Hydrogenation of Borylated Arenes.

A cis-selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by rhodium cyclic (alkyl)(amino)carbene (Rh-CAAC) is reported. The reaction tolerates a variety of boron-protecting groups and provides direct access to a broad scope of saturated, borylated carbo- and heterocycles with various functional groups. The transformation is strategically important because the versatile saturated boronate products are difficult to prepare by other methods. The utility of the saturated cyclic building blocks was demonstrated by post-functionalization of the boron group.