Pyrethroid acids

Same measures of stereocontrol had previously been observed in approaches to pyrethroid acids involving intramolecular enolate alkylation. As outlined in Figure 3, workers at Sumitomo have investigated the cyclization of a methyl ketone enolate (5). They obtained a 9 1 ratio of cis trans products upon ring closure initiated by sodium hydroxide. The methyl ketone was subsequently converted to the corresponding carboxylic acid via the haloform reaction. 

We chose to explore the intramolecular alkylation of amide enolates as a potential stereoselective route to cis pyrethroid cyclopropane carboxylates. If the relationship between the stereoselection in enolate formation and ring closure is operable, amide enolates would be an excellent means of developing a stereoselective synthesis of cis products (8). Furthermore, recent progress in achieving enantioselection in the intermolecular alkylation of chiral amide enolates would provide a means of obtaining optically active pyrethroid acids (Figure 6) (9-13). 

The chemistry of the pyrethroid acids has been reviewed.778 In the following sections A, S, and L represent compounds with the artemisyl, santolinyl, and lavandulyl skeleta respectively. 

In this section, we have made an attempt at selectivity, in view of the very large amount of literature produced as a result of the commercial interest in chrysanthemic acid and the pyrethroids. In addition to a review in Japanese of the synthesis and reactions of chrysanthemic acid, there is an excellent review of the pyrethroid acids with an exhaustive literature list up to 1980. We shall only try to complete the latter. Many syntheses are destined as general routes for the preparation of substituted chrysanthemic acids, and those in which the isopropylidene methyl groups are replaced by halogen atoms. 

Isoprenoid acid [55, 74] Hydroxy carboxylic acids [75] Pyrethroid acids [58, 62, 76]... 

Pyrethroid acids [62] Arylpropionic acids [72, 77, 78] Benzoxazoleacetic acids [68] Benzoxazoleacetic acid [79] Chrysanthemic acid [80] 2-Methylbutyric acid [59]... 

Substantial effort has been put into utilizing the optically active natural hydrocarbons (-h)"a-pinen and (-h)-A-3-caren for synthesis of chrysanthemic acid, permethric acid and other pyrethroid acids. These reactions are explained in Sect. I.3.6.5. 

Caronaldehyde 155 prepared by ozonolysis of chrysanthemic acid 1 provided Elliott with an extremely versatile source for many interesting new racemic and optically active pyrethroid acids (Reaction scheme 99) [242] by applying the Wittig-reaction. 

Synthesis of Other Important Cyclopropane Pyrethroid Acids... 

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