| Plant growth regulator is a kind of organic compound with plant hormone function synthesized by artificial methods. In order to seek good plant growth regulators, we have modified the main structure of 1,3,4-thiadiazole and synthesisized 26 new acyl thioureas, 8 new 1,3,4-thiadiazole Schiff bases by Bioisosterism Principles and Substructure Link Wory.By consulting concerning literatures, we reviewed the biological activities of 1,3,4-thiadiazoles , acyl thiourea and the synthesis methods of acyl thiourea.Target compounds I, II, III are synthesized by nucleophilic addition of amino heterocycle with acyl isothiocyanates in anhydrous and aprotonic solvent.Reaction of 2-amino-5-trifluoromethyl- 1,3,4-thiadiazole in anhydrous acetonitrile gave 26 new acyl thioureas. At the same time , Reaction of 2-amino- 1,3,4-thiadiazole with aryl aldehyde gave 8 new 1,3,4-thiadiazole Schiff bases. IR, MS, 1H NMR and elementary analysis comfirm their structure, their physical-chemical properties and spectrum data and synthesis condition of the target compounds were reported firstly. The main structures of the target compounds were as follows: I. N-(5-trifluoromethyl-1 ,3,4-thiadiazol-2-yl)-N'-aryl acyl thioureaII .N-(5-trifluoromethyl-l,3,4-thiadiazol-2-yl )-N'-aroxyl actyl thioureaIII.N-[5-(4'-pyridyl)-l,3,4-thiadiazol-2-yl ]-N'-aryl acyl thiourea IV. Schiff bases of 1,3,4- thiadiazoleThe plant growth regulating activity was tested by taking root and wheat sheath on the target compounds and the cucumber cotyledon expansion, preliminary results indicated that many of acyl thioureas exhibited higher auxin and cytokinin activity. The auxin activity of compound I d, I h, I k, II e, IIh, IIj, IIIb and IV e was weekly higher than that of p-indolyl acetic acid, The cytokinin activity of compound I b, I k, II d, II g , II hand IIIb was higher than that of 6-fiirylmethyl purine.The auxin and cytokinin activity of compound Ik, Hh and Illb are both high.
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