Photocatalytic Defluorinative Borylation of α-(Trifluoromethyl)styrenes

Abstract The defluorinative radical borylation of α-(trifluoromethyl)styrenes is a novel access to diverse difluoroalkene-aminoboranes in good yields. Using the boryl radical precursor borobetaine gives the key boryl radical that reacts with the α-(trifluoromethyl)styrene forming the initial C–B bond. Then a radical-polar crossover mechanism releases fluoride to provide a difluoroalkene product bearing the aminoborane synthetic handle. The difluoroalkene motif is of interest as a potent carbonyl bioisostere that has been shown to enhance biological activity and reactivity. The presence of the aminoborane moiety allows further functionalization such as Suzuki–Miyaura cross-coupling of the borylated products, which is demonstrated using complex aryl bromides. Various post-functionalizations demonstrate difluoroalkene-aminoboranes to be valuable building blocks for the construction of complex, high-value molecules.