Phosphines catalyzed nucleophilic addition of azoles to allenes: synthesis of allylazoles and indolizines

Triphenylphosphine was used as nucleophilic catalyst for umpolung addition of azoles to electron-deficient allenes. This strategy offers a simple and efficient method for functional allylation of azoles under neutral conditions and affords heterocyclic substituted Michael olefins. Furthermore, this catalytic methodology has been extended to addition-cyclization reactions between electron-deficient allenes or alkynes and pyrrole-2-carboxaldehyde in the presence of catalytic amount of tributylphosphine. In such conditions, substituted indolizine-7-carboxylates are easily obtained.