We described a general approach to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered heteroaromatic rings as thiophenes, furans and pyrroles through a 6π-elctrocyclization reaction of keteniminium salts. We investigated various substituents not only on the aromatic rings, but also at C-2 and on the nitrogen atom of the keteniminium salt. In particular, we have determined the electronic requirements of the nitrogen substitution to secure the efficient formation of the corresponding keteniminium salt. A clear relation between the pK_a of the amine leading to the formation of the keteniminium salt and the yield obtained for benzothiophene is established and should find broad application to other reactions involving these intermediates. Additional insight on the ease of this 6π-electrocyclization reaction was gained through competition reactions and DFT calculations.

我们描述了通过酮亚胺盐的6π-电子环化反应将3-氨基苯并噻吩和3-氨基噻吩与5-元杂芳族环稠合为噻吩，呋喃和吡咯的一般方法。我们不仅研究了芳环上的各种取代基，而且还研究了烯酮铵盐的C-2和氮原子上的各种取代基。特别是，我们确定了氮取代的电子要求，以确保有效形成相应的酮亚胺盐。pK _a之间的明确关系确定胺的形成导致烯属铵盐的形成，并确定了苯并噻吩的收率，应将其广泛应用于涉及这些中间体的其他反应中。通过竞争反应和DFT计算，获得了对该6π-电环化反应的难易程度的其他见解。