Diversity in Gold‐Catalyzed Formal Cycloadditions of Ynamides with Azidoalkenes or 2 H ‐Azirines: [3+2] versus [4+3] Cycloadditions

Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2 H ‐azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2 H ‐azirine species afford pyrrole products with two regioselectivities when the C β ‐substituted 2 H ‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1 H ‐benzo[ d ]azepine products instead.