Table 1 The optimization of reaction parameters

From: Catalytic enantioselective construction of axial chirality in 1,3-disubstituted allenes

View full size image

Entry

1

R

Temp (°C)

Procedure

T (h)

Yielda of 3 (%)b

1c

1a-OAc

Et

30

A

17

64 (3a-Et) (69)

2c

1a

Et

30

A

17

80 (3a-Et) (69)

3

1a

Me

30

B

10

89 (3aa) (60)

4

1a

Me

30

C

4

88 (3aa) (87)

5

1a

Me

5

C

10

85 (3aa) (90)

6

1a

Me

0

C

15.5

88 (3aa) (88)

7

1a

Et

5

C

19

91 (3a-Et) (82)

8

1a

n-Pr

5

C

19

88 (3a-Pr-n) (84)

9

1a

i-Pr

5

C

30

83 (3a-Pr-i) (81)

  1. Procedure A: [Pd(π-cinnamyl)Cl]2 (0.005 mmol), (R)-(−)-DTBM-SEGPHOS (0.012 mmol), and K2CO3 (0.4 mmol) in NMP (1.0 mL) were stirred first at 30 °C for 30 min, then 1a-OAc (or 1a) (0.2 mmol)/NMP (0.5 mL) and malonate (0.4 mmol)/NMP (0.5 mL) were added sequentially and the resulting mixture was stirred at 30 °C
  2. Procedure B: [Pd(π-cinnamyl)Cl]2 (0.005 mmol), (R)-(−)-DTBM-SEGPHOS (0.012 mmol), K2CO3 (0.4 mmol), 1a (0.2 mmol)/THF (0.5 mL), and malonate (0.4 mmol)/THF (1.5 mL) were added together and the resulting mixture was stirred at 30 °C
  3. Procedure C: [Pd(π-cinnamyl)Cl]2 (0.005 mmol), (R)-(−)-DTBM-SEGPHOS (0.012 mmol), K2CO3 (0.4 mmol), and malonate (0.4 mmol)/THF (1.5 mL) were stirred at rt for 30 min, then 1a (0.2 mmol)/THF (0.5 mL) was added and the resulting mixture was stirred at specified temperature as shown in Table 1
  4. aIsolated yield after column chromatographic separation on silica gel
  5. bThe numbers in the parentheses are ee values determined by chiral HPLC analysis
  6. cNMP was used as solvent instead of THF
Back to article page