An efficient method for the synthesis of 1-isopropyl-4-isothiocyanato-4-methylcyclohex-1-ene has been developed with p-menth-3-en-1-amine as raw material. Next, a number of p-menth-3-en-1-amine thiourea derivatives (4a-f) have been obtained from the reactions between 1-isopropyl-4-isothiocyanato-4-methylcyclohex-1-ene and cyclohexylamine or the reactions between p-menth-3-en-1-amine and different isothiocyanates. Then, the herbicidal activities of these compounds were evaluated. The result indicated that some of these newly synthesised compounds displayed remarkable herbicidal activities against annual ryegrass. In addition, the derivative containing cyclohexane ring (4a) displayed much higher herbicidal activity against annual ryegrass than the derivatives containing benzene ring.
Keywords: annual ryegrass; herbicidal activity; p-Menth-3-en-1-amine thiourea derivatives; synthesis.