Efficient Phosphorus Catalysts for the Halogen‐Exchange (Halex) Reaction

Abstract

New families of monomeric to dendritic, and monocationic to multicationic (PNP) compounds have been prepared and tested as catalysts in halogen exchange (Halex) reactions. Some of them allow an increase in the efficiency of these reactions which are performed in some cases under the mildest conditions reported up to now.

Cu-Catalyzed Fluorination of Diaryliodonium Salts with KF

“…On the laboratory scale, two of the most common nucleophilic fluorination methods are halide exchange between aryl chlorides and alkali metal fluorides (MF) 3 and reactions of diaryliodonium salts with MF. 4 Both of these processes are generally limited by the requirement for high temperatures (typically >100 °C) and by poor reactivity of electron rich substrates.…”

“…This substitution pattern is often challenging to access in nucleophilic fluorination reactions due to the high propensity of 2-chloropyridines in to participate S N Ar. 3 …”

Further Development of Weakly Coordinating Cations: Fluorinated Bis(triarylphosphoranylidene)iminium Salts

“…The synthesis is a modified protocol of Lacour et al. for unsubstituted [PPN][Cl] . However, in contrast to this previous study we do not deprotonate [Ph 3 PNH 2 ]Cl with n BuLi and then treat it with freshly prepared Ph 3 PCl 2 .…”

“…This is mainly due to its bulkiness, the well‐distributed positive charge, and its low Lewis acidity, which are characteristic of the class of WCCs. Other advantages are the hydrophobic nature, which leads to nonhygroscopic salts, the possibilities for metathesis, the ease of production, and its usability in a great variety of solvents . Examples in which WCCs have been successfully applied for better crystal growth are [Co(CO) 4 ] − [14] and [M 2 (CO) 10 ] 2− (M=Cr, Mo) .…”

“…Another synthetic route to [PPN] + was described by Lacour et al [15] They used isolated triphenylaminophosphonium chloride, which can be prepared by the reactiono ft riphenylphosphine,h exachloroethane, and ammonia,w hich was further treated with nBuLi to form Ph 3 PNLi. By adding freshly prepared Such weakly coordinating cations as [PPN] + can be used for the isolationo ff ragile complex anions.…”