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EJNMMI Radiopharmacy and Chemistry

Table 1 Reduction of [11C] benzyl isocyanate to [11C] benzylformamide ([11C]1)a

From: Rapid one-pot radiosynthesis of [carbonyl-11C]formamides from primary amines and [11C]CO2

Entry

NaBH4 Equiv.

Temp (°C)

Time (min)

RCY of [11C]3 (%)

RCY of [11C]2 (%)

RCY of a unknown radioactive by-product (%)

RCY of [11C]1 (%)

1b

15

150

15

0

47

53

0

2

10

20

10

33 ± 6

35 ± 8

23 ± 5

11 ± 1

3

5

20

10

2 ± 1

16 ± 4

3 ± 1

77 ± 3

4

15

20

10

57 ± 4

16 ± 3

17 ± 5

0

5

15

60

10

42 ± 4

38 ± 4

28 ± 8

0

6

15

0

10

80 ± 4

9 ± 4

6 ± 3

0

7

15

0

15

79 ± 6

10 ± 2

8 ± 2

0

8

15

0

5

60 ± 3

15 ± 4

8 ± 4

8 ± 4

9

15

0

2

60 ± 2

13 ± 4

9 ± 1

14 ± 2

  1. aReaction conditions for all entries: [11C]CO2 was bubbled at 0 °C for 2 min in a solution of benzylamine (4.7 μmol, 1 equiv.) and BEMP (3.7 equiv.) in diglyme (75 μL). At end of delivery (EOD, 2 min) a solution of POCl3 (11.5 equiv.) in diglyme (75 μL) was added in the same vial, allowing the reaction for 2 min at 0 °C. A solution of NaBH4 (0.89–2.67 mg, 5–15 equiv.) in diglyme (50 μL) was then added. The reduction occurred at 0–60 °C for 2–15 min. Trapping efficiency (TE) > 95% for all entries. n = 3. RCY (non-isolated) is the percentage of product radioactivity divided by total radioactivity observed in an analytical HPLC chromatogram
  2. bn = 1
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