Visible Light Activation of Boronic Esters Enables Efficient Photoredox C(sp2)–C(sp3) Cross-Couplings in Flow

Abstract

We report herein a new method for the photoredox activation of boronic esters. Using these reagents, an efficient and high throughput continuous flow process was developed to perform a dual iridium and nickel catalysed C(sp2)–C(sp3) coupling by circumventing solubility issues associated with potassium trifluoroborate salts. Formation of an adduct with a pyridine-derived Lewis base was found to be essential for the photoredox activation of the boronic esters. Based on these results we were able to develop a further simplified visible light mediated C(sp2)–C(sp3) coupling method using boronic esters and cyano heteroarenes under continuous flow conditions