Phosphane‐Catalyzed [3+2] Annulation of Allenoates with 3‐Nitro‐2H‐chromenes: Synthesis of Tetrahydrocyclopenta[c]chromenes

The synthesis of carbocyclic‐fused chromene derivatives based on allene chemistry is described. The phosphane‐catalyzed [3+2] annulation reactions of allenic esters with 3‐nitrochromenes have been established affording 3a‐nitro‐tetrahydrocyclopenta[c]chromenes in good yields (up to 87 %) with high stereo‐ and regioselectivity. Quantum chemical calculations, carried out at the DFT level of theory, were in agreement with the observed selectivity. The trichlorosilane‐mediated reduction of the 3a‐nitro‐tetrahydrocyclopenta[c]chromenes into the corresponding amines is also reported. The phosphane‐catalyzed [3+2] annulations of allenoates with 3‐nitrochromenes are described allowing the synthesis of 3a‐nitro‐tetrahydrocyclopenta[c]chromenes with high stereo‐ and regioselectivity. Quantum chemical calculations corroborate the experimental results. 3a‐Nitro‐tetrahydrocyclopenta[c]chromenes are converted into the corresponding amines by HSiCl3‐mediated reduction.