Substituted diphenyl ether derivatives of the formula (I), ##STR3## wherein A stands for halogen or a cyano group;
X stands for hydrogen or halogen; PA1 Y stands for hydrogen or halogen; PA1 Z stands for oxygen or sulfur; PA1 R stands for a C.sub.1-3 alkylene group substituted by a C.sub.1-4 alkyl group; and PA1 R.sub.1 stands for a C.sub.1-10 alkyl group PA1 a) reacting the (S) enantiomer or racemate of a lactic acid ester of the formula (II), ##STR4## wherein R is a methyl or ethyl group, with an at least stoichiometric amount of a 2-chloro-5-(2-chloro-4-trifluoromethylphenoxy)benzoyl halide, preferably the chloride, suitably in the presence of an acid binding agent; or PA1 b) reacting the (S) enantiomer or racemate of an alkyl 2-halopropionate of the formula (III), ##STR5## wherein R stands for a methyl or ethyl group and Hal is chlorine or bromine, with 2-chloro-5-(2-chloro-4-trifluoromethylphenoxy)benzoic acid, preferably in the presence of an aza-compound, such as 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU). PA1 a) reacting the (S) enantiomer or racemate of a lactic acid ester of the formula (II), wherein R is a methyl or ethyl group, with 2-chloro-5-(2-chloro-4-trifluoromethylphenoxy)benzoyl halide, preferably the chloride in a solvent, preferably in the presence of an acid binding agent; or PA1 b) reacting the(S) enantiomer or racemate of an alkyl 2-halopropionate, preferably of alkyl 2-bromopropionate of the formula (III), where R is a methyl or ethyl group and Hal is chlorine or bromine, with 2-chloro-5-(2-chloro-4-trifluoromethylphenoxy)benzoic acid in a solvent, suitably in the presence of an aza-compound, preferably in the presence of 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU),
are described in the German patent specification (DE-PS) No. 3,029,728.
Although the compounds of the formula (I) according to the present invention are within the scope of the formula (1) of the German patent specification (DE-PS) No. 3,029,728, only a single compound namely, (RS)-1'-ethoxycarbonylethyl 2-bromo-5-(2-chloro-4-trifluoromethylphenoxy)benzoate is disclosed in the patent specification cited above.
Neither the (S)-enantiomers nor racemates of the compounds according to the present invention, nor their preparation, physical and chemical characteristics and herbological properties are defined in the patent specification cited above. Thus, these compounds have not been prepared and are therefore novel.
There is a constant demand for novel compounds capable of inhibiting the development of an undesired vegetation. The principal aim of the research consists in the selective inhibition of the development of weeds in the most frequent cases such as wheat, maize, rice soy bean or cotton. The uncontrolled growth of weeds is accompanied by a significant loss of production whereby the gain of the grower (farmer) is lowered and the expenses of the consumer become higher.