title: Resolution and rotational barriers of quinolinone and acridone sulfenamide derivatives: demonstration of the S-N chiral axis.
abstract: Achiral (8a) and chiral (8b) N-(2,4-dinitrobenzenesulfenyl)acridone derivatives were synthesized. Addition of the chiral solvating agent (S)- 2,2,2-trifluro-1-(anthryl)ethanol to 8a rendered the enantiotopic groups on the acridone ring diastereotopic and anisochronous, thus allowing the estimation of a lower limit for the rotational barrier about the S-N bond (18.7 kcal mol(-)(1)) by NMR spectroscopy. 8b and the previously reported chiral sulfenamide 5 (Raban, M.; Martin, V. A.; Craine, L. J. Org. Chem. 1990, 55, 4311) were resolved on a Chiracel OD HPLC column. This constitutes the first resolution of stereostable enantiomers of a compound in which the chirality is due only to the presence of the S-N chiral axis. The rotational barriers of both compounds are nearly equal (22.7-22. 8 kcal mol(-)(1) at 303.7 K) and are the largest determined to date for the rotation about the S-N bond in sulfenamides. The relatively high enantiomerization barrier for 8b is remarkable since the peri positions are unsubstituted.
authors: Department of Chemistry, Ben Gurion University of the Negev, Beer-Sheva 84105, Israel.
authors: M
authors: M
authors: Ben-David Blanca
authors: C
authors: C
authors: Yamamoto
authors: Y
authors: Y
authors: Okamoto
authors: S E
authors: SE
authors: Biali
authors: D
authors: D
authors: Kost