Propiolic acid, acidity

The reaction of propiolic acid or its esters with 2-aminothiazole yields 7H-thiazolo[3.2o]pyTimidine 7-one (109) (Scheme 74) (273), The reaction probably proceeds by initial nucleophilic attack of 2-aminothiazole on the sp C followed by intramolecular addition of ring nitrogen to spC. 

The only reported example of nucleophilic addition to a C C bond is intramolecular it is observed when propiolic acid is added to 2-aminothiazole producing (109) (see p. 53). 

The best direct synthetic route to uracil is probably the classical procedure from malic acid and urea in concentrated sulfuric acid (26JA2379), despite efforts to use maleic acid, urea and polyphosphoric acid (71S154) or propiolic acid, urea and a little concentrated sulfuric acid (77JOC2185) to achieve the same result. However, the most convenient source (apart from purchase) is to convert 2-thiouracil (937 X = S) into uracil by boiling with aqueous chloroacetic acid (52MI21300) or perhaps by oxidation with DMSO in strong sulfuric acid (74S491). 

The reaction of bromine with (pyrazol-4-yl)acrylic acid and its esters and the subsequent dehydrobromination of the products have been investigated by Finar and Okoh [73JCS(P1)2008]. Attempts to dehydrobrominate bromoacrylic acids (20) to 3-( 1 -phenylpyrazol-4-yl)propiolic acids 22 failed, but were successful when bromoesters 21 were used (Scheme 32). 

Propiolsaure, /. propiolic acid, propionsatier, a. of propionic acid, propionate of. Propionsaure, /. propionic acid. 

Ammonium sulfide, 3, n Ammonium thiocyanate, 7, 48 Ammonolysis, 4, 3 7, 16 o-Amyl alcohol, 1, 4, 10 Amyl alcohol, active, 7, 77 mo-Amyl Bromide, 1,1, 2, 4, 10 w-Amyl Methyl Ketone, 7, do -Amyl propiolic acid, 7, 62 Analysis of Benzoylhydroperoxide, 8,32 Analysis of Benzoylperoxide, 8, 31 Anhydro-o-Hydroxymercoribenzoic Acid, 7, 3... 

The trans cinnamic acid and phenyl propiolic acid data involve fits of essentially the same precision at o-, m-, and p- positions (SD =. 05 . 02). However, the RMS of these sets is quite low, and consequently, / values of. 200 prevail. The interpretation of these results is therefore uncertain. To the extent that the results of Table VII are meaningful, it is of particular interest that Kj =p°Ip =. 68 for the phenyl propiolic acid, whereas for the tram cinnamic acids, K° = 1.02. These results suggest that in contrast to the ortho substituted benzoic acids, the lines of field forces in the ortho substituted phenyl propiolic acids do (partly at least) penetrate regions of hi dielectric solvent. The results for the tram cinnamic acids would then indicate some (but not complete) exclusion of solvent resulting from the presence of the vinyl hydrogens. These interesting results from the application of eq. (1) clearly need to be confirmed by additional studies. 

Data are extant in the literature for two other sets of ethynylene compounds. The sets studied are reported in Table XXXIII. Results of correlation are set forth in Table XXXIV and values of Pr in Table XXXV. The ionization constants of 3-substituted propiolic acids, which were first correlated with the Hammett equation by Charton (18), gave an excellent correlation with eq. (2) (set 22-27-1). The results are very much improved by the elimination of the value for X = H (set 33-27-2). The composition of the electrical effect corresponds approximately to that of the Op constants. The magnitude of the electrical effect is significantly less than that observed for the rrans-3-substituted acrylic acids. 

There are almost no studies of substituent effects on additions to carbon-carbon triple bonds extant in the literature. Bowden and Price (208) have reported a correlation of rates of addition of hydrogen bromide to 3-substituted propiolic acids with the Hammett equation using the Op constants. Unfortunately, there are only three substituents in the set. Sufficient data are available for a single set of 1,3-dipolar cycloaddition. The set studied is shown in Table XXXIII, and the results of the correlation are in Table XXXIV. The correlation was significant the delocalized effect is predominant in this set. 

Propiolic acid, 58,43 Propionaldehyde, 58, 80, 82 Propionic anhydride, 57, 111 Propionyl chloride, 58, 85... 

The kinetics, products, and stereochemistry of the addition of HC1, HBr, and HI to propiolic acid in water have been studied.28 The addition is predominantly trans to give the cz s-3-haloacrylic acid. Both the rate of addition and the selectivity giving trans-addition increase with the nucleophilicity of the halide in water (i.e., I- > Br > Cl-). The order of reactivity is also consistent with the order of the softness of the nucleophiles. The reaction is first order in propiolic acid and the halide anion. It was proposed that the addition involves two mechanistic pathways a major /ra/z.v-addition via a transient carbanion formed with specific geometry and a minor cO-addition process (Scheme 10.2). 

After acetylenedicarboxylates, esters of propiolic acid are the second common group of reagents for 1,3-dipolar cycloaddition with azides. They react fast, and the yields of products are high. However, because the reacting... 

Sterically crowded selones and 4 -methoxyselenopivalophenone cyclize with propiolic acid to yield 2H,6H-l,3-oxaselenin-6-one derivatives115 (Scheme 33). 

Propenyl acetate, a74 2-Propenylamine, a74 Propenylanisole, ml07 2/-2-Propenyl-2-propen-1 -amine, d30 (2-Propenyl)thiourea, a97 Propiolic acid, p248 Propyl alcohol, p201... 

The intermolecular reaction of phenols with propiolic esters occurs in the presence of a Pd(OAc)2 catalyst to afford coumarin derivatives directly.48,48a An exclusive formation of 5,6,7-trimethoxy-4-phenylcoumarin is observed in the Pd(OAc)2-catalyzed reaction of 3,4,5-trimethoxyphenol with ethyl phenylpropiolate in TFA (Equation (46)). Coumarin derivatives are obtained in high yields in the cases of electron-rich phenols, such as 3,4-methylenedioxyphenol, 3-methoxyphenol, 2-naphthol, and 3,5-dimethylphenol. A similar direct route to coumarin derivatives is accomplished by the reaction of phenols with propiolic acids (Equation (47)).49 A similar reaction proceeds in formic acid at room temperature for the synthesis of coumarins.50,50a Interestingly, Pd(0), rather than Pd(n), is involved in this reaction. 

Propiolic acids. The ylide derived from 1 converts aldehydes into propiolic esters or the acids in 50-70% yield. 

Property taxes, 9 533-534 Property-temperature relationships, of vitreous silica, 22 416-417 P-Propiolactone, polymerization of, 14 259 Propiolic acid, 5 34t Propionaldehyde... 

Additions at the triple bond. The catalytic hydrogenation of acetylenes gives predominantly the cis isomer. The reason is obvious. Both the hydrogen atoms approach the double bond from the same side from the side of the catalyst. The hydrogenation of phenyl propiolic acid is an example. 

Similarly phenyl propiolic acid is first reduced to phenyl propargyl alcohol which then forms a complex with LiAlH4 and decomposition of the latter with water gives cinnamyl alcohol. 

Propiolic acid, 1086 Propioloyl chloride, 1065 3-Propynethiol, 1152 3-Propynol, 1147... 

Potassium hydrogen tartrate, 1462 /s-Propcnc-l,2,3-tricarboxylic acid, 2342 Propiolic acid, 1086 2,5-Pyridinedicarboxylic acid, 2696 Pyruvic acid, 1150... 

Ethyl propiolate Propiolic acid, ethyl ester (8) 2-Propynoic acid, ethyl ester (9) (623-47-2)... 

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