Pd-PEPPSI-IPent^An Promoted Deactivated Amination of Aryl Chlorides with Amines under Aerobic Conditions

Abstract

We report herein a highly efficient Pd-catalyzed amination by "bulky-yet-flexible" Pd-PEPPSI-IPent complexes. The relationship between the N-heterocyclic carbenes (NHCs) structure and catalytic properties was discussed. Sterically hindered (hetero)aryl chlorides and a variety of aliphatic and aromatic amines can be applied in this cross-coupling, which smoothly proceeded to provide desired products. The operationally simple protocol highlights the rapid access to C-N bond formation under mild conditions without the exclusion of air and moisture.

BIAN‐NHC Ligands in Transition‐Metal‐Catalysis: A Perfect Union of Sterically Encumbered, Electronically Tunable N‐Heterocyclic Carbenes?

“…Buchwald–Hartwig amination of sterically hindered and electronically deactivated substrates catalyzed by Pd‐BIAN‐IPent catalyst 18 (Scheme 19). [53] This highly practical cross‐coupling was conducted under aerobic conditions using KO t Bu as a base in dioxane at 100 °C.…”

Bulky N‐Heterocyclic‐Carbene‐Coordinated Palladium Catalysts for 1,2‐Addition of Arylboron Compounds to Carbonyl Compounds

“…In contrast, substrates bearing reactive and strong electron-withdrawing functional groups such as formyl, nitro, and cyano required the use of 0.05 mol% PhS-IPent-CYP (entries 7-9). Further, heteroarylboronic acids such as 2,6-dimethoxy-3-pyridyl-, 2-benzofuranyl-, and 2-benzothiophenylboronic acid were easily converted to the desired products at a catalyst loading of 0.03 mol% (entries [10][11][12]. However, the reaction of substrates bearing cyano or pyridyl groups, which coordinate strongly to palladium complexes, required a higher temperature of 70°C (entries 9 and 10).…”

“…[6a,c] It is well known that the effect of N-heterocyclic carbene (NHC) ligands on palladium catalysis is strongly related to their steric bulk, with increased flexible steric bulk leading to more effective catalysis. [9,10] Thus, a reasonable increase in the bulkiness due to the 2,6-diisopropylphenyl groups on IPr-CYPs has the potential to further improve the catalytic activity for 1,2-addition reactions. In fact, H-IPr*-CYP with highly hindered and less flexible 2,6-bis(diphenylmethyl)-4-methylphenyl groups shows better catalytic activity than H-IPr-CYP but lower catalytic activity than PhS-IPr-CYP.…”

Acenaphthene-Based N-Heterocyclic Carbene Metal Complexes: Synthesis and Application in Catalysis

“…A significant number of palladium(II) complexes bearing C 2 symmetry have been synthesized by the Tu and Liu research groups, independently (Scheme 9). First, complexes possessing only simple alkyl substituents in the ortho position of the aniline, such as mesityl or DIPP derivatives (25a-c [35,[59][60][61], 25d-g [62] and 25h-i [43,63]) were obtained in a moderate 48-68% yield. Further research in this area resulted in the synthesis of the highly sterically hindered palladium(II) complexes 25j-n [46] and 25n [41], containing benzhydryl substituents, in comparable yields.…”