Copper‐Catalyzed Recyclable Synthesis of ( Z )‐3‐Alkylideneisoindolinones by Cycloisomerization of 2‐Alkynylbenzamides in Ionic Liquids

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The cycloisomerization of readily available 2‐alkynylbenzamides has been conveniently carried out with CuCl 2 as catalyst under basic conditions in 1‐ethyl‐3‐methylimidazolium ethyl sulfate (EmimEtSO 4 ) as an unconventional solvent. The process leads to ( Z )‐3‐alkylideneisoindolin‐1‐ones in a chemo‐, regio‐, and stereoselective manner. The catalyst/solvent/base system could be recycled several times without appreciable loss of activity. The structures of representative products, that are, ( Z )‐3‐benzylidene‐2‐phenylisoindolin‐1‐one and ( Z )‐3‐pentylidene‐2‐phenylisoindolin‐1‐one, have been confirmed by X‐ray diffraction analysis, and DFT (density functional theory) calculations have been carried out to clarify the roles exerted by the base and CuCl 2 in favoring the reaction course leading to ( Z )‐3‐alkylideneisoindolinones.