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.
We performed an efficient practical and systematic optical resolution method for gem-dihalo- and monohalocyclopropanecarboxylic acids and utilizing chiral 1,1'-binaphthol monomethyl ether (R)- as the key auxiliary. Direct esterification of with (R)- gave two 1R- and 1S-diastereomeric esters with marked different R(f) values, both of which were easily separated using simple column chromatography. Monodehalogenation of separated chiral esters using t-BuMgCl and cat. Co(dppe)(2)Cl(2) gave two 1,2-trans- and 1,2-cis-diastereomers with markedly different R(f) values, both of which were similarly separated using simple column chromatography. The obtained diastereomers and were easily hydrolyzed to the desired enantiopure acids (>99%) and (>99%), respectively, with recovery of (R)-, both in good to excellent yields. Utilizing the present method, important chiral agrochemicals, carpropamid and fencyclate , were readily synthesized. Pyrethroid with three asymmetric centers was efficiently synthesized in a much better yield compared with the reported method.
Yasukochi
Hiroaki
H
Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan. tanabe@kwansei.ac.jp.
Atago
Takayuki
T
Tanaka
Akihiro
A
Nakatsuji
Hidefumi
H
Yoshida
Eri
E
Kakehi
Akikazu
A
Nishii
Yoshinori
Y
Tanabe
Yoo
Y
D018360:Crystallography, X-Ray; D003521:Cyclopropanes / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D055095:Optics and Photonics; D010575:Pesticides / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
D003521:Cyclopropanes; D004987:Ethers; D010575:Pesticides; C015766:cyclopropanecarboxylic acid