Ethyl acetylenecarboxylate

The three-component reaction of l,5-dimethyl-l/7-pyrrole-2-carbonitrile 1375, 277-azaphosphirene tungsten complex 1376 and ethyl acetylenecarboxylate 1377 led to the formation of the regioisomeric 277-1,2-azaphospholone complexes 1378 and 1379 (ratio 8 1) (Scheme 263) <2002POL119>. Complex 1378 was formed predominantly... 

As shown in Equation (30), furan reacted with ethyl acetylenecarboxylate under gold-catalyzed conditions to form the hydroarylation product that contained a (Z)-alkene selectively <2003EJO3485>. 

Cyclic /1-ketoesters have been treated with strong base (NaH/toluene CH3ONa/CH3OH) and afterwards with acetylenecarboxylates or ethyl propiolates. From the reaction mixture the corresponding cycloalkenes, enlarged by two carbon atoms, can be isolated in 50-70 % yield. In the transformations of / -ketoesters, given in Scheme IV/8, no intermediate could be detected. Therefore and because of the strong basic conditions used, the concept of a concerted reaction must be rejected in these cases, and a simple polar concept is preferred... 

These systems uniformly have at least one pyrimidine ring, and they are readily formed from aminodiazines, incorporating the amidine moiety, with bifunctional electrophiles serving as three-carbon fragments. In this way, most frequently, 0x0 derivatives are obtained. Alkoxymethyl-enemalonates and 2-benzoylamino-3-dimethylaminopropenoate convert the amines into 4-oxo isomers via, sometimes isolable, intermediates 2-oxo and/or 4-oxo isomers may be formed with acetylenecarboxylic or acrylic acid derivatives or with ethyl acetoacetate. The decisive factors for the regiochemistry have not yet been fully explored. The base-induced rearrangement of ethyl 2-diazanyl-5-oxo-2,5-dihydroisoxazole-4-carboxylates is also a powerful approach to the bicyclic systems. It gives 3-ethoxycarbonyl-2-hydroxy-4-oxo derivatives which present a versatile substitution pattern for further functionalization. A further important aspect of the synthetic methods discussed above is their wide applicability for preparation of the benzo-fused derivatives. 

In this reaction, the phenylhydrazone of ethyl acetoacetate was isolated as an intermediate and converted into the product. Further intermediates were detected by means of C-NMR spectroscopy [137]. Acetylenecarboxylic esters also react with hydrazines to give pyrazolones. 

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