Copper-Catalyzed Hydroamination of Allenes: from Mechanistic Understanding to Methodology Development

Experimental and theoretical mechanistic studies on the Cu­(OTf)₂-catalyzed hydroamination reaction of terminal allenes with secondary amines reveal that in situ generated cationic Cu­(I) is the catalytically active species and explain the observed regio- and stereoselectivity for the unbranched <i>E</i> product. Insight into the structure of the relevant transition states allowed the generalization of this methodology to allenamides and <i>N-</i>allenylcarbamates under unprecedentedly mild and functional-group-tolerant conditions. Chelation effects by the amide oxygen in addition to electronic effects explain the high innate reactivity of this class of substrates