Chlorination of Pyrrole. N-Chloropyrrole: Formation and Rearrangement to 2- and 3-Chloropyrrole

N-Chloropyrrole (2) was formed in 65–72% yield when pyrrole (1) in CCl₄ was chlorinated with aqueous NaOCl. This intermediate rearranged in methanol to give chloropyrroles by two distinct reactions: a thermal rearrangement which gave 2-chloropyrrole (3) and an acid-catalyzed intermodular reaction which gave 2-chloropyrrole (3), 3-chloropyrrole (4), and 2,5-dichloropyrrole (5). Nucleophilic attack on the N-Cl bond of 2 was demonstrated by reactions in the presence of CN⁻ and SCN⁻. In the latter case, 2-(thiocyano)pyrrole was formed.