Phosphorus, Sulfur and Silicon, 2002, Vol. 177:2143
C
Copyright 2002 Taylor & Francis
1042-6507/02 $12.00 + .00
DOI: 10.1080/10426500290095070
SYNTHESIS OF 1,1-DIFLUOROOLEFINS VIA
WITTIG-HORNER-EMMONS REACTION
Hou-Jen Tsai
Chung Cheng Institute of Technology, Republic of China
(Received July 29, 2001; accepted December 25, 2001)
In the presence of a catalytic amount of cuprous bromide CuBr
and cosolvent acetonitrile acylation of [(diethoxyphosphinyl)diflu-
oromethyl]zinc bromide (EtO)2P(O)CF2ZnBr, which was prepared
from diethyl(bromodifluoromethyl)phosphonate (EtO)2P(O)CF2Br and
zinc powder with an appropriate acylating reagents such as acetyl
chloride CH3C(O)Cl, ethyl oxalyl chloride ClC(O)CO2Et, methyl oxalyl
chloride ClC(O)CO2CH3, diethylcarbamoyl chloride ClC(O)NEt2, or
ethyl chloroformate ClC(O)OEt in the solvent of monoglyme or
triglyme gives diethyl 2-oxo-1,1-difluoropropylphosphonate (EtO)2-
P(O)CF2C(O)CH3, ethyl difluoro(diethoxyphosphinyl)pyruvate (EtO)2-
P(O)CF2C(O)CO2Et, methyl difluoro(diethoxyphosphinyl)pyruvate
(EtO)2P(O)CF2C(O)CO2Me, N,N-diethyl difluoro(diethoxyphosphinyl)
acetamide (EtO)2P(O)CF2C(O)NEt2 and ethyl (diethoxyphosphinyl)
difluoroacetate (EtO)2P(O)CF2C(O)OEt occurs in good yields, respec-
tively. However, in the preparation of (EtO)2P(O)CF2C(O)CO2Et, if
the acylation reaction was carried out at room temperature for 24 h in
the presence of 1.5% of cuprous bromide and without using acetonitrile
as cosolvent, an analogous nerve agent diethyl fluorophosphonate
(EtO)2P(O)F and (EtO)2P(O)CF CFP(O)(OEt)2 were observed. Treat-
ment of a THF solution of diethyl 2-oxo-1,1-difluorophosphonate
derivatives (EtO)2P(O)CF2C(O)R (R CH3, CO2Et, CO2Me, NEt2, OEt)
with Grignard reagents R0MgX via a Wittig-Horner-Emmons reaction
produces 1,1-difluoroolefins R0(CH3)C CF2, R0(CO2Et)C CF2 and
R0(NEt2)C CF2.
Address correspondence to Hou-Jen Tsai, Department of Applied Chemistry, Chung
Cheng Institute of Technology Ta-Hsi, Tao-Yuan, Taiwan, R.O.C.
E-mail: hjtsai@ccit.edu.tw
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