1190837-95-6Relevant articles and documents
Synthesis of 2H-furo[2,3-c]pyrazole ring systems through silver(I) ion-mediated ring-closure reaction
Mili?iūnait?, Vaida,Paulavi?iūt?, Rūta,Arba?iauskien?, Egl?,Martynaitis, Vytas,Holzer, Wolfgang,?a?kus, Algirdas
, p. 679 - 684 (2019/04/17)
Fused pyrazole ring systems are common structural motifs of numerous pharmaceutically important compounds. Nevertheless, access to 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-pyra-zoles as a key step. The required intermediate hydroxyalkynyl substrates for this reaction were prepared by a Pd-catalyzed coupling of 4-iodo-1-phenyl-1H-pyrazol-3-ol with ethyne derivatives. The structures of the obtained target compounds were unequivocally confirmed by detailed 1H, 13C and 15N NMR spectroscopic experiments, HRMS and a single-crystal X-ray diffraction analyses. This silver(I)-mediated 5-endo-dig 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.
DMF-catalyzed direct and regioselective C-H functionalization: Electrophilic/nucleophilic 4-halogenation of 3-oxypyrazoles
Liu, Yuanyuan,He, Guangke,Chen, Kai,Jin, Yin,Li, Yufeng,Zhu, Hongjun
experimental part, p. 5323 - 5330 (2011/11/13)
A novel, straightforward, and highly regioselective 4-chlorination of 3-oxypyrazole derivatives in boiling thionyl chloride (SOCl2) in the presence of catalytic N,N-dimethylformamide (DMF) has been developed. This reaction likely proceeds through a DMF-catalyzed electrophilic/nucleophilic chlorination mechanism and involves electrophilic attack by SOCl2 and nucleophilic substitution by Cl- as the key steps. Based on this mechanism, the corresponding 4-bromination and 4-iodination of 3-oxypyrazoles have also been achieved in good yield by adding Br- and I -, respectively, to the reaction system. This halogenation method enables quick access to many original 4-halo-3-oxypyrazole series. A novel DMF-catalyzed electrophilic/nucleophilic 4-halogenation of 3-oxypyrazole derivatives has been developed. This halogenation procedure provides quick access to many novel 4-halo-3-oxypyrazole series.
