Transformation chrysanthemic acid

The synthesis of compounds 39, 41, and 43 by the ODPM rearrangement opens a novel photochemical route to chrysanthemic acid and other cyclopropane carboxylic acids present in pyrethrins and pyrethroids [52]. In fact, aldehyde 43 can be transformed to tran -chrysanthemic acid by simple oxidation. This new synthetic route to ecologically benign insecticides competes with the one previously described by us using the 1-ADPM rearrangement of p,y-unsaturated oxime acetates [30,53]. 

Intramolecular cyclopropanation using diazoesters is a powerful synthetic tool. Diazoesters are readily prepared from the corresponding alcohol via House s methods56-57. Numerous examples using the application of this transformation in synthesis have been reported. These include the potent synthetic pyrethroid NRDC 182 (22)58, (1 R)-( )-cis-chrysanthemic acid (23)59, the highly strained bicyclic system 2460, antheridic acid 2561,62 and cycloheptadiene 26 (equations 33-37). 

Analogous to these cyclizations, a simple, efficient approach to racemic c -chrysanthemic acid, a convenient intermediate in the synthesis of the exceptionally potent insecticide delta-methrine, has been reported from 2,2,5,5-tetramethylcyclohexane-l,4-dione. Successively, this dione was partially reduced to the 4-hydroxycyclohexanone and then transformed... 

Reaction of methyl 4-bromo-2-methoxycarbonyl-4-methylpent-2-enoate (24) with 3.2 equivalents of sodium cyanide in dimethyl sulfoxide at 20 °C for 3 hours leads to the formation of dimethyl 3-cyano-2,2-dimethylcyclopropane-l,l-dicarboxylate (25) which is readily de-methoxycarbonylated to give tra 5-3-cyano-2,2-dimethylcyclopropanecarboxylic acid (26) in 67% overall yield. This compound can be conveniently transformed into chrysanthemic acid and hemicaronic aldehyde. ... 

Photochemical decomposition of pyrethrins and synthetic analogues can be slowed down by the simultaneous use of antioxidants and photoscreens. In the course of decomposition, chrysanthemic acid, phenylacetic acid, benzyl alcohol, benzaldehyde and benzoic acid are formed from resmethrin (32) as decomposition products and, at the same time, the furan ring undergoes an oxidative transformation (Ueda et al., 1974) ... 

The foregoing prospectus for the chrysanthemic acid synthesis represents enantioselective transformations of the first kind (Scheme 39, equation i). The second kind (equation ii) is represented by studies directed toward the (+) and (—) grandisol enantiomers (183). 

Even sugar can be transformed into 1-R-chrysanthemic acid [118] via a multistep procedure. Likewise, optically active pantolactone 78 [119] can be reduced, ketalized, mesylated and later on subjected to cyanide exchange to give 79. 

In view of the importance of the pyrethrin insecticides, new methods for the efficient isomerization of the cyclopropanyl moiety from the unnatural cw-series to the natural frans-compounds are important. It has now been shown that cw-chrysanthemic acid (5) can be transformed quantitatively to the frans-acid using 0.06 M-(PhCN)2pdCl2 as the catalyst in 5.5 h (Scheme 10). The reaction was shown to be very sensitive to the quantity of catalyst used, and obviously proceeded more rapidly at higher concentrations. Nevertheless, this mild method compares very favourably with alternative isomerization procedures. 

The chiral ally diazoester 18 is prepared from (R.Ri-tartaric acid and provides the cyclopropane derivative 19 as a single diastereomer which can be transformed into (+)-e -chrysanthemic acid51. 

---