Chloride Acetylene-dicarboxylic acid

Acetylene dicarboxylic acid esters react analogously [446]. Methyl buty-nene reacts at 80 °C and a pressure of 700 atm in the presence of bis-tri-phenylphosphine palladium-(Il)-chloride to give 1.2-dimethyl propene-(l)-dicarboxylic acid-(1,3) diethyl ester [448],... 

Mesoionic 4-amino-l,2,3,5-thiatriazoles constitute the only class of mesoionic 1,2,3,5-thiatriazoles known. They are prepared by the reaction of l-amino-l-methyl-3-phenylguanidine with approximately 2 equivalents of thionyl chloride with pyridine as solvent (88ACS(B)63>. They are obtained as the yellow 1 1 pyridine complexes (17). The dark-violet mesoionic 1,2,3,5-thiatriazole (18) was liberated on treatment with aqueous potassium carbonate (Scheme 3). The structure is established on the basis of elemental analysis and spectroscopic data. In particular, the IR spectrum is devoid of NH absorptions. Compound (18) exhibits a long-wavelength absorption at 463 nm in methanol. When mixed with an equivalent amount of pyridinium chloride, complex (17) is formed and the absorption shifts to 350 mn. The mesoionic thiatriazoles are sensitive towards mineral acids and aqueous base and although reaction takes place with 1,3-dipolarophiles such as dimethyl acetylene-dicarboxylate, a mixture of products were obtained which were not identified. 

Treatment of 1-methylbenzotrisizole (81) with dimethyl acetylene-dicarboxylate gave the 2 1 adduct 82, which on reduction with stannous chloride in hydrochloric acid gave the pyrrolo compound 83. It has recently been demonstrated that the product from the reaction of the acetylenic ester with the benzimidazole 4 is the pyrroloquinoxalinone 57 ... 

Fumaroyl chloride is a useful acetylene equivalent in the Diels-Alder reaction. After hydrolysis of the adduct to the dicarboxylic acid, oxidative decarboxylation serves to generate the olefin double bond. 

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