Abstract: Alpha-isopropyl-p-chlorophenylacetic acid, which is an acid moiety of the pyrethroidal ester pesticides is subjected to optical resolution using optically active alpha-phenyl-beta-p-tolylethylamine or optically active alpha-phenylethylamine, as the optical resolution agent. The reaction of the acid with the amine is carried out in a hydrophobic organic solvent, such as aliphatic and aromatic hydrocarbons, in the presence of water, until the desired salt of the acid with the amine is separated therein through selective crystallization.

Abstract: Optically active cyclopentenolones, which are useful as an intermediate of pyrethroid insecticides, are produced from racemic cyclopentenolones according to the following procedures; (1) asymmetric hydrolysis of racemic carboxylate esters of the cyclopentenolones, (2) nitrate- or sulfonate-esterification of the asymmetrical hydrolysis products, and (3) hydrolysis of the esterification products.

Abstract: Optically active cyclopentenolones, useful as an intermediate to be directed to pyrethroid insecticide, are produced starting from the optically active cyclopentenolones with the opposite configuration, through the formation of their nitrate ester, followed by the hydrolysis with inversion of configuration.

Abstract: A process for producing N-alkylbenzothiazolone derivatives of the formula (I), ##STR1## wherein R.sub.1 is a hydrogen, chlorine, bromine, fluorine atom or a methyl group, and R.sub.2 is an alkyl group having 1 to 5 carbon atoms, from 2-halogenobenzothiazole derivatives of the formula (II), ##STR2## wherein R.sub.1 is as defined above and X is a chlorine, bromine or fluorine atom, which is a starting material, through the intermediate of 2-alkoxybenzothiazole derivatives of the formula (III), ##STR3## wherein R.sub.1 and R.sub.2 are as defined above, or benzothiazolone derivatives of the formula (IV), ##STR4## wherein R.sub.1 is as defined above.

Abstract: A process for producing 3-methyl-2-(4-halophenyl)butyronitrile, which is an important intermediate for the production of insecticides, in a high yield and a high purity even on a commercial scale comprising reacting a p-halophenylacetonitrile having a p-halobenzyl alcohol content of not more than 1.0 % by weight, with an isopropyl halide having an isopropyl alcohol content of not more than 1.0 % by weight.

Abstract: A method for preparing a 3-methyl-2-(4'-halogenophenyl)-butyronitrile which comprises alkylating a p-halogenophenylacetonitrile by reacting the p-halogenophenylacetonitrile with an isopropyl halide in the presence of an aqueous alkali metal hydroxide solution, using an organic guaternary ammonium salt as a catalyst.

Abstract: The present invention provides a process for preparing racemic allethrolone which comprises reacting (-) allethrolone with hydroxylamine to form the corresponding allethrolone.oxime and then hydrolyzing the oxime in water or a mixture of water and an organic solvent miscible with water in the presence of an acid.

Abstract: A process is provided for preparing racemic allethrolone which comprises reacting (-) allethrolone with phosphorus chloride compounds in the presence of a Lewis acid, and hydrolyzing the racemic 4-chloro-allethrone thus obtained.