- Practical chemo-enzymatic process for the preparation of (1R,cis)-2-(2,2-dihaloethenyl)-3,3-dimethylcyclopropane carboxylic acids
-
A practical chemo-enzymatic process for the preparation of optically active (1R,cis)-2-(2,2-dichloro (or dibromo)ethenyl)-3,3-dimethylcyclopropane carboxylic acids (permethrinic or deltamethrinic acids) from racemic 1,1,1-trichloro-2-acetoxy-4-methyl-3-pentene is described. The key intermediate, enantiopure (R)-1,1,1-trichloro-2-hydroxy-4-methyl-3-pentene, is prepared by a lipase catalysed kinetic resolution of the racemic acetate. The reaction mixture, containing (R)-alcohol and the unreacted (S)-acetate, is directly acetylated by a haloacetyl halide, and the products are separated by distillation. The (S)-acetate is racemized, and the (R)-haloacetate is transformed to the corresponding glycinate hydrochloride, followed by diazotization to (R)-1,1,1-trichloro-4-methyl-3-penten-2-yl diazoacetate. The stereoselective carbenic dediazotization of the (R)-diazoacetate furnishes the optically active (1R,4R,5S)-6,6-dimethyl-4-trichloromethyl-3-oxobicyclo[3.2.0]hexan-2-one, which is transformed to the desired enantiopure (1R,cis)-permethrinic or deltamethrinic acid in high optical yield (>99% ee) and overall chemical yield of 10-15%.
- Fishman, Ayelet,Kellner, Dorit,Ioffe, David,Shapiro, Evgeny
-
-
- Biocatalytic preparation of (R)-(-)-1,1,1-trichloro-2-hydroxy-4-methyl-3-pentene, a synthon for potent agricultural pyrethroids
-
Asymmetric hydrolysis of acetate (±)-2 mediated by B.subtilis provided a very simple and cheap method for obtaining alcohol (R)-(-)-1a in high chemical yield and optical purity (ee ≥ 98%).
- Muljiani,Gadre,Modak,Pathan,Mitra
-
p. 239 - 242
(2007/10/02)
-
- AN UNUSUAL REACTION OF TRICHLOROMETHANE WITH ACYLALS IN THE INTERPHASE CATALYSIS CONDITIONS.
-
Aldehyde diacetates ract with trichloromethane in the standard interphase catalysis conditions to form α-trichloromethylcarbinols or their acetates depending on temperature and time of the reaction.
- Kryshtal, G. V.,Bogdanov, V. S.,Yanovskaya, L. A.
-
p. 3607 - 3610
(2007/10/02)
-
- Electrochemical synthesis of insecticide intermediates
-
1,1,1-Trihalo-4-methylpentenes, carrying 2-substituents selected from those conjugate bases of Bronsted acids which are leaving groups in beta eliminations, are reduced electrochemically to 1,1-dihalo-4-methylpentadienes, intermediates in the synthesis of pyrethroid insecticides.
- -
-
-