CHAPTER 9: Aminoenyne (2-Aminobuta-1,3-Enyne) Catalysis: In situ Generation and Synthetic Applications in Organic Reactions

Activation of ynones in the presence of an amine catalyst generated the intermediates 2-aminobuta-1,3-enynes (aminoenyne), which resembled the dienamine intermediates except that they possessed a triple bond in the place of a double bond. The generated aminoenyne intermediates participated as mild nucleophiles in various reactions, such as the asymmetric aldol reaction with aryl aldehydes, organocascade reactions with aldehydes and indane-1,3-diones through a reflexive-Michael reaction, a reflexive-Michael reaction with active olefinic compound 2-(2-oxoindolin-3-ylidene)malononitriles and a Mannich/reflexive-Michael/protonation reaction sequence with cyclic N-sulfonylimines. In addition, aminoenynes were also observed as intermediates in the direct α-vinylidenation of aldehydes and a subsequent cascade γ-alkynylation by synergistic utilization of gold and amine catalysis.