Azomethine ylides derived from 3, 4-dihydropyrrolo [1, 2-a] pyrazinium salts undergo 1, 3- dipolar cycloaddition reactions to yield 5, 6-dihydrodipyrrolo [1, 2-a: 2′, 1′-c]-pyrazine and 5, 6-dihydroimidazo [1, 2-a]-pyrrolo [2, 1-c] pyrazin-4-inium-2-olate and 2-thiolate derivatives. S-Methylation followed by nucleophilic displacement of methylthio group converted the 2-thiolate derivatives into new conjugated betaines.
[Peresada, V. P.; Medvedev, O. S.; Likhosherstov, A. M.; Skoldinov, A. P. Pharmaceutical Chemistry Journal, 1987 , vol. 21, # 9 p. 619 - 624 Khimiko-Farmatsevticheskii Zhurnal, 1987 , vol. 21, # 9 p. 1054 - 1059]