Ligand­controlled Regiodivergent C-H Alkenylation of Pyrazoles and its Application to the Synthesis of Indazoles

Title
Ligand­controlled Regiodivergent C-H Alkenylation of Pyrazoles and its Application to the Synthesis of Indazoles
Authors
임상민김현태하혜리강근희김옥순류호Abul Kalam Biswas백무현주정민
Keywords
alkenylation; C-H activation; indazole; palladium; pyrazole
Issue Date
2017-12
Publisher
Angewandte Chemie international edition
Citation
VOL 56, NO 51-16266
Abstract
Regioselective C4-, C5-, and di-alkenylations of pyrazoles were achieved. An electrophilic Pd catalyst generated by trifluoroacetic acid (TFA) and 4,5-diazafluoren-9-one (DAF) leads to C4-alkenylation, whereas KOAc and mono-protected amino acid (MPAA) ligand Ac-Val-OH give C5-alkenylation. A combination of palladium acetate, silver carbonate, and pivalic acid affords dialkenylation products. Annulation through sequential alkenylation, thermal 6 pi-electrocyclization, and oxidation gives functionalized indazoles. This comprehensive strategy greatly expands the range of readily accessible pyrazole and indazole derivatives, enabling useful regiodivergent C-H functionalization of pyrazoles and other heteroaromatic systems.
URI
http://pubs.kist.re.kr/handle/201004/67493
ISSN
1433-7851
Appears in Collections:
KIST Publication > Article
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