Easy Access to γ-Iodo-gem-Diborylated-Cyclopentanes and Bicyclic Cyclopropanes

A formal atom transfer radical [3+2] annulation (ATRAn) reaction between different homoallyl radical precursors and 1,1-diborylethene was developed. It provides a rapid access to polysubstituted cyclopentanes containing a gem-diboronic ester moiety. The synthetic utility of theses uniquely functionalized 5-membered rings is highlighted by their easy conversion to attractive borylated building blocks such as 1-borylated bicyclo[3.1.0]hexanes. The ATRAn reaction was extended to homopropagylic radicals giving access to unique allylic gem-diboronic esters that could be used in allylboration of aldehydes.