Collect. Czech. Chem. Commun. 2000, 65, 651-666
https://doi.org/10.1135/cccc20000651

Sterically Crowded Heterocycles. XII. Atropisomerism of (1-Aryl-3,5-diphenyl-1H-pyrrol-2-yl)(phenyl)methanones

Robert Klvaňaa, Radek Pohla, Jan Pawlasa, Jan Čejkab, Hana Dvořákovác, Richard Hrabalc, Stanislav Böhma,*, Bohumil Kratochvílb and Josef Kuthana

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic
b Department of Solid State Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic
c Laboratory of Nuclear Magnetic Resonance, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic

This article is part of serial Sterically crowded heterocycles.

Abstract

Some 1-(2-substituted phenyl)- and 1-(1-naphthyl)-2,4,6-triphenylpyridinium perchlorates were treated with potassium hexacyano ferrate(III)-potassium hydroxide reagent to give the title pyrroles. Restricted rotation around the C-N bond in the products is demonstrated by NMR experiments with homochiral shift reagents, by semiempirical PM3 calculations as well as using their atropodiastereoselective and enantioselective transformations. Racemisation barriers for the (R)-2-(N-methyl-N-phenylcarbamoyl) derivative were estimated from NMR and polarimetric measurements.

Keywords: Pyrroles; Pyridinium salts; Atropisomerism; Axial chirality; Biaryls; Racem- isation; Semiempirical calculations; X-Ray diffraction.

References: 25 live references.