Radical-Polar Crossover Reactions of Dienylboronate Complexes: Synthesis of Functionalized Allylboronic Esters.

Radical-polar crossover reactions of dienylboronate complexes are applied to the synthesis of functionalized secondary and tertiary allylboronic esters. The transition-metal-free three-component coupling uses readily accessible dienylboronate esters as substrates in combination with various sp/sp carbon nucleophiles and commercial alkyl iodides as radical precursors. In the visible light-initiated radical chain process, two new C-C bonds are formed, and the E-double bond geometry in the product allylboronic esters is controlled with good to excellent selectivity.