Table 1 Reaction optimization for shifting the equilibrium of labelling among [18F]1b, [18F]TsF and [18F]1a

From: A protocol for controlled reactivity shift in the 2,2-difluorovinyl motif used for selective S–18F and C–18F bond formation

Entry (substrate)

Additive

RCY (%)

[18F]TsF

[18F]1a

[18F]1b

1 (1a)

Air

14.9 ± 0.8

51.1 ± 0.8

34.3 ± 0.8

2 (1a)

N2

4.9 ± 0.8

9.1 ± 2.1

62.3 ± 2.9

3 (1a)

i-PrOH, N2

3.3 ± 2

19.3 ± 0.6

63.3 ± 1

4 (1a)

N2/CuOAc, TEMPO

63.4 ± 2

19.6 ± 2

1.7 ± 1

5 (1a)

CuOAc, Air

9.4 ± 2

71.7 ± 2

traces

6 (1a)

CuCN, Air

29.6 ± 2

27 ± 1

14.5 ± 3

7 (1a)

CuBH4

traces

6.4 ± 1

71.5 ± 3

8 (1a)

N2/CuOAc TEMPO, phosphite

23.5 ± 2

29.0 ± 2

44.1 ± 3

9 (1a)

(Bu)4SnH

9.9 ± 0.6

4.1 ± 1

2.6 ± 1

10 (1a)

No additive

34.3 ± 2

31.4 ± 0.9

22.1 ± 1

11 (1a)

i-PrOH, air

16.5 ± 0.7

5.9 ± 1

52.6 ± 1.3

12 (1a)

Et3SiH, Ag (II)

37.9 ± 1

28.4 ± 2

6.5 ± 0.5

13 (1a)

TEMPO, Et3SiH, Ag (II)

25.8 ± 1

48.1 ± 1

19.8 ± 1

14 (1a)

Et3SiH, 2-propanol, Ag (II)

37.3 ± 1.3

6.9 ± 0.6

50.3 ± 2

15 (1a)

TEMPO, Et3SiH, 2-propanol, Ag (II)

22.1 ± 2

7.2 ± 2

61.3 ± 0.8

16 (1a)

TEMPO, Et3SiH, 2-propanol,

15.8 ± 0.7

8.2 ± 1

74.0 ± 1.6

17 (1a)

TEMPO, Et3SiH,2-methyl-2-butanol

3.0 ± 0.8

0 ± 1

86.7 ± 1

18 (1a)

TEMPO, Et3SiH, 2-methyl-2-butanol (1 mL) no DMSO

55.4 ± 2

0 ± 2

36.2 ± 2

  1. The starting material (1a) 17 µmol was dissolved in DMSO (1 mL) containing Et3SiH (1 equiv.) and 2-methyl-2-butanol (10%, v:v). Radio-HPLC was used to confirm the product formation and the corresponding proportions. RCY= Radiochemical yields are given in %age. Data are mean values ± SD for each reaction performed in triplicates.
Back to article page