Kinetic studies acetylenedicarboxylate reactions

In a kinetic study of the Diels-Alder addition of 24 dienophiles with cyclopenta-diene and 9,10-dimethylanthracene, TCNE was found to be the most reactive. Paquette treated the azepinone (1) with maleic anhydride or N-phenylmaleimide in the temperature range 35-120° but failed to obtain a crystalline adduct. Reaction occurred when (1) was heated with dimethyl acetylenedicarboxylate without solvent at 130°, but the yield of adduct was only 20%. In contrast, a solution of equivalent amounts of (1) and TCNE in tetrahydrofurane at room temperature had an initial violet-brown color which faded completely in 30 min. to pale yellow and the adduct (2) was obtained in qnantitative yield. 

The reaction of tin phenoxides with diethyl acetylenedicarboxylate gives a mixture of products. Additionally, Kinart has found that the yield of vinylphenols obtained as products of the reaction of tri-n-butyltin phenoxides increases in the following order tri-n-butyl-(2-methoxyphenoxy)tin < tri-n-butyl-(o-tolyloxy)tin tri-n-butylphenoxytin < tri-n-butyl-(p-tolyloxy)tin. Although kinetic studies have not been carried out, the comparison of the yields seems to indicate that tri-n-butyl-(p-tolyloxy)tin is the most reactive of the four phenoxides mentioned above. The yields and the ratio of ethers and vinylphenols that were obtained from each reaction are given in Table 6.3.9. Again, as was observed for amination, tri-n-butyl-(2,6-dimethoxyphenoxy)tin exhibited different behavior in comparison to other phenoxides. Its reaction... 

A kinetic study and mechanistic investigation by UV spectrophotometry has been carried out on the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates and NH-acids (such as Harman acids). A Bronsted-type plot of the derived second-order rate constants for the reactions of a series of primary amines (in water) with benzoyl methyl... 

An ab initio smdy suggests that the formation of a Diels-Alder adduct [i.e. (23)] from reaction between 1-methylpyrrole and dimethyl acetylenedicarboxylate is favoured over the formation of a possible Michael-type addition product (24). Both pathways involve an initial electrophilic substitution at the 2-position of the pyrrole to form a zwitterionic intermediate. A review, in Chinese, concerns a number of electrophilic substitutions of pyridine. A kinetic study has been made of the reaction between 4,6-dinitrobenzofuroxan (25) and various anilines in acidic H2O-DMSO... 

Theoretical, NMR, kinetic, and mechanistic investigations of the reaction between triphenylphosphine, dialkyl acetylenedicarboxylates, and phenols have been reported " Mechanistic studies have provided insight into the phosphine-catalysed asymmetric additions of malonate esters to y-substituted allenoates and allenamides ... 

Other reactions studied include reduction of the triple bond of a-acetylenic esters and nitriles by tributyltin hydride in methanol electroreductive cyclization of acetylenic halides at a mercury cathode the trimerization and tetramerization of cyclo-octyne in the presence of various transition metals the kinetics of bromination of alka-l,3-diynes, of permanganate oxidation of acetylenedicarboxylic acid, and of iodination of propiolic acid the participation of the triple bond in reactions of various acetylenes of the general formula (225) and the trimerization of but-2-yne with tolyl-palladium chloride to give a [Pg.48]

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