Optimization of amounts of (S)-3a and rac-5^a.

Entry	Amount of (S)-3a (mmol)	Amount of rac-5 (mmol)	(ΔδR/S)b (ppm)
1	0.0125	0.05	0.02
2	0.025	0.05	0.03
3	0.05	0.05	0.04
4	0.1	0.05	0.06
5	0.1	0.0125	0.06
6	0.1	0.025	0.06
7	0.1	0.1	0.06

^aIn NMR tube, the CSA (S)-3a (0.0125–0.1 mmol) and rac-5 (0.0125–0.1 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.