Table 1 Optimization of the reaction conditions

From: Cu-catalyzed asymmetric regiodivergent electrosynthesis and its application in the enantioselective total synthesis of (-)-fumimycin

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Entry

L

1

2

T

Results of 3

Results of 4a

Results of 5a

1

(S,S)-L1

1a

2a

10 °C

68% yield, 38% e.e.

–

–

2

(R)-L2

1a

2a

10 °C

54% yield, 34% e.e.

–

–

3

(R)-L3

1a

2a

10 °C

52% yield, 3% e.e.

–

–

4

(S,Sp)-L4

1a

2a

10 °C

61% yield, 89% e.e.

–

–

5

(S,Sp)-L5

1a

2a

10 °C

71% yield, 92% e.e.

–

–

6a

(S,Sp)-L5

1a

2a

−10 °C

57% yield, 92% e.e.

–

–

7

(S,Sp)-L5

1b

2a

−10 °C

65% yield, 93% e.e.

16% yield, 97% e.e.

–

8

(S,Sp)-L5

1c

2a

−10 °C

–

66% yield, 87% e.e.

–

9

(S,Sp)-L5

1d

2a

−10 °C

–

83% yield, 81% e.e.

–

10

(S,Sp)-L4

1d

2a

−10 °C

–

80% yield, 95% e.e.

–

11

(S,Sp)-L4

1d

2b

−10 °C

–

–

78% yield, 92% e.e.

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  1. Reactions were performed by using racemic ketimine ester 1 (0.15 mmol), hydroquinone 2 (0.225 mmol), Cu(MeCN)4BF4 (10 mol%), L (12 mol%), KOAc (0.3 mmol), nBu4NClO4 (0.07 M), and THF (4 mL) under constant-current conditions in an undivided cell. Enantiomeric excess was analyzed by chiral HPLC.
  2. nBu4NClO4 tetrabutylammonium perchlorate, 1-Nap 1-naphthyl, Me methyl, Bn benzyl.
  3. a1a was recovered in 30% yield with 98% e.e.
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