N‐Heterocyclic Carbenes: Useful Ligands for the Palladium‐Catalysed Direct C5 Arylation of Heteroaromatics with Aryl Bromides or Electron‐Deficient Aryl Chlorides
Pd-N-heterocyclic carbene complexes have been prepared and employed for palladium-catalysed directarylation of heteroaromatic derivatives by using aryl halides. These catalyst precursors promote the coupling of challenging aryl halides such as deactivated or congested arylbromides and also activated aryl chlorides. This procedure employs only 1 mol-% of an air-stable palladium complex. This is a
A new ferrocenyl triphosphane ligand associated to palladium was found to be an efficient catalyst for the direct coupling of highly congested, functionalised aryl bromides with a variety of heteroarenes. These coupling reactions can generally be performed by using a low‐loading (0.1–0.5 mol %) of the catalyst. The present protocol tolerates important and useful functional groups, which allows for
The direct 5-arylation of furans at very lowcatalystloading using Pd(OAc)2 as catalyst without added ligand proceed in high yields. Turnover numbers up to 10000 have been obtained for the coupling of several activated aryl bromides. A wide range of functions on the furan or aryl bromide is tolerated.
Tandem Transformations via Friedel–Crafts Acylation Followed by a Ring-Expansion, Ring-Opening, and Cycloisomerization Sequence
作者:Hun Young Kim、Kyungsoo Oh
DOI:10.1021/acs.orglett.8b03881
日期:2019.2.1
A tandem synthetic route to a diverse array of cyclic compounds has been developed from Friedel–Craftsacylation of alkynes followed by the microwave irradiation of β-chlorovinyl ketone intermediates. The stereoisomeric β-chlorovinyl ketone intermediates smoothly underwent a thermal α-vinyl enolization and ring expansion to vinyl and carbocyclic furans as well as cyclopetene derivatives in good to