Oxa-heterocyclic compounds such as benzofurans, chromenes, and chromanes constitute a diverse array of biologically active materials. Furthermore, extended π-conjugated systems, in which oxa-heteroaromatic and benzene rings are condensed alternately, have been exploited as components of photoelectronic devices. Thus, the development of efficient synthetic approaches toward these valuable classes of heterocycles has been pursued. Among those precedented heterocyclization methods, domino cyclodehydrogenation and cycloisomerization reactions are highly attractive as they could produce elaborate heterocyclic frameworks from readily available starting materials in an atom-efficient manner. Herein, we wish to report the novel multimode domino ring-forming reactions of o-phenylenediyne-linked bis(arenol)s (aromatic diyne systems) and its analogous aromatic enyne systems to provide unique fused oxa-heterocycles, which are otherwise difficult to synthesize.
