On the Enantioselective Phosphoric-Acid-Catalyzed Hantzsch Synthesis of Polyhydroquinolines

A reinvestigation
of a chiral phosphoric-acid-catalyzed four-component
Hantzsch enantioselective synthesis of polyhydroquinolines reported
in 2009 is presented. In our hands, when the reaction was performed
with fidelity to the original report using a chiral enantiopure phosphoric
acid catalyst, no enantioselectivity was observed. Unlike in the original
report, enantioselectivity results are backed by baseline separation
of the enantiomers by HPLC analyses on chiral stationary phase with
UV and chiroptical detection.