Table 1 Optimisation of the model reactionView full size image

From: Desymmetric esterification catalysed by bifunctional chiral N-heterocyclic carbenes provides access to inherently chiral calix[4]arenes

Entrya

Alcohol

pre-Catalyst

Time

(h)

Yieldb

(3, %)

Yieldb

(4, %)

Erc

(3)

1d

MeOH

pre-C1

48

n.d.

n.d.

59:41

2

2-naphthol

pre-C1

15

58

11

52:48

3

2-naphthol

pre-C2

15

51

13

64:36

4

2-naphthol

pre-C3

1

61

15

98:2

5

2-naphthol

pre-C4

1

63

13

98:2

6e

2-naphthol

pre-C3

30

37

5

57:43

7f

2-naphthol

pre-C3

1

62

13

60:40

8g

2-naphthol

pre-C3

1

61

27

83:17

9h

2-naphthol

pre-C3

72

24

–

81:19

10i

2-naphthol

pre-C3

1

68

10

98:2

11i,j

2-naphthol

pre-C3

1

84

8

98:2

  1. Er enantiomeric ratio.
  2. aReactions performed with 1a (0.06 mmol), corresponding alcohol 2 (0.05 mmol), Cs2CO3 (0.075 mmol), DQ (0.06 mmol), and precatalyst (20 mol%) in DCM (1.0 ml) at room temperature.
  3. bIsolated yield after column chromatography.
  4. cDetermined by chiral HPLC analysis.
  5. dReaction performed with 1a (0.05 mmol) and methanol (0.25 mmol).
  6. eUsing Rb2CO3 as a base.
  7. fUsing DMSO as a solvent.
  8. gUsing MTBE as a solvent.
  9. hUsing MnO2 as an oxidant.
  10. iWith 10 mol% of pre-C3.
  11. jUsing 0.10 mmol Cs2CO3.
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