Arylpropiolates

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. 

Reactions of quinoline Reissert compounds were less satisfactory than those of the corresponding isoquinolines. The hydrochloride of 64 with DMAD gave 65 in only 7% yield in methylene chloride ethanol, and 10% in DMF. From a study of the mechanism of the 1,3-dipolar addition of Reissert salts to arylpropiolate esters, McEwen et a/.499 concluded that a concerted cyclization was more probable than a two-step process. 

The reaction between arylpropiolates and 1,2-mercaptoalcohols is catalysed by BU3P which initiates a-S-addition to the triple bond and the umpolung adduct then cyclises to give 3-arylidene-l,4-oxathian-2-ones 70 <07OL3925>. 

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. ... 

Scheme 22. Intramolecular Cyclizalion of Arylpropargyl Arylpropiolate Esters...

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. 

Tellurol esters react with phosphoranes at room temperature to give a-acylphos-phiranes 103 (Eq. 70) [128]. The reaction with arylpropiolates gives (Z)-P-aryl-telluro-a,p-unsaturated esters 104 with high stereoselectivity (Eq. 71) [129]. 

Amino derivatives of pyran-4-one are available from arylpropiolate esters by reaction with the lithium enolate of -acetylmorpholine and cyclisation of the resulting acetylenic P-ketoamides (94S43). 

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]. 

Alkynes with EWGs such as propiolate are poor substrates for the coupling with halides. Therefore, instead of inactive propiolate, triethyl orthopropiolate (11) is used for the coupling with aryl halides to prepare the arylpropiolate 12. The... 

The above-described protocol can also be employed in the synthesis of propargyl substituted propiolates. These reactive intermediates can be transformed in a CuAAC to yield 1,2,3-triazolylmethyl arylpropiolates 56 in a one-pot fashion applying the concept of sequential catalysis in generally excellent yields considering the formation of four new bonds and a bondforming efficiency of 73—87%. It is noteworthy that the CuAAC... 

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... 

Although, there are methods for obtaining rhodanine derivatives such as Kno-evenagel condensation, the one-pot method for synthesis of these derivatives is a prevailing option to reduce the synthetic steps and raise efficacy of the method. For example, the reaction of dithiocaibamates (prepared in situ from amines and CS2) and arylpropiolates in the presence of PBU3 as a catalyst (Table 9.4) led to alkylidine rhodanine-based scaffolds [20],... 

Triazole Derivatives. The synthesis of 4,5-disubstituted 1,2,3-triazoles using sodium polystyrylsulfinate resin 43 was first reported by Huang and coworkers (Scheme 12.17). The synthesis involved the reaction between arylpropiolates and sodium azide followed by oxidation. Resin-bound ethyl polystyrylsulfonylacetate 68 was prepared using ethyl 2-bromoacetate in DMF with potassimn iodide and tetrabutylammonium iodide as a phase transfer catalyst. Subsequent reaction of resin 68 with benzaldehyde using piperidine as a catalyst afforded arylidene polystyrylsulfonyl acetate 69. CycUzation of 69 with sodium azide in DMSO at 120°C for 5h afforded the 1,2,3-txiazoles 70a. 

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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