1. In the presence of electron-donating substituents in the molecules of mono-substituted diacetylenes, the nucleophilic addition of amines occurs at the outer atom of the terminal acetylenic bond. 2. In the enamines of acetylenic aldehydes formed under these conditions, there is a great tendency to hydration (by water or aqueous amines at low temperatures). 3. A convenient method for the synthesis of the enamines ofβ-ketoaldehydes having independent synthetic interest is offered.