Reactivity of 5-aminopyrazoles bearing a cyclopropyl group at C3-position in palladium-catalyzed direct C4-arylation.

Pyrazole derivatives bearing a cyclopropyl group at C3-position and an amino substituent at C5 were successfully employed in palladium-catalyzed direct arylations. These couplings were performed using air-stable PdCl(C 3 H 5 )(dppb) catalyst associated to KOAc as inexpensive base, and afforded regioselectively the C4-arylated pyrazoles without decomposition of the cyclopropyl unit and formation of amination products. A wide variety of functional groups on the aryl bromide including electron-withdrawing and electron-donating ones such as nitrile, nitro, propionyl, ester, trifluoromethyl, chloro, fluoro or methoxy was tolerated. Moreover, from 5-aminopyrazoles bearing N -2′-bromoaryl or 2′-bromobenzenesulfonamide substituent on the amino group, intramolecular Pd-catalyzed direct arylations allowed the formation of tricyclic compounds by formation of 5- or 6-membered rings. © 2018 Elsevier Science. All rights reserved. [ABSTRACT FROM AUTHOR]