Table 1 Optimization of reaction conditions

From: Stereoselectivity control in Rh-catalyzed β-OH elimination for chiral allene formation

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Entry

[Rh]

solvent

T (oC)

Yield, ee§ of (R)-3aa (%)

Recovery of (S)-1a (%)

yield of (R)-4aa

yield of (S)-5aa

1

[Cp*RhCl2]2

1,4-Dioxane

50

0, /

98

0

0

2

Rh2(OAc)4

1,4-Dioxane

50

0, /

99

0

0

3

[Rh(COD)Cl]2

1,4-Dioxane

50

65, 93

11

3

6

4

[Rh(COE)2Cl]2

1,4-Dioxane

50

0, /

97

0

0

5

[Rh(C2H4)2Cl]2

1,4-Dioxane

50

0, /

95

0

0

6

[Rh(NBD)Cl]2

1,4-Dioxane

50

3, /

95

0

0

7

Rh(NBD)2BF4

1,4-Dioxane

50

0, /

96

0

0

8

[Rh(COD)OH]2

1,4-Dioxane

50

89, 97

0

0

10

9

[Rh(COD)OH]2

1,4-Dioxane

rt

91, 98

0

0

9

10

[Rh(COD)OH]2

THF

rt

87, 98

/

/

5

11

[Rh(COD)OH]2

DME

rt

81, 98

/

/

4

12

[Rh(COD)OH]2

Et2O

rt

83, 91

/

1

16

13

[Rh(COD)OH]2

MTBE

rt

82, 92

/

1

16

14

[Rh(COD)OH]2

Ethyl acetate

rt

87, 99

/

/

13

15

[Rh(COD)OH]2

Acetone

rt

55, 97

34

/

2

16

[Rh(COD)OH]2

MeOH

rt

57, 93

/

30

10

17

[Rh(COD)OH]2

DCM

rt

8, /

82

0

3

18

[Rh(COD)OH]2

DCE

rt

9, /

78

0

3

19

[Rh(COD)OH]2

Toluene

rt

19, 92

57

1

9

20

[Rh(COD)OH]2

DMF

rt

15, 94

81

/

/

21

[Rh(COD)OH]2

MeCN

rt

/, /

100

/

/

22#

[Rh(COD)OH]2

1,4-Dioxane

rt

94, 98

0

0

8

  1. Reaction conditions: (S)-1a (0.2 mmol), PhB(OH)2 (0.4 mmol), and [Rh] (5 mol%) in solvent (1 mL) at T oC unless otherwise noted. Yield and recovery were determined by 1H NMR analysis using dibromomethane as the internal standard. § Determined by HPLC analysis. # 2.5 mol% of [Rh(COD)OH]2 was used. Cp* (pentamethylcyclopentadienyl), COD (1,5-cyclooctadiene), COE (cyclooctene), NBD (2,5-norbornadiene), THF (tetrahydrofuran), DME (1,2-ethanediol dimethyl ether), MTBE (methyl tert-butyl ether), DCM (dichloromethane), DCE (1,2-dichloroethane), DMF (N,N-dimethylformamide).
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