Ruthenium-Catalyzed Cycloaddition of Azides and Selenoalkynes with Built-in "Catch-and-Release" Functionality.

Click reactions with a "catch-and-release" functionality featuring both cross-linking and bond cleavage may have unique biomedical applications. However, despite the high demand, such reactions are rarely known in the toolbox of biochemists. Herein we introduce a robust click reaction of selenoalkynes that not only facilitates mild cross-linking with azides but also permits exceptionally facile cleavage of the C─Se bond in the adducts. This highly efficient ruthenium-catalyzed protocol features high chemoselectivity and regioselectivity, mild conditions, broad substrate scope, and good tolerance of functional groups and solvents. The compatibility with air and water as well as biomolecules has been demonstrated in parallel with the "catch-and-release" functionality.