Stereospecific total synthesis of the potent synthetic pyrethroid NRDC 182

Practical Chemo-Enzymatic Process for the Preparation of (1R,cis)-2-(2,2-Dihaloethenyl)-3,3-dimethylcyclopropane Carboxylic Acids

“…Crystallization from hexane gave ( R )- 4 (0.93 g; yield = 36%; ee >98%; conversion of ( R )- 6 = 84%): [α] 20 D −12.6 ± 0.3. These data correspond to those in the literature. , …”

“…In the search for a suitable generic process, we evaluated a method developed by Kondo and Hatch for FMC Corp. (Scheme ) . This comprised the stereoselective intramolecular cyclization of the chiral ( R )-1,1,1-trichloro-4-methyl-3-penten-2-yl diazoacetate, 2 , into the chiral (1 R ,4 R ,5 S )-6,6-dimethyl-4-trichloromethyl-3-oxobicyclo[3.2.0]hexan-2- one, 3 , which was then transformed into (1 R , cis )- 1a in one step.…”

“…The optically active oxabicyclolactone, (1 R ,4 R ,5 S )- 3 , was opened by a Boord-type reaction using zinc powder. Methanol simplified the isolation of the reaction product and was therefore used as solvent instead of acetic acid . Refluxing in methanol afforded the desired permethrinic acid, (1 R , cis )- 1a , in 93% yield and with more than 98% ee of the 1 R, 3 S- enantiomer.…”

Pyrethroid insecticides. Chapter III: Synthesis of 3-phenoxy mandelonitrile

“…The resulting acetate (S)-1c can be directly used (Scheme 17) 57 or deprotected to the cyanohydrin then acylated with a permethrinic acid chloride (Scheme 14, entry a). 50 The lipase selected and the conditions used are very important for the success of the process especially for industrial purposes. The key factors are: the accessibility of the lipase, the selectivity of the process, the nature of the enantiomers formed, the pH of the medium, the ease of recovery of the cyanohydrin and/or its acetate, the efficiency of the recycling of the compounds possessing the unwanted (R)-stereochemistry and the reuse of the lipase.…”

Inter- and intramolecular reactions of 1-deoxy-1-thio-1,6-anhydrosugars with α-diazoesters: synthesis of the tagetitoxin core by photochemical ylide rearrangement

“…Initially, triacetate 3 was treated with methanolic ammonia to afford triol 18, and re-protection of the 2-and 4-hydroxyl groups was effected with di-tert-butylsilyl dichloride and silver nitrate 21 to yield 19 (Scheme 5). Acetoacetylation of the remaining secondary alcohol using 2,2,4-trimethyl-1,3-dioxin-4-one 22 afforded 20, and subsequent diazo transfer with p-acetamidobenzenesulfonyl azide 23 gave the requisite diazoester 21.…”