Bis(oxo/thioxothiazolinyl) aromatic compounds - Synthesis and conformational assignment

A series of bis(oxo/thioxothiazolinyl) aromatic atropisomers with two chira l C(aryl)-N(heterocycle) axes was synthesized. The separation of antiparall el, parallel diastereomers was achieved by chromatography on silica. Confor mational assignment for the bis-thione atropisomers la,b-4a,b and bis-one a tropisomers 9a,b-12a,b was based on polarimetric results in analytical chir al chromatography on microcrystalline cellulose triacetate. The relationshi p conformation-H-1 NMR chemical shifts, found for the bis-thiones and bis-o nes was successfully applied for the conformational assignment of thione-on e atropisomers not assigned by chiral liquid chromatography.