An example of a tetrazine Diels-Alder cycloaddition. 1,2,4,5 Tetrazines such as 3,6-dimethyl-1,2,4,5-tetrazine can react with dienophiles such as alkenes and alkynes forming formal [4+2] Diels-Alder adducts. These adducts instantly undergo a retro Diels-Alder step, releasing nitrogen. In the case of alkenes, after rearrangement, isomeric dihydropyradazines are typically formed.