2‑Aminobenzenesulfonamide-Containing Cyclononyne as Adjustable Click Reagent for Strain-Promoted Azide–Alkyne Cycloaddition

The synthesis of 2-amino­benzene­sulfon­amide-containing cyclononyne (ABSACN), starting from 2-nitro­benzene­sulfon­amide and but-2-yne-1,4-diol via Mitsunobu and Nicholas reactions, is described for the development of an adjustable alkyne reagent in click reactions. In a strain-promoted azide–alkyne cycloaddition (SPAAC) reaction, the reactivity of the alkyne is controlled by introducing various N-functionalities. The structure–reactivity relationship is found to be influenced by a transannular hydrogen bond between amino and sulfonyl groups.