Communication
Entry 1). The scope of the methodology was further investi- Co
CO
. The sealed reaction vessel was heated using a microwave
2
8
gated on heteroarenes. The 11C-acetylation of 2-chlorothio-
cavity at the desired temperature for 1 min with active cooling,
after which the vial was cooled to room temperature. The crude
reaction mixture was diluted with the mobile phase (acetonitrile/
water, 1:1), and the radiochemical conversion (RCC) was established
with radio-HPLC.
phene resulted in a 31 % RCC into the desired aryl methyl ket-
one product (Table 2, Entry 9). Interestingly, RCCs of the same
1
1
magnitude, 16–22 %, were observed for the formation of [ C]2-
acetylpyridine independently of the halide substrate being
used (Table 2, Entry 8).
1
1
Acknowledgments
We thank all members of the PET group at the Karolinska Insti-
tutet for all their support.
Finally, [ C]2 was prepared on a preparative scale. 1500 MBq
1
1
(
40.4 mCi) isolated product [ C]2 was obtained in a 43 decay-
1
1
corrected radiochemical yield (RCY) calculated from CH3I
delivered to the reaction vessel. The RCP was higher than 99 %,
and the specific radioactivity was 230 GBq μmol–
1
Keywords: Radiochemistry · Carbon-11 · Positron emission
–
1
(
6212 Ci mmol ). The reported specific radioactivity is on a sim-
tomography · Carbonylation · Cobalt · Carbonyl ligands
11
11
ilar magnitude as other C-radioligands labelled using CH3I
in our laboratory. The product identity was confirmed by co-
elution on HPLC with UV and radioactive detection. However,
there was a discrepancy between the obtained RCY and the
previously measured analytical RCC (Table 1, Entry 5). This dis-
crepancy could be predominantly attributed to losses during
isolation of the product (e.g. at the injection to the HPLC, on
the column and during collection). In addition, about 10 % of
the radioactivity remained in the head-space at the end of the
reaction.
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Experimental Section
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No-carrier-added 11CH4 production was performed using a PET
cyclotron, followed by previously described gas-phase conversion
[
11
11
[3c]
11
of CH to CH3I. The produced CH I was trapped in vial con-
4
3
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3
Received: January 21, 2016
to a second vial equipped with a rubber septum, pre-charged with
Published Online: May 23, 2016
Eur. J. Org. Chem. 2016, 2775–2777
www.eurjoc.org
2777
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