A facile and unprecedented synthesis of 2,3-diiodinated or 2,6-diiodinated diarylether/thioether derivatives through regioselective Ullmann-type cross couplings of 5-substituted-1,2,3-triiodobenzene and phenols/thiophenols is described. Remarkably, the coupling reactions are simply controlled by the type of nucleophiles and the nature of C5 substituent at 1,2,3-triiodoarenes providing the internal or terminal coupling products in high regioselectivity and good isolated yields. Noticeable steric and electronic effects were clearly observed on both 1,2,3-triiodoarene and nucleophile. The highest yields were isolated from a combination between either electron-poor 1,2,3-triiodoarenes and phenols or electron-rich 1,2,3-triiodoarenes and thiophenols. The optimized conditions were found to be suitable for several functional groups. Using this methodology, mammary carcinoma inhibitor BTO-956 is prepared in only one step with excellent regioselectivity and good isolated yield. This report discloses the first method to make 2,3-diiodinated and 2,6-diiodinated diarylethers/thioethers in one step that is efficient, regioselective, general in scope and truly remarkable precursors for other transformations.
Transition-Metal-Free Suzuki-Type Coupling Reactions
