The anion derived from diethyl α-fluorobenzyl phosphonate (EtO)2P(O)-CFHPh (2) and lithium diisopropylamide in THF underwent the reaction with aldehydes and ketones to afford a moderate to good yields of phenyl substituted fluoro-olefins RR′C=CFPh (6).
A Novel Intramolecular Horner-Wadsworth-Emmons Reaction: A Simple and General Route to .alpha.-Fluoro-.alpha.,.beta.-unsaturated Diesters
作者:Hou-Jen Tsai、Alagappan Thenappan、Donald J. Burton
DOI:10.1021/jo00102a038
日期:1994.11
Diethyl (fluorocarbethoxymethyl)phosphonate (1), prepared from triethyl phosphite and ethyl bbromofluoroacetate, reacts with n-butyllithium in THF to give the phosphonate carbanion 2. Addition of the pregenerated carbanion 2 to a THF solution of methyl or ethyl oxalyl chloride at -78 degrees C forms the acylated phosphonate (EtO)(2)P(O)CF(COCO(2)R)CO(2)Et (3). In situ reaction of 3 with Grignard reagents affords alpha-fluoro-alpha,beta-unsaturated diesters R'(CO(2)R)C=CFCO(2)Et in moderate to good yields with high E-stereoselectivity. The reaction is applicable to primary, secondary, and tertiary alkyl, alkenyl, alkynyl, aryl, cyclohexyl, and perfluorinated Grignard reagents. The assignment of E and Z configuration is based on NOE experiment. The E/Z ratio of unsaturated diesters formed in the reaction varies with the metal ion and cosolvent. However, solvents and bases have little influence on the stereoselectivity.
STEREOSELECTIVE SYNTHESIS OF MONOFLUORO-OLEFINS FROM DIISOPROPYL (CARBOETHOXYFLUORO-METHYL)PHOSPHONATE
作者:Hou-Jen Tsai、Shyi-Chen Wu
DOI:10.1080/10426500008042107
日期:2000.6.1
Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate [(i-PrO)(2)P(O)CFCO2Et]Li--(+) 2 followed by in situ nucleophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH3)(CO2Et)C=CFCO2Et 4 or 75% of the E-isomer of alpha-fluoro-beta-vinyl-alpha,beta-unsaturated diester (E,Z)-(CH2=CH)(CO2C2H5)C=CFCO2Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH3)(CO2Et)C=CFCO2Et 4 with 79% E-stereoselectivity. The E/Z ratio of (CH2=CH)(CO2Et)C=CFCO2Et 5 depends on the HMPT or DMPU cosolvents present in the reaction mixture.
An expedient synthesis of α-fluoro-α,β-unsaturated diesters
作者:Hou-Jen Tsai、Alagappan Thenappan、Donald J. Burton
DOI:10.1016/s0040-4039(00)60990-5
日期:1992.10
Acylation of [(EtO)2P(O)CFCO2Et]-Li+ (2) with alkyloxalyl chlorides followed by subsequent reaction of the acylated phosphonates with Grignard reagents provides the title compounds in moderate to good yields with high E-stereoselectivity.
Isolation and Characterization of intermediate in the Synthesis of α-Fluorodiesters
作者:Hou-Jen Tsai
DOI:10.1002/jccs.199800082
日期:1998.8
AbstractThe anion [(EtO)2P(O)CFCO2Et]−Li+, pregenerated from its precursor diethyl (carboethoxyfluoromethyl)phosphonate (EtO)2P(O)CFHCO2Et and n‐butyllithium, was added via syringe to a THF solution of ethyl oxaiyl chloride to yield an acylated phosphonate (EtO)2P(O)CF(COCO2Et)CO2Et. In situ reaction with Grignard reagents RMgX produces the α‐fluorodiesters (E,Z)‐R(CO2Et)C=CFCO2Et in good yields. In contrast, addition of ethyl oxalyl chloride to a THF solution of diethyl (carboethoxyfluoromethyl)phosphonate anion gives an isolated intermediate (EtO)2P(O)CFCO2Et(CO2Et)C=CFCO2Et. Subsequent reaction of this isolated intermediate with Grignard reagents also affords a one‐pot synthesis of the α‐fluorodiesters with high E‐stereoselectivity. The E‐stereoselectivity increases when HMPT or DMPU is used as a cosolvent in the preparation of diethyl 2‐fluoro‐3‐phenylfumarate (E,Z)‐Ph(CO2Et)C=CFCO2Et.