Synthesis of substituted 3-iodocoumarins and 3-iodobutenolides via electrophilic iodocyclization of ethoxyalkyne diols

摘要

A convenient and general synthesis of various 4-substituted 3-iodocoumarins and 4,5-disubstituted 3-iodobutenolides is described via an exclusive 6-endo-dig iodocyclization of 3-ethoxy-1-(2-alkoxyphenyl)-2-yn-1-ols and 5-endo-dig iodocyclization of 1-alkoxy-4-ethoxy-3-yn-1,2-diols, respectively. The reaction is carried out under very mild conditions using I_2 in CH_2Cl_2 or toluene at room temperature. Oxygens in OMe and OMOM groups were used as efficient nucleophiles for this intramolecular cyclization to obtain the products in good to excellent yields.