Chalcogenoalkynes: Precursors for the Regioselective Preparation of 2‐Chalcogeno‐1‐halonaphthalenes through [4+2] Cycloaddition

Abstract Chalcogenoalkynes and o ‐alkynylbenzaldehydes reacted in the presence of copper(II) salt to give the [4+2] cycloadducts 2‐chalcogeno‐1‐halonaphthalenes in good yields (46–89 %) and high regioselectivities. The methodology was carried out by using CuCl 2 or CuCl 2 /LiBr in 1,2‐dichloroethane (DCE) at 80 °C. The potential and generality of this system was evaluated by using a variety of chalcogenoalkynes including aromatic, substituted aromatic, and aliphatic substrates having both sulfur and selenium atoms. In this sequence, due to the ability of the chalcogen atoms to stabilize charges, these substituents exert regiocontrol that guides the selectivity.