Table 1 Exploration of amine catalyzed enantioselective direct β-functionalization of 3-phenyl-propionaldehyde*.

From: Organocatalytic enantioselective β-functionalization of aldehydes by oxidation of enamines and their application in cascade reactions

 

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Entry

Cat.

Oxidant

Solvent

T (°C)

t (h)

Yield (%)†

ee (%)‡

1

I

IBX

CH2Cl2

RT

18

10

71

2

I

DMP

CH2Cl2

RT

18

<5

—

3

I

PIDA

CH2Cl2

RT

18

<5

—

4

I

DDQ

CH2Cl2

RT

18

<5

—

5

I

CAN

CH2Cl2

RT

18

<5

—

6

I

IBX/NMO§

CH2Cl2

RT

18

<5

—

7

I

IBX

DMSO

RT

18

<5

—

8

I

IBX/NMO∥

DMSO

RT

18

<5

—

9

I

IBX

EtOH

RT

18

55

55

10

I

IBX

Et2O

RT

18

8

73

11

I

IBX

Toluene

RT

18

24

76

12

I

IBX

Toluene

0

48

56

92

13

I

IBX

Toluene

0

48

68

92

14

II

IBX

Toluene

0

48

50

93

15

III

IBX

Toluene

0

48

38

99

16

IV

IBX

Toluene

0

48

0

—

  1. Abbreviations: DMP, Dess–Martin periodinane; PIDA, penyliodine (III) diacetate.
  2. * Unless stated otherwise, the reaction was carried out with 1a (0.10 mmol), IBX (0.10 mmol), 2 (0.05 mmol) and catalyst (0.01 mmol) in 0.6 ml of solvent for a specified time. The mixture was then directly purified by silica gel chromatography.
  3. † Isolated yield for two steps.
  4. ‡ ee was determined by HPLC analysis (Chiralcel AD) of compound 4a by reduction of aldehyde 3a.
  5. §NMO: 4-methylmorpholine N-oxide (0.24 mmol) and IBX (0.24 mmol) used.
  6. ∥Reaction condition: 4-NMO (0.24 mmol) and IBX (0.24 mmol) in DMSO was stirred at 65 °C.
  7. ¶0.015 mmol of I was used.
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