Synthesis of some 5-aryl-2,2′-dipyrromethenes as analogs of prodigiosin†

摘要: Three new dipyrromethenes have been synthesized as analogs of prodigiosin: 3-methoxy-5-phenyl-2,2′-dipyrromethene (10a), 3-methoxy-4 -pentyl-5-phenyl-5′-methyl-2,2′-dipyrromethene (10b), and 3-methoxy-4′-pentyl-5′-methyl-5-(2″-thienyl)-2,2′-dipyrromethene (10c). The Michael addition ethyl glycinate to an appropriate arylidenemalonate, quenched with chloroformate followed by a Dieckmann cyclization gave diethyl 1-ethoxycarbonyl-3-oxo-5-phenyl thienylpyrrolidine-2,4-dicarboxylate, 2a 2b. Methylation the highly enolic keto-esters, oxidation N-ethoxycarbonylpyrroles led, after elaboration pyrrole nucleus, 2-phenyl- 2-thienyl-4-methoxypyrroles. acid catalyzed condensation these arylmethoxypyrroles either pyrrole-2-carboxaldehyde or 5-methyl-4-pentylpyrrole-2-carboxaldehyde led 10a, 10b 10c.