Synthetic Entry into 1‑Phosphono-3-azabicyclo[3.1.0]hexanes

3-Azabicyclo­[3.1.0]­hex-2-en-1-yl phosphonates were prepared in a five-step reaction route from β-ketophosphonates. The key steps in this sequence are an atom-transfer radical cyclization and an unforeseen lithium–halogen exchange with n-BuLi. The cyclization reaction proceeds with excellent diastereoselectivity. The resulting cyclic imines were reduced, and 3-azabicyclo[3.1.0]­hexan-1-yl phosphonates were obtained.