Enantioselective A3 Reactions of Secondary Amines with a Cu(I)/Acid–Thiourea Catalyst Combination

Pyrrolidine and related amines undergo asymmetric A3 reactions in the presence of copper iodide and an easily accessible cocatalyst possessing both a carboxylic acid and a thiourea moiety. Propargylamines are obtained with up to 96% ee, and catalyst loadings can be as low as 1 mol %. Pyrrolidine-derived propargylamines, in the absence of directing groups, can be transformed to the corresponding allenes without loss of enantiopurity.