Synthesis, Structures and DFT Computational Studies of [3.1.1]Metacyclophanes Containing Benzofuran Rings

Abstract

[3.1.1]Metacyclophane ([3.1.1]MCP) 6 a containing two benzofuran rings was obtained by treatment of [3.3.3]MCP-dione 5 with trimethylsilyl iodide. The precursor 5 was synthesized using (p-tolylsulfonyl)methyl isocyanide (TosMIC) as the cyclization reagent. The 1H-NMR spectrum of 6 a at room temperature reveals that it undergoes very fast conformational changes relative to the NMR time scale and that the phenolic hydrogen forms weak intramolecular hydrogen bonding with the oxygen of one of the benzofurans. O-Methylation of 6 a afforded the calixarene analogue, macrocyclic [3.1.1]MCP 7 a whose 1H-NMR spectrum reveals that it adopts a cone-likeconformation in solution at room temperature and the alkoxy group is pointing above and away from the macrocyclic cavity.