Generation of cationic 2-azabutadienes from N,S-acetals and their use for the regio- and diastereoselective synthesis of 1,2,3,4-tetrahydroquinolines by intermolecular [4π ⁺ + 2π ] cycloadditions

Publication Type

Journal contribution (peer reviewed)

Authors

Beifuss, U.; Ledderhose, S.; Ondrus, V.

Year of publication

2005

Published in

ARKIVOC

Band/Volume

Part (v)/5

Page (from - to)

147-73

Substituted 1,2,3,4-tetrahydroquinolines and related N-heterocycles are formed highly regio- and diastereoselectively with yields ranging from 57 to 100% by intermolecular polar [4π⁺ + 2π] cycloadditions of cationic 2-azabutadienes and various dienophiles. The cationic 2-azabutadienes can be generated in situ by Lewis acid mediated heterolytic cleavage of N,S-acetals. Best results have been obtained using a new mixed Lewis acid consisting of a mixture of TiCl₄ and PPh₃.