Although it is less reactive than pyrrole in S E , it still has problems with polyhalogenations, so it is required to use dilute halogens and at low temperatures. NBS and NCS can also be used.


The presence of a nucleophilic solvent produces a nucleophilic addition that requires the use of basic medium or heating to help rearomatization of the furan.

Stage 1. Furan attack on bromine.


Stage 2. Addition of the nucleophile to position 5.


Stage 3. Rearomatization with the help of base or heating.