title: A forgotten chiral spiro compound revisited: 3,3'-dimethyl-3H,3'H-2,2'-spirobi[[1,3]benzothiazole].
abstract: The title compound was obtained as a side product during dimerization-oxidation steps of the carbene generated from N-methylbenzothiazolium iodide. Chromatography on (S,S)-Whelk O1 column showed on cooling a typical plateau shape chromatogram indicating an exchange between two enantiomers on the column. The thermal barrier to racemization was determined (85 kJ.mol(-1) at 10 °C) by dynamic high-performance liquid chromatography (DHPLC).The absolute configuration of the first (M) and second eluted (P) enantiomers on the (S, S)-Whelk O1 column was established by comparing the reconstructed circular dichroism (CD) spectra from the CD detector signal and the calculated CD spectrum of the (P) enantiomer. Mass spectrometry revealed that 3,3'-dimethyl-3H,3'H-2,2'-spirobi[[1,3]benzothiazole] can be viewed as a masked thiophenate attached to a benzothiazolium framework.
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Angélique
authors.initials: A
authors.lastname: Lindamulage De Silva
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Vesna
authors.initials: V
authors.lastname: Risso
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Jean
authors.affiliation: Spectropôle, Aix Marseille Université, Marseille, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Giorgi
authors.affiliation: Spectropôle, Aix Marseille Université, Marseille, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Monnier
authors.affiliation: Spectropôle, Aix Marseille Université, Marseille, France.
authors.forename: Jean-Valère
authors.initials: JV
authors.lastname: Naubron
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vanthuyne
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Farran
authors.affiliation: Aix Marseille Université, Centrale Marseille, CNRS, iSm2 UMR 7313, 13397, Marseille, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Roussel
keywords: axial chirality; carbene dimerization; oxidation of carbene dimer; racemization barrier; spiro heterocycle