Cyclodextrin-promoted free-radical dediazoniation of benzenediazonium ions

Abstract

The effect of β-cyclodextrin (β-CD) on the decomposition of benzenediazonium ions is reported. Dediazoniation of substituted benzenediazonium ions (X =p-Me, p-Cl, and p-NO₂) is accelerated by β-CD and proceeds via a radical pathway to form XC₆H₅, irrespective of the nature of the substituent X or the atmosphere (N₂ or O₂). In contrast, trehalose and permethylated β-CD exhibit no enhancement of rate and reduce the yields of XC₆H₅. The cyclodextrin-promoted dediazoniation exhibits both saturation kinetics and competitive inhibition. The observations described are explained in terms of a mechanism involving (i) the specific formation of a syn-arylazo ether via an inclusion complex formed between the benzenediazonium ion and β-CD and (ii) subsequent homolytic scission of the syn-arylazo ether.