Silver‐Catalyzed Aerobic Oxidative Decarboxylative Coupling of Arylpropiolic Acids with H‐Phosphine Oxides: Mild and Facile Synthesis of β‐Oxophosphine Oxides

Abstract

Highly functionalised benzofurans have been prepared from ortho‐hydroxyphenones and 1,1‐dichloroethylene. The key intermediate, a chloromethylene furan, smoothly rearranged into the corresponding benzofuran carbaldehyde under acidic conditions. Some mechanistic investigations have been performed and several biologically active benzofurans have been synthesised.

Phosphorylation of Carboxylic Acids and Their Derivatives with P(O)–H Compounds Forming P(O)–C Bonds

“…Wang and co-workers also achieved the oxidative phosphorylation of 3-arylpropynoic acids with secondary H-phosphine oxides (2 equiv, a relatively loading) through silver catalysis. 27 It should be noted that the aliphatic alkynoic acids showed poor or no reactivity in all the three catalytic systems. As for the mechanism, Tang and Wang's proposals were similar and more rationalized.…”

Copper-Catalyzed Decarboxylative Atom Transfer Radical Addition of Iododifluoroacetate to Alkynyl Carboxylic Acids

“…However, the unsaturated acceptors have been strictly limited to terminal alkenes and alkynes and, thus, are still hampered by the instability and low availability of the corresponding unsaturated substrates. In our continuous efforts to develop transition-metal-catalyzed fluoroalkylation methods, we envisioned that alkynyl carboxylic acids, readily available coupling partners in metal-catalyzed decarboxylative coupling reactions, could be feasible precursors to terminal unsaturated compounds (Scheme b). Herein, we report the first example of copper-catalyzed decarboxylative atom transfer radical addition of alkynyl carboxylic acids, initiated by fluoroalkyl radicals generated by copper catalysts, affording fluoroalkylated alkenyl iodides in a highly efficient way…”

Decarboxylative cross-coupling reactions for P(O)–C bond formation

“…Subsequently, the addition of the phosphorus radical A to the a-position of the triple bond of the cupric carboxylate B gave the radical intermediate C, which was ultimately trapped by a hydroxyl radical to provide the intermediate D. The synthesis of b-oxophosphine oxides in moderate to good yields (40-73%) was also reported by Zeng and co-workers through the reaction of corresponding alkynyl acids with Hphosphine oxides using Ag 2 CO 3 as an efficient catalyst in ethanol at room temperature and air conditions. 27 Other silver salts such as Ag 2 O, AgOAc, and AgOTf were also found to promote this reaction, albeit with lower yields. Under optimized conditions, both dialkyl and diaryl phosphine oxides were well tolerated.…”

“…The synthesis of β-oxophosphine oxides in moderate to good yields (40–73%) was also reported by Zeng and co-workers through the reaction of corresponding alkynyl acids with H-phosphine oxides using Ag 2 CO 3 as an efficient catalyst in ethanol at room temperature and air conditions. 27 Other silver salts such as Ag 2 O, AgOAc, and AgOTf were also found to promote this reaction, albeit with lower yields. Under optimized conditions, both dialkyl and diaryl phosphine oxides were well tolerated.…”