NIS-promoted carbochalcogenation of styrenes: regioselective C-3 alkylation of pyrazolo[1,5-<i>a</i>]pyrimidines

An <i>N</i>-iodosuccinimide (NIS) mediated transition metal and solvent-free, regioselective multicomponent cascade reaction is developed for the C-3 alkylation of pyrazolo[1,5-<i>a</i>]pyrimidines <i>via</i> a three-component reaction of styrenes, diaryl dichalcogenides and pyrazolo[1,5-<i>a</i>]pyrimidines. This operationally simple, cost-effective and rapid reaction furnishes C-3 functionalized pyrazolo[1,5-<i>a</i>]pyrimidines in good to excellent yields. The reaction is scalable and operates <i>via</i> an electrophilic substitution mechanism.