Pyrethroid alcohols

The first significant success in creating a photostabilized pyrethroid with high insecticidal activity was achieved through use of the 3-phenoxybenzyl alcohol moiety. A further step was the finding that 2-aryl-3-methylbutyric acid esters of pyrethroid alcohols were both photostable and... 

Often the purpose of a substitution reaction at a saturated center is to correct stereochemistry. An example is provided in the Sumitomo approach to pyrethroid alcohols where the undesired isomer is inverted in the presence of the required one (Scheme 22.1).2... 

The results show that 2-methyl[1,1 -biphenyl]-3-methanol is an effective pyrethroid alcohol. It has been shown that this is true not only for pyrethroid esters but also for their isosteric replacements such as oxime ethers. 

Fig. 35.7. Pyrethroid alcohol modification - conformation of preferred substituent pattern, e.g., in 16 (a) and 18 (b).

More recently, benzylesters or the esters of pyrethroid alcohol of the still open chain ester similar to 217a have proved to be of special interest, maybe for patent reasons, for preparations of the cis-Z-isomer [417]. Similarly, the optically active ester of 1-R-cis-caronaldehyde with the alcohol of bifenthrin 218 together with the new and... 

This alcohol 312 was the first one conveying very high insecticidal activity to its pyrethroid esters, and must be regarded as the direct forerunner of modem pyrethroid alcohols. The technical process for resmethrin 315 (Reaction scheme 219) builds up a furane ring in a classical manner [676, 677]. 

Chemically more interesting are transesterifications e.g., of methylchrysanthemates with a substituted furfurol acetate in the presence of sodium methoxide [769], of permethric acid ethylester with metaphenoxy benzyl alcohol and sodium methoxide at elevated temperatures [770, 771] or the transesterification of the acetate of the latter alcohol, (but also with other acetates of pyrethroid alcohols [772]) in the presence of titanium alcoholates to give permethrin 372 [774,775]. In the last reaction an originally cis/trans 58/42 ratio changed to cis/trans 44/56. 

R = furyl, CH3S, acetyl R = common pyrethroid alcohol new acids... 

R R R = alkyl, hal, CN, H, phenyl y = a-CN-pyrethroid alcohol novel acid... 

R = perhalo C1-C4 alkyl R = pyrethroid alcohol residue new acid... 

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