title: Rhodium-catalyzed oxidative C-H activation/cyclization for the synthesis of phosphaisocoumarins and phosphorous 2-pyrones.
abstract: Rhodium-catalyzed cyclization of phosphinic acids and phosphonic monoesters with alkynes has been developed. The oxidative annulation proceeds with complete conversion of phosphinic acid derivatives and allowed the atom-economic preparation of useful phosphaisocoumarins with high yield and selectivity. The reaction is tolerant of extensive substitution on the phosphinic acid, phosphonic monoester and alkyne, including halides, ketone, and hydroxyl groups as substituents. Furthermore, we found that alkenylphosphonic monoesters proceed to give a wide range of phosphorus 2-pyrones through oxidative annulation with alkynes. Mechanistic studies revealed that C-H bond metalation was the rate-limiting step.
authors.affiliation: Department of Chemistry, Kangwon National University, Chuncheon 200-701 (Republic of Korea), Fax: (+82) 33-253-7582.
authors.forename: Youngchul
authors.initials: Y
authors.lastname: Park
authors.forename: Jungmin
authors.initials: J
authors.lastname: Seo
authors.forename: Sangjune
authors.initials: S
authors.lastname: Park
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Yoo
authors.forename: Phil Ho
authors.initials: PH
authors.lastname: Lee
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D002384:Catalysis; D003374:Coumarins / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D012238:Rhodium / Q000737:chemistry*
chemical_list: D000480:Alkynes; D003374:Coumarins; D009943:Organophosphorus Compounds; D012238:Rhodium
keywords: CH activation; alkynes; annulation; cyclization; phosphorous heterocycles; rhodium