Synthesis and properties of the chlorination products of methyl 4‐Amino‐2‐Hydroxy‐Benzoate. II

Abstract

AbstractWhereas methyl 1,3,3,5,5,6‐hexachloro‐cyclohexanedione‐2,4‐carboxylate‐1 (XIV) was obtained by the chlorination of methyl 4‐amino‐2‐hydroxy‐benzoate (XIII) (P.A.S. methyl ester) in a mixture of glacial acetic acid and hydrochloric acid (s.g. 1.19), chlorination of XIII in carbon tetrachloride yielded two isomers with gross formula C8H4O3NCl7 (XXIII and XXIV), to which the structure of a methyl 1,3,3,5,5,6‐hexachloro‐4‐chlorimino‐cyclohexanone‐2‐carboxylate‐1 is assigned. The isomerism of XXIII and XXIV is thought to be of the syn‐anti type with regard to the attachment of the chlorine atom to the nitrogen. Reduction with stannous chloride converted both XXIII and XXIV into methyl 4‐amino‐3,5‐dichloro‐2‐hydroxy‐benzoate (XV). Hydrolysis of the two isomers led to the same nitrogen‐free compound C8H4O4Cl0, which is believed to be a stereo‐isomer of XIV and to which consequently the same name is attributed (XXV). With regard to the chlorine atoms attached to the carbon atoms 1 and 6, XIV is supposed to be the cis and XXV the trans form. Both XIV and XXV could be converted into methyl 3,5‐dichloro‐2,4‐dihydroxy‐benzoate (XVIII) by reduction. A mixture of XIV and XXV was obtained by chlorination of XIII, XV, XVIII and methyl 2,4‐dihydroxy‐benzoate in glacial acetic acid alone. In alkaline medium XXV decomposed, dichloro acetic acid and monomethyl trichloroglutaconate being the decomposition products. With hypochlorous acid XXV reacted to give trichloro‐acetic acid and methyl pentachloro‐glutarate (XXVI). Aniline converted XIV and XXV into two isomeric addition products: C14H11O4NCl6. Whereas XXV is reduced to XVIII by an aqueous potassium iodide solution, XIV yielded a compound for which the structure of a methyl 1,3,5,5,6‐pentachloro‐2‐hydroxy‐cyclohexene‐2‐one‐4‐carboxylate‐1 (XXIX) is made plausible. Further reduction converts XXIX into XVIII. Our view on some of the structures is supported by evidence from U.V. and I.R. spectra. Of several compounds tested, XXIV showed a considerable fungicidal activity.