Synthesis of 3‐Aminotetrahydrofurans and Tetrahydrofuro[2,3‐b]furans by Gold‐Catalyzed Cyclization of 3‐Aminopent‐4‐yn‐1‐ols

A gold‐catalyzed reaction of 3‐aminopent‐4‐yn‐1‐ols is described. 2‐Arylidene‐3‐aminotetrahydrofurans were synthesized via intramolecular nucleophilic cyclization of the hydroxy group with the activated alkyne. When the reaction was carried out with phenols as an additional nucleophile and Sc(OTf)3 as an activating reagent, tetrahydrofuro[2,3‐b]benzofurans were obtained. The reaction proceeded via a deaminative nucleophilic substitution of 3‐aminopent‐4‐yn‐1‐ols with phenols, followed by a successive intramolecular cyclization of the two hydroxy groups with the activated alkyne. When 1,3‐dicarbonyl compounds were used as the nucleophile, the corresponding substituted tetrahydrofuro[2,3‐b] furans were formed. To further understand the nature of this reaction, the intramolecular nucleophilic addition of alkynyl diol intermediate with gold complex were investigated as a model substrate using DFT calculations.