Silver-promoted Decarboxylation Coupling Of Aromatic Carboxylic Acids With Sodium Benzene Sulfinates

Aromatic carboxylic acid has been widely concerned by chemists because of its low price,low toxicity,wide range of sources,easy storage,easy modification and so on.Based on these features,aromatic carboxylic acids are often involved in the synthesis of organic compounds and decarboxylation coupling is one of the important reactions.Although there are many decarboxylation coupling reactions,there are relatively few reports on decarboxylation coupling reactions with sodium sulfinates.Based on the above research background,sulfones compounds with high biological and pharmacological activity were synthesized in moderate to good yields in this paper by using silver salt as the promoter,aromatic carboxylic acid and sodium benzene sulfonate derivatives as the substrate,and 1,10-phenanthrene as the ligand in trifluorotoluene solvent at 160°C for 18 hours.Firstly,a serious of experiments had been carried out to explore the effects of the types and dosage of silver salts,ligand types and dosage,solvent types,temperature and other variables.The best conditions for the reaction were explored and the target product was obtained with the yield of 81%.Secondly,we extended the substrates according to the optimal reaction conditions.It was found that substrates with electron-withdrawing groups such as chlorine,bromine,trifluoromethyl or electron-donating groups such as methyl and methoxy on o-nitrobenzoic acid could react well with sodium p-methylbenzosulfonate.Next,we expanded the scope of sodium benzene sulfinates.We found that the halogen,trifluoromethyl and nitro groups on the aromatic ring were all well tolerated,giving the desired products in moderate to good yields.It should be noted that sodium cyclopropanesulfinate,an aliphatic sodium sulfinate,also proved to be a good substrate,delivering the desired product in 67%yield.Finally,through mechanism experiments and literature research,we proposed the mechanism of this paper.Initially,the reaction of aromatic carboxylic acid with Ag₂CO₃gives silver carboxylate,which in turn affords the aryl-Ag（I）species by the loss of a molecule of carbon dioxide.Meanwhile,sodium sulfinate is oxidized by Ag（I）to generate an oxygen-centered radical,which could be easily resonated to sulfonyl radical.Subsequently,the sulfonyl radical reacts with aryl-Ag（I）species to provide the Ag（II）intermediate.Finally,reductive elimination of the Ag（II）intermediate gives the decarboxylative coupling product.