Buchwald‐Hartwig Amination of Coordinating Heterocycles Enabled by Large‐but‐Flexible Pd‐BIAN‐NHC Catalysts**
摘要:
AbstractA new class of large‐but‐flexible Pd‐BIAN‐NHC catalysts (BIAN=acenaphthoimidazolylidene, NHC=N‐heterocyclic carbene) has been rationally designed to enable the challenging Buchwald‐Hartwig amination of coordinating heterocycles. This robust class of BIAN‐NHC catalysts permits cross‐coupling under practical aerobic conditions of a variety of heterocycles with aryl, alkyl, and heteroarylamines, including historically challenging oxazoles and thiazoles as well as electron‐deficient heterocycles containing multiple heteroatoms with BIAN‐INon (N,N′‐bis(2,6‐di(4‐heptyl)phenyl)‐7H‐acenaphtho[1,2‐d]imidazol‐8‐ylidene) as the most effective ligand. Studies on the ligand structure and electronic properties of the carbene center are reported. The study should facilitate the discovery of even more active catalyst systems based on the unique BIAN‐NHC scaffold.
Palladium-Catalyzed N-Arylation of 2-Aminothiazoles
作者:Meredeth A. McGowan、Jaclyn L. Henderson、Stephen L. Buchwald
DOI:10.1021/ol300178j
日期:2012.3.16
A method for the Pd-catalyzed coupling of 2-aminothiazole derivatives with aryl bromides and triflates is described. Significantly, for this class of nucleophiles, the coupling exhibits a broad substrate scope and proceeds with a reasonable catalyst loading. Furthermore, an interesting effect of acetic acid as an additive is uncovered that facilitates catalyst activation.