title: Unveiling the uncatalyzed reaction of alkynes with 1,2-dipoles for the room temperature synthesis of cyclobutenes.
abstract: 2-(Pyridinium-1-yl)-1,1-bis(triflyl)ethanides have been used as 1,2-dipole precursors in a metal-free direct [2+2] cycloaddition reaction of alkynes. Starting from stable zwitterionic pyridinium salts, the electron deficient olefin 1,1-bis(trifluoromethylsulfonyl)ethene is generated in situ and immediately reacted at room temperature with an alkyne to afford substituted cyclobutenes. Remarkably, this mild and facile uncatalyzed protocol requires neither irradiation nor heating.
authors.affiliation: Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040-Madrid, Spain. alcaideb@quim.ucm.es.
authors.forename: Benito
authors.initials: B
authors.lastname: Alcaide
authors.forename: Pedro
authors.initials: P
authors.lastname: Almendros
authors.forename: Israel
authors.initials: I
authors.lastname: Fernández
authors.forename: Carlos
authors.initials: C
authors.lastname: Lázaro-Milla
mesh_terms: D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D061565:Cycloaddition Reaction; D011726:Pyridinium Compounds / Q000737:chemistry*; D013696:Temperature
chemical_list: D000475:Alkenes; D000480:Alkynes; D011726:Pyridinium Compounds; C558934:butylene