Thiophene-Fused π‑Systems from Diarylacetylenes and Elemental Sulfur

A simple
yet effective method for the formation of thiophene-fused
π-systems is reported. When arylethynyl-substituted polycyclic
arenes were heated in DMF in the presence of elemental sulfur, the
corresponding thiophene-fused polycyclic arenes were obtained via
cleavage of the ortho-C–H bond. Thus, arylethynylated
naphthalenes, fluoranthenes, pyrenes, corannulenes, chrysenes, and
benzo­[c]­naphtho­[2,1-p]­chrysenes were effectively converted into the corresponding
thiophene-fused π-systems. Apart from polycyclic hydrocarbons,
thiophene derivatives are also susceptible to this reaction. The practical
utility of this reaction is demonstrated by preparations on the decagram
scale, one-pot two-step reaction sequences, and multiple thiophene
annulations.

本研究报道了一种简便且高效的噻吩稠合π体系（thiophene-fused π-systems）合成方法。当芳基乙炔基取代的多环芳烃在单质硫存在下于N,N-二甲基甲酰胺（DMF）中加热时，通过邻位C-H键的断裂，即可得到相应的噻吩稠合多环芳烃。据此，芳基乙炔基取代的萘、荧蒽、芘、碗烯、屈以及苯并[c]萘并[2,1-p]屈可高效转化为对应的噻吩稠合π体系。除多环烃类底物外，噻吩衍生物同样可适用于该反应。该反应的实用价值通过十克级规模制备、一锅两步反应序列以及多次噻吩环化反应得到了验证。