Optimization of molar ratio of (R)-4 and rac-8^a.

Entry	Amount of rac-8 (mmol)	(ΔδR/S)b (ppm)
		CH̲	Ar-CH̲3	CH̲3
1	0.0125	No resol.	0.04	0.04
2	0.025	No resol.	0.05	0.05
3	0.05	No resol.	0.05	0.06
4	0.1	0.16	0.13	0.09
5	0.2	0.09	0.06	0.05

^aIn NMR tube, the CSA (R)-4 (0.1 mmol) and rac-8 (0.0125–0.2 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.