Preparation of Partially Saturated Furo[3,2-c]- and Furo[2,3-c]annulated N-Heterocycles

Practical, multi-gram routes to three med-chem-relevant partially saturated furo[3,2-c]- and furo[2,3-c]annulated N-heterocycles are described. The key β‑(furyl)ethylamine intermediates were accessed via DPPA-mediated Curtius rearrangement, replacing the traditional Henry/LAH sequence and eliminating stoichiometric metal-hydride reductions. The tetrahydrofuropyridine cores were then assembled through Pictet-Spengler cyclization, while a previously unavailable dihydrofuropyridinone was obtained via Dieckmann/Feist-Benary annulation. All sequences proceed in ≤6 steps from commercial starting materials.