Rapid Room-Temperature 11C-Methylation of Arylamines with [11C]Methyl Iodide Promoted by Solid Inorganic-Bases in DMF
[11C]Methyl iodide is the most widely used reagent for labeling radiotracers with carbon‐11 (t1/2 = 20.4 min) for molecular imaging with positron emission tomography. However, some substrates for labeling, especially primary arylamines and pyrroles, are sluggishly reactive towards [11C]methyl iodide...
Saved in:
Published in | European Journal of Organic Chemistry Vol. 2012; no. 7; pp. 1303 - 1310 |
---|---|
Main Authors | , , , |
Format | Book Review Journal Article |
Language | English |
Published |
Weinheim
WILEY-VCH Verlag
01.03.2012
WILEY‐VCH Verlag Wiley Wiley-VCH |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | [11C]Methyl iodide is the most widely used reagent for labeling radiotracers with carbon‐11 (t1/2 = 20.4 min) for molecular imaging with positron emission tomography. However, some substrates for labeling, especially primary arylamines and pyrroles, are sluggishly reactive towards [11C]methyl iodide. We found that insoluble inorganic bases, especially Li3N or Li2O, effectively promote rapid reactions (≤ 10 min) of such substrates with no‐carrier‐added [11C]methyl iodide in N,N‐dimethylformamide (DMF) at room temperature to give 11C‐methylated products in useful radiochemical yields. In particular, we discovered that some primary arylamines in Li3N/DMF were converted into their corresponding formanilides, and that these were readily N‐methylated with [11C]methyl iodide, which preceded easy basic hydrolysis to the desired [11C]N‐methyl secondary arylamines. The use of a solid base permitted selective reaction at an arylamino group and, in some cases, avoided undesirable side reactions, such as ester group hydrolysis. An ultrasound device proved useful to provide remote and constant agitation of the radioactive heterogeneous reaction mixtures but imparted no ultrasound‐specific chemical effect.
Solid inorganic‐bases in DMF promote rapid 11C‐N‐methylation of primary arylamines at room temperature when agitated with ultrasound, often through reactive N‐formyl intermediates. |
---|---|
Bibliography: | istex:62C21FA5FDF352AC2A4F0B0915840053F4153AD5 National Institute of Mental Health ark:/67375/WNG-P4QWS6Z8-0 ArticleID:EJOC201101499 National Institutes of Health (NIH) ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1434-193X 1099-0690 |
DOI: | 10.1002/ejoc.201101499 |