¹H and ¹³C NMR assignments of all three isomeric o‐fluoronaphthaldehydes and three o‐fluorophenanthrene aldehydes

Abstract

Three isomeric o-fluoronaphthaldehydes, 9-fluorophenanthrene, and three previously unreported o-fluorophenanthrene aldehydes were analyzed in detail by multiple NMR techniques to provide unambiguous assignment of structures and resonances. The six aldehydes serve as the key starting materials for novel chiral ligands used in highly enantioselective rhodium-catalyzed asymmetric hydrogenation reactions.

Development of the BIPI ligands for asymmetric hydrogenation

“…Detailed NMR analyses using 19 F HOESY were used to make positive assignments. 14 The aldehyde was then converted to imidazoline 20 using a one-pot imidazoline synthesis recently reported. 15 The same sequence described in Scheme 3 was then used for the final three steps.…”