- Practical, general, and systematic method for optical resolution of gem-dihalo- and monohalocyclopropanecarboxylic acids utilizing chiral 1,1′-binaphtholmonomethyl ethers: Application to the synthesis of three chiral pesticides
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We performed an efficient practical and systematic optical resolution method for gem-dihalo- and monohalocyclopropanecarboxylic acids 1 and 5 utilizing chiral 1,1′-binaphthol monomethyl ether (R)-2 as the key auxiliary. Direct esterification of 1 with (R)-2 gave two 1R- and 1S-diastereomeric esters 3 with marked different Rf values, both of which were easily separated using simple column chromatography. Monodehalogenation of separated chiral esters 3 using t-BuMgCl and cat. Co(dppe)2Cl2 gave two 1,2-trans- and 1,2-cis-diastereomers 4 with markedly different Rf values, both of which were similarly separated using simple column chromatography. The obtained diastereomers 3 and 4 were easily hydrolyzed to the desired enantiopure acids 1 (>99%) and 5 (>99%), respectively, with recovery of (R)-2, both in good to excellent yields. Utilizing the present method, important chiral agrochemicals, carpropamid 6 and fencyclate 7, were readily synthesized. Pyrethroid 9 with three asymmetric centers was efficiently synthesized in a much better yield compared with the reported method. The Royal Society of Chemistry 2008.
- Yasukochi, Hiroaki,Atago, Takayuki,Tanaka, Akihiro,Nakatsuji, Hidefumi,Yoshida, Eri,Kakehi, Akikazu,Nishii, Yoshinori,Tanabe, Yoo
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supporting information; experimental part
p. 540 - 547
(2008/10/09)
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- Highly regioselective Friedel-Crafts reactions of electron-rich aromatic compounds with pyruvate catalyzed by Lewis acid-base: Efficient synthesis of pesticide cycloprothrin
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An efficient synthesis of aromatic lactate esters is reported via highly regioselective Friedel-Crafts reactions of electron-rich aromatic compounds with pyruvate ester promoted by TiCl4 in the presence of basic Al 2O3. The utility of the reaction is shown by the efficient synthesis of the pesticide cycloprothrin in high yield.
- Si, Yu-Gui,Chen, Jun,Li, Fan,Li, Jin-Hua,Qin, Ye-Jun,Jiang, Biao
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p. 898 - 904
(2007/10/03)
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- Investigation of Readily Available Chiral Compounds for Preparative Scale Resolutions
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Diastereoisomeric esters were formed by reaction of racemic carboxylic acids with the readily available hydroxy lactone derivatives, 2,3-O-isopropylidene-D(+)-ribono-1,4-lactone, D(-)-2-hydroxy-3,3-dimethylbutyro-1,4-lactone (D(-)-pantolactone) and 1,2-O-isopropylidene-(+)-a-D-glucofuranurono-6,3-lactone.In all cases separation of the diastereoisomeric esters was achieved by crystallization and/or chromatography.Purity of the diastereoisomers could be determined by h.p.l.c. or by 1H n.m.r.Hydrolysis under mild basic conditions followed by treatment with acid gave optically pure carboxylic acids.The facile separation by crystallization and/or chromatography of diastereoisomers prepared from racemic endo-1,4,5,6,7,7-hexachlorobicyclohept-5-ene-2-carboxylic acid suggested that the resolved acid may be useful as a resolving agent.This was shown by separation of diastereoisomers formed from the resolved acid and racemic 1-(3'-phenoxyphenyl)prop-2-yn-1-ol and racemic 1-cyano-1-(3'-phenoxyphenyl)methanol respectively.Optically pure 1-(3'-phenoxyphenyl)prop-2-yn-1-ol was obtained by hydrolysis of the separated diastereoisomers.
- Duke, Colin C.,Wells, Robert J.
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p. 1641 - 1654
(2007/10/02)
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- 2,3-Isopropylidene ribonic acid, 1,4-lactones
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Racemic carboxylic acids are resolved into their enantiomers using optically active enantiomers of four lactones as resolving agents. The four lactones are 2,3-isopropylidene-ribonic acid-1,4-lactone, 1,2-isopropylideneglucofuranurono-3,6-lactone, 2-hydroxy-3,3-dimethyl-1,4-butyrolactone and 3,4-isopropylidene-arabino-1,5-lactone. Novel diastereoisomeric esters of the acids with the lactones are disclosed.
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- Insecticidal esters
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The (+), (-) and (±) forms of the compounds of formula I STR1 wherein R1 is hydrogen or a methoxy, ethoxy, propoxy, methylthio, ethylthio, propylthio, fluoro, chloro, bromo, methyl, ethyl, nitro or amino group, and R2 is a hydrogen o
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