Synthesis of polyfluorinated arylhydrazines, arylhydrazones and 3-methyl-1-aryl-1H-indazoles
Polyfluorinated arylhydrazones were synthesized starting from 1-(4-amino-tetrafluorophenyl)ethanone and polyfluorinated arylhydrazines by action of p-toluenesulfonic acid in good yields. The resulting mixtures of E- and Z-isomers were next treated with K2CO3 in MeCN at room temperature. Under these mild reaction conditions Z-isomers underwent intramolecular nucleophilic cyclization to form 3-methyl-1-aryl-1H-indazole derivatives, while E-isomers were not active and were isolated unchanged. Molecular and crystal structures of prepared polyfluorinated (E)-arylhydrazones as well as selected 3-methyl-1-aryl-1H-indazoles were solved by the X-ray diffraction analysis. Meanwhile, the polyfluorinated acetophenone reacted with hydrazine in THF in the absence of a catalyst through a condensation–nucleophilic substitution cascade process to form a 3-methyl-1H-indazole derivative in excellent yield.
Oxyanion steering and CH-π interactions as key elements in an N-heterocyclic carbene-catalyzed [4 + 2] cycloaddition
The N-heterocyclic carbene catalyzed [4 + 2] cycloaddition has been shown to give γ,δ-unsaturated δ-lactones in excellent enantio- and diastereoselectivity. However, preliminary computational studies of the geometry of the intermediate enolate rendered am
Allen, Scott E.,Mahatthananchai, Jessada,Bode, Jeffrey W.,Kozlowski, Marisa C.
supporting information; scheme or table
p. 12098 - 12103
(2012/09/22)
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