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N.C.A. 11 C‐labelling of benzenoid compounds in ring positions: Synthesis of nitro‐[1‐ 11 C]benzene and [1‐ 11 C]aniline
Author(s) -
Steinbach J.,
Mäding P.,
Füchtner F.,
Johannsen B.
Publication year - 1995
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580360104
Subject(s) - chemistry , aniline , nitro , yield (engineering) , benzene , radiosynthesis , medicinal chemistry , ring (chemistry) , derivatization , nitro compound , organic chemistry , high performance liquid chromatography , alkyl , materials science , microbiology and biotechnology , in vivo , metallurgy , biology
The paper describes the first method for n.c.a 11 C‐ring labelling of benzenioid compounds having a reactive group for further derivatization by use of the known principle of synchronous six‐electron cyclization of hexatriene systems into aromatics. Nitro‐[ 11 C]methane ( 1 ) prepared from cyclotron‐produced [ 11 C]carbon dioxide reacts in the presence of t‐BuOK with 5‐dimethylaminopenta‐2,4‐dienylidene‐dimethylammonium perchlorate ( 2 ) to form 6‐nitro‐1‐dimethylamino‐[6‐ 11 C]hexatriene ( 3 ) follow by cyclization/ aromatization into nitro‐[1‐ 11 C]‐benzene ( 4 ) at increased temperatures. Starting from 1 , nitro‐[1‐ 11 C]benzene of a radiochemical purity of about 92 % and a mean specific radioactivity of 1 Ci/μmol was obtained within 7 min. Related to [ 11 C]CO 2 , the reproducible radiochemical yield of 4 (decay‐corrected) was 80±5 %. Reduction of 4 by heating the above reaction mixture with aqueous Na 2 S gave [1‐ 11 C]aniline ( 5 ) of aradiochemical purity of about 81 %. The reproducible radiochemical yield of 5 (decay‐corrected) in relation to [ 11 C]CO 2 was 65±5 %, the synthesis time from 1 was 18 min.