Beilstein J. Org. Chem.2019,15, 679–684, doi:10.3762/bjoc.15.62
derivatives of the aromatic 2H-furo[2,3-c]pyrazole ring system is still quite limited, and their chemistry and functional properties remain largely underexplored. The current study investigates routes to construct this system from easily accessible starting materials using metal-catalyzed reactions. A simple
and efficient procedure to access the 2H-furo[2,3-c]pyrazole ring system was developed by employing the silver(I) ion-mediated ring-closure reaction of 4-alkynyl-3-hydroxy-1-phenyl-1H-pyrazoles as a key step. The required intermediate hydroxyalkynyl substrates for this reaction were prepared by a Pd
cyclization of readily available 4-alkynyl-3-hydroxy-1H-pyrazoles can be used as an efficient method to access many novel 2,5-disubstituted 2H-furo[2,3-c]pyrazoles.
Keywords: 5-endo-dig cyclization; 2H-furo[2,3-c]pyrazole; pyrazole; silver(I) catalyst; Sonogashira coupling; Introduction
Heterocyclic ring
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Graphical Abstract
Scheme 1:
Preparation of hydroxyalkynyl substrates from 1-phenyl-1H-pyrazol-3-ol (1).