- Synthesis of polysubstituted pyridines from oxime acetates using NH4I as a dual-function promoter
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Pyridine formation with oxime acetates as the building blocks under metal-free conditions is described. Ammonium iodide has proved to be a highly efficient promoter for oxime N-O bond reduction and subsequent condensation reactions, whereby it played a dual-function role in the transformation. While the three-component reaction of oxime acetates, benzaldehydes, and 1,3-dicarbonyls proceeded well with the assistance of a stoichiometric amount of ammonium iodide, the condensation of oximes and acroleins was enabled by using a catalytic initiator to afford substituted pyridines. By this protocol, substituted pyridine products were generated in moderate to excellent yields with tolerance towards a broad range of functional groups.
- Xia, Yujia,Cai, Jinhui,Huang, Huawen,Deng, Guo-Jun
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p. 124 - 129
(2017/12/27)
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- Metal-Free Assembly of Polysubstituted Pyridines from Oximes and Acroleins
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Transition-metal-catalyzed synthesis of N-heterocycles from oximes has been previously well established. In this paper, for the first time a metal-free protocol with the combinational employment of iodine and triethylamine has been demonstrated to be effective to trigger the oxime-based synthesis of pyridines with high chemo-selectivity and wide functional group tolerance. A broad range of functional pyridines were prepared in moderate to excellent yields. While neither iodine nor triethylamine could trigger this transformation, mechanistic experiments indicated a radical pathway for the reaction. The resultant 2-aryl-substituted pyridines have been proved to be versatile building blocks in a range of transition-metal-catalyzed C-H functionalization reactions. (Chemical Equation Presented).
- Huang, Huawen,Cai, Jinhui,Tang, Lichang,Wang, Zilong,Li, Feifei,Deng, Guo-Jun
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p. 1499 - 1505
(2016/03/01)
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- Palladium-catalyzed multi-component synthesis of steroidal A- and D-ring fused 5,6-disubstituted pyridines under microwave irradiation
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The preparation of steroidal A-, D-ring fused 5,6-disubstituted pyridines and nonsteroidal substituted pyridines is described form Pd(OAc)2 catalyzed multi-component reaction of steroidal/nonsteroidal β-halovinyl aldehyde, alkyne and benzylamin
- Shekarrao, Kommuri,Nath, Dipankar,Kaishap, Partha Pratim,Gogoi, Sanjib,Boruah, Romesh C.
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p. 1126 - 1133
(2013/10/08)
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- Modular pyridine synthesis from oximes and enals through synergistic copper/iminium catalysis
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We describe here a [3+3]-type condensation reaction of O-acetyl ketoximes and α,β-unsaturated aldehydes that is synergistically catalyzed by a copper(I) salt and a secondary ammonium salt (or amine). This redox-neutral reaction allows modular synthesis of a variety of substituted pyridines under mild conditions with tolerance of a broad range of functional groups. The reaction is driven by a merger of iminium catalysis and redox activity of the copper catalyst, which would initially reduce the oxime N-O bond to generate a nucleophilic copper(II) enamide and later oxidize a dihydropyridine intermediate to the pyridine product.
- Wei, Ye,Yoshikai, Naohiko
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supporting information
p. 3756 - 3759
(2013/04/23)
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- Highly efficient synthesis of isoquinolines via nickel-catalyzed annulation of 2-iodobenzaldimines with alkynes: Evidence for dual pathways of alkyne insertion
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(Chemical Equation Presented) A wide range of substituted isoquinolines were synthesized via a highly efficient nickel-catalyzed annulation of the tert-butyl imines of 2-iodobenzaldehydes and various alkynes; examination of the regiochemistry of isoquinol
- Korivi, Rajendra Prasad,Cheng, Chien-Hong
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p. 5179 - 5182
(2007/10/03)
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- Synthesis of isoquinolines and pyridines by the palladium-catalyzed iminoannulation of internal alkynes
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A wide variety of substituted isoquinoline, tetrahydroisoquinoline, 5,6-dihydrobenz[f]isoquinoline, pyrindine, and pyridine heterocycles have been prepared in good to excellent yields via annulation of internal acetylenes with the tert-butylimines of o-iodobenzaldehydes and 3-halo-2-alkenals in the presence of a palladium catalyst. The best results are obtained by employing 5 mol % of Pd(OAc)2, an excess of the alkyne, 1 equiv of Na2CO3 as a base, and 10 mol % of PPh3 in DMF as the solvent. This annulation methodology is particularly effective for aryl- or alkenyl-substituted alkynes. When electron-rich imines are employed, this chemistry can be extended to alkyl-substituted alkynes. Trimethylsilyl-substituted alkynes also undergo this annulation process to afford monosubstituted heterocyclic products absent the silyl group.
- Roesch, Kevin R.,Zhang, Haiming,Larock, Richard C.
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p. 8042 - 8051
(2007/10/03)
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- A Novel Formation of Phenyl-Substituted Pyridines by the Reaction of N-(Diphenylphosphinyl)-1-azaallyl Anions with α,β-Unsaturated Carbonyl Compounds. A New Synthetic Equivalent of Primary Vinylamines
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The N-phosphinyl-1-azaallyl anions, which were derived from the corresponding imine or enamine reacted with α,β-unsaturated carbonyl compounds to afford phenyl-substituted pyridines along with 1-propanone and 1,5-pentanedione derivatives.A plausible mechanism involving a sequence of Michael addition and intramolecular aza-Horner-Wittig reaction is described, and the 1-azaallyl anions were found to behave as a synthetic equivalent of primary vinylamines.
- Kobayashi, Tomoshige,Kawate, Hiroshi,Kakiuchi, Hidetaka,Kato, Hiroshi
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p. 1937 - 1942
(2007/10/02)
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