Acetylenedicarboxylic acid esters

Acetylenedicarboxylic acid ester reacts with (184) in benzene-pentene at 20 °C to give the 3 1 adduct (185) (77AG(E)177). 

Acetylenedicarboxylic acid esters and related activated alkynes are routinely used as dipolarophiles for diazo dipoles. Recent examples include the use of diazo compounds 20 (49), 23 (51), and 24 (52) (Scheme 8.7), 25 (56) (Scheme 8.8), diazoacetaldehyde dimethylacetal (41) (which after cycloaddition and deprotection gave the corresponding pyrazole-3-carbaldehyde), ethyl 3-diazopyruvate (270), p-tolyl-trifluoromethyldiazomethane (271), bis(trifluoromethyl)diazomethane (272), and diazomethylenephosphoranes (60). 

Ammonium ylides generated in this way are useful as a route to alkenes. Of more interest, nonstabilizcd immonium ylides can be prepared in situ from imines and trapped with a dipolarophile. This sequence provides a route to pyrrolines by reaction of azomethine ylides with acetylenedicarboxylic acid esters. 

The cycloaddition chemistry of pyridones (695) is quite analogous to that of the a-pyrones (79CC1091). Pyridones will react under high pressure conditions with acetylenedicarboxylic acid esters to furnish cycloadducts (696) which when heated expel a molecule of an isocyanate to yield substituted aromatics (697 Scheme 163). 

The last factor often is the one that determines the reaction rates of [4+2]-cycloadditions. This factor allows one to understand, for example, why the cycloadditions of ethene or acetylene with butadiene (cf. Figure 15.1) occur only under rather drastic conditions, while the analogous cycloadditions of tetracyanoethene or acetylenedicarboxylic acid esters are relatively rapid. As will be seen, a simple orbital interaction between the reagents at the sites where the new a bonds are formed is responsible for this advantageous reduction of the activation energies of the latter two reactions. 

Quinoxalinones result from the reaction of o-phenylenediamines and acetylenedicarboxylic acid, as exemplified by the synthesis of 3,6,7-trimethylquinoxalin-2-one (18) The corresponding condensation reactions with acetylenedicarboxylic acid esters yield 3-alkoxycarbonyl-methylenequinoxalin-2-ones, which on hydrolysis and rearrangement give... 

Ring expansion by 2 C-atoms with acetylenedicarboxylic acid esters... 

The products of the reaction of acetylenedicarboxylic acid esters with 4,5-dihydro- 1 //-pyrazole-1 -carbothioamides and 3,4,5,6-tetrahydro-2/f-1,2,4-triazepine-3-thiones have been characterized by Danilkina et by the use of NMR parameters including Vhc and couplings. In particular, the /h5C4 couplings of 5.0 Hz observed for methyl esters of (2Z)-[2-(3-methyl-4,5-dihydro-l TZ-pyrazol-1-yl)-4-oxo-1,3-thiazol-5(4//)-ylidene]ace-tic acids have provided evidence that the exocyclic double bonds in these compounds are of the Z configuration, which corresponds to the mechanism reported by the authors for the trans addition of the SH group to the triple bond in DM AD. 

Hekmatshoar and coworkers synthesized benzo-A -heterocycles using nano-CuO as the heterogeneous catalyst (Sadjadi et al., 2010). Several benzoxazinone, benzothiazinone, and quinoxalinone derivatives were rapidly assembled in good to excellent yields from the aromatic amines and acetylenedicarboxylic acid esters (Scheme 4.49). The water-resistant catalysts were environmentally benign, and could be easily synthesized, stored, and recycled. 

Isocyclics from enamines and acetylenedicarboxylic acid esters s. 18, 759... 

Azavinylogous amidinium salts (188 equation 103) were obtained by treatment of triazenes with methyl iodide. Acetylenedicarboxylic acid ester reacts with the diazonium salt (189 equation 104) via cycloaddition to give the imidazolium salt (190). ... 

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