Intramolecular Aza-Piancatelli Rearrangement of Alkyl- or Arylamines Promoted by PPh3/Diethyl Azodicarboxylate.

A novel method for the construction of 1-azaspirocycles from 5-alkyl-/-arylamine furylcarbinols though intramolecular aza-Piancatelli rearrangement was developed. By using PPh3/diethyl azodicarboxylate instead of a Lewis acid, 1-azaspirocyclic compounds were obtained in good yields and the reaction temperature was reduced to room temperature. In addition, substrates with groups that are sensitive to high temperatures or Lewis acids are tolerated under these reaction conditions. This is the first method that is applicable not only to 5-(N-arylaminoalkyl)furylcarbinols with better yields but also to 5-(N-alkylaminoalkyl)furylcarbinols.