A synthetic method to construct boron-handled cyclic molecules was developed based on a radical borylation/cyclization cascade of 1,6-enynes. The process was initiated by the chemo- and regio-controlled addition of an N-heterocyclic carbene-boryl radical to an alkene or alkyne, followed by ring closure to afford boron-substituted cyclic skeletons. Further molecular transformations of the cyclic products to synthetically useful building blocks were also demonstrated.