The Chiral Switch of Metolachlor: The Development of a Large‐Scale Enantioselective Catalytic Process

Blaser, Hans‐Ulrich; Hanreich, Reinhard; Schneider, Hans‐Dieter; Spindler, Felix; Steinacher, Beat

doi:10.1002/3527602151.ch3

Cited by 29 publications

(31 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A significant example is the development of a catalytic homogenous enantioselective hydrogenation process (hydrogen, Ir‐Josiphos catalyst) for the transformation of arylimine to the ( S )‐configurated direct arylamine precursor used in the technical preparation of the grass herbicide ( S )‐metolachlor (around 80% ee). This is the largest catalytic asymmetric transformation process run today (>10 000 tons year −1 ) …”

Section: The Stereochemistry Approach In Agrochemistrymentioning

confidence: 99%

See 1 more Smart Citation

Current status of chirality in agrochemicals

Jeschke

2018

Pest Management Science

153

View full text Add to dashboard Cite

The agrochemical industry is searching continuously for new pesticides to develop products that have optimal efficacy, lower application rates in the field, increased selectivity, favourable toxicological and environmental safety, enhanced user friendliness and better economic viability. One strategy by which to achieve these ambitious goals makes use of the unique properties of molecules containing asymmetric centres. In the past, many natural products and their congeners have been a source of inspiration in the design of new active ingredients, and the molecular structures of the resulting compounds have become increasingly complex; some 30% contain fragments with asymmetric centres. However, despite enormous progress in catalytic asymmetric processes over the past decade, few agrochemicals are produced in an enantiomerically pure or enriched form on an industrial scale. Since 2007, ∼ 43% of the 44 products launched (insecticides, acaricides, fungicides, nematicides and herbicides) contain one or more asymmetric centres in the molecule (∼ 47%) and most have been launched as racemic mixtures of enantiomers or diastereomers. This review provides an overview of the current status of chiral agrochemicals launched over the past 10 years and describes the inherently connected challenges of modern agricultural chemistry by managing important aspects resulting from the stereochemistry of these innovative products. © 2018 Society of Chemical Industry.

show abstract

Section: The Stereochemistry Approach In Agrochemistrymentioning

confidence: 99%

“…This is the largest catalytic asymmetric transformation process run today (>10 000 tons year −1 ). 13…”

Section: Catalytic Asymmetric Synthesismentioning

confidence: 99%

Current status of chirality in agrochemicals

Jeschke

2018

Pest Management Science

153

View full text Add to dashboard Cite

show abstract

“…[12] Blaser et al reported that a marine microbial community degraded the R-enantiomer of dichlorprop (DCPP) only and that the S-enantiomer remained unaffected, demonstrating enantioselectivity in the degradation of DCPP. [10] Liu et al found that the S-enantiomer of the herbicide persisted longer than the R-form in silt and sandy loam soils, but shorter in a clay loam soil. A study showed that soil incubation partially converted the R-enantiomer to the S-form.…”

Section: Introductionmentioning

confidence: 98%

“…[9] This chiral switch has been implemented in a number of countries since 1997 (e.g., United States in 1997, Canada in 1998, South Africa in 1998, Australia in 1999). [10] The phenoxy carboxylic acids are a class of highly effective, broad-spectrum herbicides with low toxicity. The racemate of each herbicide contains a pair of enantiomers, with only the R-form being active.…”

Section: Introductionmentioning

confidence: 99%

Enantioselectivity in toxicity and degradation of dichlorprop-methyl in algal cultures

Hong¹,

Yuan²,

Shen³

et al. 2008

Journal of Environmental Science and Health, Part B

View full text Add to dashboard Cite

Enantioselectivity in the toxicity and degradation of the herbicide dichlorprop-methyl (2,4-DCPPM) in algal cultures was studied. Enantioselectivity was clearly observed in the toxicity of racemic 2,4-DCPPM and its two enantiomers. R-2,4-DCPPM showed low toxicity to Chlorella pyrenoidosa and Chlorella vulgaris, but higher toxicity to Scenedesmus obliquus. The observed toxicity was ranked: R-2,4-DCPPM>S-2,4-DCPPM>>Rac-2,4-DCPPM; the toxicity of R-2,4-DCPPM was about 8-fold higher than that of Rac-2,4-DCPPM. Additionally, 2,4-DCPPM was quickly degraded, in the initial 12 h, and different algae cultures had different enantioselectivity for the 2,4-DCPPM enantiomers. There was no significant enantioselectivity for 2,4-DCPPM in Chlorella vulgaris in the initial 7 h. However, racemic 2,4-DCPPM was degraded by Scenedesmus obliquus quickly, in the initial 4 h, much quicker, in fact, than the S- or R-enantiomers (racemate>R->S-), indicating that the herbicide 2,4-DCPPM was absorbed enantioselectively by Scenedesmus obliquus. The rapid formation of 2,4-DCPP suggested that 2,4-DCPPM adsorbed by algal cells was catalytically hydrolyzed to the free acid, a toxic metabolite. The production rates of 2,4-DCPP were as follows: Scenedesmus obliquus>Chlorella pyrenoidosa>Chlorella vulgaris, consistent with the degradability of 2,4-DCPPM. Scenedesmus obliquus had quick, but different, degradative and uptake abilities for R-, S-, and Rac-2,4-DCPPM. The R- and S- enantiomers were not hydrolyzed in the first 12 h, while both enantiomers were hydrolyzed slowly after that. These results indicate that some physical and chemical properties of compounds are of importance in determining their enantioselective toxicity and degradation. The ester and its metabolite likely played an important role in enantioselective toxicity to the three algae.

show abstract

“…19 Likewise, production of many flavors, fragrances, chiral polymers, advanced materials with nonlinear optical properties, ferroelectric liquid crystals, etc., depends on the availability of chiral building blocks. [20][21][22][23][24] Particularly, enantiomerically pure secondary alcohols are valuable resources for the synthesis of numerous pharmaceuticals. The need for enantiopure drugs has been improved in recent years and, hence, chiral alcohols are in demand.…”

Section: Introductionmentioning

confidence: 99%

Piano-stool Ru(II)-benzene complexes bearing D/L-alanine derived chiral aroylthiourea ligands for asymmetric transfer hydrogenation of ketones in water

2018

View full text Add to dashboard Cite

The new water soluble chiral Ru(II)-benzene complexes of the type [RuCl 2 (η 6-C 6 H 6)L] were obtained from the reactions between [RuCl 2 (η 6-C 6 H 6)] 2 and the chiral aroylthiourea ligands (L) derived from unprotected D/L-alanine and characterized. The solid-state structure of representative complexes was confirmed by single crystal X-ray diffraction technique. The Ru(II)-benzene complexes catalyzed the asymmetric transfer hydrogenation (ATH) of aromatic ketones to their enantiopure secondary alcohols. The reactions were carried out in the presence of formic acid-triethylamine mixture in water, and the product alcohols were obtained with excellent conversions (up to 99%) and enantiomeric excesses (up to 99%). The scope of the catalytic system was extended to various aromatic ketones. The catalytic activity of the present water-soluble Ru-benzene complexes toward enantioselective reduction of ketones was considerably higher than that of p-cymene analogues in water.

show abstract

The Chiral Switch of Metolachlor: The Development of a Large‐Scale Enantioselective Catalytic Process

Cited by 29 publications

References 0 publications

Current status of chirality in agrochemicals

Current status of chirality in agrochemicals

Enantioselectivity in toxicity and degradation of dichlorprop-methyl in algal cultures

Piano-stool Ru(II)-benzene complexes bearing D/L-alanine derived chiral aroylthiourea ligands for asymmetric transfer hydrogenation of ketones in water

Contact Info

Product

Resources

About