Table 1 Optimization for Rh(III)-catalyzed DKR-ATH of 1aa

From: Stereodivergent synthesis of chiral succinimides via Rh-catalyzed asymmetric transfer hydrogenation

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entry

catalyst

Hydrogen donor

Solvent

conv. (%)

eeanti (%)

eesyn (%)

dr (anti/syn)

1

(R,R)-cat.1

HCO2H:Et3N (5:2)

MeOH

<5

–

–

–

2

(S,S)-cat.2

HCO2H:Et3N (5:2)

MeOH

<5

–

–

–

3

(S,S)-cat.3

HCO2H:Et3N (5:2)

MeOH

23

84

–

84:16

4

(R,R)-cat.4

HCO2H:Et3N (5:2)

MeOH

99

−96

–

90:10

5

(R,R)-cat.5

HCO2H:Et3N (5:2)

MeOH

90

−95

–

92:8

6

(R,R)-cat.6

HCO2H:Et3N (5:2)

MeOH

84

−96

–

95:5

7

(S,S)-cat.6

HCO2H:Et3N (5:2)

MeOH

85

96

–

95:5

8

(S,S)-cat.6

HCO2H:Et3N (5:2)

hexane

<5

–

–

–

9

(S,S)-cat.6

HCO2H:Et3N (5:2)

EtOH

71

93

–

97:3

10

(S,S)-cat.6

HCO2H:Et3N (5:2)

DCM

66

95

–

93:7

11

(S,S)-cat.6

HCO2H:Et3N (5:2)

THF

81

99

–

96:4

12

(S,S)-cat.6

HCO2H:Et3N (5:2)

dioxane

97

99

–

93:7

13

(S,S)-cat.6

HCO2H:Et3N (5:2)

toluene

>99

95

–

98:2

14

(S,S)-cat.6

HCO2H:Et3N (5:2)

EtOAc

>99

99

–

98:2

15b

(S,S)-cat.6

HCO2H:Et3N (2:0.02)

EtOAc

>99

–

96

2:98

16c

(S,S)-cat.6

HCO2H:Et3N (2:0)

EtOAc

>99

–

93

<1:99

17d

(S,S)-cat.6

iPrOH

iPrOH

<5

–

–

–

18e

(S,S)-cat.6

HCO2Na

iPrOH

<5

–

–

–

  1. aConditions: Catalyst/1a (0.1 mmol) ratio of 1:50 in 1 mL of solvent, HCO2H/Et3N azeotropic mixture (20 μL) at 25 °C for 12 h. Conversions (conv.) were determined by 1H NMR analysis. Enantiomeric excesses (ee) and diastereomeric ratios (dr) were determined by HPLC analysis using a chiral stationary phase.
  2. bHCO2H (2.0 equiv.) was used.
  3. cHCO2H (2.0 equiv.) was used for 48 h.
  4. dKOtBu (3.0 equiv.) was used in 1.0 mL of iPrOH at 60 °C for 12 h.
  5. eHCO2Na (5.0 equiv.) was used in 2.0 mL of iPrOH /H2O (1.0 mL/1.0 mL) at 60 °C for 12 h.
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