Use of the curtius rearrangement of acryloyl azides in the synthesis of 3,5-disubstituted pyridines: mechanistic studies.

A series of disubstituted pyridine derivatives was synthesized from the corresponding acryloyl azides by acetic acid-promoted cycloaddition. This represents a novel and convenient synthetic approach to the symmetric 3,5-disubstituted pyridines. The nature of the substituent on the double bond and the utilized solvent were found to be crucial to the yield of pyridines. The reactivity of the acid-promoted cycloaddition increases with the presence of aryl groups, such as phenyl and pyridinyl. We also explored the comprehensive mechanism by the acid-promoted cycloaddition of 13C-labeled cinnamoyl azide. The symmetric 3,5-disubstituted pyridines were synthesized from acryloyl azides by acetic acid-promoted trimolecular condensation.