Azomethines carboxylic acid amides

Carboxylic acid amides from azomethines CH N CONH ... 

A new reagent for activating carboxylic acids for amide formation is the phosphonate (396). The azomethine imine (397), obtained from diphenyl-keten and diethyl azodicarboxylate, forms the 1,3-cyclo-adduct (398) with... 

Solid-phase synthesis of pyrroles was reported by Mjalli et al. " Pyrroles were prepared via Rink resin-bound mesoionic munchnones (Scheme 11.12). Munchnones behave as azomethine ylides in 1,3-dipolar cycloaddition. Cycloadditions with alkynes give pyrroles after aromatization and spontaneous release of carbon dioxide. A set of compounds was obtained from simple starting materials, aldehyde, amine, carboxylic acid, and isocyanide via the Ugi four-component condensation. Trifluoroacetic acid released highly substituted pyrroles as amides from the Rink resin in high overall yield and purity. A related method via the miinchnone pathway was reported by Strocker et al., and two pyrroles were obtained in 4% and 17% yields. 

---