Synthesis of Highly Substituted Pyridazines through Alkynyl Boronic Ester Cycloaddition Reactions

A highly regioselective transformation of tetrazines through a cycloaddition reaction with alkynyl boronic esters provides highly substituted pyridazine boronic esters as intermediates for CO and CC bond-forming reactions (see scheme). Functionalization reactions of the CB bond, such as oxidation and the Suzuki cross-coupling, show the versatility of these species.