Cyclopropanation of Terminal Alkenes via Sequential Atom Transfer Radical Addition – 1,3-Elimination

An operationally simple protocol to affect an atom transfer radical addition (ATRA) of commercially available ICH₂Bpin to terminal alkenes has been developed. The intermediate iodide can be transformed in a one-pot process into the corresponding cyclopropane upon treatment with tetrabutylammonium fluoride (TBAF). This method is highly selective for the cyclopropanation of unactivated terminal alkenes over non-terminal alkenes and electron deficient alkenes. Due to the mildness of the procedure, a wide range of functional groups such as esters, amides, alcohols, ketones, and vinylic cyclopropanes are well tolerated. The whole reaction sequence relies on simple reagents such dilauroyl peroxide (DLP) and TBAF and can be run on multi-gram scales in ethyl acetate as a solvent.