The study of several fundamental biological processes requires the use of direct, reliable and sensitive methods that allows a rapid and efficient detection of diverse analytes. Recently, the design and synthesis of fluorophores with emission of fluorescence in the region of near-infrared (NIR) contribute to the development of new analytical techniques for obtaining in vivo images by fluorescence, allowing the study of physiological important processes, related to various diseases. In this context, BODIPY is a class of chromophores that is gaining a lot of relevance due to its excellent properties. Due to their promising features, BODIPYs have become synthetic targets for obtaining new fluorescent sensors in recent decades. The most commonly reported methods to introduce selenium into the BODIPY core consists of the metal-catalyzed cross-coupling reaction, radical mechanisms, or nucleophilic substitution reactions.
In this work, the synthesis of new seleno-BODIPYs is presented. The synthesis strategy was focused on the preparation of 2,6-dihalogenated BODIPYs, aiming to perform the nucleophilic substitution reaction in order to replace the halogen by the chalcogen residue. Instead, performing this reaction, it was observed the maintenance of halogens and the insertion of “PhSe” groups in the 3 and 5 positions. The procedure consisted on a reaction of 2,6-dibrominated BODIPY with PhSeH, generated in situ (Ph2Se2/NaBH4 system), under N2 atmosphere, at room temperature. The products were completely characterized by NMR and HRMS spectrum. After a mechanistic investigation it was possible to conclude that the main mechanism that was governing the reaction was the Oxidative Nucleophilic Hydrogen Substitution (ONHS). Thus, new compounds containing bromine and selenium were obtained (Figure 1) in high yields (77%) through a simple and fast procedure.