There are many studies on the reactions between OH-acids and acetylenic esters in the presence of various nucleophilic catalysts such as triphenylphosphine [1–5], trialkylphosphites [6], alkyl isocyanides [7–9], and tertiary amines [10, 11]. In most cases, the reaction was viewed as starting from the initial formation of a zwitterionic intermediate derived from the addition of a nucleophilic catalyst to an activated alkyne [1–11]. The azide anion usually reacts as a nucleophile in ...
