3- Arylpropiolic acids

Rate-determining protonation to give a vinyl cation rather than 1,4 addition of water has been proposed as the most consistent mechanism (25) for the acid-catalyzed hydration of arylpropiolic acids in aqueous sulfuric acid. Hydration of arylpropiolic acid closely resembles the acid-catalyzed isomeriza-... 

C and 2.4 — 5.3 for Ae hydration of arylpropiolic acids at 25°C in 50% sulfuric acid. The rates of both reactions give a linear correlation when plotted against Ho, with a slope of near unity and both reactions have comparable high negative entropies of activation. 

Arylpropiolic acids lose carbon dioxide when refluxed with water. or a solution of sodium bicarbonate and cupric chloride. Yields of phenylacetylenes containing nuclear halo, alkoxyl, and nitro groups are in the range of 40-67%. Alkylphenylacetylenes, C,H,C=CR, may be made directly from a-alkylcinnamic acid dibromides, C4H5 CHBrCRBrCO,H, by dehydrohalogenation and decarboxylation. ... 

Using a a scale determined from ionisation of arylpropiolic acids in 50% ethanol. From the Hammett a values, a p-value of+0.76 results. 

The selenodecarboxylation of cinnamic acid derivatives 554 with diaryldiselenides promoted by (diace-toxyiodo)benzene in acetonitrile affords vinyl selenides 555 in moderate yields (Scheme 3.220). A similar reaction of arylpropiolic acids gives the respective alkynyl selenides in 60-90% yields [604]. 

The reaction between esters of arylpropiolic acids and esters of thio-glycollic acids, using sodium methoxide in benzene as basic catalyst, leads to a mixture of the hydroxythiophencarboxylic acid esters (26) and (26a), in contrast to what had been reported earlier. Only (26), however, is... 

While terminal alkynes are typically used for metal-catalyzed hydrothiolation reactions, the treatment of 1-alkynylphosphines 18 with a variety of thiols in the presence of Pd(OAc)2 resulted in (Z)-isomers 19 through a preferential coordination of the substrate phosphine to a Pd metal center 20 followed by nucleophilic attack of thiol and protonolysis.In 2010, Liu and co-workers reported on the Cu-catalyzed decarboxylative cross-coupling of arylpropiolic acids 21 with thiols for the synthesis of vinyl sulfides 22 with high stereoselectivity for (Z)-isomers. ... 

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