Au I Iminophosphorane Complexes as Efficient Catalysts for the Cycloisomerization of Alkynyl Amides under Air, at Room Temperature, and in Aqueous or Eutectic-Mixture Solutions.

New iminophosphorane-phosphine AuI complexes [AuCl(κ1 -P-Ph2 PCH2 P{=NP(=S)(OR)2 }Ph2 )] (3 a,b) and [Au2 Cl2 (μ2 -P,S-Ph2 PCH2 P{=NP(=S)(OR)2 }Ph2 )] (4 a,b) proved to be general, very efficient, and recyclable (up to four consecutive runs) catalysts for the cycloisomerization of alkynyl amides in water or choline chloride-based eutectic mixtures as green solvents. Remarkably, this cycloisomerization reaction took place under mild conditions (low catalyst loading, at room temperature, and in the absence of cocatalysts or protecting atmosphere) to give the corresponding alkylidene lactams by employing an efficient and sustainable methodology.