Synthesis and Auxin-like Activity of Halogenated Alkylphenoxyacetic Acids

Synthetic auxins are widely used nowadays as plant growth regulators and necessary components of media for micropropagation. Hence, the search for and development of novel auxin-like compounds is an important goal at the intersection of chemistry and biology. In this study, we have suggested alkylphenols as starting materials for the preparation of halogenated phenoxyacetic acids, which are well-known synthetic auxins, to decrease their possible phytotoxicity. Alkylphenoxyacetic acids were obtained with good yields, and their selective halogenation was studied. N-halogensuccinimides and molecular bromine in dioxane were shown as suitable reagents since they allowed for p-halogenophenoxyacetic acids to be synthesized with high yields. We further investigated the auxin-like activity of several obtained compounds. It was estimated that all of them stimulate tobacco Nicotiana tabacum L. pollen germination at concentrations 10−6–10−7 M with the maximum effect up to 157%. For the most efficient compounds, the germination of tobacco (Nicotiana tabacum L.) and corn (Zea mays) seeds was studied, as well as seedling growth. The results demonstrate the efficacy of obtained compounds as synthetic auxins, showing that alkylphenols are prospective starting materials for such compounds.