Chiral aminals: Powerful auxiliaries in asymmetric synthesis

Abstract

Chiral aminals are prepared from chiral C2 symmetrical diamines and aldehydes. The chiral imidazolidine ring exerts its stereocontrol either through stericor chelation effects. Reaction of aqueous glyoxal with diamine 1 results in a new chiral synthon 6; this “chiron” is a useful precursor for α-hydroxy aldehydes and for α-amino aldehydes. An aminal of nicotinaldehyde 7 reacts stereoselectively with organocopper reagents to afford a chiral dihydropyridine, which is a starting point for several short asymmetric syntheses of indolo- and benzoquinolizine alkaloids. © 1996, Walter de Gruyter GmbH, Berlin/Boston. All rights reserved.