Abstract
The reaction of 1-methyl-2-pyrrolidone dimethylacetal (IV) with dimethyl acetylenedicarboxylate (I) was carried out expecting the formation of the simple dihydroazepine derivative. However, the products actually obtained were the indoline derivative (VI), the isomeric pyrrolidone derivatives (VII and VIII) and the tetracarbomethoxy-1, 3-butenyl pyrroline derivative (IX) when dioxane was used as the solvent, while the 1 : 1 adduct (X) was found to be the main product when the reaction was carried out in benzene. On the other hand, when 1-methyl-2-methylmercapto-2-pyrroline (XIII) was employed, the desired product (XIV) was obtained as a main product along with VI, VII, the Diels-Alder adduct (XV), and dimethyl 2, 3-bis-methylmercaptosuccinate (XVI).
