Dimerisation of aryl-substituted bicyclobutanes (BCBs): revealing a new mode of 1,3-dipolar background reactivity

We present a detailed investigation of dimerisation reactions involving bicyclo[1.1.0]butanes (BCBs), catalysed or mediated by Lewis or Brønsted acids. The study is supported by optimisation experiments for distinct dimers and corresponding mechanistic analyses, including DFT investigations. By carefully selecting the reaction conditions, the dimerisation outcome can be directed toward the formation of the desired product. The observed processes reveal a novel type of 1,3-dipolar reactivity in BCBs involving aryl substituents, which holds potential for the construction of new molecular scaffolds that are inaccessible through conventional synthetic methods.