title: Synthesis and Intramolecular Azo Coupling of 4-Diazopyrrole-2-carboxylates: Selective Approach to Benzo and Hetero [c]-Fused 6H-Pyrrolo[3,4-c]pyridazine-5-carboxylates.
abstract: A high yield synthesis of fluorescent benzo, thieno, and furo [c]-fused methyl 7-aryl-6H-pyrrolo[3,4-c]pyridazine-5-carboxylates, including unprecedented heterocyclic skeletons, was performed by the transformation of methyl 4-aminopyrrole-2-carboxylate into the corresponding diazo compound, followed by intramolecular azo coupling under acid conditions onto a nucleophilic aryl or hetaryl group in the 3-position. Azo coupling is completely regioselective and, according to DFT calculations, a kinetically controlled reaction. N-Methylation of 1,3-disubstituted 2H-pyrrolo[3,4-c]cinnolines occurs selectively at N5 under kinetic control, leading exclusively to 5-methyl-5H-pyrrolo[3,4-c]cinnoline derivatives.
authors.affiliation: St. Petersburg State University , Institute of Chemistry, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
authors.forename: Ekaterina E
authors.initials: EE
authors.lastname: Galenko
authors.affiliation: St. Petersburg State University , Institute of Chemistry, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Galenko
authors.affiliation: St. Petersburg State University , Institute of Chemistry, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
authors.forename: Alexander F
authors.initials: AF
authors.lastname: Khlebnikov
authors.affiliation: St. Petersburg State University , Institute of Chemistry, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
authors.forename: Mikhail S
authors.initials: MS
authors.lastname: Novikov
authors.affiliation: St. Petersburg State University , Institute of Chemistry, 7/9 Universitetskaya nab., St. Petersburg, 199034 Russia.
authors.forename: Julia R
authors.initials: JR
authors.lastname: Shakirova