Cross-Coupling and Dehalogenation Reactions Catalyzed by (N-Heterocyclic carbene)Pd(allyl)Cl Complexes

Abstract

A series of well-defined, air- and moisture-stable (NHC)Pd(allyl)Cl (NHC = N-heterocyclic carbene) complexes has been used in several catalytic reactions: Suzuki-Miyaura cross-coupling, catalytic dehalogenation of aryl halides, and aryl amination. The scope of the three processes using various substrates was examined. A general system involving the use of (IPr)Pd(allyl)Cl as catalyst and NaO(t)Bu as base has proven to be highly active for the Suzuki-Miyaura cross-coupling of activated and unactivated aryl chlorides and bromides, for the catalytic dehalogenation of aryl chlorides, and for the catalytic aryl amination of aryl triflates. All reactions proceed in short reaction times and at mild temperatures. The system has also proven to be compatible with the microwave-assisted Suzuki-Miyaura cross-coupling and catalytic dehalogenation processes, affording yields similar to those of the conventionally heated analogous reactions.

Preparation of poly(fluorene)s using trans‐bis(dicyclohexylamine)palladium diacetate as a catalyst: Scope and limitations

“…Palladium-mediated dehalogenation is a well-understood process that occurs via b-hydride elimination from Ar-Pd(II)-alkoxy species followed by reductive elimination of ArH. 52,53 As the aptitude of the used alcohols to undergo b-hydride elimination decreases in the order 2-PrOH > EtOH > MeOH, the decrease in the molecular weight and bromine endgroup content can be readily rationalized in a comparison of, for example, PF6-10, PF6-7, and PF6-3. Protiodeboronation is known to occur when aqueous conditions are used.…”

Controlled Microwave Heating in Modern Organic Synthesis

“…[275] This catalytic system is compatible with microwave conditions and rapid couplings were observed within 1.5 minutes at 120 8C. The conventionally heated reactions (60 8C) required several hours to reach completion.…”

Shape‐Switchable Azo‐Macrocycles

“…While the disappearance of the signal of the iodine atoms perfectly fits with the expectations for a completed substitution reaction the analytical data should be treated with a degree of skepticism. Dehalogenation is a well known side reaction during palladium catalyzed coupling reactions [149] [247] and thus, the disappearance of the iodine signals is not necessarily proof that all iodine atoms have been replaced by a dodec-1-ynyl chain. The halide can be substituted by a hydrogen atom in a palladium catalyzed cross coupling reaction, but the reaction between acetylenes and the aryl iodides are highly favored over the dehalogenation.…”

“…The halide can be substituted by a hydrogen atom in a palladium catalyzed cross coupling reaction, but the reaction between acetylenes and the aryl iodides are highly favored over the dehalogenation. [247][248]…”