Pd(II)-Catalyzed, Picolinamide-Assisted, Z-Selective γ-Arylation of Allylamines to Construct Z-Cinnamylamines

Abstract

Investigations of Pd(II)-catalyzed, picolinamide-assisted, γ-C(sp2)–H activation and Z-selective arylation of allylamines are reported. The reactions of N-allylpicolinamides with various aryl iodides in the presence of the catalyst Pd(OAc)2 and additive AgOAc have led to the selective γ-arylation of allylamines to construct various cinnamylamines with moderate to good yields and good to high E/Z ratios. To obtain good E/Z ratios, the Pd(II)-catalyzed arylation reaction of N-allylpicolinamides was probed using different additives, directing groups, and reaction conditions. The Pd(II)-catalyzed arylation of an allylamine containing both γ-C(sp2)–H and γ-C(sp3)–H bonds afforded moderate yields of the γ-C(sp2)–H and γ-C(sp3)–H bisarylated cinnamylamines. Although Heck-type γ-arylations of allylamines have generally afforded the E-cinnamylamines, the bidentate directing group picolinamide-directed arylations of allylamines were found to be Z-selective. A plausible mechanism was proposed for the observed regioselectivity and Z-selective arylation of N-allylpicolinamides. Additionally, the Pd(II)-catalyzed arylation of an N-allyl-5-methylisoxazole-3-carboxamide afforded the E-cinnamylamines plausibly via a ligand-free Heck-type reaction mechanism.