Thiophene‐3,4‐dicarbaldehyde 1 reacts in the presence of 2‐mercaptoethanol to yield N‐aryl‐5,6‐dihydro‐4‐oxo‐4H‐thieno[3,4‐c]pyrroles 2 and N‐aryl‐4‐arylimino‐5,6‐dihydro‐4H‐thieno[3,4‐c]pyrroles 3, while thiophene 2,3‐dicarbaldehyde 4 reacts with aromatic amines to give N‐aryl‐5,6‐dihydro‐6‐oxo‐4H‐thieno[2,3‐c]pyrroles 5 in good yields. Labeling experiments and nmr spectral analysis give evidences for the possible reaction mechanism.
Umsetzung der Brom‐ oder Iodimidazole (I) mit EtMgBr und anschließend mit Triethylorthoformiat gibt die Acetale (II), deren Hydro1ysate, die Formyl‐Derivate (III), mit NBS zu den Brom‐formyl‐imidazolen (IV) reagieren.
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