REACTIVITY OF CONDENSED THIOPHENES IN THE DIELS-ALDER REACTION - THE REACTIVITY OF 3-AMINOTHIENO[3,4 3',4'] BENZO[B]PYRANONE - 3-AMINOTHIENO[3,4-C]QNINOLINE AND OF 5-AMINO-7-SUBSTITUTED THIENO[3,4-D]PYRIDAZINONE TOWARD ELECTRON-POOR OLEFINS AND ACETYLENES/

The thieno [3,4:3',4'] benzo [b] pyranone (3b) and the thieno [3,4-c] quinoline (3c) are prepared via reacting 4-methylcoumarin-3-carbonitri le (9a) and 4-methyl-2-oxo-1,2-dihydroquinolin-3-carbonitrile (9b) wit h elemental sulphur. Similarly the thieno [3,4:3`,4`] naphtho [1,2-b] pyran (11) is prepared from reaction of (10) and elemental sulphur. Th e condensed thiophenes (3b,c) and (11) react with a variety of electro n-poor olefins to yield products of addition followed by hydrogen sulp hide elimination. The reaction of (3b,c) and (11) with ethyl propiolat e in refluxing dioxane/acetic acid mixture affords the condensed thiep ins (24a,c). The nature of product of reaction of (3b,c) and (11) with dimethyl acetylenedicarboxylate is dependent on applied reaction cond itions. Thus the reaction of (3b,c) and (11) with dimethyl acetylenedi carboxylate in refluxing dioxane afforded condensed thiepins while at 250 degrees C products of addition and desulfurization are obtained. W hereas thienopyridazinones (la,b) react with ethyl acrylate and diethy l fumarate to yield thiadiazaacenaphthenones (31a-c) respectively, com pounds (1a,b) react with N-phenylmaleimide to yield phthalazine (32). The thienopyridazinone (1c) failed to react with the same reagents und er similar conditions. Copyright (C) 1996 Elsevier Science Ltd.