Iron-Catalyzed Radical-Mediated 1,3-Azidoalkylation of Bicyclo[1.1.0]butanes: Access to 1,1,3,3-Tetrasubstituted Cyclobutanes via Strain Release

An iron-catalyzed proton-coupled electron transfer (PCET)-mediated radical 1,3-azidoalkylation of bicyclo[1.1.0]butanes (BCBs) with diazo compounds and TMSN 3 is presented. Iron-catalyzed PCET activates diazo compounds to generate alkyl radicals rather than the more common carbenes. These radicals undergo addition to BCBs, followed by iron-mediated azide transfer, affording highly functionalized 1,1,3,3-tetrasubstituted cyclobutanes with good yields and stereoselectivity.