title: 2-(Pyridinium-1-yl)-1,1-bis(perfluoroalkylsulfonyl)ethan-1-ide: A Practical Reagent for Synthesis of Strongly Acidic 1,1-Bis(perfluoroalkylsulfonyl)alkanes.
abstract: On mixing (RfSO2)2CH2(Rf=perfluoroalkyl), paraformaldehyde, and substituted pyridines, a three-component reaction proceeded smoothly to give unusual zwitterions bearing both pyridinium and stabilized carbanion moieties in good to excellent yields. Of these, 2-fluoropyridinium derivatives rapidly dissociated in acetonitrile to give equilibrium mixtures of the zwitterions and (RfSO2)2C=CH2/2-fluoropyridine, as confirmed by detailed variable-temperature NMR studies. The dynamic behavior of such 2-fluoropyridinium compounds allows them to be used as shelf-stable, easy-to-handle sources of (RfSO2)2C=CH2. With these reagents, strongly acidic carbon acids (RfSO2)2CHR were synthesized, which served as a new type of acid catalysts. Moreover, C-C bond-forming reactions with a ketene silyl acetal proceeded efficiently with Tf2C=CH2generated in situ.
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Hikaru
authors.identifier: http://orcid.org/0000-0003-4638-5113
authors.initials: H
authors.lastname: Yanai
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Ryuta
authors.initials: R
authors.lastname: Takahashi
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kotani
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hakamata
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo, 192-0392, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsumoto
keywords: Lewis acids; acidity; multicomponent reactions; organocatalysis; zwitterions