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

Abstract

New iminophosphorane-phosphine Au^I 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.