Preparation of 3-Bromo-1,2,4,5-tetrazine

In this synthetic procedure, a seven-step protocol for the preparation of monosubstituted 3-bromo-1,2,4,5tetrazine is presented. The procedure features efficient transformations and purification methods starting from commercially readily available starting materials and affords the title compound on a gram scale with 13% overall yield in reliable purity (> 97 %). Detailed experimental procedures, supported by images and additional notes, allow the preparation of a valuable advanced building block, enabling further applications in bioconjugation, protein labelling, bio-orthogonal chemistry, heterocycle syntheses, high energy materials, and drug release, among others.