19867-89-1Relevant articles and documents
New synthesis of 2-aryl- and 2-hetarylpyrroles from 1-propargylbenzotriazole
Katritzky,Li,Gordeev
, p. 93 - 96 (1994)
1-(3-Lithiopropargyl)benzotriazole reacts with N-tosylarylimines to give adducts which undergo cycloelimination on treatment with ethanolic sodium hydroxide to afford 2-aryl- and 2-hetarylpyrroles in 45-60% yields. Treatment of 1-(1,3-dilithiopropargyl)benzotriazole successively with 1 equivalent of an alkyl halide followed by N-tosyl(1-naphthyl)imine and then ethanolic sodium hydroxide gives the corresponding 5-alkyl-2-(1-naphthyl)pyrroles in 43-56% yields.
σ-Bond initiated generation of aryl radicals from aryl diazonium salts
Chan, Bun,McErlean, Christopher S. P.,Nashar, Philippe E.,Tatunashvili, Elene
, p. 1812 - 1819 (2020/03/17)
σ-Bond nucleophiles and molecular oxygen transform aryl diazonium salts into aryl radicals. Experimental and computational studies show that Hantzsch esters transfer hydride to aryl diazonium species, and that oxygen initiates radical fragmentation of the diazene intermediate to produce aryl radicals. The operational simplicity of this addition-fragmentation process for the generation of aryl radicals, by a polar-radical crossover mechanism, has been illustrated in a variety of bond-forming reactions.
Radical Arylation of Anilines and Pyrroles via Aryldiazotates
Hofmann, Josefa,Gans, Eva,Clark, Timothy,Heinrich, Markus R.
, p. 9647 - 9656 (2017/07/22)
The radical arylation of anilines and pyrroles can be achieved under transition-metal- and catalyst-free conditions by using aryldiazotates in strongly alkaline aqueous solutions. The aryldiazotates act as protected diazonium ions, which do not undergo azo coupling with electron-rich aromatic substrates, but can still serve as an aryl radical source at slightly elevated temperatures. Based on an improved preparation of aryldiazotates in aqueous solution, homolytic aromatic substitutions of anilines and pyrroles were conducted with good overall yields and high regioselectivity. Moreover, DFT calculations provided further mechanistic insights.
Chromoselective Photocatalysis: Controlled Bond Activation through Light-Color Regulation of Redox Potentials
Ghosh, Indrajit,K?nig, Burkhard
supporting information, p. 7676 - 7679 (2016/07/07)
Catalysts that can be regulated in terms of activity and selectivity by external stimuli may allow the efficient multistep synthesis of complex molecules and pharmaceuticals. Herein, we report the light-color regulation of the redox potential of a photocatalyst to control the activation of chemical bonds. Light-color control of the redox power of a photocatalyst introduces a new selectivity parameter to photoredox catalysis: Instead of changing the catalyst or ligand, alteration of the color of the visible-light irradiation adjusts the selectivity in catalytic transformations. By using this principle, the selective activation of aryl–halide bonds for C?H arylation and the sequential conversion of functional groups with different reduction potentials is possible by simply applying different colors of light for excitation of the photocatalyst.