1.3‐Dipolare Cycloadditionen, 68. Additionen der Nitriloxide an CN‐Mehrfachbindungen

Synthesis and properties of pyrrolin-2-ones

“…4-Hydroxypyrrolidin-2-one (3). The procedure described below was adapted from the method of Balenovic et al 7 for the synthesis of the unisolated intermediate 4-amino-3-hydroxybutyric acid and the method of Tomita8 for the final cyclization to 3. A stirred mixture of methyl 4-phthalimidocrotonate (150 g, 0.612 mol) and 1.5 L of 6 N HC1 was refluxed for 16 h. The mixture was then kept at 0-5 °C for 4 h and the precipitated phthalic acid was filtered and washed twice with 50 mL of H20.…”

Cyanogen: A Versatile Reagent for Diversity-Oriented Synthesis

“…An interesting discrepancy was observed during the cycloaddition of aromatic nitrile oxides with cyanogen (Scheme 17). Bast and co-workers reported 53 that the reaction of benzonitrile oxide with cyanogen smoothly afforded 1,2,4-oxadiazole 17-3 in 73% isolated yield. Alternatively, Ried and Fulde 54 proposed that the reaction of benzonitrile oxides under the similar reaction conditions gave bis (1,2,4-oxadiazoles) 17-1a-c.…”

2,3,4,5-Tetrahydro-2,4-diimino-1,3,5-triazin-1-ium salts in the reaction of carbodiimides with N-alkylnitrilium salts

“…6 However, electron-withdrawing substituents or Lewis acid catalysis enhance the reactivity of nitriles towards nucleophiles and 1,3-dipolar species. 6,7 Thus, nitrilium salts react smoothly with a variety of nucleophiles and 1,3-dipoles. Cycloadditions of organic azides to nitrilium salts 1 lead to trisubstituted tetrazolium salts.…”