Optimization of molar ratio of (S)-BINOL (1) and rac-6^a.

Entry	Amount of rac-6 (mmol)	(ΔδR/S)b (ppm)
1	0.0125	0.09
2	0.025	0.09
3	0.05	0.08
4	0.075	0.07
5	0.1	0.07
6	0.125	0.06

^aIn NMR tube, the (S)-BINOL (1) (0.1 mmol) and rac-6 (0.0125–0.125 mmol) were dissolved in chloroform-d (0.6 mL) and after shaking the NMR tube for 30 seconds, ¹H-NMR spectrum was recorded on a 400 MHz NMR spectrometer at 25 °C.

^bCalculated from the ¹H-NMR spectrum.