A Domino Route toward Polysubstituted Pyrroles from 2-Imidazolines and Electron-Deficient Alkynes.

The reaction of 1,2-disubstituted 2-imidazolines with electron-deficient alkynes proceeds as a pseudo-three-component process and forms imidazolidines with an N-vinylpropargylamine fragment. Heating the resulting imidazolidines in xylene on air leads to an effective formation of polysubstituted pyrroles through a domino sequence of aza-Claisen rearrangement/transannular nucleophilic addition/oxidative ring opening reactions. The direct one-pot transformation of 2-imidazolines to pyrroles has been also realized.