4-Fenchylthiosemicarbazide (4) was synthesized from (－)-fenchone by a three-step reaction in a yield of 45%. A series of 4-fenchylthiosemicarbazones (5a～5k) were obtained by the condensation of 4 with aryl aldehydes in 83%～98% yields. Cyclization of 5 in the presence of K3[Fe(CN)6] afforded eleven undocumented 2-aryl-5-fenchylamino-1,3,4-thiadiazoles (6a～6k) in yields of 71%～91%. The structures of 5 and 6 were established on the basis of IR, NMR spectra and elemental analysis, and the structure of 6d was confirmed by X-ray single-crystal diffraction analysis. The crystal of 6d belongs to monoclinic, space group P2(1) with cell parameters a＝1.18719(10) nm, b＝1.48814(18) nm, c＝1.21629(12) nm, β＝118.113(2)°, Mr＝343.48, V＝1.8953(3) nm3, Z＝4, Dc＝1.204 Mg/m3, λ＝0.071073 nm, μ(Mo Kα)＝0.181 mm－1 and F(000)＝736.

Key words: thiosemicarbazone, 1,3,4-thiadiazole, crystal structure, synthesis, fenchone