Radical Borylation/Cyclization Cascade of 1,6-Enynes for the Synthesis of Boron-Handled Hetero- and Carbocycles

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.