Bridged 2,2'-biazole derivatives by 1,3-dipolar cycloaddition

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 convened the 2-thiolate derivatives into new conjugated betaines