Reductive Transformations of Polyfunctional Nitro Compounds: Synthesis of Methyl 7‐Aminoalkanoates and Five‐Membered Cyclic Nitrones ‐ Inter‐ and Intramolecular 1,3‐Dipolar Cycloadditions

Using ammonium formate and Pd/C, acetals 1 and 3 are converted into the amines 2 and 4 , respectively, whereas unprotected nitro ketones as 5, 7, 9 , and 11 furnish five‐membered nitrones in good yields. With these nitrones 1,3‐dipolar cycloadditions to acrylonitrile and trimethyl(vinyl)silane are described. The regio‐chemistry of these reactions, giving mixtures of 5‐substituted and 4‐substituted isoxazolidines in most cases, can be explained by the frontier‐orbital model. One example of an intramolecular nitrone cycloaddition ( 27 → 28 ) demonstrates the potential of this approach for construction of polycyclic compounds.