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. 2019 Nov 25;11(3):851–855. doi: 10.1039/c9sc04534a

Condition optimization for catalytic asymmetric hydrogenation of 1a.

graphic file with name c9sc04534a-u1.jpg
Entry Sub Ligand Conv.b (%) eec (%)
1d 1a (Rc,Sp)-DuanPhos 89 n.d.
2e 1b (Rc,Sp)-DuanPhos >99 98
3 1c (Rc,Sp)-DuanPhos n.r. n.d.
4 1b (R,R)-QuinoxP* >99 97
5 1b (S)-SegPhos >99 17
6 1b (S)-BINAP >99 10
7 1b (R,R)-iPr-DuPhos >99 3
8 1b (R,S)-Cy-JosiPhos >99 14
9 1b (R)-BIPHEP >99 −30
10 1b (R,R)-Ph-BPE >99 −86
11 1b (S,S)-f-Binaphane >99 61
12 1b (2S,4S)-BDPP >99 59
13e,f,g 1b (Rc,Sp)-DuanPhos >99(99) 99
graphic file with name c9sc04534a-u2.jpg
a

Unless otherwise mentioned, the reactions were performed with 1 (0.1 mmol), Rh(NBD)2BF4 (10 mol%), and a ligand (11 mol%) in 1.0 mL THF at 50 °C for 15 h.

b

Determined by crude 1H NMR.

c

Determined with chiral HPLC.

d

The reaction was performed in iPrOH.

e

Rh(NBD)2BF4 (1.0 mol%) and ligand (1.05 mol%) were used.

f

Isolated yield in parentheses.

g

1,2-DCE was used as the solvent. Pin = 2,3-dimethyl-2,3-butanediol; dan = 1,8-diaminonaphthalene.