Intramolecular [3 + 2]-cycloadditions of azomethine ylides derived from secondary amines via redox-neutral C-H functionalization.Org Lett. 2014 Nov 21; 16(22):5910-3.OL
Azomethine ylides are accessed under mild conditions via benzoic acid catalyzed condensations of 1,2,3,4-tetrahydroisoquinolines or tryptolines with aldehydes bearing a pendent dipolarophile. These intermediates undergo intramolecular [3 + 2]-cycloadditions in a highly diastereoselective fashion to form polycyclic amines with four new stereogenic centers. Challenging substrates such as piperidine, morpholine, and thiomorpholine undergo the corresponding reactions at elevated temperatures.