Synthesis of Borylated Orphaned Cyclopropanes through a Boron-Enabled Cycloisomerization Reaction

Cyclopropanes are important building blocks that are used widely in the pharmaceutical and agrochemical industries. However, synthesizing highly substituted cyclopropanes has proven to be challenging. Herein, we disclose a new strategy to prepare borylated cyclopropanes through the use of a boron-enabled cycloisomerization reaction. The method relies on the generation of a triplet biradical through an energy transfer process. Subsequent 1,2-boron shift leads to the formation of a triplet 1,3-biradical, which is poised to undergo radical recombination in concert with intersystem crossing. The generated borylated cyclopropanes are useful intermediates, as a variety of highly substituted cyclopropanes can be easily prepared.