Chemistry Reference
In-Depth Information
and stirring was continued for a further 0.25 h. The mixture was then left to stand
for a further 1.5 h before being diluted with diethyl ether (1200 mL) and washed
with H
2
O (300 mL). The aqueous phase was extracted with diethyl ether (300 mL)
and the combined organic phases were washed with aq. NaHCO
3
solution (3
300
mL) and brine (300 mL), and dried (MgSO
4
). After concentration under reduced
pressure, the residue was redissolved in dichloromethane (200 mL) and silica gel
(60 g) was added. The slurry was stirred for 14 h, and then filtered and con-
centrated under reduced pressure. Crystallization of the residue from benzene
(50 mL) yielded compound 624 (5.44 g). Purification of the mother liquor by
flash chromatography (silica gel, 40
70% diethyl ether in petroleum ether)
yielded a further 2.16 g of 624 (30%) as white crystals (benzene; mp 178-179
C
(dec.)).
The reaction of 2-fluoro-2,2-dinitroethylamine 625 with acid chlorides has been
used to prepare a variety of fluorodinitroethyl-substituted amides, carbamates, and
ureas [441]. Carbamates have also been prepared by the addition of alcohols to 2-
fluoro-2,2-dinitroethyl isocyanate.
!
60
!
NO
2
NO
2
NO
2
NO
2
NO
2
NO
2
COCl
2
pyridine
N
N
N
NEt
3
625
F
F
F
F
F
Cl
N
CO
NH
2
O
2
N
O
2
N
O
2
N
O
2
N
O
O
627
625
626
628
COCl
2
PhH, NEt
3
, rt
NO
2
F
OH
O
2
N
630
NO
2
F
O
Cl
O
2
N
O
NO
2
NO
2
NO
2
NO
2
N
629
F
F
F
NH
2
O
O
2
N
O
2
N
pyridine
O
631
625
Typical procedure. N,O-Bis(2-fluoro-2,2-dinitroethyl)carbamate 631 [441]:
N-(2-Fluoro-
2,2-dinitroethyl) carbamoyl chloride 626: To a solution of phosgene (11.5 g) (for a safe
source, see Chapter 7) in benzene (50 mL), a solution of 2-fluoro-2,2-dinitroethyl-
amine (17.7 g) and pyridine (9.5 g) in benzene (30 mL) was added dropwise at 5-
10
C. After completion of the addition, the mixture was heated to 50
C for 1 h
and the solvents were removed in vacuo. The residual oil was diluted to a volume of
100 mL with dichloromethane and reacted further as described below.
To 40 mL of the above solution of crude fluorodinitroethylcarbamoyl chloride 626,
2-fluoro-2,2-dinitroethanol 630 (5.6 g) was added, followed, dropwise and with
cooling in an ice bath, by pyridine (3.1 g). The mixture was stirred at room tem-
perature for 2 h, diluted with dichloromethane (100 mL), washed with dilute sul-
furic acid, dried, and concentrated. Repeated chilling, filtration, and concentration
of the mother liquor gave several fractions of N,O-bis(2-fluoro-2,2-dinitroethyl)-
carbamate 631 containing diminishing amounts of N,N
0
-bis(2-fluoro-2,2-dinitro-
ethyl)urea as an impurity. The yield of crude product amounted to 3 g. The product
was purified by recrystallization from dichloromethane/hexane; mp 63-64
C.
