The ring-opening/functionalization of 1-pyrrolines by cyanoacetylenes or acetylenic ketones (20–80 °C, MeCN, H2O) affords δ-keto aminoacrylonitriles and δ-keto aminoenones, mostly as the Z-isomers, in up to 85% yields. The synthesis involves C(2)–N bond cleavage in the intermediate hemiaminal resulting from the intermediate 1,3(4)-dipolar 1-pyrroline/acetylene complexes and water.
Key words
cleavage reactions - electrophilic acetylenes - multicomponent reactions - 1-pyrrolines - zwitterions