- Aryne [3 + 2] cycloaddition with N-sulfonylpyridinium imides and in situ generated N-sulfonylisoquinolinium imides: A potential route to pyrido[1,2-b]indazoles and indazolo[3,2-a]isoquinolines
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The aryne [3 + 2] cycloaddition process with pyridinium imides breaks the aromaticity of the pyridine ring. By equipping the imide nitrogen with a sulfonyl group, the intermediate readily eliminates a sulfinate anion to restore the aromaticity, leading to the formation of pyrido[1,2-b]indazoles. The scope and limitation of this reaction are discussed. As an extension of this chemistry, N-tosylisoquinolinium imides, generated in situ from N′-(2-alkynylbenzylidene)-tosylhydrazides via an AgOTf-catalyzed 6-endo-dig electrophilic cyclization, readily undergo aryne [3 + 2] cycloaddition to afford indazolo[3,2-a]-isoquinolines in the same pot, offering a highly efficient route to these potential anticancer agents.
- Zhao, Jingjing,Li, Pan,Wu, Chunrui,Chen, Hongli,Ai, Wenying,Sun, Renhong,Ren, Hailong,Larock, Richard C.,Shi, Feng
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supporting information; experimental part
p. 1922 - 1930
(2012/04/23)
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- Azides: Part VII-Thermolysis of p-Toluenesulphonylazide and Ethyl Azidoformate in Pyridine and Its Derivatives; Evidence for an Electronic Equilibrium for N-Iminopyridinium Ylides
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The thermolysis of p-toluenesulphonylazide and ethyl azidoformate in pyridine, ethyl isonicotinate and 2,6-dicarbethoxypyridine has been studied.Thermal rearrangement to the corresponding diazepines via a diazanorcardiene intermediate can not be achieved either by the application of positive nitrogen pressure or in the presence of several high boiling solvents.The detailed IR, PMR and X-ray photoelectron spectral analyses of the N-iminopyridinium ylides reveal a new electronic configuration for the ylides.
- Ayyangar, N. R.,Bambal, R. B.,Srinivasan, K. V.
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