molecular oxygen
-
(Chemical Equation Presented) The mild, efficient, and general aerobic aromatization of Hantzsch 1,4-dihydropyridines was realized at room temperature with 5 mol % of 9-phenyl-10-methylacridinium Perchlorate as the photocatalyst, which could be easily rec
- Fang, Xinqiang,Liu, You-Cheng,Li, Chaozhong
-
p. 8608 - 8610
(2008/02/13)
-
- A convenient method for the oxidation of Hantzsch 1,4-dihydropyridines with N-bromo succinimide
-
A convenient and mild method for the conversion of Hantzsch 1,4-dihydropyridines to pyridines using N-bromo succinimide at room temperature in excellent yields has been described.
- Nagarajan,Anthonyraj,Muralidharan,Saikumar,Perumal
-
p. 826 - 828
(2007/10/03)
-
- Microwave-assisted oxidative aromatization of Hantzsch 1,4-dihydropyridines using manganese dioxide
-
4-Aryl- and 4-alkyl-1,4-dihydropyridines, prepared by microwave-assisted Hantzsch reaction, are readily and efficiently aromatized in only one minute using commercial manganese dioxide in the absence of an inorganic support at 100 °C under microwave irradiation. This rapid procedure is more efficient than microwave-assisted aromatization using Pd/C, iodine or o-iodoxybenzoic acid (IBX) and gives the dehydrogenated or 4-dealkylated product in 91-100% yield (13 examples). Georg Thieme Verlag Stuttgart.
- Bagley, Mark C.,Lubinu, M. Caterina
-
p. 1283 - 1288
(2007/10/03)
-
- A detailed investigation into the oxidation mechanism in Hantzsch 1,4-dihydropyridines by ethyl a-cyanocinnamates and benzylidenemalononitriles
-
A mechanism for the oxidation of Hantzsch 1,4-dihydropyridine (HEH) by substituted ethyl a-cyanocinnamates (1) and benzylidenemalononitriles (2) has been critically investigated. Replacement of HEH by HEH-4,4-d2 and HEH-N-d gave the observed kinetic isotope effects (KIE) of 5.3-6.0 and 1.2-1.3 for the reactions with 1 and 2, respectively, which suggests C4-H bond dissociation is involved in the rate-limiting step and that the N-H bond dissociation is a non-rate-limiting step. The positive ρ values of 1.78 and 1.67 for the reactions of HEH with 1 and 2, respectively, clearly demonstrate the electrophilic nature of the substrates in the transition state (TS) and so indicate that the hydrogen lost from HEH must be a hydride-like species. Correlation analyses on the kinetics, KIE's and activation parameters showed excellent linear dependence on the electronic properties of remote substituents and added further credence to the proposed one-step hydride transfer mechanism. Detailed investigation of the activation parameters not only confirmed the direct HT- mechanism, but also revealed experimentally, for the first time, an entropy-controlled compact TS for the HEH-modeled NAD(P)H oxidations.
- Zhu, Xiao-Qing,Zou, Hong-Ling,Yuan, Ping-Wei,Cao, Lei,Cheng, Jin-Pei
-
p. 1857 - 1861
(2007/10/03)
-
- Reaction of Nitric Oxide with Amines
-
Reactions of nitric oxide (NO) with amines in organic solvents were studied using Hantzsch dihydropyridines and aromatic primary amines as substrates. Hantzsch dihydropyridines are readily oxidized by nitric oxide to give the corresponding pyridines in quantitative yields. The addition of oxygen accelerates the reaction rate considerably. On the other hand, aromatic primary amines give deaminated products by the reaction with nitric oxide only in the presence of oxygen in ethereal solvents or chloroform.
- Itoh, Takashi,Nagata, Kazuhiro,Matsuya, Yuji,Miyazaki, Michiko,Ohsawa, Akio
-
p. 3582 - 3585
(2007/10/03)
-
- AN UNUSUAL AROMATIZATION OF HANTZSCH-TYPE 4-ANTIPYRYL-1,4-DIHYDROPYRIDINES
-
Under acidic conditions, Hantzsch-type 4-antipyryl-1,4-dihydropyridines undergo an elimination of the 4-substituent to yield 4-unsubstituted pyridines and antipyrine.The mechanism and scope of the reaction are discussed.
- Eynde, Jean-Jacques Vanden,Mayence, Annie,Maquestiau, Andre,Anders, Ernst
-
p. 815 - 822
(2007/10/02)
-
- A novel application of the oxidizing properties of pyridinium chlorochromate : Aromatization of Hantzsch 1,4-dihydropyridines
-
diethyl 1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylates can be readily oxidized under neutral conditions using pyridinium chlorochromate adsorbed on a solid support.
- Eynde, Jean-Jacques Vanden,Mayence, Annie,Maquestiau, Andre
-
p. 463 - 468
(2007/10/02)
-
- Synthesis, molecular structure, and complexation of 1,4-dihydropyridines containing ligands for intramolecular complexation of metal electrophiles
-
A series of 4-substituted Hantzsch 1,4-dihydropyridines has been synthesized.Substituents at the 4-position include 2-pyridyl, 2-imidazolyl, and 1-methyl-2-imidazolyl.By use of various acetoacetic ester derivatives methoxy and methylthio groups have been introduced in the ester side chains at the 3,5-positions.A representative example is bis(2-methoxyethyl) 1,4-dihydro-2,6-dimethyl-4-(1H-imidazol-2-yl)-3,5-pyridinedicarboxylate (5h).The crystal structure of bis1,4-dihydro-2,6-dimethyl-4-(1H-imidazol-2-yl)-3,5-pyridinedicarboxylate (5i) has been determined.The imidazole group at the 4-position is located in a pseudo-axial position.In the 13C- and 1H-NMR spectra line doubling is seen in the 4-imidazole-substituted derivatives.This is apparently the result of slow tautomerization.Various complexes with Zn(NO3)2*4H2O have been prepared but no crystal structures could be obtained.These 1,4-dihydropyridines have little capacity, either in the presence or absence of metal ions, to carry out reductions.This may be the result of a stereoelectronic effect caused by the (presumably) equatorial orientation of the hydrogen (hydride) to be donated.
- Kaptein, Bernard,Kellogg, Richard M.,Bolhuis, F. van
-
p. 388 - 395
(2007/10/02)
-
- Kinetic Investigation on the Hydrogen Transfer from Dihydropyridines to Hydrazyls
-
The results of a kinetic study on the hydrogen transfer between different dihydropyridines and mono-, bis- and trishydrazyls of the tricyanobenzene series are described.The reactions have been found to obey in all cases a second-order law.The influences of solvent medium, redox-potentials of the reactants and temperature on the rates of reactions have been investigated. - Keywords: Dihydropyridines, Hydrazyls, Hydrogen Transfer, Kinetics
- Abou-Elenien, G.,Rieser, J.,Ismail, N.,Wallenfels, K.
-
p. 391 - 394
(2007/10/02)
-
- N-Quaternary Heterocyclics: Part IX- Synthesis and Reactions of 8,9,10,11-Tetrahydrobenzothiazoloquinazolin-7-ium Perchlorate and Related Systems
-
The title compound 8,9,10,11-tetrahydrobenzothiazoloquinazolin-7-ium perchlorate (I) on reduction with sodium borohydride, sodium cyanoborohydride or Hantzsch reagent in non-oxygenic solvents or aq. sodium hydroxide solution gives 2-(o-aminophenyl)
- Singh, Harjit,Gandhi, C. S.,Lal, K. B.,Bal, M. S.
-
p. 844 - 847
(2007/10/02)
-
- DIARYLHYDROXYMETHYLATION OF PYRIDINE N-OXIDE BY THE RADICAL ANIONS OF SOME AROMATIC KETONES
-
In the reaction of the ketyls 4-phenylbenzophenone and phenyl 1-naphthyl ketone with pyridine N-oxide phenyl-4'-biphenylyl-2-pyridylcarbinol N-oxide, phenyl-4'-biphenylyl-2-pyridylcarbinol, phenyl-1'-naphthyl-2-pyridylcarbinol, and dimerization products (bipyridyls) vere obtained.The ketyl of phenyl 5-acenaphthenyl ketone does not form condensation products.In contrast to pyridine, pyridine N-oxide does not enter into the Emmert reaction.
- Kurbatova, A. S.,Kurbatov, Yu. V.,Dmitrieva, N. M.
-
p. 567 - 570
(2007/10/02)
-