Regioselective Cycloaddition of 3‐Azetidinones and 3‐Oxetanones with Alkynes through Nickel‐Catalysed Carbon–Carbon Bond Activation

Get in the ring! The first examples of transition-metal-catalysed C-C bond activation of 3-azetidinones and 3-oxetanones are reported. In the presence of a nickel catalyst and alkynes, a regioselective and high-yielding [4+2] cycloaddition occurs, leading to the formation of pyridinones, pyranones and eventually 4,5-disubstituted 3-hydroxypyridines (see scheme).