title: Site-selective electrophilic cyclization and subsequent ring-opening: a synthetic route to pyrrolo[1,2-a]quinolines and indolizines.
abstract: An efficient strategy for the synthesis of pyrrolo[1,2-a]quinolines and indolizines from pyranoquinolines via site-selective electrophilic cyclization and subsequent opening of pyran ring using silver/iodine under mild reaction conditions is described. This approach involves the preferential attack of the pyridyl nitrogen over aryl ring and leads to the formation of 5-endo-dig cyclized products. Quantum chemical calculations between C-N (ΔE(a) = 9.01 kcal/mol) and C-C (ΔE(a) = 31.31 kcal/mol) bond formation were performed in order to rationalize the observed site selectivity. Structure of the products were confirmed by the X-ray crystallographic studies. Iodo-substituted compounds generated by the electrophilic iodocyclization were further diversified via Pd-catalyzed cross-coupling reactions.
authors.affiliation: Synthetic Organic Chemistry Research Laboratory, Department of Chemistry, University of Delhi, Delhi, 110007, India.
authors.forename: Trapti
authors.initials: T
authors.lastname: Aggarwal
authors.forename: Sonu
authors.initials: S
authors.lastname: Kumar
authors.forename: Devendra K
authors.initials: DK
authors.lastname: Dhaked
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Tiwari
authors.forename: Prasad V
authors.initials: PV
authors.lastname: Bharatam
authors.forename: Akhilesh K
authors.initials: AK
authors.lastname: Verma
mesh_terms: D002384:Catalysis; D003432:Cross-Linking Reagents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003500:Cyclization; D007212:Indolizines / Q000138:chemical synthesis*; D015394:Molecular Structure; D010165:Palladium / Q000737:chemistry*; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry; D011789:Quantum Theory; D011804:Quinolines / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D003432:Cross-Linking Reagents; D007212:Indolizines; D011758:Pyrroles; D011804:Quinolines; D010165:Palladium