(E,E)-1,5-Cyclooctadiene: a small and fast click-chemistry multitalent.

Two in one--We show here that the highly strained trans,trans-diolefin (E,E)-1,5-cyclooctadiene can perform efficiently two different click reactions at fast reaction rates. It is capable of first undergoing [3+2] cycloadditions with 1,3-dipoles at a reaction rate comparable to that of strained cyclooctynes. The resulting cycloadduct can then perform a much faster inverse-electron-demand Diels-Alder reaction with tetrazines, effectively linking an azide to a tetrazine. Thus, (E,E)-1,5-cyclooctadiene could have many applications in chemical biology and polymer chemistry.