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

Abstract

Halogenative annulation reactions of alkyne-tethered N- and O-containing arenes is a general strategy being employed in the construction of various halogenated N- and O-heterocycles. The methods 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 technologies of halogenative annulation methods to construct aryl-fused halogenated N- and O-heterocycles are examined with focus on more recent technologies, encompassing various participating roles of the halogenating agents. Additionally, future directions for this age-old, but still very useful, reactions will be considered.

Facile synthesis of diiodoheteroindenes and understanding their Sonogashira cross-coupling selectivity for the construction of unsymmetrical enediynes

“…Electrophile-promoted cyclization of functionalized alkynes is a valuable tool for the synthesis of halogen-substituted heterocycles. [1][2][3][4][5][6][7] The reaction is suitable for different nucleophilic functional groups and alkynes. The most recent examples of electrophile-promoted cyclization for "halogen" electrophiles open access to oxazinoindolones, 8 3-sulfonamido-4-haloisocoumarins, 9 sulfonamido-substituted polyaromatic compounds, 10 medium-sized oxacycles, 11 iodofuranones, 12 iodothiazines, 13 highly distorted fused helicenes 14,15 and optically active tricyclic piperazine scaffolds through dearomative ipso-cyclization.…”