Free radical reactions to generate alkenes and/or ionic reactions to generate hydroximoyl chlorides when β-nitrostyrenes react with triethylaluminium or diethylaluminium chloride

Article abstract of DOI:10.1039/a807156j

β-Nitrostyrenes 1 react with triethylaluminium or diethylaluminium chloride in diethyl ether solution and under nitrogen or argon to generate the alkenes 2 and the hydroximoyl chlorides 3 after work-up with ice-cold, cone, hydrochloric acid. The formation of the alkenes 2 is proposed to be a free-radical reaction via NO₂/alkyl substitution since the yields of the alkenes 2 are increased in the presence of benzoyl peroxide (Bz₂O₂) and decreased in the presence of galvinoxyl. Only the alkenes 2 are produced with a high stereoselectivity for the E isomers when β-nitrostyrenes react with triethylaluminium in the presence of one to two equivalents of Bz₂O₂ as free-radical initiator. The mechanism of the generation of the hydroximoyl chlorides 3 is proposed to proceed through a 1,4-addition pathway to produce nitronates A, then the protonated nitronates B or the nitroso cations C are trapped by chloride ion to form the final products. The yields of compounds 3 are also improved by the presence of Lewis acids such as MgCl₂. Medium to high yields of the hydroximoyl chlorides 3 and traces or low yields of the alkenes 2 are generated when triethylaluminium or diethylaluminium chloride react with β-nitrostyrenes in the presence of three equivalents of MgCl₂ under argon.

Full text of DOI:10.1039/a807156j

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Free radical reactions to generate alkenes and/or ionic reactions to
generate hydroximoyl chlorides when â-nitrostyrenes react with
triethylaluminium or diethylaluminium chloride
Cheng-Ming Chu, Ju-Tsung Liu, Wen-Wei Lin and Ching-Fa Yao*
Department of Chemistry, National Taiwan Normal University, 88 Sec. 4, Tingchow Road,
Taipei, Taiwan 116 R.O.C.
Received (in Cambridge) 14th September 1998, Accepted 28th October 1998
β-Nitrostyrenes 1 react with triethylaluminium or diethylaluminium chloride in diethyl ether solution and under
nitrogen or argon to generate the alkenes 2 and the hydroximoyl chlorides 3 after work-up with ice-cold, conc.
hydrochloric acid. The formation of the alkenes 2 is proposed to be a free-radical reaction via NO2/alkyl substitution
since the yields of the alkenes 2 are increased in the presence of benzoyl peroxide (Bz2O2) and decreased in the
presence of galvinoxyl. Only the alkenes 2 are produced with a high stereoselectivity for the E isomers when β-nitro-
styrenes react with triethylaluminium in the presence of one to two equivalents of Bz2O2 as free-radical initiator.
The mechanism of the generation of the hydroximoyl chlorides 3 is proposed to proceed through a 1,4-addition
pathway to produce nitronates A, then the protonated nitronates B or the nitroso cations C are trapped by chloride
ion to form the final products. The yields of compounds 3 are also improved by the presence of Lewis acids such as
MgCl2. Medium to high yields of the hydroximoyl chlorides 3 and traces or low yields of the alkenes 2 are generated
when triethylaluminium or diethylaluminium chloride react with β-nitrostyrenes in the presence of three equivalents
of MgCl2 under argon.
Ar
H
Introduction
+
C
C
Et3Al or Et2AlCl
Reactions of non-stabilized organometallic reagents, such as
the alkyl derivatives of lithium,1 magnesium,2 zinc,3 and cop-
per,4 with conjugated nitroalkenes to generate nitroalkanes or
carbonyl compounds have been studied in recent years. Reac-
tions of trialkylaluminium and triorganoaluminium–ether
complexes with α,β-unsaturated nitroalkenes to give 1,4-
alkylated products in high yield have been reported.5 It is
also reported that β-nitrostyrenes can react with dialkylzinc,6
organomanganese,7 t-BuHgX/KI,8 trialkylgallium9 or trialkyl-
borane10 reagents, respectively, to generate alkenes and/or
nitroalkanes and the mechanism is proposed to be an ionic or
free-radical reaction. Barton has shown that the nitroolefins
reacted with thiopyridone-based esters to generate α-nitro sul-
fides by free-radical chain reactions.11 It was concluded that
nitroalkenes are highly reactive conjugate acceptors and useful
intermediates in organic synthesis and can react with non-
stabilized nucleophiles to generate different products under
different work-up conditions.1–11
In 1989 Kunz observed that dialkylaluminium chlorides react
with α,β-unsaturated carboxylic acid derivatives to give 1,4-
addition products.12 This interesting study indicates that dialkyl-
aluminium chlorides also can be used as nucleophiles in the
Michael reaction. In this paper, we report the reactions of β-
nitrostyrenes 1 with triethylaluminium or diethylaluminium
chloride to generate free-radical and/or ionic products depend-
ing upon the reaction conditions.
R
NO2
1
conc. HCl(aq)
R
Ar
H
Cl
+
C
C
Ar
C
C
R
Et
NOH
Et
2
3
a: Ar = Ph, R = H
b: Ar = 4-MeC6H4, R = H
c: Ar = 4-MeOC6H4, R = H
d: Ar = 4-FC6H4, R = H
e: Ar = 4-CF3C6H4, R = H
f: Ar = 2-MeOC6H4, R = H
g: Ar = 2-MeC6H4, R = H
h: Ar = 2-CF3C6H4, R = H
i: Ar = 2-thienyl, R = H
j: Ar = 2-furyl, R = H
k: Ar = Ph, R = Ph
l: Ar = Ph, R = Me
Results and discussion
Reactions of β-nitrostyrenes 1 with triethylaluminium or
diethylaluminium chloride in diethyl ether solution at 40 or
60 ЊC (oil-bath temperature) and under nitrogen or argon gave
two products after the reaction intermediates were slowly added
to ice-cold, conc. hydrochloric acid. One of the products was
assigned to be the 1-arylbut-1-ene 2 and the other was the
hydroximoyl chloride 3 according to their H, 13C NMR, IR,
and mass spectra after flash column chromatographic puri-
fication (Table 1).
1
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52
47

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Table 1 Reactions of β-nitrostyrenes 1 with Et3Al or Et2AlCl under nitrogen or argon
Entry
Substrate
Et3Al or Et2AlCl
Conditionsa
2 (%)b
3 (%)b
2:3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
1a
1a
1b
1b
1b
1b
1b
1b
1c
1d
1e
1e
1f
1g
1g
1h
1i
1i
1j
Et3Al
Et2AlCl
Et3Al
N2, 60 ЊC, 4 h
N2, 60 ЊC, 7 h
N2, 60 ЊC, 2 h
Ar, 60 ЊC, 3 h
N2, dark, rt, 9 h
N2, 60 ЊC, 2 h
N2, 60 ЊC, 9 h
Ar, 60 ЊC, 9 h
N2, 40 ЊC, 3 h
N2, rt, 18 h
N2, 40 ЊC, 2 h
N2, 40 ЊC, 6 h
N2, 40 ЊC, 6 h
N2, 40 ЊC, 5.5 h
N2, 40 ЊC, 6 h
N2, 40 ЊC, 5 h
N2, 40 ЊC, 5 h
N2, 40 ЊC, 6 h
N2, rt, 5 h
2a (24)
2a (22)
2b (30)
2b (25)
2b (18)
2b (19)
2b (38)
2b (28)
2c (19)
2d (24)
2e (25)
2e (24)
2f (29)
2g (43)
2g (32)
2h (39)
2i (18)
2i (tr)
3a (49)
3a (36)c
3b (35)
3b (57)a
3b (41)e
3b (33) f
3b (51)g
3b (44)h
3c (38)
3d (32)
3e (40)
3e (32)
3f (31)
3g (29)
3g (55)
3h (28)
3i (27)
33:67
38:62
46:54
30:70
31:69
37:63
43:57
39:61
33:67
43:57
38:62
43:57
48:52
60:40
37:63
58:42
40:60
<1:99
45:55
33:67
45:55
19:81
Et3Al
Et3AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et3Al
Et3Al
Et3Al
Et2AlCl
Et3Al
Et3Al
Et2AlCl
Et3Al
Et3Al
Et2AlCl
Et3Al
Et3Al
Et2AlCl
Et3Al
3i (51)
2j (22)
2k (29)
2k (35)
2l (14)
3j (27)
1k
1k
1l
N2, 40 ЊC, 4 h
N2, 40 ЊC, 6 h
N2, 40 ЊC, 8 h
3k (58)
3i (43)
3l (58)i
a Oil-bath temperature. b Isolated yields, tr = trace. c 11% Unchanged compound 1a was recovered. d 15% Unchanged compound 1b was recovered.
e 40% Unchanged compound 1b was recovered. f 48% Unchanged compound 1b was recovered. g 10% Unchanged compound 1b was recovered.
h 17% Unchanged compound 1b was recovered. i 9% Unchanged compound 1l was recovered.
Fig. 2 Molecular structure of compound 3h.
Fig. 1 Molecular structure of compound 3f.
chemistry of compounds 3f and 3h has been determined by
X-ray crystallography. Structures are shown in Fig. 1 (3f) and
The formation of the different products indicates that tri-
ethylaluminium and diethylaluminium chloride can generate
the alkenes 2 and the hydroximoyl chlorides 3 simultaneously
under similar experimental and work-up conditions. It is also
found that triethylaluminium is always more reactive than
diethylaluminium chloride when substrates 1a (entries 1 and 2),
1b (entries 3 and 6 or entries 4 and 8), 1e (entries 11 and 12),
and 1k (entries 20 and 21), respectively, reacted with triethyl-
aluminium or diethylaluminium chloride under the same condi-
tions. Usually conjugate addition was predominant with the
yields of the hydroximoyl chlorides 3 higher than the alkenes
2 when β-nitrostyrenes 1 reacted with triethylaluminium or
diethylaluminium chloride. However, with the ortho substituted
β-nitrostyrenes 1f (entry 13), 1g (entry 14), or 1h (entry 16), the
results were reversed and the yields of the alkenes 2 were almost
equal to or even higher than those of hydroximoyl chlorides 3
when triethylaluminium was used. These different results can
be attributed to the steric effect of the OCH3, CH3, and CF3
groups at the ortho position of the benzene ring. The stereo-
Fig. 2 (3h) and crystal data are listed in Table 2.†,13
Our previous work on the Michael addition of Grignard or
organolithium reagents to β-nitrostyrenes showed that high
yields of the hydroximoyl halides, nitrile oxides, or carboxylic
acids were formed when the nitronates were treated with ice-
cold, conc. hydrohalic or sulfuric acid solutions.14 A blue or
green color always appeared when the nitronates were added to
the acids. A similar blue-green color was observed again when
the intermediates, aluminium nitronates A, were slowly added
to ice-cold, conc. hydrochloric acid. The blue-green color indi-
cated that the hydroximoyl chlorides 3 were formed from the
† Full crystallographic details, excluding structure factor tables, have
been deposited at the Cambridge Crystallographic Data Centre
(CCDC). For details of the deposition scheme, see ‘Instructions for
Authors’, J. Chem. Soc., Perkin Trans. 1, available via the RSC web page
(http://www.rsc.org/authors). Any request to the CCDC for this material
should quote the full literature citation and the reference number 207/
277. See http://www.rsc.org/suppdata/perkin1/1999/47/ for crystallo-
graphic files in .cif format.
48
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52

View Article Online
protonated nitronates B or the nitroso cations C, then inter-
mediates B or C were trapped by chloride ion to yield a nitroso
compound and this rearranged to give the final products
(Scheme 1).
R
Ar
Et
H
Ar
H
+
+σ
N
C
C
Et2AlCl or Et3Al
O
R
NO2
-σ Al
O
Lewis acids play an important role in the ionic reactions lead-
ing to hydroximoyl chlorides 3. Thus, when three equivalents of
MgCl2 were added to the solution, the yields of products 3 were
improved substantially when triethylaluminium or diethylalu-
minium chloride was also used under nitrogen or argon (Table
3). It appeared that MgCl2 coordinated with the oxygen of the
nitro group, as did the aluminium center of the organoalu-
minium reagents, to promote the ionic transfer of the ethyl
group to the β-nitrostyrenes. Similar results are also observed
when diethylzinc reacts with β-nitrostyrenes in Et2O and in the
Et
Cl (or Et)
1
R
H
R
Ar
C
C
H
N
O
Ar
C
C
Et
+
N
0
oC, conc. HCl(aq)
OH
O
Et
6
presence of MgBr2/MgCl2 or copper salts15 as catalyst. We
Al Cl (or Et)
Et
OH
were also surprised to find that substrates 1c, 1f, 1i, 1j, and 1l
reacted with diethylaluminium chloride or triethylaluminium to
generate medium to high yields (57–95%) of the hydroximoyl
B
A
_
+ H2O
H2O
Table 2 Crystallographic and refinement data for compounds 3f
and 3h
R
R
Cl
C
3f
3h
R
H
_
Cl
Cl
Ar
C
C
+
N
Ar
C
N=O
Ar
C
C
Empirical formula
Crystal system
Space group
Cell dimensions
a/Å
b/Å
c/Å
C11H14ClNO2
Monoclinic
P21/a
C11H11ClF3NO
Orthorhombic
Pcab
NOH
Et
Et
H
Et
O
3
C
Scheme 1
9.133(3)
13.3169(19)
9.4793(11)
94.343(16)
1149.5(5)
0.17 × 0.27 × 0.33
227.69
7.870(3)
12.720(4)
23.955(7)
chlorides 3, while only a trace or none of the alkenes 2 (entries
3, 6, 9, 10, and 12) was observed. These results indicate that the
methoxy, thienyl, and furyl groups also can coordinate with the
aluminium reagents to promote the transfer of the ethyl group
to the β-nitrostyrenes and the presence of the methyl group will
increase the steric hindrance to retard the free-radical reaction.
Hydroximoyl halides are important intermediates in organic
synthesis. Compared with the method of dehydration of pri-
mary nitro compounds (Mukaiyama–Hoshino),16 oxidation of
aldoximes17 or the reaction of TiCl4 with nitroalkenes18 to gen-
erate nitrile oxides or hydroximoyl chlorides, we found that
alkylation and chlorination also could occur in a one-pot reac-
tion to give medium to high yields of the hydroximoyl chlorides
3 from reactions of conjugated nitroalkenes with organoalu-
minium reagents.
The mechanism of the formation of alkenes 2 is proposed to
be a free-radical non-chain reaction. The free-radical reaction is
obviously stimulated by photolysis or by dibenzoyl peroxide
(Table 4).19,20 Only 37–63% yields of the alkenes 2 were gener-
ated when solutions of β-nitrostyrenes 1 and triethylaluminium
were irradiated with a 275 W General Electric sunlamp at
~30 ЊC. It is known that an SH2 reaction can occur readily at
an aluminium center.20,21 The yields of the alkenes 2 were also
increased dramatically (35–80%) when one or two equivalents
of benzoyl peroxide were added to the system at rt and in the
β (Њ)
V/Å3
2397.9(13)
0.51 × 0.45 × 0.46
265.66
8
1079.86
1.472
0.34
0.70930
49.8
Nonius (CAD-4)
θ/2θ
0 < h < 9,
0 < k < 15,
0 < l < 28
2107
1489
0.94–1.00
155
Crystal size/mm
Formula weight
Z
4
F(000)
455.94
1.316
0.31
0.70930
49.8
Nonius (CAD-4)
θ/2θ
Ϫ10 < h < 10,
0 < k < 15,
0 < l < 11
2020
1358
0.96–1.00
137
0.039
0.028
2.63
0.016
0.200
Ϫ0.210
Dc/g cmϪ3
µ/mmϪ1
λ/Å
2θ (max)
Diffractometer
Scan mode
hkl mode
No. unique reflections
No. obsd Io > 2.5σ(Io)
Transmission factors
Parameters
R*
Rw*
Goodness of fit*
Maximum ∆/σ
D-map maximum/e ÅϪ3
D-map minimum/e ÅϪ3
0.046
0.036
4.13
0.004
0.220
Ϫ0.320
¹
* R = Σ|Fo Ϫ Fc|/ΣFo, Rw = [Σw(Fo Ϫ Fc)2/Σw(Fo)2]², GOF = [Σw(Fo Ϫ
¹
Fc)2/(Nobsd Ϫ Nparam)]².
Table 3 Reactions of β-nitrostyrenes with Et3Al or Et2AlCl in the presence of 3 equivalents of MgCl2 under nitrogen or argon
Entry
Substrate
Et3Al or Et2AlCl
Conditions
2 (%)
3 (%)
2:3
1
2
3
4
5
6
7
8
9
1a
1b
1c
1d
1e
1f
1g
1h
1i
Et3Al
Et3Al
Ar, 60 ЊC, 2.5 h
N2, 60 ЊC, 3 h
Ar, 60 ЊC, 4 h
Ar, 40 ЊC, 17 h
Ar, 40 ЊC, 10 h
Ar, 50 ЊC, 6 h
Ar, 60 ЊC, 11 h
Ar, 40 ЊC, 12 h
Ar, 40 ЊC, 2 h
Ar, rt, 8 h
2a (17)
2b (12)
2c (tr)
2d (26)
2e (22)
2f (tr)
2g (26)
2h (35)
2i (tr)
3a (83)
3b (72)
3c (95)
3d (67)
3e (77)
3f (78)
3g (69)
3h (60)
3i (57)
3j (62)
3k (60)
3l (70)
17:83
14:86
<1:99
28:72
22:78
<1:99
27:73
37:63
<1:99
<1:99
36:64
<1:99
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et3Al
10
11
12
1j
1k
1l
2j (tr)
2k (33)
2l (tr)
N2, 40 ЊC, 5 h
N2, 50 ЊC, 3 h
Et3Al
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52
49

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Table 4 Reactions of β-nitrostyrenes with Et3Al under nitrogen
Entry
Substrate
Conditions
2 (%)
3 (%)
2:3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1a
1a
1a
1b
1b
1b
1c
1d
1d
1e
1e
1f
Bz2O2, 10 mol%, rt, 13 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 2 equiv., rt, 13 h
Bz2O2, 2 equiv., rt, 5.5 h
Bz2O2, 1 equiv., hν, 2 h
galvinoxyl 50 mol%, hν, 4 h
Bz2O2, 2 equiv., rt, 4.5 h
Bz2O2, 2 equiv., rt, 4 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 5 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 4.5 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 8 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 5 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 4 h
Bz2O2, 1 equiv., hν, 1.5 h
Bz2O2, 1 equiv., rt, 5 h
Bz2O2, 1 equiv., hν, 2 h
Bz2O2, 1 equiv., rt, 4 h
Bz2O2, 1 equiv., hν, 1.5 h
Bz2O2, 1 equiv., rt, 4 h
Bz2O2, 1 equiv., hν, 2 h
2a (56)
2a (50)
2a (61)
2b (70)
2b (55)
2b (17)
2c (35)
2d (72)
2d (61)
2e (68)
2e (59)
2f (52)
2f (54)
2g (72)
2g (60)
2h (62)
2h (63)
2i (65)
2i (54)
2j (43)
2j (37)
2k (80)
2k (62)
2l (40)
2l (38)
3a
3a
3a
3b
3b
3b (tr)
3c
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
85:15
>99:1
>99:1
>99:1
3d
3d
3e
3e
3f
1f
3f
1g
1g
1h
1h
1i
3g
3g
3h
3h
3i
1i
3i
1j
3j
1j
3j
1k
1k
1l
3k (14)
3k
3l
1l
3l
absence of irradiation. After observation of the positive effect
of benzoyl peroxide, we also added 50 mol% of galvinoxyl, an
efficient scavenger for free radicals,22 to the reaction system.
With substrate 1b unchanged starting material was recovered
(74%) and only a 17% yield of compound 2b was formed after
the solution was irradiated with a sunlamp for 4 h (entry 6). It is
also reported that only E products can be formed no matter
which (E)- or (Z)-β-nitrostyrenes are used.6 Based on literature
reports6–10 and our results (Tables 1–3), we can conclude that
the substitution of the nitro group by the ethyl group appar-
ently involves the radical addition/elimination with little evi-
dence of a chain process. This proposed mechanism in Scheme
2 is totally different from Hassner’s proposed mechanism.7 One
route to generate a variety of arylated (E)-alkenes in the pres-
ence of the radical initiator.
Experimental
General
All reactions were performed in flame- or oven-dried glassware
under a positive pressure of nitrogen or argon. Air- and
moisture-sensitive compounds were introduced by the use of a
syringe or cannula through a rubber septum. Compounds 1a–e,
1h–j, diethylaluminium chloride. triethylaluminium and conc.
hydrochloric acid (37%) were purchased from Aldrich. Com-
pounds 1f,g,24 1k,25 and 1l 26 were prepared according to or by
modifying the literature procedures. Diethyl ether was distilled
from sodium–benzophenone ketyl and was degassed prior to
reactions. Analytical TLC was performed with E. Merck silica
gel 60F254 glass plates, and flash chromatography by the use of
E. Merck silica gel 60 (230–400 mesh). GCMS were recorded on
an HP 5890 GC/HP 5970B MSD spectrometer, and MS or
high-resolution MS (HRMS) were measured by a JEOL JMS-
hν
+
2 CO2
[PhC(O)O]2
2 PhC(O)O •
2 Ph
•
+
PhC(O)O
or
Et3Al (or Et2AlCl)
•
Et
+
PhC(O)OAlEt2
•
(or PhC(O)OAlEtCl)
PhAlEt2 (or PhAlEtCl)
NO2
1
D300 or JEOL JMS-HX1 10 spectrometer. H and 13C NMR
+
Ph
Et3Al (or Et2AlCl)
Et
•
+
•
spectra were recorded on a JEOL Ex-400 or a Varian Gemini-
200 spectrometer. All NMR data were obtained in CDCl3
solution and chemical shifts δ are given in ppm relative to SiMe4.
J-Values are given in Hz. Elemental analyses were performed
by a Perkin-Elmer 2400 instrument. IR spectra were recorded
in the FT mode by a JASCO IR-7000 spectrometer. All mp
were determined with a MEL-TEMPII apparatus and were
uncorrected.
Ar
H
C
Ar
C
+
Et
•
H
R
NO2
R
Et
1
Ar
H
Typical procedure for the reaction of â-nitrostyrenes 1 with
triethylaluminium or diethylaluminium chloride (see Table 1)
C
C
+
NO2•
R
Et
A solution of 5 mmol of Et3Al in 30 ml of diethyl ether was
prepared from the commercially available 1.0 M Et3Al in hex-
ane. To this solution was slowly added a 0.1 M solution of
(E)-β-nitrostyrene 1a in diethyl ether (2 mmol in 20 ml) and
the stirred mixture was refluxed at 60 ЊC (oil-bath temper-
ature) under nitrogen. After the starting material had disap-
peared (4 h), the solution was slowly added to 100 ml of ice-
cold, conc. hydrochloric acid and stirred for 30 min before
extraction with CH2Cl2. The CH2Cl2 solution was washed with
brine, dried over MgSO4, filtered, and evaporated to obtain an
2
Scheme 2
possibility is that the addition of the ethyl radical generates the
benzylic radical which undergoes β-elimination to yield the
final product 2.8,10,23 The generation of the (E)-1-arylbut-1-ene
2 indicated that the addition of the ethyl radical to β-
nitrostyrenes 1 is regioselective. All these results showed that
triethylaluminium reagent provides a highly stereoselective
50
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52

View Article Online
oily mixture. The crude NMR yields of the products 2a (24%)
and 3a (49%) were measured by using toluene or dibromometh-
ane as an internal standard and the results are shown in Table 1.
Flash column chromatography was used to separate the prod-
ucts by use of hexane to obtain (E)-1-phenylbut-1-ene 2a as the
least polar product, then use of hexane–ethyl acetate (99:1) as
eluent to obtain the other product, 2-phenylbutanohydroximoyl
chloride 3a. Similar procedures were enacted when diethyl-
aluminium chloride reacted with (E)-β-nitrostyrene 1a to obtain
M(37Cl), 267.0451. Found: Mϩ, 267.0466; Calc. M(35Cl),
265.0481. Found: Mϩ, 265.0479.
2-(2-Methoxyphenyl)butanohydroximoyl chloride 3f. This
compound was recrystallized from hexane–ethyl acetate as
blocks, mp 114 ЊC; 1H NMR (CDCl3) δ 8.35 (s, 1H), 7.30–7.21
(m, 2H), 7.00–6.87 (m, 2H), 4.25 (t, J 7.4, 1H), 3.83 (s, 3H), 2.13
(dquin, J 14.6 and 7.4, 1H), 1.82 (dquin, J 14.6 and 7.4, 1H) and
0.93 (t, J 7.4, 3H); 13C NMR (CDCl3) δ 157.38, 144.13, 128.46,
128.12, 127.19, 120.63, 110.75, 55.52, 46.26, 25.20 and 11.80;
MS (EI) m/z (rel int) 229 [(M ϩ 2)ϩ, 27%], 227 (Mϩ, 89), 198
(100), 196 (95), 174 (17), 163 (54), 161 (39), 121 (42), 91 (39) and
77 (13); HRMS (EI) Calc. for C11H14ClNO2: M(37Cl), 229.0684.
Found: Mϩ, 229.0703; Calc. M(35Cl), 227.0713. Found: Mϩ,
227.0710 (Calc.: C, 58.03; H, 6.20; N, 6.15%. Found: C, 58.1; H,
6.1; N, 6.2). The X-ray crystal data are listed in Table 2 and the
X-ray molecular structure is presented in Fig. 1.
1
products 2a (22%) and 3a (36%). The H NMR coupling con-
stants (15.8–16.0 Hz) of the vinyl protons and the IR absorp-
tion at ~960 cmϪ1 indicate that the configurations are E for the
alkenes 2a–2l. All 1H and 13C NMR spectra of the alkenes 2a–2l
are consistent with the literature reports.6,9,10,27 All spectral data
of the hydroximoyl chlorides 3a–3l are shown below.
1
2-Phenylbutanohydroximoyl chloride 3a. H NMR (CDCl3)
δ 8.08 (s br, D2O exchangeable, 1H), 7.39–7.23 (m, 5H), 3.69 (t,
J 7.6, 1H), 2.16 (dquin, J 13.8 and 7.6, 1 H), 1.90 (dquin, J 13.8
and 7.6, 1H) and 0.93 (t, J 7.6, 3H); 13C NMR (CDCl3)
δ 145.47, 138.97, 128.63, 128.17, 127.51, 54.17, 25.54 and 11.85;
GCMS (EI) m/z (rel int) 161 (12%), 132 (100), 105 (16) and 77
(41); HRMS (EI) Calc. for C10H12ClNO: M, 197.0627. Found:
Mϩ, 197.0617; CIMS (CH4) 200 [(M ϩ 3)ϩ, 20%] and 198
[(M ϩ 1)ϩ, 59].
1
2-(2-Methylphenyl)butanohydroximoyl chloride 3g. H NMR
(CDCl3) δ 8.52 (s, 1H), 7.32–7.16 (m, 4H), 3.95 (t, J 7.4, 1H),
2.37 (s, 3H), 2.18 (dquin, J 14.8 and 7.4, 1H), 1.86 (dquin,
J 14.8 and 7.4, 1H) and 0.93 (t, J 7.4, 3H); 13C NMR (CDCl3)
δ 144.33, 136.97, 136.79, 130.61, 127.28, 127.03, 126.34, 49.71,
25.85, 19.56 and 11.82; MS (EI) m/z (rel int) 214 [(M ϩ 3)ϩ,
15%], 212 [(M ϩ 1)ϩ, 51] and 77 (24); HRMS (EI) Calc. for
C11H13ClNO: (M Ϫ 1), 210.0686. Found: m/z, 210.0686.
1
2-(4-Methylphenyl)butanohydroximoyl chloride 3b. H NMR
(CDCl3) δ 8.20 (s br, 1H), 7.25–7.11 (m, 4H), 3.65 (t, J 7.6, 1H),
2.33 (s, 3H), 2.12 (dquin, J 14.8 and 7.6, 1H), 1.87 (dquin,
J 14.8 and 7.6, 1H) and 0.92 (t, J 7.6, 3H); 13C NMR (CDCl3)
2-[2-(Trifluoromethyl)phenyl]butanohydroximoyl chloride 3h.
This compound was recrystallized from hexane–ethyl acetate as
1
blocks, mp 100–102 ЊC; H NMR (CDCl3) δ 8.00 (s br, 1H),
δ
144.63, 137.16, 135.91, 129.32, 127.97, 53.75, 25.51,
7.70–7.34 (m, 4H), 4.14 (t, J 7.4, 1H), 2.23 (dquin, J 14.8 and
7.4, 1H), 1.85 (dquin, J 14.8 and 7.4, 1H) and 0.93 (t, J 7.4, 3H);
13C NMR (CDCl3) δ 143.07, 138.27 (q, J 1.56), 132.18, 129.07
(q, J 29.78), 128.90, 127.45, 126.15 (q, J 61.0), 124.29 (q,
J 275.28), 49.90 (q, J 1.92), 27.65 and 11.80; GCMS (EI) m/z
(rel int) 267 [(M ϩ 2)ϩ, tr], 265 (Mϩ, tr), 229 (7%), 200 (100),
152 (15), 145 (14), 134 (17) and 95 (5); HRMS (EI) Calc. for
C11H11ClF3NO: M(37Cl), 267.0452. Found: Mϩ, 267.0454; Calc.
M(35Cl), 265.0482. Found: Mϩ, 265.0479; CIMS (CH4) 268
[(M ϩ 3)ϩ, 5%] and 266 [(M ϩ 1)ϩ, 16] (Calc.: C, 49.73; H, 4.17;
N, 5.27%. Found: C, 50.4; H, 4.2; N, 5.0). The X-ray crystal
data are listed in Table 2, and the X-ray molecular structure is
presented in Fig. 2.
20.97 and 11.85; MS (EI) m/z (rel int) 213 [(M ϩ 2)ϩ, 33%], 211
(Mϩ, 100), 182 (97), 175 (2), 105 (92), 91 (17) and 77 (10);
HRMS (EI) Calc. for C11H14ClNO: M(37Cl), 213.0734.
Found: Mϩ, 213.0751; Calc. M(35Cl), 211.0764. Found: Mϩ,
211.0767; CIMS (CH4) 214 [(M ϩ 3)ϩ, 4%] and 212 [(M ϩ 1)ϩ,
12].
2-(4-Methoxyphenyl)butanohydroximoyl chloride 3c. 1H NMR
(CDCl3) δ 8.82 (s, 1H), 7.22 (d, J 8.6, 2H), 6.88 (d, J 8.6, 2H),
3.88 (s, 3H), 3.65 (t, J 7.6, 1H), 2.14 (dquin, J 13.6 and 7.6, 1H),
1.86 (dquin, J 13.6 and 7.6, 1H) and 0.93 (t, J 7.6, 3H); 13C
NMR (CDCl3) δ 158.93, 144.95, 130.92, 129.11, 114.00, 55.20,
53.27, 25.52 and 11.80; GCMS (EI) m/z (rel int) 229
[(M ϩ 2)ϩ, tr], 227 (Mϩ, tr), 191 (15%), 162 (100), 134 (14), 119
(11), 91 (20) and 77 (32); HRMS (EI) Calc. for C11H14ClNO2:
M(37Cl), 229.0683. Found: Mϩ, 229.0703; Calc. M(35Cl),
227.0713. Found: Mϩ, 227.0692.
2-(2-Thienyl)butanohydroximoyl chloride 3i. 1H NMR
(CDCl3) δ 7.90 (s br, 1H), 7.23–6.97 (m, 3H), 4.01 (t, J 7.4, 1H),
2.13 (dquin, J 14.2 and 7.4, 1H), 1.98 (dquin, J 14.2 and 7.4,
1H) and 0.97 (t, J 7.4, 3H); 13C NMR (CDCl3) δ 143.73, 142.01,
126.73, 125.56, 124.68, 48.95, 26.84 and 11.80; MS (EI) m/z (rel
int) 205 [(M ϩ 2)ϩ, 20%], 203 (Mϩ, 41), 186 (7), 176 (36), 174
(100), 157 (12), 138 (24) and 97 (17); HRMS (EI) Calc. for
C8H10ClNOS: M(37Cl), 205.0142. Found: Mϩ, 205.0148.
1
2-(4-Fluorophenyl)butanohydroximoyl chloride 3d. H NMR
(CDCl3) δ 8.20 (s br, 1H), 7.27–7.23 (m, 2H), 7.04–6.98 (m, 2H),
3.67 (t, J 7.6, 1H), 2.12 (dquin, J 14.6 and 7.6, 1H), 1.86 (dquin,
J 14.6 and 7.6, 1H) and 0.91 (t, J 7.6, 3H); 13C NMR (CDCl3)
δ 162.1 (d, J 246.3), 144.10, 134.5 (d, J 3.7), 129.60 (d, J 9.2),
115.5 (d, J 22.0), 53.37, 25.63 and 11.84; MS (EI) m/z (rel int)
217 [(M ϩ 2)ϩ, 17%], 215 (Mϩ, 52), 198 (24), 188 (28), 186 (80),
169 (20), 162 (26), 150 (47), 134 (41), 109 (100) and 107 (21);
HRMS (EI) Calc. for C10H11ClFNO: M(37Cl), 217.0484.
Found: Mϩ, 217.0500; Calc. M(35Cl), 215.0539. Found: Mϩ,
215.0531.
2-(2-Furyl)butanohydroximoyl chloride 3j. 1H NMR (CDCl3)
δ 8.40 (s br, 1H), 7.37 (dd, J 2.0 and 0.8, 1H), 6.34 (dd, J 3.4 and
2.0, 1H), 6.23 (dd, J 3.4 and 0.8, 1H), 3.84 (t, J 7.4, 1H), 2.02
(dquin, J 14.6 and 7.4, 1H), 2.00 (dquin, J 14.6 and 7.4, 1H) and
0.96 (t, J 7.6, 3H); 13C NMR (CDCl3) δ 152.19, 142.21, 142.13,
110.35, 107.29, 47.44, 23.62 and 11.44; MS (EI) m/z (rel int) 189
[(M ϩ 2)ϩ, 1%], 187 (Mϩ, 12), 160 (7), 158 (46), 122 (23), 109
(80), 106 (83), 94 (49), 81 (100), 79 (64), 77 (58) and 62 (46);
HRMS (EI) Calc. for C8H10ClNO2: M(37Cl), 189.0370. Found:
Mϩ, 189.0358; Calc. M(35Cl), 187.0400. Found: Mϩ, 187.0385.
2-[4-(Trifluoromethyl)phenyl]butanohydroximoyl chloride 3e.
1H NMR (CDCl3) δ 8.90 (s br, 1H), 7.59 (d, J 8.0, 2H), 7.42 (d,
J 8.0, 2H), 3.76 (t, J 7.4, 1H), 2.18 (dquin, J 14.6 and 7.4, 1H),
1.91 (dquin, J 14.6 and 7.4, 1H) and 0.93 (t, J 7.4, 3H); 13C
NMR (CDCl3) δ 143.54, 143.02, 129.82 (q, J 32.46), 128.51,
125.59 (q, J 3.83), 124.09 (q, J 272.61), 53.88, 25.44 and 11.70;
MS (EI) m/z (rel int) 267 [(M ϩ 2)ϩ, 5%], 265 (Mϩ, 16), 250
(15), 237 (15), 200 (19), 193 (20), 173 (22), 159 (100), 145 (19),
115 (18) and 69 (13); HRMS (EI) Calc. for C11H11ClF3NO:
2,2-Diphenylbutanohydroximoyl chloride 3k. The mp of this
compound was 98–100 ЊC after recrystallization from hexane–
1
ethyl acetate; H NMR (CDCl3) δ 7.84 (s, 1H), 7.35–7.26 (m,
10H), 2.52 (q, J 7.4, 2H) and 0.77 (t, J 7.4, 3H); 13C NMR
(CDCl3) δ 146.97, 141.67, 129.49, 127.89, 127.02, 60.08, 32.15
and 9.67; MS (EI) m/z (rel int) 275 [(M ϩ 2)ϩ, 13%], 273 (Mϩ,
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52
51

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2 G. D. Buckley, J. Chem. Soc., 1947, 1494; G. D. Buckley and E. J.
Ellery, J. Chem. Soc., 1947, 1497; M. S. Ashwood, L. A. Bell, P. G.
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3 W. Langer and D. Seebach, Helv. Chim. Acta, 1979, 62, 1710.
4 A.-T. Hanson and M. Nillson, Tetrahedron, 1982, 38, 389; S. Stiver
and P. Yates, J. Chem. Soc., Chem. Commun., 1983, 50; C.
Retherford, M.-C. P. Yeh, I. Schipor, H. G. Chen and P. Knochel,
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Tetrahedron Lett., 1991, 32, 441; C. Jubert and P. Knochel, J. Org.
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5 A. Pecunioso and R. Menicagli, Tetrahedron, 1987, 43, 5411; J. Org.
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Chem., Int. Ed. Engl., 1992, 31, 1587.
46), 256 (46), 244 (23), 208 (97), 192 (37), 178 (100), 165 (75),
153 (44), 129 (78), 115 (30), 105 (16), 91 (41) and 77 (17);
HRMS (EI) Calc. for C16H16ClNO: M(37Cl), 275.0891. Found:
Mϩ, 275.0892; Calc. M(35Cl), 273.0921. Found: Mϩ, 273.0909
(Calc.: C, 70.20; H, 5.89; N, 5.12. Found: C, 70.4; H, 5.6; N,
5.4%).
2-Methyl-2-phenylbutanohydroximoyl chloride 3l. 1H NMR
(CDCl3) δ 8.90 (s br, 1H), 7.39–7.21 (m, 5H), 2.24–1.98 (m, 2H),
1.58 (s, 3H) and 0.86 (t, J 7.6, 3H); 13C NMR (CDCl3) δ 148.57,
143.64, 128.45, 126.92, 126.42, 51.26, 31.37, 28.60 and 8.62; MS
(EI) m/z (rel int) 213 [(M ϩ 2)ϩ, 30%], 211 (Mϩ, 100), 182 (67),
176 (20), 147 (61), 130 (42), 115 (55), 104 (70), 91 (71) and 77
(44); HRMS (EI) Calc. for C11H11ClNO: m/z(37Cl), 211.0764.
Found: m/z, 211.0764, (Calc. for C11H14ClNO: C, 62.41; H, 6.67;
N, 6.62. Found: C, 63.4; H, 6.5; N, 6.9%).
7 I. N. N. Namboothiri and A. Hassner, J. Organomet. Chem., 1996,
518, 69.
8 G. A. Russell and C.-F. Yao, Heteroatom Chem., 1992, 3, 209.
9 Y. Han, Y.-Z. Huang and C.-M. Zhou, Tetrahedron Lett., 1996, 37,
3347.
10 C.-F. Yao, C.-M. Chu and J.-T. Liu, J. Org. Chem., 1998, 63, 719.
11 D. H. R. Barton, H. Togo and S. Z. Zard, Tetrahedron, 1985, 41,
5507.
12 H. Kunz and K. J. Pees, J. Chem. Soc., Perkin Trans. 1, 1989,
1168.
Typical procedure for the reaction of â-nitrostyrene with triethyl-
aluminium or diethylaluminium chloride in the presence of MgCl2
(see Table 3)
β-Nitrostyrene 1a was slowly added, as described above, to a
solution of triethylaluminium or diethylaluminium chloride
which contained MgCl2 (3 equiv.) as the Lewis acid catalyst and
under argon. The hydroximoyl chloride 3a was the major prod-
uct when the mixture was quenched with ice-cold, conc. hydro-
chloric acid. The experimental results are shown in Table 3.
13 Full crystallographic details, excluding structure factor tables, have
been deposited at the Cambridge Crystallographic Data Centre
(CCDC). For details of the deposition scheme, see ‘Instructions for
Authors’, J. Chem. Soc., Perkin Trans. 1, available via the RSC Web
page (http://www.rsc.org/authors). Any request to the CCDC for
this material should quote the full literature citation and the
reference number 207/277.
14 C.-F. Yao, W.-C. Chen and Y.-M. Lin, Tetrahedron Lett., 1996, 37,
6339; C.-F. Yao, K.-H. Kao, J.-T. Liu, C.-M. Chu, Y. Wang, W.-C.
Chen, Y.-M. Lin, W.-W. Lin, M.-C. Yan, J.-Y. Liu, M.-C. Chuang
and J.-L. Shiue, Tetrahedron, 1998, 54, 791.
15 A. Alexakis, J. Vastra and P. Mangency, Tetrahedron Lett., 1997, 38,
7745.
16 T. Mukaiyama and T. Hoshino, J. Am. Chem. Soc., 1960, 82, 5339.
17 M. Christl and R. Huisgen, Chem. Ber., 1973, 106, 3345.
18 G. Kumaran and G. H. Kulkarni, Tetrahedron Lett., 1994, 35, 5517;
J. Org. Chem., 1997, 62, 1516.
19 G. W. Kabalka and R. F. Daley, J. Am. Chem. Soc., 1973, 95,
4428.
20 A. G. Davies and B. P. Roberts, J. Chem. Soc. B, 1968, 1074.
21 P. J. Krusic and J. L. Kochi, J. Am. Chem. Soc., 1969, 91, 3942.
22 P. D. Barlett and T. Funahashi, J. Am. Chem. Soc., 1962, 84, 2596.
23 D. P. Curran, N. A. Porter and B. Giese, in Stereochemistry of
Radical Reactions, VCH, Weinheim, 1995, pp. 149, 268.
24 N. Rabjohn, in Org. Synth., 1963, Coll. Vol. IV, 573.
25 F. G. Bordwell and E. W. Garbisch, Jr, J. Org. Chem., 1962, 27,
3049.
Typical procedure for the reaction of â-nitrostyrene with triethyl-
aluminium in the presence of benzoyl peroxide as free-radical
initiator (see Table 4)
A 0.1 M diethyl ether solution of β-nitrostyrene 1a (20 ml, 2
mmol) was added to 5 mmol of triethylaluminium in 30 ml of
diethyl ether containing 0.1–2.0 equiv. of benzoyl peroxide and
the solution was irradiated with a GE 275W sunlamp and
stirred under nitrogen at rt. After the starting material had dis-
appeared, the solution was worked up as described above to
obtain, as a single product, the alkene 2a (Table 4).
Acknowledgements
Funds provided by the National Science Council of the Repub-
lic of China (Grant No. NSC 88-2113-M-003-001), and X-ray
data collected and processed by Professor C.-H. Ueng and
Mr T.-S. Kuo of the National Taiwan Normal University, are
gratefully acknowledged.
26 H. Ohta, N. Kobayashi and K. Ozaki, J. Org. Chem., 1989, 54,
1802.
27 L. A. Paquette and G. D. Maynard, J. Org. Chem., 1989, 54, 5054;
C. Zioudrou, I. Moustakali-Mavridis, P. Chrysochou and G. J.
Karabatsons, Tetrahedron, 1978, 34, 3181; B. R. James and C. G.
Young, J. Organomet. Chem., 1985, 285, 321.
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Paper 8/07156J
52
J. Chem. Soc., Perkin Trans. 1, 1999, 47–52