Collect. Czech. Chem. Commun. 1998, 63, 662-680

Synthesis of Some New Functionalized 2,4,4,6-Tetraphenyl-4H-thiopyrans and Study on Their Photocolouration

Jiří Kroulíka, Martin Chadima, Miroslav Polášekb, Stanislav Nešpůrekc and Josef Kuthana

a Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic
b J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic
c Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic


A series of nineteen new 2,4,4,6-tetraphenyl-4H-thiopyrans both symmetrically and asymmetrically functionalized in the 3- and 5-positions of the 4H-thiopyran ring (-Br, -NO2, -CN) and/or in the 4-positions of the 2- and 6-phenyl groups (-Br, -CN, -OMe, -CO-Ph, -COCF3, -CO2H) was prepared and the influence of the substituents on their photocolouration was followed. The title compounds were prepared by substitution reactions of the parent thiopyrans or by cyclization of suitably substituted 1,3,3,5-tetraarylpentane-1,5-diones. The substances lacking the 3,5-substituents exhibited blue or green UV-photocolouration while the 3- and/or 5-substituted species did not. Typical bleaching process for a selected compound is analyzed in terms of dispersive first-order kinetics.

Keywords: Thiopyrans; Cyanodebromination; Lithiodebromination; Photocolouration; Hypervalent structures; Photochromism; Photochemistry.