An expedient four-component domino protocol for the regioselective synthesis of highly functionalized pyranopyrazoles and chromenopyrazoles via nitroketene-N,S-acetal chemistry under solvent-free condition
摘要:
Combinatorial library of pyranopyrazoles and chromenopyrazoles was regioselectively synthesized in excellent yield from ethylacetoacetate, hydrazinehydrate, substituted aldehyde/salicylaldehyde with nitroketene-N,S-acetal in the presence of piperidine under solvent-free condition (SFC) in an eco-benign manner. This novel strategy excludes tedious extraction, chromatographic separation and recrystallization processes. The final product could be obtained by simple filtration by the addition of ethanol to the reaction mixture. This domino protocol generates biologically significant heterocycles with the formation of C-C, C=C, C-N, C=N, C-O bonds and one stereo-centre in a single operation via condensation/Knoevenagel/Michael/annulation sequences. (c) 2014 Elsevier Ltd. All rights reserved.
Four-Component Domino Strategy for the Combinatorial Synthesis of Novel 1,4-Dihydropyrano[2,3-<i>c</i>]pyrazol-6-amines
作者:Selvaraj Kanchithalaivan、Sathiyamoorthi Sivakumar、Raju Ranjith Kumar、Palani Elumalai、Qazi Naveed Ahmed、Anil K. Padala
DOI:10.1021/co4000997
日期:2013.12.9
An efficient one-pot four-component domino protocol for the combinatorial synthesis of novel 1,4-dihydropyrano[2,3-c]pyrazol-6-amines has been achieved. This transformation presumably occurs via cyclization- Knoevenagel condensation-Michael addition-tautomerism- intramolecular O-cyclization-elimination sequence of reactions. The significant features of this reaction include expedient one-pot process, short reaction time, no column chromatographic purification, excellent yield, and readily available starting materials.
An expedient four-component domino protocol for the regioselective synthesis of highly functionalized pyranopyrazoles and chromenopyrazoles via nitroketene-N,S-acetal chemistry under solvent-free condition
Combinatorial library of pyranopyrazoles and chromenopyrazoles was regioselectively synthesized in excellent yield from ethylacetoacetate, hydrazinehydrate, substituted aldehyde/salicylaldehyde with nitroketene-N,S-acetal in the presence of piperidine under solvent-free condition (SFC) in an eco-benign manner. This novel strategy excludes tedious extraction, chromatographic separation and recrystallization processes. The final product could be obtained by simple filtration by the addition of ethanol to the reaction mixture. This domino protocol generates biologically significant heterocycles with the formation of C-C, C=C, C-N, C=N, C-O bonds and one stereo-centre in a single operation via condensation/Knoevenagel/Michael/annulation sequences. (c) 2014 Elsevier Ltd. All rights reserved.