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The regioselective ipso-formylation of electron-rich, 3,4-push-pull-substituted 2-chlorothiophenes under Vilsmeier-Haack conditions was performed in good yields. The synthetic scope of this new reaction was explored using various halothiophenes, chloroanilines, and 1-methyl-3-chloroindole. In comparison with their structural C-H analogs the chlorinated thiophenes, anilines, and the indole proved to be less reactive toward electrophilic attack by chloromethyleniminium salts.

The unique synthesis of 3‐amino‐4‐nitrothiophenes 2 provides easy access to reference species of a new family of push‐pull substituted thiophenes. The chemoselective modification of 2 into suitable derivatives was accomplished by selective S‐oxidation of the vinylsulfanyl unit, followed by substitution of the vinylsulfinyl group of 3 by nucleophiles. Dihalothiophenes were formed this way in very good yields. A subsequent selective dehalogenation at the 2, 5 or 2 and 5 positions also proved feasible, and the push‐pull unit was untouched. The new 2,5‐dihalothiophenes could be interesting monomers for conducting polymers.

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Neben einer Literaturübersicht (48 Zitate) wird die Partialsynthese von Chrysophanol (II) ausgehend von Aloin (I), dem wirksamen Anthron‐Glucosi von Aloe und Senna, sowie die Oxidation der in Chrysarobin enthaltenen Anthrone zu Physcion (III) mit CrO3 und dessen Umwandlung in Frangula‐ Emodin (IV) durch AlCl3/NaCl‐Schmelze beschrieben.