Pyreno-1,2,4-triazines as multifunctional luminogenic click reagents

Several examples of 1,2,4-triazines that contain a pyrene fragment attached to the C5 position and a carbonyl functional group at the C3 position of the triazine ring have been prepared. While pyrene is a widely used luminophore, the carboxylic acid group at C3 is a convenient handle for further functionalization and significantly facilitates the Inverse Electron Demand Diels-Alder (IEDDA) reaction with strained alkenes and alkynes. The pyreno-1,2,4-triazine derivatives were investigated in reactions with the strained dienophiles BCN, TCO, and s-TCO. The rates were compared with reference to parent 1,2,4-triazine 10 with an unsubstituted C3 position which was synthesised through thermal decarboxylation of acid 6. The structure reactivity relationship was investigated theoretically showing that the predictive power of computational analysis benefits from extensive transition state conformer searches.