Electrochemical Intramolecular C–S Bond Formation Leading to Thienoacene Derivatives

The formation of carbon-sulfur bond is one of the fundamental and significant transformations in organic synthesis because C-S bonds are abundant and significant skeleton in the field of pharmaceuticals and material science. For instance, thienoacene derivatives, such as [1]benzothieno[3,2- b ][1]benzothiophene (BTBT) and dinaphtho[2,3- b :2’,3’- d ]thiophene (DNT), have received considerable attention as key building blocks for organic field effect transistors (OFETs). Recently, several novel methods for the construction of carbon-heteroatom bonds have been reported. In particular, electrochemical C–H activation reactions have received considerable attention as straightforward and attractive approaches for the construction of C–O, C–N, and C–S bonds. However, to the best of our knowledge, there has been no report on the application of the electrochemical C–S bond formation for the synthesis of thienoacene derivatives, although they should be a simple and attractive approach to thienoacene derivatives. From this perspective, we are focusing on an electrochemical C–S bonds formation for the synthesis of thienoacene derivatives, such as [1]benzothieno[3,2- b ]benzo[2,3- d ]furan (BTBF) and [1]benzothieno[3,2- b ]benzo[2,3- d ]thiophene (BTBT). We herein report the first electro-oxidative dehydrogenative C–S bond formation promoted by electrogenerated [Br + ] for the synthesis of BTBF and BTBT. Figure 1