Cross-Coupling Reactions of Monosubstituted Tetrazines.

A Ag-mediated Pd-catalyzed cross-coupling method for 3-bromo-1,2,4,5-tetrazine with boronic acids is presented. Electronic modification of the 1,1'-bis(diphenylphosphine)ferrocene (dppf) ligand was found to be crucial for good turnover. Using this fast method, a variety of alkyl-, heteroatom-, and halide-substituted aryl- and heteroaryl-tetrazines were prepared (29 examples, up to 87% yield).