Direct C–H Alkenylation of Functionalized Pyrazoles

Abstract

We have developed inter- and intramolecular C-H alkenylation reactions of pyrazoles. The catalyst, derived from Pd(OAc)2 and pyridine, enabled the oxidative alkenylation of pyrazoles containing a variety of functional groups at the C4 position. Activated alkenes, including acrylate, acrylamide, and styrene derivatives, and enamides could be installed in this process. The sequential C-H alkenylation and cyclization reactions gave rise to fused bicyclic pyrazoles, providing a new strategy to annulate readily available pyrazole compounds.

C−H Alkenylation of Pyrroles by Electronically Matching Ligand Control

“…Furthermore, sequential alkenylation could be applied to pyrroles having electron‐withdrawing groups. For example, C3‐alkenylation of 4 g with Pd(OAc) 2 and Cu(OAc) 2 afforded 4,5‐dialkenyl pyrrole 7 a having different alkenyl groups (Scheme ) . Subsequent thermal 6π‐electrocyclization and oxidation facilitated ring closure, producing the multi‐substituted indole 7 b …”

A Facile Regioselectively Synthesis of 2‐Alkenylbenzo[1,2‐b:4,5‐b’]dithiophene by Pd/Cu/Ag‐Catalyzed C‐H Functionalization

“…In terms of atom‐economy and eco‐tolerance, Pd–assisted C−H functionalization of heteroarenes appears to be straightforward . After the first direct oxidative Heck reaction reported by Moritani and co‐workers, a number of Pd‐based catalytic systems have been developed to become a powerful tool for the direct alkenylation of arenes and heteroarenes . However, to the best of our knowledge, the site‐selective C‐2 Pd‐catalyzed alkenylation of BDT has not yet been explored.…”

Selectivity of amidrazones towards activated nitriles – synthesis of new pyrazoles and NMR investigation

“…16 Pyrazoles have also found use as bifunctional ligands for metal catalysis, 17,18 as model systems to study excited-state intramolecular proton transfers, 19 as artificial receptors, 20,21 and as the backbone to numerous scorpionate ligands. 22 For all these reasons, pyrazole synthesis continues to attract interest. Herein we describe the synthesis of new pyrazoles via the reaction of amidrazones with activated alkenes.…”