Palladium-Catalyzed Decarboxylative Coupling of Alkynyl Carboxylic Acids with Aryl Tosylates

Abstract

Decarboxylative coupling reactions of alkynyl carboxylic acids with aryl tosylates were developed in the presence of a palladium catalyst. Among the commercially available phosphine ligands, only 1-dicyclohexylphosphino-2-(di- tert –butylphosphino-ethyl)ferrocene (CyPF- t Bu) showed good reactivity. The reaction took place smoothly and gave the decarboxylative coupled products in moderate to good yields. This demonstrates the excellent functional group tolerance toward alkyl, alkoxy, fluoro, thiophenyl, ester, and ketone groups. In addition, alkyl-substituted propiolic acids, such as octynoic and hexynoic acids, were coupled with phenyl tosylate to provide the desired products. We found that the electronic properties of the substituents on the phenyl ring in arylpropiolic acids are an important factor. The order of reactivity was found to be aryl iodide > aryl bromide > aryl tosylate > aryl chloride. However, aryl chloride-bearing electron-withdrawing groups showed higher reactivity than those bearing aryl tosylates.

Recent Expedition inPd‐CatalyzedSonogashira Coupling and Related Processes†

“…Song and Lee demonstrated a catalyst system of Pd(PPh 3 )Cl 2 / CyPF t ‐Bu and Cs 2 CO 3 for the coupling of alkynyl carboxylic acids and aryl tosylates (Figure 6). [ 140 ] Competitive coupling experiments were carried out with aryl halides/ tosylates. It was found that phenyl tosylates were less active than aryl iodides and bromides, but they were more active than aryl chlorides in this decarboxylative Sonogashira coupling.…”

Palladates of the [NHC⋅H][Pd(NH2)(CC)Cl2] Type as Effective Pre‐catalysts for the Formation of C−C and C−N Bonds

“…Spectroscopic data for catalysts and reaction products as well as additional references (Ref. [23,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]).…”

Cross‐Electrophile Coupling between Two Different Tosylates Enabled by Nickel/Palladium Cooperative Catalysis

“…The electrophilic cross‐coupling reactions catalyzed by dual nickel/palladium have been achieved between two different electrophiles (Figure 1A), primarily encompassing the following types:1) C(sp 2 )−Br and C(sp 2 )−OTf (aryl bromides and aryl triflates); [6a] 2) C(sp 2 )−Cl and C(sp 2 )−OTf (aryl chlorides and aryl triflates); [6b] 3) C(sp 2 )−OTs and C(sp 2 )−OTf (aryl tosylates and aryl triflates [6c,d] as well as between gem ‐difluorovinyltosylate and aryl triflates or cyclic vinyl triflates [6e] ); 4) C(sp 2 )−Br and C(sp 2 )−OTs (aryl bromides and 2,2‐difluorovinyl tosylates) [6f] . In comparison to aryl halides, aryl tosylates can be easily obtained from phenols, making them more appealing due to the abundance of phenols [8a,b] . However, there has been limited research on cross‐electrophile coupling reactions involving aryl tosylates due to their high stability [8] .…”