Halogenative Annulation Reactions of Alkyne-Tethered N-and O -Containing Arenes: Methods for Accessing Aryl-Fused Halogenated N-and O -Heterocycles

Halogenative annulation of alkyne-tethered N- and O -containing arenes represents a general strategy for the construction of various halogenated N- and O-heterocycles. The methods employed are useful in producing valuable synthetic building blocks carrying C(sp2)- halide functional groups, which are useful synthetic handles, especially for cross-coupling reactions and a myriad of other transformations. When the alkyne is tethered to the heteroatom via an aromatic ring, the reaction gives rise to aryl-fused halogenated heterocycles. In this Short Review, various past and present halogenative annulation methods to construct aryl-fused halogenated N- and O-heterocycles are examined, with a focus on more recent technologies and the various roles of the participating halogenating agents. Additionally, future directions for this age-old, but still very useful, reaction are considered.