Hypervalent Iodine-Mediated Synthesis of Ortho-Iododiaryl Ethers and Subsequent Annulation to Biologically Relevant Heterocycles

Abstract

Owing to the low toxicity, meticulous reactivity and high stability, the hypervalent iodine reagents have garnered considerable attention in different functional group transformations in organic synthesis. In recent years, λ3-iodanes, in particular diaryliodonium salts have been extensively employed as an arylating agent in the presence, as well as absence of transition metal catalyst. Notably, the use of diaryliodonium salts always associated with the loss of stoichiometric amounts of aryl iodide. Besides, when unsymmetrical diaryliodonium salts are used, the selective arylation is often questionable. In this context, use of other hypervalent iodine reagents for selective arylation in an economical way is interesting. At this point, our effort towards the selective synthesis of ortho-iododiaryl ethers using commercially viable phenyl iododiacetate (PIDA) as well as aryl iodide in the presence of oxidant is presented in this thesis. Subsequent annulation of ortho-iododiaryl ethers to biologically potent dibenzofurans and coumestans using reusable Pd/C is also investigated. Additionally, the so formed ortho-iododiaryl ethers were transferred in to 2-phenoxy diarylacetylenes using Sonogashira coupling reaction. Iron-catalyzed intramolecular hydroarylation of internal alkynes to dibenz [b,f ]oxepines through 7-endo-dig annulation was also illustrated.