Alkynyl transmetalation triggered by a nucleophilic attack

We report an interesting alkynyl transmetalation process in the cyclization of π-Au, σ-M acetylides (M = Pd, Ni, Pt) bearing a N -propiolic formamidine moiety. The cyclization was triggered by nucleophilic attack and afforded 5-membered heterodinuclear M/Au vinylidene species through a 5- exo-dig mode followed by ring-opening and recyclization to give their 6-membered endo -isomers at an elevated temperature. This suggests that the regiochemistry (5- exo vs. 6- endo ) observed in the cyclization is kinetically and thermodynamically controlled. The mechanism of the domino cyclization/ring-opening/recyclization reaction is analyzed by DFT calculations. A domino cylization/ring-opening/recyclization reaction involving an alkynyl transmetalation was triggered by nucleophilic attack, and the gem -dinuclear Ni/Au and Pt/Au vinylidene intermediates was obtained by cyclization of π-Au, σ-M acetylides.