Synthesis of Five- and Six-Membered Dihalogenated Heterocyclic Compounds by Electrophile-Triggered Cyclization

Highly substituted dihalogenated dihydrofurans, dihydropyrroles, and dihydro-2<i>H</i>-pyrans bearing alkyl, vinyl, aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I₂, IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling reactions. The presence of trace amount of water is essential for this electrophilic cyclization.