Reactions of azides with electrophiles: New methods for the generation of cationic 2-azabutadienes. Synthesis of 1,2,3,4-tetrahydroquinolines and 1,2-dihydroquinolines via a hetero Diels-Alder reaction

Article abstract of DOI:10.1002/ijch.199700007

Two methods for the generation of iminium ions of the type ArN⁺(X)=CHR (X = H or alkyl, R = H or alkyl) are reported: (1) the Bronsted-acid-promoted rearrangement of benzylic azides and (2) the intermolecular Schmidt reactions of azides XN₃ (X = aliphatic) with benzylic carbocations derived from benzylic alcohols ArCH(R)OH. The iminium ions ArN⁺(X)=CHR behave as cationic 2-azabutadienes in the presence of alkenes and alkynes, producing 1,2,3,4-tetrahydroquinolines and 1,2-dihydroquinolines by a hetero Diels-Alder reaction.