Metal-catalysed Hydroboration of Amide-containing Styrenes

Hydroboration of alkenes is one of the most important methods for preparing alkylboron reagents. While alkylboronic esters are considered to be functional group compatible reagents, methods to prepare them do not always show the same tolerance. In this work, we explore the hydroboration of amide-containing styrenes using catalysts derived from Cu, Ir and Rh. Tertiary amides were found to be compatible with each method we tested. However, secondary amides, with an acidic NH bond, were only successfully hydroborated with Ir and Rh catalysts, but not the Cu-catalyst. The selectivity of hydroboration was consistent with previous findings, with Cu giving only branched products, Ir giving linear only products, and Rh favouring branched products though with variable regioselectivity. Finally, an amide-containing benzylic boronic ester was successfully used in a range of transformations of the boron group, including Cu-catalysed amination, Suzuki-Miyaura cross coupling, and oxidation.