Table 1 Optimization of the reaction conditionsa

From: Diastereoselective synthesis of multi-substituted cyclobutanes via catalyst-controlled regiodivergent hydrophosphination of acyl bicyclobutanes

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Entry

Catalyst

Solvent

T (°C)

3a

3a

4a 

4a

Yield (%)b

d.r.c

Yield (%)b

d.r.c

1

MgI2

THF

25

17

7:1

<5

–

2

ZnCl2

THF

25

23

2:1

0

–

3

CuI

THF

25

80

3:1

0

–

4

CuBr

THF

25

78

4:1

<5

–

5

CuCl

THF

25

95

16:1

0

–

6

Cu(CH3CN)4PF6

THF

25

92

6:1

0

–

7

Cu(OAc)2

THF

25

81

3:1

0

–

8

CuF2

THF

25

38

1:1

10

2:1

9

CuCl2

THF

25

49

5:1

38

6:1

10

CuBr2

THF

25

17

2:1

44

7:1

11

CuCl

toluene

25

90

18:1

0

–

12

CuCl

CH2Cl2

25

97

6:1

0

–

13

CuCl

MeOH

25

50

15:1

0

–

14

CuCl

THF

25

93

12:1

0

–d

15

CuCl

THF

60

97

>20:1

0

–

16

–

THF

25

0

–

0

–

17

–

THF

60

22

–

0

–e

18

CuBr2

toluene

25

9

4:1

33

3:1

19

CuBr2

CH2Cl2

25

12

2:1

15

2:1

20

CuBr2

DMSO

25

24

2:1

64

3:1

21

CuBr2

DMA

25

19

1:1

56

4:1

22

CuBr2

DMF

25

13

2:1

55

12:1

23

CuBr2

DMF

25

26

3:1

69

6:1f

24

CuBr2

DMF

25

64

15:1

36

9:1g

25

CuBr2

DMF

25

8

1:1

70

9:1 f,h

26

CuBr2

DMF

60

16

1:1

78

>20:1f,h

  1. a1a (0.2 mmol), 2 (0.24 mmol) and catalyst (10 mol%) in solvent (2.0 mL) stirred at T °C for 24 h, then quenched  with H2O2.
  2. bCombined NMR yield determined by 1HNMR spectroscopy with CH2Br2 as an internal standard.
  3. cDetermined by 1H NMR spectroscopic analysis of the crude reaction product.
  4. dCs2CO3 (0.5 equiv) was added.
  5. eThe reaction mixture was stirred at 60 °C for 48 h.
  6. f1a (0.2 mmol) and 2 (0.4 mmol) were used.
  7. g1a (0.4 mmol) and 2 (0.2 mmol) were used.
  8. hLiBr (1.0 equiv) was added.
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