Highly nucleophilic dipropanolamine chelated boron reagents for aryl-transmetallation to iron complexes

Abstract

New aryl- and heteroarylboronate esters chelated by dipropanolamine are synthesised directly from boronic acids. The corresponding anionic borates are readily accessible by deprotonation and demonstrate an increase in hydrocarbyl nucleophilicity in comparison to other common borates. The new borates proved competent for magnesium or zinc additive-free, direct boron-to-iron hydrocarbyl transmetallations with well-defined iron(ii) (pre)catalysts. The application of the new borate reagents in representative Csp2-Csp3 cross-coupling led to almost exclusive homocoupling unless coupling is performed in the presence of a zinc additive.