Vinyl cation-mediated intramolecular hydroarylation of alkynes using pyridinium reagents

Once considered to be exotic species of limited synthetic utility, vinyl cations have recently been shown to be highly versatile intermediates in a variety of processes. Here, we report a method for the synthesis of aryl-substituted benzocycloheptenes and -hexenes using the hydrotriflate salt of an electron-poor pyridine as a uniquely efficient proton source for a vinyl cation mediated Friedel-Crafts cyclization. The mild conditions made possible by this reagent allowed a range of simple and functionalized alkynes bearing pendant aryl groups to serve as suitable substrates for this scalable and convenient protocol.

Automated summary

In this study, a method for the synthesis of aryl-substituted benzocycloheptenes and -hexenes using vinyl cation mediated Friedel-Crafts cyclization was reported. The hydrotriflate salt of an electron-poor pyridine was used as a unique and efficient proton source in this process. The mild conditions enabled a wide range of alkynes to be used as substrates in this scalable and convenient protocol.