Stereoselective Aminoiodination of Activated Alkynes with Organoiodine(III) Reagents and Amines via Multiple-Site Functionalization: Access to Iodinated Enamines and N-Aryl Indoles
A stereoselective aminoiodination of activated alkynes with PhI(OAc)2 and amines via multiple-site functionalization to afford (Z)diethyl 2-(diphenylamino)-3-iodomaleate derivatives with superior yields has been described. The key feature of this reaction is the incorporation of iodide and aryl group concurrently in the same molecule in a stereoselective manner by employing PhI(OAc)2 as electrophilic reagent as well as iodide and aryl group source. The high stereoselectivity of the reaction can be explained based on the structure of the possible intermediates, the conformations of which controlled by the hydrogen bonding, steric hindrance and electrostatic attractions. This reaction proceeds under mild conditions, providing various dialkyl 2-(diphenylamino)-3-iodomaleates by a single operation starting from activated alkynes. The robustness of our strategy is revealed by making of bis (dialkyl 2-(diphenylamino)-3-iodomaleate) derivatives involving formation of four new C-N bonds and two C-I bonds with a single step. The synthesized inactive 3° enamines (dialkyl 2-(diphenylamino)-3-iodomaleates) could be further transformed into highly substituted indoles via Pd catalyzed C-H and C-I activation under non-acidic conditions.