. Author manuscript; available in PMC: 2022 Nov 8.

Published in final edited form as: Angew Chem Int Ed Engl. 2021 Oct 7;60(46):24573–24581. doi: 10.1002/anie.202109694

Table 5.

Comparison of carboxylic acid cocatalyst for regioisomeric pyrazole carboxaldehyde substrate ^[a]



Entry	Carboxylic Acid	Corresponding Product	er
1	3-CF₃-5-Ar^F-C₆H₃CO₂H	22	96:4
2	TrCO₂H	22	>99.5:0.5
3	4-NMe₂-C₆H₄CO₂H	22	98:2
4	3-CF₃-5-Ar^F-C₆H₃CO₂H	23	97:3
5	TrCO₂H	23	65:35
6	4-NMe₂-C₆H₄CO₂H	23	75:25
7	3-CF₃-5-Ar^F-C₆H₃CO₂H	24	55:45
8	TrCO₂H	24	78:22
9	4-NMe₂-C₆H₄CO₂H	24	75:25

^[a]

Reactions were performed at 0.05 mmol scale Enantioselectivity was measured by HPLC with chiral stationary phase. Ar^F = 3,5-CF₃-C₆H₃. PhMe used as solvent for 22 and 23. 1,2-DCE used as solvent for 24.