Conformational properties and chiral separation of dibenzo[b,f]thieno[3,4-d]-fused oxepines and thiepines

Abstract

The dynamic properties of planar chiral 1-hydroxymethyl-substituted dibenzo[b,f]thieno[3,4-d]-fused oxepine and thiepine derivatives have been investigated by use of variable-temperature nuclear magnetic resonance spectroscopy combined with line-shape analysis, chiral column chromatography, and molecular modelling. NMR data and computational studies revealed the height of the energy barrier for ring inversion in thiepine derivatives was sufficient to enable the existence of a pair of conformational enantiomers at ambient temperature. Their resolution was achieved by chiral column high-performance liquid chromatography (HPLC). The absolute conformation of the enantiomers is proposed. This is the first chromatographic separation of planar chiral enantiomers of [b,d,f]-fused thiepine derivatives.

Electrophilic Cyanative Alkenylation of Arenes

“…(See the Supporting Information for the X-ray structures of 13b,e–g . ) In fact, from all cyclohepta-1,3,5-trienes prepared, only the more sterically demanding 13e and 13f could be resolved into the corresponding enantiomers by chiral stationary phase chromatography (IG-u, Hex/ i PrOH 99:1, 298 K for 13e ; and IG-u, Hex/ i PrOH 97:3, 288 K for 13f ). Moreover, for 13e , which hardly racemizes at room temperature, the circular dichroism spectra of both isolated fractions were measured.…”