Application of alkyl 3-dimethylamino-2-(1H-indol-3-yl)propenoates in the synthesis of 3-heteroarylindoles

Methyl and ethyl 3-dimethylamino-2-(indol-3-yl)propenoate were prepared from alkyl 3-indoleacetates and tert-butoxy-bis(dimethylamino)methane. Upon treatment of these two N,N-dimethylenaminones with α-heteroarylamines as N,N-1,3-dinucleophiles, condensed indolylpyrimidones as meridianine analogues were obtained in poor to moderate yields, while intramolecular condensations with C,O-1,3-dinucleophiles furnished condensed indolylpyranones. Similarly, reaction with hydrazinium chloride led to indolylpyrazolol, while with 3-chloro-6-hydrazinopyridazine only the dimethylamine substitution took place to give the corresponding hydrazone.