Direct Arylation Of Heteroaromatics Research Articles

ChemInform Abstract: Pd‐Catalyzed Direct Arylation of Heteroaromatics Using (Poly)halobenzenesulfonyl Chlorides as Coupling Partners: One Step Access to (Poly)halo‐Substituted Bi(hetero)aryls.

ChemInform Abstract: Pd‐Catalyzed Direct Arylation of Heteroaromatics Using (Poly)halobenzenesulfonyl Chlorides as Coupling Partners: One Step Access to (Poly)halo‐Substituted Bi(hetero)aryls.

Pd‐Catalysed Direct Arylation of Heteroaromatics Using (Poly)halobenzenesulfonyl Chlorides as Coupling Partners: One Step Access to (Poly)halo‐Substituted Bi(hetero)aryls

AbstractThe reactivity of (poly)halo‐substituted benzenesulfonyl chlorides for Pd‐catalysed desulfitative arylation was investigated. 2‐, 3‐ and 4‐bromobenzenesulfonyl chlorides react nicely to afford arylated heteroarenes in moderate to high yields without cleavage of the C–Br bonds, allowing further transformations. A minor influence upon reaction yeilds was found to be exerted by the bromo substituent on the benzene ring. Even 4‐iodobenzenesulfonyl chloride, di‐ and tri‐bromobenzenesulfonyl chlorides were successfully coupled with a range of heteroarenes without cleavage of the C–Br or C–I bonds and very regioselective arylations were observed in all cases. The reaction was also found to tolerate bromo substituents on the heteroarene.

Unexpected Dual Role of Titanium Dioxide in the Visible Light Heterogeneous Catalyzed C–H Arylation of Heteroarenes

The direct arylation of heteroaromatics with an easily accessible and recyclable, heterogeneous TiO2 catalyst and visible light was developed. Electron-rich as well as electron-poor heteroarenes could be applied in this transformation, and the corresponding products were isolated in very good yields. Azoethers were detected as reactive intermediates, and the unexpected role of TiO2 in their formation as well as reaction was established.

ChemInform Abstract: Palladium‐Catalyzed Direct Arylation of Heteroaromatics with Functionalized Bromopyridines.

AbstractElectron‐withdrawing substituents at the pyridyl moiety favor the process.

Highly Dispersed Palladium–Polypyrrole Nanocomposites: In‐Water Synthesis and Application for Catalytic Arylation of Heteroaromatics by Direct C–H Bond Activation

AbstractPd@PPy hybrid catalytic materials are synthesized in water via redox polymerization reaction of pyrrole with [Pd(NH3)4Cl2]. The nanocomposites formed are composed of highly dispersed palladium particles which are either zerovalent or easily reducible, and are embedded in spherical polypyrrole globules. A unique combination of high palladium dispersion (NP size: 2.4 nm) and elevated palladium content (35 wt%) is obtained. The components of these novel nanocomposites are characterized by means of FTIR, XPS, XRD, SEM, and TEM microscopy techniques. The process of formation in solution is also monitored using UV‐visible and DLS techniques. The application of these novel hybrid nanomaterials in the palladium‐catalyzed direct arylation of heteroaromatics is reported. High efficiency in C–C bond formation is obtained using these materials. Furans and thiophenes are arylated by using bromoarenes. Pd@PPy nanocomposites can efficiently couple n‐butyl furan and n‐butyl thiophene with bromobenzene and bromoquinoline, as well as with activated or deactivated electron‐poor and electron‐rich functionalized bromoarenes. Thus, a clean reaction process is developed that combines the absence of organic ligand in catalytic reactions and easy recovery of Pd@PPy nanocomposite via simple filtration. Preliminary kinetic and post‐catalysis studies suggest a molecular or colloidal soluble active species. These very active species are efficiently delivered by the nanocomposites and susceptible to a surprisingly uniform back redeposition within the polypyrrole support.