N-Alkynyl Imides (Ynimides): Synthesis and Use as a Variant of Highly Labile Ethynamine
摘要:
This study describes the first reliable synthesis of N-alkynyl imides (ynimides). This was accomplished with a copper-catalyzed coupling reaction between alkynyl(triaryl)bismuthonium salts and five-membered imides. We also found that it was possible to utilize N-ethynyl phthalimide as a variant of the highly labile ethynamine. 4-Amino-1,2,3-triazole was successfully obtained via the CuAAC reaction of N-ethynyl phthalimide with azide followed by hydrazinolysis of the phthaloyl protecting group.
Metal-catalyzed reactions of ynimides with alcohols to afford β-ketoimides and oxazoles are demonstrated. The triple bond of ynamides is generally activated by mineral acids or metal salts to lead to the regioselective addition of nucleophiles at the α-C-atom, because of the inherent electronic bias. In contrast, the two neighboring carbonyl groups of ynimides decrease the electron density of the triple