Efficient Synthesis of Substituted 3‐Azabicyclo[3.1.0]hexan‐2‐ones from 2‐Iodocyclopropanecarboxamides Using a Copper‐Free Sonogashira Coupling

The copper‐free Sonogashira coupling between N‐substituted cis‐ 2‐iodocyclopropanecarboxamides and terminal aryl‐, heteroaryl‐alkynes or enynes, followed by 5‐exo‐dig cyclization of the nitrogen amide onto the carbon–carbon triple bond, provides a remarkably efficient access to a variety of substituted 4‐methylene‐3‐azabicyclo[3.1.0]hexan‐2‐ones in excellent yields. Protonation of these latter enamides generates bicyclic N‐acyliminium ions that can be involved in Pictet–Spengler cyclizations leading to new 3‐azabicyclo[3.1.0]hexan‐2‐ones, possessing a quaternary stereocenter at C4, with high diastereoselectivities. This strategy constitutes an attractive complementary alternative to the classical route that relies on the addition of organometallic reagents to cyclopropyl imides.