NCA C-11 LABELING OF BENZENOID COMPOUNDS IN RING POSITIONS - [C-11] ANISOLE DERIVATIVES

The synthesis route to n.c.a. 3-nitro-[3-C-11]anisole (3) by use of th e principle of synchronous six-electron cyclization of hexatriene syst ems into aromatics is described and discussed. Nitro-[C-11]-methane (1 ) reacts with the prepared precursor 2-methoxy-penta-2,4-dienylidene-1 -dimethylammonium tetrafluoroborate (2b) in the presence of BuLi to fo rm dimethylamino-4-methoxy-6-nitro-[6-C-11]hexatriene (IA, IB), follow ed by cyclization/ aromatization into 3. Starting from 1, 3-nitro-[3-C -11]anisole of a radiochemical purity of about 65 % and a mean specifi c radioactivity of 1 Ci/mu mol was obtained within 10 min. Related to [C-11]CH3NO2, the reproducible radiochemical yield of 3 (decay-correct ed) was 60+/-5 %. Reduction of 3 by heating the above reaction mixture with aqueous Na2S gave 3-amino-[3-C-11]anisole (4) of a radiochemical purity of about 50 %. The reproducible radiochemical yield of 4 (deca y-corrected) in relation to 1 was 45+/-5 %, the synthesis time from 1 was 16 min.