Biological evaluation of newly synthesized aryl(thio)carbamoyl derivatives of 1- and 1-(2-aminoethyl)-piperazines

Twelve 1-methyl and acetyl-4-substituted piperazines, evaluated as potential herbicides and plant growth regulators, were synthesized by condensation of 1-methyl-piperazine and 1-[2-(acetylamino)ethyl]-4-acetyl-piperazine with the corresponding aryliso(thio)cyanates. These piperazines, which incorporate a piperazine ring and aryl(thio)carbamoyl groups connected directly or through an ethylene group, are new chemical families of herbicides and cytokinin mimics. Structure–activity relationships for the screened compounds were evaluated and discussed. The greatest herbicidal activity against Triticum aestivum was observed with compounds that contained the three structural elements: piperazine ring, ethylene group and 4-fluorophenylcarbamoyl group. Compounds having a combination of two active moieties–piperazine ring and 4-halogenophenylthiocarbamoyl group, also showed high herbicidal activity against T. aestivum. The compound, in which the un-substituted phenylcarbamoyl group was directly connected to the piperazine ring, showed cytokinin-like activity and significantly stimulated betacyanin synthesis in Amaranthus caudatus.