Two Directing Groups Used for Metal Catalysed <i>Meta</i>‐C−H Functionalisation Only Effect <i>Ortho</i> Electrophilic C−H Borylation

Abstract

Two templates used in <i>meta</i>-directed C-H functionalisation under metal catalysis do not direct <i>meta</i>-C-H borylation under electrophilic borylation conditions. Using BCl₃ only Lewis adduct formation with Lewis basic sites in the template is observed. While combining BBr₃ and the template containing an amide linker only led to amide directed <i>ortho</i> C-H borylation, with no pyridyl directed <i>meta</i> borylation. The amide directed borylation is selective for the <i>ortho</i> borylation of the aniline derived unit in the template, with no <i>ortho</i> borylation of the phenylacetyl ring - which would also form a six membered boracycle - observed. In the absence of other aromatics amide directed <i>ortho</i> borylation on to phenylacetyl rings can be achieved. The absence of <i>meta</i>-borylation using two templates indicates a higher barrier to pyridyl directed <i>meta</i> borylation relative to amide directed <i>ortho</i> borylation and suggests that bespoke templates for enabling <i>meta</i>-directed electrophilic borylation may be required.