title: Search for conglomerate in set of [7]helquat salts: multigram resolution of helicene-viologen hybrid by preferential crystallization.
abstract: Investigation of a set of 12 [7]helquat salts by X-ray crystal diffraction led to identification of conglomerate behavior in bis(trifluoroacetate) salt [2][CF(3)CO(2)](2). This is to demonstrate that a systematic search for conglomerates can be performed for a given helicenoid enabling straightforward multigram resolution via preferential crystallization. Subsequently, preferential crystallization of this chiral helicene-viologen hybrid has been established to obtain pure P and M enantiomers on a multigram scale, 5 g each. Furthermore, preparation of nonracemic samples of [7]helquat 2 via diastereomeric (R,R)-dibenzoyltartrate salts is described, and determination of absolute configuration and racemization barrier is also reported.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo n. 2, 166 10 Prague 6, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Vávra
authors.forename: Lukáš
authors.initials: L
authors.lastname: Severa
authors.forename: Ivana
authors.initials: I
authors.lastname: Císařová
authors.forename: Blanka
authors.initials: B
authors.lastname: Klepetářová
authors.forename: David
authors.initials: D
authors.lastname: Šaman
authors.forename: Dušan
authors.initials: D
authors.lastname: Koval
authors.forename: Václav
authors.initials: V
authors.lastname: Kašička
authors.forename: Filip
authors.initials: F
authors.lastname: Teplý