Ligand-Free Ag(I)-Catalyzed Carboxylation of Terminal Alkynes with CO₂

Abstract

A convenient approach to selectively prepare a wide range of functionalized propiolic acids was developed by AgI-catalyzed carboxylation of terminal alkynes using carbon dioxide as carboxylative agent under ligand-free conditions.

Silver tungstate: a single-component bifunctional catalyst for carboxylation of terminal alkynes with CO2 in ambient conditions

“…16 Subsequently, several silver salts were investigated. Most of the tested silver compounds exhibited poor to moderate activity without any additive at room temperature (entries [6][7][8][9][10][11][12][13][14]. Interestingly, when Na 2 WO 4 was added to the AgNO 3 -catalyzed system, the yield of 2a dramatically improved from 54% to 72%.…”

“…For 1,4-diethynylbenzene, biscarboxylative product 2ja was formed as the major product with 64% yield and 24% yield of the monocarboxylative product 2jb, which was also detected (entry 10). Aliphatic alkynes (entry 11) and heteroaromatic acetylenes (entries [12][13][14][15] were also found to be suitable substrates. In agreement with the DFT calculation, 3-ethynylpyridine showed lower activity when compared with 2-ethynylpyridine (entry 12 vs. 13), indicating that the acidity of the alkyne proton strongly impacts on the activity.…”

“…The AgI catalytic system was developed by Lu et al with a relatively high CO 2 pressure and the catalytically active species was investigated by density functional theory (DFT) studies. 13 Gooßen et al found that the AgBF 4 -catalyzed carboxylation reactions could be conducted under atmospheric pressure of CO 2 in dimethyl sulfoxide (DMSO) at 50°C. 14 With the poly-NHC-Ag (NHC, N-heterocyclic carbene) catalytic system developed by Zhang et al, the carboxylation of terminal alkynes under ambient CO 2 pressure and room temperature was achieved.…”

Making C–C Bonds from Carbon Dioxide via Transition-Metal Catalysis

“…These observations suggest that strong coordination between the electron-rich metal center and ligand activates the CO 2 Terminal alkynes display relatively acidic C-H bonds (pK a * 25) and can undergo carboxylation at elevated temperatures and pressures [40,41]. In the presence of a catalyst [58], mild carboxylations have been reported with copper and silver salts, both with [59][60][61] and without [62][63][64][65] external halide reagents to trap the formed carboxylate ( Fig. 6).…”

Transition Metal-Catalyzed Carboxylation of Organic Substrates with Carbon Dioxide

“…In 2011, Lu and co-workers reported the ligand-free carboxylation of terminal alkynes catalyzed by AgI (1 mol%) under mild conditions (50 C, 2 bar CO 2 ) using CsCO 3 as base in DMF [103]. Previously, the group had developed the coppercatalyzed carboxylative alkylation between terminal alkynes, allylic chlorides, and CO 2 [90].…”