Thiazolidinone acaricides

Use pattern Hexythiazox is a thiazolidinone acaricide which has ovicidal, larvicidal and nymphicidal activities against many kinds of phytophagous mites infesting pome fruits, stone fruits, citrus, vegetables and other food crops. On these mites, hexythiazox works by both contact and stomach action... 

The discovery of the thiazolidinone acaricides in the laboratories of Nippon Soda started during work on fungicidal thiazolo[2,3-ib]triazine derivatives when a weak miticidal activity was observed with derivative 5. 

Stereoselective Synthesis and Acaricidal Activity of Novel Thiazolidinones... 

Hexythiazox, tra/2s 5-(4-chlorophenyl)-N cyclohexyl-4-methyl-2 Oxothiazolidine-3-carboxamide, is a new potent acaricide which has a unique thiazolidinone structure. It has broad acaricidal spectrum and excellent ovicidal, larvicidal and nymphcidal actions. Its synthesis requires stereoselective processes because the trans configuration at positions 4- and 5- in the thiazolidinone structure is essential for acaricidal activity. We have studied the stereoselective synthesis of phenylpropanolamines as key-intermediates of hexythiazox derivatives and established the novel stereoselective synthetic methods for trans thiazolidinones from phenylpropanolamines. 

In the course of development research of fungicidal heterocyclic compounds, we found acaricidal activity among N-substituted carboxamide derivatives of some 5-membered heterocyclic compounds. In order to inquire into their activity, we synthesized and tested various skeletal compounds. We found that N-cyclohexyl-4,5-disubstituted thiazolidinone carboxamides have very high ovicidal and larvicidal activity against spider mites both in Panonychus and Tetranychus species (2-3). After development research for optimization, hexythiazox was selected as one of the representative compounds and introduced into the market in 1985. It is now widely used for the control of spider mites in fruits and vegetables in Europe and North America as well as in Japan. 

Therefore, we focussed our attention on the synthesis of the trans isomers and examined the effect of heterocyclic structures. The thiazolidinone and oxazolidinone derivatives (4) showed acaricidal activity but the compounds having the structure of imidazolidine, oxazine and aziridine were not active at all ( Table 3 ). 

Table 2. Acaricidal Activity of 2-Thiazolidinones against T.urticae. (Reproduced with permission from Ref. 3. Copyright 1987 Pesticide Science Society of Japan.)...

As mentioned above, the stereochemistry of the thiazolidinone structure is quite important for acaricidal activity. In order to regulate the stereochemistry, a number of synthetic pathways were considered as shown in Scheme 1. In this scheme, we focused our attention on aziridines, chloroamines and aminoalcohols as key-intermediates. We investigated the synthetic process to obtain both cis and trans or erythro and threo isomers of these intermediates (5-6). Here we intend to describe the stereoselective synthesis of the trans isomers which are important for the acaricidal activity ( Schemes 2-4 ). 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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