Synthesis of Tyrosol 1,2,3-Triazole Derivatives and Their Phytotoxic Activity against Euphorbia heterophylla .

The synthesis and phytotoxic activity of a series of tyrosol 1,2,3-triazole derivatives are reported herein. Target compounds were synthesized through the copper(I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC), known as click reaction, and these were tested for phytotoxic activity on leaves of wild poinsettia ( Euphorbia heterophylla ), fleabane ( Conyza sumatrensis ), and tropical spiderwort ( Commelina benghalensis ). These are three highly noxious agricultural weeds that challenge available weed control methods, including the use of chemical herbicides. Twenty-five compounds were synthesized and tested. None of the compounds showed phytotoxic activity against C. benghalensis and C. sumatrensis , but almost all of them produced yellowing, bleaching, and necrosis on leaves of E. heterophylla . Two of the tyrosol 1,2,3-triazole derivatives produced more extensive lesions than those produced by the commercial herbicide diquat, used as a positive control ( p ≤ 0.05). When applied on leaves of E. heterophylla , these compounds interfered with the stomatal conductance, net photosynthesis, internal carbon concentration, transpiration rate, water-use efficiency, and chlorophyll A and B contents. The interference of such compounds on such photosynthesis-related variables indicates that tyrosol 1,2,3-triazole derivatives may be capable of lowering the competitiveness of E. heterophylla and acting as additional tools for managing this competitive weed in agricultural lands.