R. Vydzhak, S. Panchishin
Sep 24, 2008
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Journal
Russian Journal of General Chemistry
Abstract
Pyrano[2,3-c]pyrroles constitute a poorly explored class of fused heterocyclic compounds. We have found only one publication where the synthesis of such compounds containing an alkoxycarbonyl or carboxy group in the 2-position has been described [1]. We have developed a new synthetic approach to pyrano [2,3-c]pyrrole-4,7-dione derivatives on the basis of methyl (E)-6-phenyl-2,4-dioxohex-5-enoate (I) [2]. By heating equimolar amounts of compound I, aromatic aldehyde IIa or IIb, and 2-aminothiazole (III) in glacial acetic acid for a short time we obtained the corresponding 5-aryl-3-hydroxy-4-(3-phenylprop-2enoyl)-1-(1,3-thiazol-2-yl)-1,5-dihydro-2H-pyrrol-2ones IVa and IVb in moderate yield. Compounds of type IV have been reported previously [3]. The structure of pyrroles IVa and IVb was confirmed by elemental analyses and IR and H NMR spectra. On heating in DMSO in the presence of a catalytic amount of iodine, compounds IVa and IVb underwent intramolecular cyclization to 5-aryl-2-phenyl-6-(1,3thiazol-2-yl)-5,6-dihydropyrano[2,3-c]pyrrole-4,7-diones Va and Vb, respectively. Such cyclization with formation of pyran ring is used in the chemistry of chromone [4, 5]. DOI: 10.1134/S1070363208080331