Process for separating pyethroid geometric isomers

Details Process for separating pyethroid geometric isomers Process for separating pyethroid geometric isomers

1986-09-26

1989-06-27

Shippen, Michael L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

C07C 5143

Patent

active

048431745

DESCRIPTION:

BRIEF SUMMARY
The invention relates to the separation of the geometrical isomers of cyclopropane carboxylic acids of formula (I) ##STR2## wherein R represents alkyl having 1 to 4 carbon atoms or halogen.
The separated geometrical isomers compared with the isomeric mixtures may be used as starting materials of novel pyrethroids having very favorable insecticidal properties.
It is known that many of the insecticidal pyrethroids, which have a substituted cyclopropane carboxylic acid skeleton, are the mixtures of geometrical and optical isomers. In recent decades much search and development has been directed to the more effective isomers and to their preparation, respectively, since a relation between the structure and the effectiveness has been found. The greater effectiveness relates not only to the greater biological activity but also to superior toxicological, environmental and optionally economical considerations.
The isomeric ratio of the synthetic, substituted cyclopropane was adjusted to the advantageous value in many ways. E.g. in the most usual synthesis of the cyclopropane ring formation (cycloaddition) the methylene transfer catalysts were varied. First of all copper and copper compounds (J. Am. Chem. Soc., 74, 5376 (1952); J. Am. Chem. Soc. 73, 5301, [1951]; Chem. Ber. 99, 2855 [1966]; Bull. Chem. Soc. Jap. 40, 2392 [1967]), organic metal complexes (Chem. Com. p. 1378 [1968]; J. Org. Chem. 16, p. 30 [1969]; J. Org. Chem. 23, p. 215 [1970]; Chem. Com. p. 1199 [1967]; Che. Com. p. 1220 [1970], J. Org. Chem. 22, C 39 [1970] were used. In case of the formation of the substituted base skeleton the mass production of the desired favorable isomers is not, however, a feasable way from an industrial, technological and economical point of view and this is also valid for the cyclopropane carboxylic acid derivatives (GB-PS 1,446,304, J. Org. Chem. 17, 381 [1952], GB-PS 1,413,491).
For the separation of the stereoisomeric (cis, trans) mixtures of substituted cyclopropane carboxylic acids the fractionated crystallization is suggested most widely in the literature (Coll. Czech. Chem. Com. 24, 2230 [1959]; Pestic. Sci. 1974, 532; Pestic, Sci. 1974, 791).
The efficiency and economy of these processes is generally not satisfactory.
The separations on the basis of solvent selectivity are also not suitable. According to these processes e.g. in case of chrysanthemic acid and permethrinic acid medium yields are obtained. Furthermore great amounts of benzene or petrolether are used for the recrystallization or digeration is performed (Coll. Czech. Chem. Com. 24, 2230 [1959]). The same may be stated for other processes based on solvent selectivity (Pestic. Sci. 1971, 245; DE-OS No. 2,439,177).
A new and witty solution is described (DE-PS No. 2,800,922) according to which two moles of cyclopropane carboxylic acid sodium salt are reacted with one mole of racemic alpha-phenylethylamine whereafter the phenylethylamine salt of the cis isomer may be separated from the sodium salt of the trans isomer. After extraction with ether from the aqueous phase the isomeric purity is, however, only 80/20 and 20/80, respectively. The disadvantage of this process is also that higher isomeric purity may be obtained by recrystallization from petrolether. This means a fractionated recrystallization with a 60% conversion calculated from the material balance.
The invention is based on the recognition that the geometrical isomers of the cyclopropane carboxylic acids of formula (I) ##STR3## may be separated with great selectivity through their salts of formula (IV) ##STR4## formed with the compounds of formula (II) ##STR5## in a suitable buffered aqueous medium.
The invention is characterized by
(a) treating a cyclopropane carboxylic acid of formula (I) ##STR6## wherein R represents alkyl having 1 to 4 carbon atoms or halogen with a compound of formula (II) ##STR7## wherein R.sup.1 and R.sup.2 are independently hydrogen, straight or branched chained alkyl having 1 to 5 carbon atoms, straight or branched chained alkenyl having 2 to 5 carbon atoms, phenyl, aralk

REFERENCES:
patent: 3666798 (1972-05-01), Matsui
patent: 4236026 (1980-11-01), Naumann
patent: 4306077 (1981-12-01), Leigh
patent: 4337352 (1982-06-01), Naumann
patent: 4599444 (1986-07-01), Foggussy
patent: 4683089 (1987-07-01), Leigh

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