Fig. 5: Mechanism study.

a, ³¹P NMR spectra: (i) (R)-BINAP(S) C1, (ii) (R)-BINAP(S) C1/S4 = 1:1, (iii) (R)-BINAP(S) C1/S4 = 1:6, (iv) (R)-BINAP(S) C1/S4/1a = 1:6:5. b, Sample preparation: (R)-BINAP(S) C1/S4 = 1:6 in HFIP, then diluted with methanol.