Deltamethric acid

Caronaldehyde hemiacetal can be transformed in a simple manner by the Corey-Fuchs reaction [107] into permethric acid, and as well its bromo-analogue deltamethric acid. Instead of triphenylphosphane, tris-(dimethylamino) phos-phane may also be used. 

Meyers et al. have reacted the yiide with a chiral bicyclic lactam to yield a tricyclic em-disubstituted cyclopropane intermediate which, after four steps, gave deltamethric acid whose esters act as very potent Insecticides (eq 7). ... 

In search of different conditions to enforce this reaction, an interesting intramolecular rearrangement of the chlorine atoms in 139 across the 4-membered ring catalyzed by tertiary amines as well as by hydrochloric acid in alcohol (Reaction scheme 90) was discovered. The newly formed cis-isomeric diequatorial a-halo-cyclobutanone 141 is now again prone to the Faworski rearrangement under mild alkaline aqueous conditions, to give the cis-permethric acid [231] or analogously, the racemic deltamethric acid as a cis/trans 80 20 mixture (Reaction scheme 90) [224, 228, 230]. 

Cis-permethric acid needs phenylethylamine [330], l-phenyl-2-tolylamine [338], ephedrine [73, 337], N-methylephedrine [73, 337], 2-N-benzylaminobutanol [306] and 4-nitrophenyldimethylaniinopropanediol and chinine [339]. The last amine resolves racemic cis-deltamethric acid [339]. Also effective in either case is the separation of the less soluble diastereoisomer of the d-menthylesters of the 1-R-adds [340]. 

Treatment of cis-caronealdehyde hemiacetal with bromoform and potassium tert.-butylate gives, without isomerization, the elongation of the formyl group into the tribromoethanol moiety and after acid-catalyzed dehydration, the lactone 158, Hal = Br, React. Scheme 100 (page 48) [382]. This is reduced by magnesium or zinc to deltamethric acid. 

Treatment of the acid 254 with zinc and ammonium chloride in Reaction scheme 179 removes only one chlorine atom [503], while insertion of dibromocarbene into 254 results in the deltamethric acid minus one methine carbon 257, according to Reaction scheme 180 [504]. 

An interesting scientific and patent issue was the product of bromination of permethric or deltamethric acid [507, 508, 509], component of tralomethrin. 

An alternative method to produce deltamethric acid 258 from permethric acid (although the former does not provide more active insecticides) without isomerization is the treatment with aluminum tribromide [342,344] (Reaction scheme 182), provided that traces of HBr are removed immediately [345] ... 

R-cis-deltamethric acid 258 can be completely dehalogenized with butyl lithium, and then acylated with chloroformic esters to give an 1-R-cis-ethynylcarboxylic ester as outhned in scheme 183 which is the precursor for the interesting 1-R-cis-Z-norisopyrethric acid 231 [510, 924] ... 

The amide of a-S-3-phenoxy mandelic acid (obtained after resolution of the racemate with (—)phenethyl amine), was esterified with 1-R-cis-deltamethric acid, then dehydrated to give deltamethrin [633]. 

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