Non-metallic Fungicides

Abstract

IN the course of investigations on the synthesis of 2-amino-4-aryl thiazoles and their derivatives, it was decided to examine their fungicidal properties, as they contain a cyclic grouping, —N—C—S—, which is present in the structure of some of the well-known fungicides¹, and the presence of lipophilic and polar substituents like aryl- and amino-groups in the thiazole nucleus is expected to increase the fungi-toxic properties of the thiazoles as reported earlier². The recent use of some thiazole derivatives as fungicides³ has greatly stimulated work in this direction. The introduction of halogens into the benzene and other aromatic nuclei of various phenolic compounds greatly increases their fungicidal properties⁴, and as bromo-derivatives are often more potent than the chloro-compounds, it was thought worth while to introduce bromine into the thiazole nuclei with the hope of augmenting their fungicidal and other activities, in the present communication, seventeen different 2-amino-4-aryl (phenyl ; p-tolyl ; p-ethyl phenyl ; p-methoxy and p-ethoxy phenyl ; β-phenylethyl and β((p-methoxy)phenyl)ethyl ; 2 : 5 dimethyl phenyl and 3 : 4 dimethylphenyl ; α- and β-naphthyl ; o- and p-hydroxy phenyl ; m- and p-amino phenyl ; p-bromo phenyl and 2-thienyl) thiazoles have been prepared by the method of King and Hlavacek⁵ by allowing different aryl methyl ketones to react with thiourea in the presence of iodine. These compounds have been brominated with bromine in acetic acid medium after protecting the amino-group either by converting it to the hydro-bromide salt or by acetylating it. In all these cases bromine entered position 5 of the thiazole nucleus. The position of bromine was ascertained by the inability of such compounds to undergo coupling with diazotized aniline, which usually takes place at position 5⁶ if it is free.