Fig. 2: Experimental and analytical investigations of the organosuperacid-bismuth binary catalytic system.
From: Superacid counteranion as flexible-coordinating ligand for asymmetric organo-bismuth catalysis

a Control reactions for catalyst evaluation. b 1H NMR (500 MHz) study for in situ-generated catalytic assembly. c Employing pre-prepared intermediate I as catalyst. d Examination of various Lewis acid catalysts and others. e Reaction using α-keto oxoester as starting material. aYield (%) was determined by 1H NMR integration. bEnantiomeric excess (ee) value was determined by chiral HPLC analysis. ent = opposite enantiomer as major form. Ac acetyl, Bpin boronic acid pinacol ester, iPr isopropyl, Me methyl, OAc acetate, OMe methoxy, OTf triflate, Ph phenyl, Tf trifluoromethanesulfonyl (triflyl).