title: Structure and unexpected chiroptical properties of chiral 4-pyrrolidinyl substituted 2(5H)-furanones.
abstract: Planar 2(5H)-furanones substituted at C4 with a chiral pyrrolidinyl group show CD spectra which are apparently due to the distortion of the C4-N1 bond of sp2 character from the plane defined by the 2(5H)-furanone ring atoms and/or due to the presence of substituents in the pyrrolidine ring. This is a new, previously not encountered structural factor determining the chiroptical properties of 2(5H)-furanones and emerging from the analysis of X-ray diffraction data and quantum mechanical DFT computations. In the presence of a C5 pseudoaxial substituent in the furanone ring, the sign of the furanone n-pi* and pi-pi* transition Cotton effects is determined primarily by the previously postulated allylic helicity rule.
authors.affiliation: Department of Chemistry, A. Mickiewicz University, Poznan, Poland. gawronsk@amu.edu.pl
authors.forename: Jacek
authors.initials: J
authors.lastname: Gawroński
authors.forename: Krystyna
authors.initials: K
authors.lastname: Gawrońska
authors.forename: Marcin
authors.initials: M
authors.lastname: Kwit
authors.forename: Karol
authors.initials: K
authors.lastname: Kacprzak
authors.forename: Urszula
authors.initials: U
authors.lastname: Rychlewska