Reaktionsverhalten von β-Oxo-carbonsäurederivaten der Anthracenreihe bei der Synthese von Thiophenen

Summary

β-Oxo-1-anthracenepropionate (3) reacts step by step with phenylisothiocyanate and α-CH-acidic halo compounds to keten-S,N-acetals4, followed by cyclocondensation to give the 4-(1-anthracenyl)-thiophene-3-carboxylates5. In contrast, the reaction of β-oxo-9-anthracenepropionate (6) with isothiocyanates and α-CH-acidic halo compounds yields 5-acyl-2-amino-3-(9-anthracenoyl)-4-hydroxy-thiophenes8. This is caused by the sterical hindrance of the keto group of the anthracene in position 9; thus, the cyclocondensation proceedsvia reaction of the ester group of the β-oxo-propionate. In the same way, 9-acetylanthracene reacts with phenylisothiocyanate and α-CH-acidic compounds to keten-S,N-acetals10 and, in an additional step, to 2-anilino-3-(9-anthracenoyl)-thiophenes11 and 2-(9-anthracenoyl)-methylene-3,4-diphenyl-2,3-dihydro-(1,3)-thiazole12, respectively. The structure of all new compounds was determinated by 2D NOESY NMR spectroscopy.