Energy transfer-enabled unsymmetrical diamination using bifunctional nitrogen-radical precursors

Vicinal diamines, especially unsymmetrical ones, are among the most common structural motifs in biologically active molecules, natural products and pharmaceuticals. While the catalytic diamination of carbon-carbon double bonds provides rapid access to diamines, these reactions are often limited to installation of undifferentiated amino functionalities through transition metals or hypervalent iodine reagent catalysis. Herein we disclose a metal-free, photosensitized dearomative unsymmetrical diamination of various electron-rich (hetero)arenes with bifunctional diamination reagents, producing a series of previously inaccessible vicinal diamines with excellent regio- and diastereoselectivity. A class of bifunctional nitrogen-radical precursors was developed to simultaneously generate two N-centred radicals with different reactivity via an energy transfer process. In addition, the protocol was also found suitable for a wide range of alkenes. Notably, the formed vicinal diamines bear two differentiated amino functionalities, and either imine or amide units could readily and orthogonally be converted to unprotected amines, thereby facilitating selective downstream transformations.

Automated summary

This study reveals a metal-free, photosensitized dearomative unsymmetrical diamination reaction, which generates two N-centred radicals with different reactivity via an energy transfer process, achieving the highly selective synthesis of vicinal diamines.