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

Ameni Sidhom (1) , Jean-François Soulé (1) , Henri Doucet (1) , Fatma Allouche (2)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 Institut Supérieur de Biotechnologies de Sfax

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 (C3H5)(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. (C) 2018 Elsevier Science. All rights reserved.

Keywords: Palladium; C-H bond functionalization; Pyrazoles; cyclopropyl; aryl bromides

Domains: Chemical Sciences; Organic chemistry; Chemical Sciences; Catalysis

Ameni Sidhom, Jean-François Soulé, Henri Doucet, Fatma Allouche. Reactivity of 5-aminopyrazoles bearing a cyclopropyl group at C3-position in palladium-catalyzed direct C4-arylation. Catalysis Communications, 2018, 115, pp.55-58. ⟨10.1016/j.catcom.2018.07.008⟩. ⟨hal-01879771⟩