Table 1 Optimization of reaction conditionsa

From: Atroposelective construction of axially chiral alkenylindole-fused nine-membered rings via catalytic asymmetric formal (4 + 5) cycloaddition

entry

Cat.

solvent

1a:2a

yield (%)b

ee (%)c

1

(R)−4a

DCE

1:1.2

12

12

2

(R)−4b

DCE

1:1.2

N.R.

-

3

(R)−4c

DCE

1:1.2

15

23

4

(R)−4d

DCE

1:1.2

5

31

5

(R)−4e

DCE

1:1.2

4

50

6

(R)−4f

DCE

1:1.2

13

79

7

(S)−4g

DCE

1:1.2

N.R.

-

8

(S)−4h

DCE

1:1.2

7

−47

9

(R)−4i

DCE

1:1.2

7

51

10

(R)−4j

DCE

1:1.2

13

85

11

(R)−4k

DCE

1:1.2

N.R.

-

12

(R)−4j

toluene

1:1.2

trace

-

13

(R)−4j

THF

1:1.2

N.R.

-

14

(R)−4j

CH3CN

1:1.2

N.R.

-

15

(R)−4j

acetone

1:1.2

N.R.

-

16

(R)−4j

EtOAc

1:1.2

N.R.

-

17

(R)−4j

DCE

1:2

20

85

18

(R)−4j

DCE

2:1

trace

-

19 d

(R)−4j

DCE

1:2

55

94

  1. aUnless otherwise indicated, the reaction was carried out on 0.1 mmol scale in the presence of 10 mol% Cat. at 30 oC in a solvent (1.0 mL) with 3 Å MS (100 mg) for 5 h.
  2. bIsolated yield.
  3. cThe ee value was determined by HPLC.
  4. dUsing 30 mol% (R)−4j. DCE = ClCH2CH2Cl. MS = molecular sieve.
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