https://doi.org/10.15255/KUI.2006.037
Published: Kem. Ind. 56 (3) (2007) 135–143
Paper reference number: KUI-37/2006
Paper type: Conference paper
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To Hetero-polycyclic Compounds by Light; Reactions of Substituted Furostilbenes

I. Škorić and M. Šindler-Kulyk

Abstract

Synthetic organic photochemistry, the chemistry of excited states of a molecule, differs from the ground state chemistry and provides a simple pathway to complicated structures, heavily obtainable by a classic synthetic approach. In this paper the polycyclic structures with oxygen, prepared by photochemical methodology of new o-substituted furan heterostilbenes are reviewed. The photochemistry of -(2-furyl)-substituted-o-divinylbenzenes 6,13,15, ,‘-di(2-furyl)-substituted o-divinylbenzenes 18–20, aryl and heteroaryl analogues of 2,3-distyrylfurans 33–36 is described. Due to steric reasons, on irradiation of -(3-substituted-2-furyl)-o-divinylbenzenes 6, the preferred photoreaction was the intramolecular [2+2]-cycloaddition and formation of the bicyclo[ 2.1.1]hexenes 10 along with the formation of the corresponding phenanthrenes 12. On the other hand, furan analogues 6 and 13 give bicyclo[3.2.1]octadiene structures in very good yield. Di-substituted o-divinylbenzene derivatives 18–20 (with a hexatriene system as part of the aromatic ring) give bicyclo[3.2.1]octadiene derivatives 21–23 by intramolecular photocycloaddition and cyclophane derivatives 24–26 by intermolecular [2+2] two-fold photoaddition reaction. Compound 20 is the most selective of these o-divinylbenzenes yielding only the exo-bicyclo[ 3.2.1]octadiene derivative 23 at low concentrations, and only the cyclophane derivative 26 at high concentrations. This reaction to 23 and 26 is due - intra- or intermolecular complexation. Contrary to these results, on the irradiation of the aryl and heteroaryl analogues of 2,3-distyrylfurans 33–36 (with a hexatriene system as part of the heteroaromatic ring) different intra- and intermolecular processes have been observed. By intramolecular [2+2]-cycloaddition, this hexatriene system gives the phototransposition products. Also observed are stilbenes and phenanthrenes as secondary products obtained from the primary formed intermolecular cyclobutane adducts.

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Keywords

photochemistry, furans, heterocycles, cycloaddition, polycycles, cyclophanes