title: Observation of Diastereomeric Interconversions of β-Sulfinylsubporphyrins as Evidence for Bowl Inversion.
abstract: B-Methoxy β-(4-methoxyphenylsulfinyl)subporphyrin and B-phenyl β-(4-methoxyphenylsulfinyl)subporphyrin were synthesized by oxidation of the corresponding β-sulfanylsubporphyrins with m-chloroperbenzoic acid and were separated into diastereomers, respectively. B-Methoxy subporphyrin diastereomers were interconverted to each other in methanol or ethanol, whereas such interconversion was not observed for B-phenyl subporphyrin diastereomers even at high temperature. Diastereomeric interconversions of B-methoxy subporphyrins were dramatically accelerated by addition of trifluoroacetic acid. These results suggest that the diastereomeric interconversions of B-methoxy subporphyrins, namely, their bowl inversions, proceed via a mechanism involving protonation-induced generation of subporphyrin borenium cations followed by nucleophilic attacks by alcohols.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan), Fax: (+81) 75-753-3970.
authors.forename: Kota
authors.initials: K
authors.lastname: Yoshida
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan), Fax: (+81) 75-753-3970. osuka@kuchem.kyoto-u.ac.jp.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
keywords: bowl inversion; chirality; diastereoselectivity; porphyrinoids; sulfoxides