Halogen-bond-assisted radical remote difunctionalization of bicyclo[1.1.1]butane skeletons†

Abstract

Transition-metal-free radical remote difunctionalization of bicyclo[1.1.1]butane skeletons in both two- and three-component fashions is presented. The reactions proceed via halogen-bond-assisted polyfluoroalkyl radical addition to newly designed 1-vinylbicyclo[1.1.1]pentanes, followed by strain-release-driven C–C bond cleavage to generate a strained cyclobutylmethyl radical. In the two-component reaction, iodine atom transfer to the resulting cyclobutylmethyl radical with polyfluoroiodides forms a broad array of strained 1,6-polyfluorocarboiodinated products, while boron atom transfer with bis(catecholato)diboron releases various strained 1,6-polyfluorocarboborylated products in the three-component reaction. This redox-neutral reaction features mild conditions, ease of operation, high atom economy, functional group tolerance, and a broad substrate scope, and offers a practical and sustainable approach for the synthesis of a range of challenging polyfluoroalkylated cyclobutane skeletons containing iodine and boron as versatile transformation handles for further useful derivatizations.