Route to the tritiation of carbon atom‐9 of carcinogenic fluorenylhydroxamic acids

The selective tritiation of the methylene carbon atom of the carcinogens, N‐fluoren‐3‐yl‐and N‐fluoren‐1‐ylacetohydroxamic acid, has been investigated. The synthesis of N‐[9‐ 3 H]fluoren‐3‐ylacetohhydroxamic acid involves hydrogenolysis of 3‐aminofluoren‐9‐one to [9‐ 3 ]fluoren‐3‐amine with LiAl 3 H 4 ‐A1C1‐. The tritiated amine is oxidized to 3‐nitro‐[9‐ 3 H]fluorene with m‐chloroperoxybenzoic and the labeled nitro compound is partially hydrogenated to the 3 H‐hydroxamic acid with 10% Pd–C catalyst in presence of acetic anhydride and triethylamine or dimethylaniline. N‐[9‐ 3 H]fluoren‐1‐ylacetohydroxamic acid may be obtained from 1‐aminofluoren‐9‐one by the same procedure. However, N‐[9‐ 3 H]fluoren‐2‐ylacetohydroxamic acid cannot be prepared in this way because reduction of 2‐aminofluoren‐9‐one with LiA1H4‐A1C1 3 does not proceed beyond the alcohol, 2‐aminofluoren‐9‐ol.