Collect. Czech. Chem. Commun. 1996, 61, 1473-1488
https://doi.org/10.1135/cccc19961473

Sterically Crowded Heterocycles. VIII. Preparative Photoisomerization of Some Imidazo[1,2-a]pyridines

Richard Kubíka, Stanislav Böhma, Jan Čejkab, Vladimír Havlíčekc, Tomáš Strnada, 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 Institute of Microbiology, Academy of Sciences of the Czech Republic, 144 20 Prague 4,Czech Republic

This article is part of serial Sterically crowded heterocycles.

Abstract

UV-Illumination of (Z)-3-(2-phenylimidazo[1,2-a]pyridin-3-yl)-1,3-diphenylprop-2-en-1-one (1a) or its 6-methyl and 6-iodo derivatives 1c and 1g resulted in minor (E)-isomers 2a, 2c, and 2g and prevailing (E,Z)-mixtures of N-(pyridin-2-yl)-[(3,5-diphenylfuran-2-yl)phenylmethylidene]amines 3a, 3c, and 3g while only corresponding furanoic derivatives 3b and 3d-3f were obtained from 5-methyl (1b), 7-methyl (1d), 8-methyl (1e), and 5-phenyl (1f) derivatives of the (Z)-ketone 1a. VIS-Illumination of (Z)-1,3-diphenyl-3-(2-phenylimidazo[1,2-a]benzo[I]quinolin-3-yl)prop-2-en-1-one (4) led to N-(benzo[h]quinolin-2-yl)-[(3,5-diphenylfuran-2-yl)phenylmethylidene]amine (5). Photoisomers 2a, 2c, 2g, 3a-3g, and 5 were isolated and the molecular structure of 3c was X-ray determined. Mechanism of the photoisomerization is discussed using semiempirical quantum chemical calculations and compared with mass spectra of compounds 1a, 2a, 3a, 1g, 2g, and 3g.

Keywords: Photoisomerization; Imidazo[1,2-a]pyridines; PM3 method; X-Ray structure determination.