N.C.A. 11C-labelled of benzoid compounds in ring positions:[11C]anisole derivatives

Article abstract of DOI:10.1002/(SICI)1099-1344(199707)39:7<585::AID-JLCR1>3.0.CO;2-7

The synthesis route to n.c.a. 3-nitro-[3-¹¹C]]anisole (3) by use of the principle of synchronous six-electron cyclization of hexatriene systems into aromatics is described and discussed. Nitro-[¹¹C]methane (1) reacts with the prepared precursor 5-dimethylamino-2-methoxy-penta-2,4-dienylidene-1- dimethylammonium tetranuoroborate (2b) in the presence of BuLi to form 1-dimethyl-amino-4-methoxy-6-nitro-[6-¹¹C] hexatriene (IA, IB), followed by cyclization/ aromatization into 3. Starting from 1, 3-nitro-[3¹¹C]]anisole of a radiochemical purity of about 65% and a mean specific radioactivity of 1 Ci/μmol was obtained within 10 min. Related to [¹¹C]CH₃NO₂, the reproducible radiochemical yield of 3 (decay-conected) was 60 ± 5 %. Reduction of 3 by heating the above reaction mixture with aqueous Na₂S gave 3-amino-[3-¹¹C]anisole (4) of a radiochemical purity of about 50 %. The reproducible radiochemical yield of 4 (decay-corrected) in relation to 1 was 45 ± 5 %, the synthesis time from 1 was 16 min.