title: Formation of condensed 1H-pyrrol-2-ylphosphonates and 1,2-dihydropyridin-2-ylphosphonates via Kabachnik-Fields reaction of acetylenic aldehydes and subsequent 5-exo-dig or 6-endo-dig cyclizations.
abstract: Kabachnik-Fields reactions of various carbocyclic or heterocyclic acetylenic aldehydes together with subsequent Lewis acid catalyzed cyclizations have been studied. It was found that 5-exo-dig versus 6-endo-dig cyclization mode strongly depends on the structure of starting materials. Thus, nonaromatic acetylenic α-anilinomethylphosphonates underwent gold(III)-catalyzed or iodine-mediated 5-exo-dig cyclization to 1H-pyrrol-2-ylphosphonates. In contrast, electron-withdrawing heteroaromatic substrates formed 1,2-dihydropyridin-2-ylphosphonate ring containing materials via an exclusive 6-endo-dig ring-closure process. The dual mode of cyclization is possible only for α-amino (2-alkynylphenyl)methylphosphonates containing a benzene ring.
authors: Department of Organic Chemistry, Faculty of Chemistry, Vilnius University , Naugarduko 24, LT-03225 Vilnius, Lithuania.
authors: Rita
authors: R
authors: Bukšnaitienė
authors: Aurelija
authors: A
authors: Urbanaitė
authors: Inga
authors: I
authors: Čikotienė
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D003500:Cyclization; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D009943:Organophosphorus Compounds; D011725:Pyridines; D011758:Pyrroles