The Preparation of Imidoyl Fluorides

Article abstract of DOI:10.1071/CH99032

The first general synthesis of imidoyl fluorides is reported here. Irradiation of the initially formed Z isomers of N-methoxybenzenecarboximidoyl fluorides led to a photoequilibrium containing both the E and Z isomers. The pure E isomers were able to be isolated from these isomeric mixtures. The n.m.r. spectra of these isomers are discussed.

Full text of DOI:10.1071/CH99032

C S I R O P U B L I S H I N G
Australian Journal
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Volume 52, 1999
© CSIRO Australia 1999
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Aust. J. Chem., 1999, 52, 807–811
.
The Preparation of Imidoyl Fluorides
Je rey E. Rowe,A,B Kam Lee,A Debra D. Dolliver C
and James E. Johnson B,C
A
School of Chemistry, La Trobe University, Bundoora, Vic. 3083.
Authors to whom correspondence should be addressed.
Department of Chemistry and Physics, Texas Woman’s University,
B
C
Denton, Texas 76204, U.S.A.
The rst general synthesis of imidoyl uorides is reported here. Irradiation of the initially formed Z
isomers of N -methoxybenzenecarboximidoyl uorides led to a photoequilibrium containing both the E
and Z isomers. The pure E isomers were able to be isolated from these isomeric mixtures. The n.m.r.
spectra of these isomers are discussed.
Introduction
dioxan (c. 70% dioxan) in the presence of a large
excess of uoride ion. The major product (>70%)
is the corresponding hydrazide which can be readily
removed from the product mixture by base extraction.
This method does not have much general application
and is a very wasteful synthesis. Compound (3) was
prepared by the reaction of the hydrogen uoride salt of
the N -methoxy amide with DAST (Et2NSF3).7 Several
compounds (2) were isolated as part of the product
mixture from the reaction of the corresponding Schi
base with elemental uorine.8 Bohme and Drechsler9
have reported the preparation of several compounds
(2; X = F) by the reaction of (2; X = Cl) with KF
in 18-crown-6.
A variety of methods have been reported for the syn-
thesis of imidoyl chloride and bromide derivatives but
only a very small number of the corresponding uoro
compounds have ever been reported. The chloro com-
pounds have been prepared by reacting the correspond-
ing amide derivative with phosphorus pentachloride1 or
triphenylphosphine and carbon tetrachloride,2,3 while
the most successful synthesis of the corresponding bromo
compounds is by the reaction with triphenylphosphine
and carbon tetrabromide.3 Alternatively, the amidine
can be reacted with sodium nitrite in the presence
of either hydrochloric or hydrobromic acid.4 None of
these methods is readily applicable to the preparation
of the corresponding uoro compounds.
Calcium uoride-supported alkali metal uorides
have been reported10,11 to react to replace chlorine
and bromine with uorine in a variety of derivatives, by
reaction in solvents such as sulfolane and acetonitrile.
For example, benzoyl uoride was prepared (80%) by
We5,6 have prepared several hydrazonoyl uorides
(1) in fairly poor yields (c. 20–25%) by solvolysing the
corresponding chloro or bromo derivative in aqueous
reacting benzoyl chloride with KF–CaF2 in acetonitrile.
6
Previous work1,2,4
has yielded a variety of halo
compounds and this paper reports their conversion
into the corresponding uoro compounds by reaction
with KF or with KF–CaF2. A more e cient synthesis
of such uoro compounds (1) and (5) was required for
continuing mechanistic studies on nucleophilic substi-
tution at the carbon–nitrogen double bond where the
uoro derivatives have shown promise as mechanistic
probes.5,12
Results and Discussion
The hydrazonoyl uorides (1a,b) and imidoyl uoride
(2a) were prepared in acceptable yields (50–65%) by
reacting the corresponding chloro or bromo compounds
(Z)-N -(2,4-Dinitrophenyl)-N -methylbenzenecarbohydrazonoyl uoride (1a), (Z)-N -(2,4-dinitrophenyl)-4-methoxy-N -methyl-
benzenecarbohydrazonoyl uoride (1b) and N -phenylbenzenecarboximidoyl uoride (2a).
Manuscript received 11 March 1999
᭧ CSIRO 1999
0004-9425/99/080807$ 05.00
10.1071/CH99032

808
Short Communications
with an excess of CaF2/KF in re uxing acetonitrile.
Compounds (1a,b) had been prepared in poor yields
previously. Compound (2a) was an unstable very
readily hydrolysed liquid. The reaction leading to
(1a) was also attempted with potassium uoride alone,
and gave almost no useful product under the same
conditions. This result presumably re ects the much
lower solubility of KF in acetonitrile compared to the
CaF2/KF reagent.
The E isomer was separated from the Z isomer by
preparative gas chromatography, or, in the case of 4-
bromo-N -methoxybenzenecarboximidoyl uoride (7d),
by separation of the isomers on a preparative silica
plate. The corresponding chloro compounds have been
reported previously by Johnson1 (the stereochemistries
reported in ref. 1 should be reversed) and the bromo
compounds by Kikugawa.14 In the preparation of the
E bromo compounds, unless great care was taken
with the photolytic conditions, the major product
was found to be the corresponding nitrile. Indeed,
Kikugawa has reported this reaction as a possible
synthetic route to nitriles.15 Gas chromatographic
analysis of the reaction mixture after irradiating (Z)-
N -methoxybenzenecarboximidoyl uoride (5a) for 5 h
indicated 49% E hydroximoyl uoride (7a) (see Scheme
1), 47% of the Z isomer (5a) and 4% benzonitrile. The
E
uorides once isolated seem to be thermally stable,
with an n.m.r. solution [in (2H)chloroform] kept at
room temperature for more than a month showing no
sign of any Z isomer. Irradiation of a benzene solution
of (1a), under similar conditions to the preparation
of (7d), led to rapid decomposition [70% of (1a) had
reacted after 30 min] with the appearance of an N -Me
resonance at 4 10 ppm but without any trace of
an N -Me resonance for the corresponding E isomer
(expected at c. 2 90 ppm—see below).
Reactions leading to compounds (5) required much
more forcing conditions. Sulfolane had previously been
used as a solvent for reactions with CaF2/KF but even
at 200 (Z)-N -methoxy-4-methylbenzenecarboximidoyl
bromide (4b) did not lead to any uoro product. How-
ever, in dimethyl sulfoxide at 150–170 , depending
on the ring substituent, the desired products were
observed. It was subsequently discovered that potas-
sium uoride alone under similar reaction conditions
led to an almost identical product mixture. For these
reactions in dimethyl sulfoxide, varying amounts of
the corresponding methyl benzothiohydroximates (6)
were also observed. These thio compounds had a
much lower volatility than the corresponding uoro
compounds, and a lower RF on silica, and could be
removed by fractional distillation of the uoro com-
pounds or by chromatography. Finger et al.13 have
also reported the preparation of methylthio compounds
during the preparation of uoropyridines by the reaction
of chloropyridines with KF in Me2SO. The inadvertent
synthesis of the previously unknown methylthio com-
pounds could produce some useful compounds for our
future mechanistic studies. Preliminary data indicate
that irradiation of the Z methylthio isomers produced
here leads to a photostationary equilibrium containing
both the Z and E isomers.
N.m.r. studies indicate that, as for all other halo
compounds in these series that have been investigated,
the thermodynamically more stable isomer has the Z
con guration. The O-methyl group resonates at a very
slightly higher eld in the E (7) than in the Z isomer
(5) (3 94 versus 3 96 ppm where R = H). For other
halo compounds these assignments based on n.m.r.
data have been con rmed by X-ray crystal structure
18
analysis.16
The E isomers of the halo compounds
(1) have never been isolated,2 but the position of the
N -methyl group at c. 3 6 ppm for (1) is consistent with
other Z isomers and is quite di erent from the position
at c. 2 9 ppm for other similar E isomers reported in
the literature.2,5 The 13C spectra are characterized by
1
very large JC
coupling constants of 320–340 Hz in
F
the Z isomers, and around 230 Hz for the E isomers of
the N -methoxybenzenecarboximidoyl uorides. This
signi cant di erence in the coupling constants could
be a useful way of distinguishing between these iso-
Ultraviolet irradiation of benzene solutions of (Z)-
(5) gave a photostationary mixture of the E and Z
isomers with a c. 1 : 1 mixture of the two isomers.
mers. Bohme and Drechsler reported 1JC
coupling
F

Short Communications
809
constants of 333–348 Hz for their compounds (2).9
Smaller couplings to the ipso carbon (20–30 Hz) and
to the ortho carbon (3–5 Hz) were also observed.
The compounds (Z)-(5) showed no or very small cou-
pling between the uorine and the O-methyl protons,
suggesting these compounds adopt the s-trans con g-
uration preferentially (shown), while for compounds
(1) there was coupling between the uorine and the
7 46, m, 4H, ArH; 7 74, d, J 7 8 Hz, 2H, ArH; 8 28, dd,
Jortho 9 4 Hz, Jmeta 2 6 Hz, 1H, ArH; 8 56, d, Jmeta 2 6
Hz, 1H, ArH. 13C n.m.r. 42 6, d, J 5 6 Hz; 117 2; 122 4;
126 7, d, JCCCF 4 4 Hz; 127 0, d, JCCF 34 4 Hz; 127 0;
128 8; 132 0; 138 9; 139 5; 146 9; 147 9, d, JCF 333 6 Hz.
(Z)-N-(2,4-Dinitrophenyl)-4-methoxy-N-methylbenzene-
carbohydrazonoyl Fluoride (1b)
This compound was prepared by a similar procedure to the
hydrazonoyl uoride (1a) except that a reaction time of 7 h
was used leading to the desired product in 65%, m.p. 148–149
(lit.5 145–147 ). 1H n.m.r. 3 57, d, JH,F 2 7 Hz, 3H, NCH3;
3 87, s, 3H, OMe; 6 95, d, J 8 8 Hz, 2H, ArH; 7 37, d, J 9 4
Hz, 1H, ArH; 7 72, d, J 8 8 Hz, 2H, ArH; 8 29, dd, Jortho
9 4 Hz, Jmeta 2 6 Hz, 1H, ArH; 8 57, d, Jmeta 2 6 Hz, 1H,
1
N -methyl group in both the 13C (c. 5 Hz) and the H
(3 Hz) spectra. For these compounds, the preferred
conformation must have the N -methyl group in fairly
close proximity to the uorine, as shown, with the
bulky dinitrophenyl group pointing outwards. Two of
the E isomers of the N -methoxybenzenecarboximidoyl
uorides (7a) (Y = H) and (7c) (Y = Cl) did show
a very small coupling between the uorine and the
O-methyl group in the proton spectrum, and, in the
case of the 4-chloro compound, also in the carbon
spectrum.
ArH. 13C n.m.r.
42 6, d, J 4 7 Hz; 55 4; 114 3; 116 5;
118 9, d, JCCF 35 2 Hz; 122 5; 127 0; 128 7; 138 6; 139 0;
146 6; 149 9, d, JCF 333 6 Hz; 162 9.
N-Phenylbenzenecarboximidoyl Fluoride (2a)
CaF2/KF (0 9 g) and N -phenylbenzenecarboximidoyl chlo-
ride (0 3 g, 0 14 mmol) in dry acetonitrile (5 ml), under an
atmosphere of nitrogen, were heated under re ux and stirred
for 18 h. The acetonitrile was removed by evaporation and the
resulting solid triturated with hexane (4 5 ml) and the hexane
Experimental
removed by evaporation to leave an oil (50%) (Found: M+
199 0795. C13H10FN requires M+ , 199 0797). 13C n.m.r.
,
General Methods
Calcium uoride was 325 mesh 99 9% from Aldrich Chemical
Company. Potassium uoride was either BDH analyical reagent
grade or the spray-dried reagent from Aldrich. Photochemical
isomerization reactions were carried out in quartz tubes placed
in a Rayonet reactor, RPR-100 (The Southern New England
Ultraviolet Company), tted with 15 low-pressure lamps (253 7
nm). The 1H n.m.r. spectra were acquired at 300 13 MHz,
and the 13C spectra at 75 47 MHz, on either a Bruker AM 300
spectrometer or a Varian Mercury 300 MHz spectrometer in
(2H)chloroform. Low-resolution mass spectra were obtained on
a Varian Saturn 3 ion-trap gas chromatograph–mass spectro-
meter. New compounds gave a single spot by t.l.c. analysis or a
single peak in the g.c./m.s., and showed the required numbers
of carbons in the 13C n.m.r. spectrum. Most compounds were
further characterized from their high-resolution mass spectra.
Elementary analysis of some compounds described in this work
was carried out by Midwest Microlab, Indianapolis, Inc. Exact
masses were obtained by the Central Science Laboratory at
the University of Tasmania.
123 3; 125 3; 128 5; 128 8; 132 2; 143 0, d, JCNCF 12 5 Hz;
148 4, d, JCF 340 7 Hz.
(Z)-N-Methoxy-4-methylbenzenecarboximidoyl Bromide (4b)
Sodium nitrite (1 6 g, 23 mmol) in water (10 ml) was
added dropwise to a stirred ice-cold solution of N -methoxy-4-
methylbenzenecarboximidamide1,19 (1 5 g, 9 1 mmol) in 50%
HBr (14 ml). The resulting solution was stirred and cooled in
an ice bath for 1 h and at room temperature for an additional
1 h. The organic product was extracted in dichloromethane
(2 15 ml). Removal of the solvent gave the desired bromo com-
pound (40%) (Found: M+ , 226 9944. C9H10BrNO requires
M+ , 226 9946). 1H n.m.r.
2 37, s, 3H, ArCH3; 4 12, s,
3H, OCH3; 7 18, d, J 8 0 Hz, 2H, ArH; 7 72, d, J 8 0 Hz,
2H, ArH. 13C n.m.r. 21 3, 62 9, 128 2, 129 1, 130 3, 131 2,
140 8.
(Z)-4-Bromo-N-methoxybenzenecarboximidoyl Bromide (4d)
This compound was prepared by a similar procedure as a
solid (56%), m.p. 36–37 (Found: M+ , 290 8898. C8H7Br2NO
Preparation of CaF2/KF Reagent
requires M+ , 290 8894). 13C n.m.r.
129 6, 131 5, 132 8.
63 1, 125 0, 129 1,
Calcium uoride (5 0 g, 0 064 mol) was added to a solution
of potassium uoride (1 2 g, 0 021 mol) in methanol (20 ml)
and the resulting slurry evaporated slowly to dryness in a
vacuum oven at 80 over 5 h. The resulting solid was ground to
(Z)-4-Chloro-N-methoxybenzenecarboximidoyl Bromide (4c)
Phosphorus pentabromide was added to 4-chloro-N -methoxy-
benzamide1 (17 99 g, 0 0970 mol) in a 100 ml three-neck
round-bottomed ask tted with condenser, drying tube, and
J-Kem temperature probe. The mixture was heated to 80 C
with stirring and held there for 212 h. The mixture was
cooled to room temperature and poured into ice-cold water
(200 ml). The resulting mixture was extracted with ether
(3 150 ml). The combined ether extracts were washed with
saturated sodium hydroxide solution (6 50 ml) and dried. The
ether was removed by evaporation to yield an amber-coloured
oil (13 87 g). Vacuum distillation of this oil gave a light yellow
a
ne powder (5 7 g) and stored in a desiccator until required.
(Z)-N-(2,4-Dinitrophenyl)-N-methylbenzenecarbo-
hydrazonoyl Fluoride (1a)
CaF2/KF (0 5 g) and N -(2,4-dinitrophenyl)-N -methyl-
benzenecarbohydrazonoyl bromide (0 16 g, 0 42 mmol) in dry
acetonitrile (5 ml), under an atmosphere of nitrogen, were heated
under re ux and stirred for 24 h. On cooling, dichloromethane
(20 ml) was added and the resulting slurry ltered to remove
the inorganic salts. The organic solution was washed with 2%
sodium hydroxide solution (to remove any hydrazide formed),
dried, and the solvent removed by evaporation. The product
was puri ed by dry column chromatography on silica with
dichloromethane/hexane (3 : 1) as the eluting solvent, followed
by recrystallization from dichloromethane/hexane, yielding a
yellow/brown crystalline solid (0 085 g, 65%), m.p. 131–133
(lit.6 131–133 ). 1H n.m.r. 3 59, d, JH,F 3 0 Hz, 3H, NCH3;
oil (13 00 g, 54 %) which solidi ed upon cooling (Found: M+
,
246 9410. C8H7BrClNO requires M+ , 246 9400). 1H n.m.r.
4 13, s, 3H, OCH3; 7 35, d, J 9 0 Hz, 2H, ArH; 7 77, d,
J 9 0 Hz, 2H, ArH. 13C n.m.r. 63 1, 128 4, 128 8, 129 2,
132 1, 136 4. G.c./m.s.: m/z 251 (M, 11%), 249 (60), 247
(44), 170 (33), 168 (100), 155 (32), 153 (99), 139 (35), 137
(98), 102 (42).

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(Z)-N-Methoxy-4-methylbenzenecarboximidoyl Fluoride (5b)
(Z)-4-Chloro-N-methoxybenzenecarboximidoyl Fluoride (5c)
KF (0 7 g, 12 mmol) and N -methoxy-4-methylbenzenecar-
boximidoyl bromide (4b) (0 54 g, 1 4 mmol), in dry dimethyl
sulfoxide (8 ml), under an atmosphere of dry nitrogen, were
heated and stirred at 158 for 22 h. On cooling the organic
products were extracted into pentane (5 8 ml). The pentane
layer was washed with water, dried and the solvent removed
by evaporation. The n.m.r. of the crude product indicated
a mixture of the desired uoro compound (5b) and methyl
(Z)-O,4-dimethylbenzothiohydroximate (6b) (c. 3 : 1 by n.m.r.).
The products were separated by dry column chromatography
on silica with dichloromethane/pentane (1 : 1) as the eluting
solvent yielding the desired product (5b) as an oil (0 18 g,
The procedure described above was used when (Z)-4-
chloro-N -methoxybenzenecarboximidoyl bromide (4c) (13 25
g, 0 0534 mol) and potassium uoride (12 41 g, 0 21 mol)
in dimethyl sulfoxide (240 ml) were heated at 150 C with
stirring for 19 h. Fractional distillation of the crude prod-
uct under vacuum gave a colourless oil (2 29 g, 23%), b.p.
c. 55 C/1 2 mmHg (Found: M+ , 187 0199. C8H7ClFNO
requires M+ , 187 0200). 1H n.m.r. 3 96, d, JH,F 1 2 Hz,
3H, OCH3; 7 38, d, J 8 4 Hz, 2H, ArH; 7 68, d, J 8 4 Hz,
2H, ArH. 13C n.m.r. 63 6; 125 3, d, JCCF 30 9 Hz; 127 2;
129 1, d, JCCCF 2 3 Hz; 137 3; 149 7, d, JCF 321 1 Hz.
G.c./m.s.: m/z 189 (M, 34%), 187 (100), 158 (10), 156 (32),
144 (8), 142 (15), 137 (23), 113 (16), 111 (45).
46%) (Found: M+ , 167 0756. C9H10FNO requires M+
167 0746). 1H n.m.r.
2 37, s, 3H, ArCH3; 3 94, s, 3H,
,
(E)-N-Methoxybenzenecarboximidoyl Fluoride (7a)
OCH3; 7 19, d, J 8 0 Hz, 2H, ArH; 7 61, d, J 8 0 Hz, 2H,
ArH. 13C n.m.r. 21 4; 63 1; 123 7, d, JCCF 30 6 Hz; 125 7,
d, JCCCF 4 0 Hz; 129 2; 141 3; 150 6, d, JCF 320 6 Hz.
Methyl (Z)-O,4-dimethylbenzothiohydroximate (6b) (0 072
g, 16%) was obtained as an oil (Found: M+ , 195 0724.
A solution of the Z imidoyl uoride (5a) (1 16 g) in benzene
(20 ml) was irradiated for 5 h. The mixture was immedi-
ately extracted with saturated sodium bicarbonate solution
(3 20 ml). The benzene extract was dried and the benzene
removed by evaporation. G.c./m.s. analysis of the resulting oil
revealed that it contained a mixture of approximately 50 : 50 of
the E and Z isomers. The geometric isomers were separated by
preparative gas chromatography. This yielded the E imidoyl
uoride (7a) as a clear oil (0 066 g, 5 7%) (Found: C, 62 5; H,
5 3; F, 12 2; N, 9 2. C8H8FNO requires C, 62 7; H, 5 3; F,
12 4; N, 9 2%). 1H n.m.r. 3 94, d, JH,F 0 8 Hz, 3H, OCH3;
7 48, m, 3H, ArH; 8 00, 7 97, dd, J 8 1, 1 8 Hz, 2H, ArH.
13C n.m.r. 63 3; 124 9, d, JCCF 35 5 Hz; 128 2; 128 4, d,
JCCCF 6 9 Hz; 131 5; 156 0, d, JCF 232 0 Hz. G.c./m.s.:
m/z 153 (M, 100%), 122 (14), 108 (33), 103 (12), 77 (62).
C
10H13NOS requires M+ , 195 0718). 1H n.m.r.
2 03, s,
3H, SCH3; 2 36, s, 3H, ArCH3; 4 02, s, 3H, OCH3; 7 20, d,
J 8 0 Hz, 2H, ArH; 7 29, d, J 8 0 Hz, 2H, ArH. 13C n.m.r.
14 9, 21 3, 62 4, 128 7, 129 2, 132 0, 139 5, 155 7.
(Z)-4-Bromo-N-methoxybenzenecarboximidoyl Fluoride (5d)
This compound was prepared by a similar procedure as
a waxy solid (90%), m.p. 35–36 (Found: M+ , 230 9695.
C8H7BrFNO requires M+ , 230 9695). 1H n.m.r. 3 94, s,
3H, OCH3; 7 48, d, J 8 7 Hz, 2H, ArH; 7 55, d, J 8 7 Hz,
ArH, 2H. 13C n.m.r. 63 2; 125 4; 125 5, d, JCCF 31 6 Hz;
127 0, d, JCCCF 3 4 Hz; 131 7; 149 5, d, JCF 321 3 Hz.
(E)-4-Chloro-N-methoxybenzenecarboximidoyl Fluoride (7c)
(Z)-N,4-Dimethoxybenzenecarboximidoyl Fluoride (5e)
The procedure described above was used to obtain a mixture
(50 : 50 by g.c./m.s.) of the E and Z isomers. The geometric
isomers were separated by preparative gas chromatography.
The E imidoyl uoride (7c) was obtained as a clear oil (Found:
C, 51 4; H, 3 6; Cl, 18 9; F, 9 8; N, 7 4. C8H7ClFNO
requires C, 51 2; H, 3 8; Cl, 18 9; F, 10 1; N, 7 5%). 1H
n.m.r. 3 94, d, JH,F 0 9 Hz, 3H, OCH3; 7 44, d, J 9 0 Hz,
2H, ArH; 7 94, d, J 9 0 Hz, 2H, ArH. 13C n.m.r. 63 5, d,
JCONCF 2 3 Hz; 123 2, d, JCCF 35 5 Hz; 128 6, d, JCCCCF
2 3 Hz; 129 8, d, JCCCF 6 8; 137 6; 155 0, d, JCF 230 4 Hz.
G.c./m.s.: m/z 189 (M, 33%), 187 (100), 158 (10), 156 (31),
144 (9), 142 (17), 137 (24), 113 (17), 111 (50).
This compound was obtained as an oil by a similar procedure
except that the temperature was maintained at 152 (yield
40%) (Found: M+ , 183 0694. C9H10FNO2 requires M+
,
183 0696). 1H n.m.r. 3 81, s, 3H, OCH3; 3 92, s, 3H, OCH3;
6 88, d, J 8 8 Hz, 2H, ArH; 7 65, d, J 8 8 Hz, 2H, ArH. 13C
n.m.r. 55 4; 63 0; 114 0; 118 9, d, JCCF 30 5 Hz; 127 4,
d, JCCCF 4 7 Hz; 150 5, d, JCF 319 3 Hz; 161 8.
(Z)-N-Methoxybenzenecarboximidoyl Fluoride (5a)
(Z)-N -Methoxybenzenecarboximidoyl bromide4 (4a) (15 02
g, 0 0702 mol) was placed in a three-neck 250 ml round-
bottomed ask tted with water-cooled condenser, nitrogen
gas inlet, and J-Kem temperature probe. Potassium uoride
(16 38 g, 0 28 mol) in dimethyl sulfoxide (240 ml) was added
to the ask with stirring. The mixture was heated to 150 C
with stirring for 14 h. The reaction mixture was cooled to
room temperature and then combined with 150 ml of saturated
sodium chloride solution. This mixture was extracted with
ether (4 150 ml). The combined ether extracts were dried and
the ether was removed by evaporation to give an amber-coloured
oil (9 04 g). Fractional distillation under vacuum gave (5a) as
a colourless oil (5 45 g, 51%), b.p. c. 45 C/5 mmHg (Found:
C, 62 6; H, 5 2; F, 12 4; N, 9 1. C8H8FNO requires C, 62 7;
H, 5 3; F, 12 4; N, 9 2%). 1H n.m.r. 3 96, s, 3H, OCH3;
7 44, m, 3H, ArH; 7 74, d, J 7 6 Hz, 2H, ArH. 13C n.m.r.
63 2; 125 7, d, JCCCF 3 7 Hz; 126 6, d, JCCF 30 6 Hz;
128 5; 130 9; 150 3, d, JCF 321 3 Hz. G.c./m.s.: m/z 153
(M, 100%), 122 (14), 108 (37), 103 (9), 77 (65).
(E)-4-Bromo-N-methoxybenzenecarboximidoyl Fluoride (7d)
A solution of the Z imidoyl uoride (5d) in pentane/ether
(3 : 1) was irradiated with a single 150 Watt mercury lamp for
4 h. The mixture of isomers was separated on a preparative
silica plate kept in the dark; hexane/dichloromethane (2 : 1)
was used as the eluting solvent. The E imidoyl uoride (7d)
was the lower RF compound and was obtained as an oil which
solidi ed on cooling (Found: M+ , 230 9706. C8H7BrFNO
requires M+ , 230 9695). 1H n.m.r.
3 92, s, 3H, OCH3;
7 55, d, J 8 6 Hz, 2H, ArH; 7 81, d, J 8 6 Hz, 2H, ArH.
13C n.m.r. 63 5; 123 9, d, JCCF 36 0 Hz; 126 3; 130 1, d,
JCCCF 6 6 Hz; 131 7; 155 4, d, JCF 230 0 Hz.
References
1
Johnson, J. E., Nalley, E. A., Kunz, Y. K., and Spring eld,
J. R., J. Org. Chem., 1976, 41, 252.
Rowe, J. E., and Hegarty, A. F., J. Org. Chem., 1984, 49,
3083.
Sakamoto, T., Mori, H., Takizawa, M., and Kikugawa, Y.,
Synthesis, 1991, 750.
Johnson, J. E., and Cornell, S. C., J. Org. Chem., 1980,
45, 4144.
Further fractional distillation gave methyl O-methylbenzo-
thiohydroximate (6a) (1 83 g, 14%) (Found: M+ , 181 0566.
C9H11NOS requires M+ , 181 0561). 1H n.m.r. 2 02, s, 3H,
SCH3; 4 02, s, 3H, OCH3; 7 39, s, 5H, ArH. 13C n.m.r.
14 9, 62 5, 128 6, 128 8, 129 4, 132 6, 155 6. G.c./m.s.: m/z
181 (M, 54%), 180 (46), 150 (19), 134 (26), 119 (100), 104
(37), 103 (36), 91 (23), 77 (42).
2
3
4

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