Modulating the reaction pathway of phenyl diazonium ions using host-guest complexation with cucurbit[7]uril

Aryl diazonium ions are known to be an important intermediate in the divergent synthesis of azo compounds and substituted aromatics. The presence of more than one electrophilic center in a diazonium ion could lead to undesirable side reactions during a synthesis. Herein, we report that the electrophilic α-carbon on a phenyl diazonium [PhN₂]⁺ ion can be selectively deactivated upon host-guest complexation with cucurbit[7]uril (CB7) in aqueous media, achieving a ∼60-fold increase in the half-life of [PhN₂]⁺. Notably, however, the electrophilic nitrogen of the encapsulated diazonium ion remains active towards diazo coupling with strong nucleophiles, allowing the formation of azo compounds using a two-month-old aqueous solution of [CB7-PhN₂]⁺. Our supramolecular approach can open new possibilities for the reactive chemistry of organic molecules in aqueous media.