Palladium(II)-catalyzed Michael-type hydroarylation of nitroalkenes using aryltins and sodium tetraarylborates

Article abstract of DOI:10.1246/bcsj.76.1423

A variety of aryltin compounds and sodium tetraarylborates can be employed for Michael-type hydroarylation reactions of nitroalkenes to afford β-arylnitroalkanes in moderate to good yields in the presence of either LiCl, MgCl₂, or CaCl₂ and a catalytic amount of palladium(II) salt (0.05 molar amount) in acetic acid. Results show that 50-70% of aryl groups out of all in these aryl compounds can be transferred to the products in this hydroarylation. The addition of a catalytic amount (0.05-0.10 molar amount) of a Lewis acid chloride, BiCl₃ or SbCl₃, much improves the product yield in some cases.

Full text of DOI:10.1246/bcsj.76.1423

Ó 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 1423–1431 (2003) 1423
Palladium(b)-Catalyzed Michael-Type Hydroarylation of Nitroalkenes
Using Aryltins and Sodium Tetraarylborates
ꢀ
Toshiyuki Ohe and Sakae Uemura
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University,
Sakyo-ku, Kyoto, 606-8501
(Received January 8, 2003)
A variety of aryltin compounds and sodium tetraarylborates can be employed for Michael-type hydroarylation
reactions of nitroalkenes to afford ꢀ-arylnitroalkanes in moderate to good yields in the presence of either LiCl, MgCl2,
or CaCl2 and a catalytic amount of palladium(b) salt (0.05 molar amount) in acetic acid. Results show that 50–70% of
aryl groups out of all in these aryl compounds can be transferred to the products in this hydroarylation. The addition of a
catalytic amount (0.05–0.10 molar amount) of a Lewis acid chloride, BiCl3 or SbCl3, much improves the product yield in
some cases.
A
variety of organoheteroatom compounds such as
turated ketones and aldehydes.2 A larger amount of PdCl2 (0.1
mmol, 0.05 molar amount to 1a) was needed for producing
3am as a major product, where more than two phenyl groups
of 2m could be transferred to the hydroarylated product
(Table 1, Entry 5). The presence of LiCl was necessary for
this catalytic system to afford the hydroarylated product effi-
ciently (Table 1, Entries 5 and 6). Instead of LiCl, the chlo-
rides CaCl2 and MgCl2 were also effective as an additive
(Table 1, Entries 7 and 8). The complex [PdCl2(PhCN)2]
was as effective as PdCl2 as a catalyst (Table 1, Entry 9),
organoborons,1 organotins,2 and organoantimonys3 have been
known to react with ꢁ; ꢀ-unsaturated ketones and aldehydes in
the presence of a catalytic amount of Pd(b) salt to give the
corresponding Michael-type hydroarylation compounds, ꢀ-
aryl-substituted saturated ketones and aldehydes, respectively.
Although there are several reports of transition metal [Rh(I),4a
Cu(b)4b]-catalyzed Michael-type hydroarylation or hydroalkyl-
ation of nitroalkenes using organoborons and organozincs,
examples that use a palladium salt as catalyst are quite rare.4c
We have now examined carefully Pd(b)-catalyzed hydroaryla-
tion of nitroalkenes using several arylheteroatom compounds
in acetic acid (AcOH) by taking the atom economy5 of aryl
groups into account and have found that aryl groups of aryltins
and sodium tetraarylborates could be transferred quite effec-
tively to the products, ꢀ-arylnitroalkanes. The addition of the
salt of a Group 15 element, such as BiCl3, SbCl3, Bi2O3 etc., in
a catalytic amount much improved the product yield in this
catalytic system in some cases. Details of the results of this
Michael-type hydroarylation are reported here.6
while [PdCl2(PPh3)2], rhodium salts such as RhCl3 3H2O,
[RhCl(CO)2]2, and [Rh3O(OAc)6(H2O)3]OAc, and copper
ꢂ
salts such as CuCl2, Cu(NO3)2 3H2O, CuCl, and CuI were
revealed to be ineffective for this hydroarylation.
ꢂ
A similar treatment of other nitroalkenes bearing a substi-
tuent on the phenyl ring of 1a, such as p-CH3C6H4CH=
CHNO2 (1b), p-CH3OC6H4CH=CHNO2 (1c), p-ClC6H4-
CH=CHNO2 (1d), p-BrC6H4CH=CHNO2 (1e), m-NO2-
C6H4CH=CHNO2 (1f), and o-NO2C6H4CH=CHNO2 (1g), af-
forded the corresponding hydroarylated products (3bm, 3cm,
3dm, 3em, 3fm, and 3gm, respectively) in moderate to good
yields (Scheme 1; Table 2, Entries 2–7), where no appreciable
substituent effects were observed. From nitroalkenes having
an alkyl group in place of an aryl group such as n-
C7H15CH=CHNO2 (1h) and c-C6H11CH=CHNO2 (1i), the
selectivity for the expected nitroalkane products became high-
er, sacrificing the formation of biphenyl (Table 2, Entries 8
and 9). The hydroarylation of ꢀ-substituted-ꢁ-nitroalkenes,
which bear a bulky alkyl substituent or heteroaryl group at
the ꢀ-carbon such as 3,3-dimethyl-1-nitro-1-butene [1j,
(CH3)3CCH=CHNO2], 2-(2-nitroethenyl)thiophene (1k, 2-
C4H3SCH=CHNO2), and 2-(2-nitroethenyl)furan (1l, 2-
C4H3OCH=CHNO2), did not proceed well, biphenyl being
the main product (Table 2, Entries 10–12). No hydroarylation
occurred for ꢁ; ꢀ-disubstituted-ꢁ-nitroalkenes such as 5 and 6,
both having a substituent on the same carbon atom where a
nitro group is present, probably due to the steric hindrance at
Results and Discussion
Palladium(b)-Catalyzed Hydrophenylation of Nitroal-
kenes Using Tetraphenyltin. At first, the catalytic system
used so far for the hydroarylation reaction of ꢁ; ꢀ-unsaturated
ketones and aldehydes with aryltin compounds was examined
for use with nitroalkenes.2 Thus, ꢀ-nitrostyrene (2-nitro-1-
phenylethene, 1a, 2 mmol) was treated with Ph4Sn (2m, 0.5
mmol, 0.25 molar amount to 1a) in the presence of PdCl2 (0.02
mmol, 0.01 molar amount to 1a) and LiCl (4 mmol, 2 molar
ꢁ
amounts to 1a) in AcOH (20 mL) at 25 C for 20 h. As a
result, biphenyl (4m) was mainly obtained together with a
Michael-type hydroarylated product, 2-nitro-1,1-diphenyl-
ethane (3am) (Scheme 1; Table 1, Entry 1). Unfortunately,
the yield of 4m much increased at a higher temperature (50
ꢁC) without any improvement of the yield of 3am (Table 1,
Entries 1–4), unlike the case of the reaction using ꢁ; ꢀ-unsa-
Published on the web July 15, 2003; DOI 10.1246/bcsj.76.1423

1424 Bull. Chem. Soc. Jpn., 76, No. 7 (2003)
Michael-Type Hydroarylation of Nitroalkenes
Scheme 1. Hydroarylation of nitroalkenes
Table 1. Pd(b)-Catalyzed Hydrophenylation of ꢀ-Nitrostyrene (1a) Using Ph4Sn (2m)a)
Isolated yield/%b)
Entry
Pd catalyst/mmol
Additive/mmol
3am
4m
1
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
0.02
0.02
0.04
0.04
0.1
0.1
0.1
0.1
0.1
LiCl
LiCl
LiCl
LiCl
LiCl
—
CaCl2
MgCl2
LiCl
4
4
4
4
4
14
12
30
12
52
5
46
45
52
23
45
32
48
39
15
31
33
31
2c)
3
4d)
5
6
7
8
9
2
2
4
[PdCl2(PhCN)2]
a) Reaction conditions: 1a (2 mmol) and 2m (0.5 mmol) in AcOH (20 mL) at 25 ꢁC for 20 h. b)
Based on 2m: 2 mmoꢁl of 3am and 1 mmꢁol of biphenyl (4m) correspond to 100% yield,
respectively. c) At 50 C for 5 h. d) At 50 C for 2 h.
the arylpalladation step (see “Plausible Reaction Scheme”).
ing a larger amount of the Michael-type hydroarylated product
(3an = 3bm) together with a smaller amount of biaryl (4n)
(Table 3, Entry 2). On the contrary, biaryl 4o was obtained as
the main product in the case of (p-ClC6H4)4Sn (2o) (Table 3,
Entry 3). Arylating reagents other than tetraaryltins were also
investigated: these include Ph3SnCl (2p), Ph2SnCl2 (2q),
Ph4Ge, Ph3Sb, Ph3Sb(OAc)2, Ph3Bi, Ph3Bi(OAc)2, PhB(OH)2,
NaBPh4 (2r), and NaB(p-CH3C6H4)4 (2s). Thus, one molar
amount of 1a was treated with one molar amount of arylating
reagent as aryl group(s) (i.e.; a quarter molar amount of Ph4Ge,
one third molar amount of 2p, Ph3Sb, Ph3Sb(OAc)2, Ph3Bi,
Ph3Bi(OAc)2, 2r, and 2s, a half molar amount of 2q, and one
molar amount of PhB(OH)2, respectively) in the presence of
PdCl2 (0.05 molar amount) and LiCl (2 molar amounts) in
The application of this reaction to 7, which could be regarded
as a ꢀ; ꢀ-disubstituted-ꢁ-nitroalkene, resulted in the major for-
mation of biphenyl (4m) together with a small amount of a
complex mixture which contained little of the corresponding
expected hydroarylated product.
It is worth noting that this type of catalytic reaction could
not be applied to such Michael-type acceptors as ꢁ; ꢀ-unsatu-
rated esters and nitriles.
Palladium(b)-Catalyzed Hydroarylation of ꢀ-Nitrosty-
rene Using Other Arylating Reagents. The hydroarylation
of 1a with some tetraaryltins was next investigated using the
above catalytic system. Thus, 1a (2 mmol) was treated with
Ar4Sn (0.5 mmol) in the presence of PdCl2 (0.1 mmol) and
ꢁ
ꢁ
LiCl (4 mmol) in AcOH (20 mL) at 25 C for 20 h. As a
result, the hydroarylation with (p-CH3C6H4)4Sn (2n) was re-
vealed to be more efficient than that with Ph4Sn (2m), afford-
AcOH at 25 C for 20 h. Among these reagents, 2q and 2r
mainly afforded the Michael-type hydroarylated product 3am
together with a small amount of biphenyl (4m), phenyl groups

T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 7 (2003) 1425
Table 2. Pd(b)-Catalyzed Hydrophenylation of Nitroalkenes
(1) Using Ph4Sn (2m)a)
Table 4. Pd(b)-Catalyzed Hydrophenylation of Nitroalkenes
(1) Using Various Arylating Reagents (2)a)
Isolated yield/%b)
Isolated yield/%b)
Entry
1
Entry
2/mmol
1
3
4m
3
4
1c)
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
3am, 52
3bm, 59
3cm, 50
3dm, 50
3em, 53
3fm, 37
3gm, 50
3hm, 68
3im, 54
39
31
33
43
35
36
47
13
9
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
2n 0.25
2n 0.25
2n 0.25
2n 0.25
2n 0.25
2n 0.25
2q 0.5
2q 0.5
2q 0.5
2q 0.5
2q 0.5
1b
1e
1h
1i
1k
1l
1b
1f
1h
1i
1k
1c
1d
1h
1k
3bn, 63
3en, 67
3hn, 43
3in, 42
3kn, 35
3ln, 22
3bm, 66
3fm, 37
3hm, 72
3im, 66
3km, 45
3cm, 61
3dm, 62
3hm, 49
3km, 52
4n, 24
4n, 20
4n,
4n,
3
3
4n, 37
4n, 50
4m, 18
4m, 16
9
4m,
4m,
3
9
10
11
12
1j
1k
1l
3jm,
3km, 24
3lm,
6
75
51
27
4m, 33
4m, 12
4m, 20
4m, 10
4m, 16
3
2r 0.33
2r 0.33
2r 0.33
2r 0.33
a) Reaction conditions: 1 (1 mmol), 2m (0.25 mmol), PdCl2
ꢁ
(0.05 mmol), and LiCl (2 mmol) in AcOH (10 mL) at 25 C
for 20 h. b) Based on 2m: 1 mmol of 3 and 0.5 mmol of
biphenyl (4m) correspond to 100% yield, respectively. c)
Double scale reaction.
a) Reaction conditions: 1 (1 mmol), PdCl2 (0.05 mmol), and
LiCl (2 mmol) in AcOH (10 mL) at 25 ꢁC for 20 h. b) Based
on 2; 1 mmol as Ar group: 1 mmol of 3 and 0.5 mmol of biaryl
(4) correspond to 100% yield, respectively.
Table 3. Pd(b)-Catalyzed Hydrophenylation of ꢀ-Nitrosty-
rene (1a) Using Various Arylating Reagents (2)a)
Isolated yield/%b)
Entry
2/mmol
mation occurs. Nitroalkenes 1k and 1l could also be used
(Table 4, Entries 5, 6, 11, and 15), but no reaction occurred
with nitroalkenes 5 and 6.
It has been well known1c that 2r partly decomposes in
AcOH as shown in Eq. 1 to produce triphenylborane and ben-
zene, indicating that one of the four phenyl groups is wasted.
Therefore, the hydroarylation was also carried out in other
solvents such as
3
4
1
2
3
4
5
6
7c)
2m 0.5
2n 0.5
2o 0.5
2p 0.67
2q 1.0
2r 0.67
2s 0.33
3am, 52
3an, 67
3ao, 13
3am, 39
3am, 70
3am, 59
3an, 19
4m, 39
4n, 19
4o, 71
4m, 44
4m, 19
4m, 12
4n,
3
NaBPh4 þ AcOH ! Ph3B þ PhH þ AcONa
ð1Þ
a) Reaction conditions: 1a (2 mmol), PdCl2 (0.1 mmol), and
LiCl (4 mmol) in AcOH (20 mL) at 25 ꢁC for 20 h. b) Based
on 2; 2 mmol as Ar group: 2 mmol of 3 and 1 mmol of biaryl
(4) correspond to 100% yield, respectively. c) Half scale re-
action.
2r
tetrahydrofuran (THF) and ethanol (EtOH), hoping to utilize
all phenyl groups. However, little of the expected product
3am was obtained in these solvents even when several basic
inorganic salts such as NaOAc, Li2CO3, LiOH H2O, and
LiOAc were added in order to make transmetallation of phenyl
groups more efficient.5e
ꢂ
being transferred more efficiently to 1a than those of 2m
(Table 3, Entries 5 and 6). In the case of Ph3Bi and
Ph3Bi(OAc)2, 4m was formed almost exclusively. During
the treatment of 2q in the presence of PdCl2 and LiCl, the
reaction mixture turned from orange solution to yellow turbid
solution, where the complexation might occur. Unexpectedly,
both 2p and 2s were not so active as an arylating reagent in this
catalytic system (Table 3, Entries 4 and 7). The reagent
Ph3Sb(OAc)2 scarcely reacted with 1a. In this catalytic sys-
tem, the reagent PhB(OH)2 was quite inactive, unlike the cat-
alytic system reported by Hayashi and co-workers.7
Arylating reagents such as 2n, 2q, and 2r were next treated
with several other nitroalkenes in this catalytic system. The
typical results are listed in Table 4. The hydroarylation of ꢀ-
nitrostyrene derivatives (1b–1f) using these reagents proceed-
ed as effectively as that of 1a, but no substituent effect was
clearly revealed (Table 4, Entries 1, 2, 7, 8, 12, and 13). The
hydroarylation was also applicable to nitroalkenes 1h and 1i
(Table 4, Entries 3, 4, 9, 10, and 14), where little biaryl for-
The Effect of Added Lewis Acid. Since it has been found
that the presence of antimony(c) chloride (SbCl3) was effec-
tive for the Michael-type hydroarylation of ꢁ; ꢀ-unsaturated
carbonyl compounds using sodium tetraarylborates and aryl-
boronic acids in AcOH,1b,c the effect of Lewis acid upon the
reaction between 1a and Ph4Sn (2m) was next examined. The
treatment of 1a (1 mmol) with 2m (0.25 mmol, 0.25 molar
amount to 1a) in the presence of PdCl2 (0.05 mmol, 0.05 molar
amount to 1a), LiCl (2 mmol, 2 molar amounts to 1a), and
SbCl3ꢁ(0.1 mmol, 0.1 molar amount to 1a) in AcOH (10 mL)
at 25 C for 20 h afforded 3am in a quite high yield together
with a diminishing amount of biphenyl (4m), where more than
three out of four phenyl groups of 1a were transferred to the
hydroarylated product (Table 5, Entry 1). This catalytic hy-
droarylation reaction was then carried out in the presence of a
Lewis acid other than SbCl3, such as SbOCl, Sb2O3, BiCl3,
Bi2O3, Bi(NO3)3 5H2O, Bi(OTf)3, BF3 OEt2, AlCl3, or InCl3.
ꢂ
ꢂ

1426 Bull. Chem. Soc. Jpn., 76, No. 7 (2003)
Michael-Type Hydroarylation of Nitroalkenes
ly more effective than SbCl3 (Table 5, Entries 3, 4, 8, and 9).8
However, the salts SbOCl and Bi(OTf)3 were slightly less ef-
fective than them (Table 5, Entries 2 and 10). Here, it is worth
noting that bismuth salt showed a remarkable activity, since
the salt was not effective in similar hydroarylations of ꢁ; ꢀ-
unsaturated aldehydes and ketones. The effect of Bi(c) salt as
a Lewis acid catalyst in many organic transformations is of
current interest9 and the present result should be another ex-
ample of such effect. The reaction proceeded even using a
reduced amount (0.05 molar amount to 1a) of BiCl3 and in a
shortened reaction time (5 h), though the yield of products
slightly lowered (Table 5, Entries 5–7). On the other hand,
Table 5. The Effect of Lewis Acid Added in the Pd-Cata-
lyzed Reaction between ꢀ-Nitrostyrene (1a) and Ph4Sn
(2m)a)
Isolated yield/%b)
Entry
Lewis Acid/mmol
3am
4m
1
2
3
SbCl3
SbOCl
Sb2O3
BiCl3
BiCl3
BiCl3
BiCl3
Bi2O3
0.1
0.1
0.05
0.1
78
77
84
83
75
74
71
85
81
74
52
10
15
10
16
8
14
14
15
9
4
5c)
6
0.1
0.05
0.05
0.05
0.1
7c)
8
the salts of a Group 13 element such as BF3 OEt2, AlCl3, and
ꢂ
InCl3 did not show any positive effects in this reaction.
By considering these results, we mainly carried out further
investigations in the presence of BiCl3 for 20 h. Thus, a sim-
ilar treatment of other nitroalkenes such as 1b, 1c, 1d, 1e, 1f,
1h, and 1i in the presence of BiCl3 afforded the corresponding
hydroarylated products (3bm, 3cm, 3dm, 3em, 3fm, 3hm, and
3im, respectively) in higher yields together with biphenyl
(4m), where slightly fewer than four phenyl groups of 2m
could be transferred to the products (Table 6, Entries 1, 3–7,
9, and 10) as observed in the reaction with 1a. The presence of
BiCl3 in the hydroarylation of 1g, 1j, 1k, and 1l using 2m did
not give any appreciable positive effect (Table 6, Entries 8,
9
10
11
Bi(NO3)3 5H2O
ꢂ
Bi(OTf)3
—
0.1
15
39
a) Reaction conditions: 1a (1 mmol), 2m (0.25 mmol), PdCl2
ꢁ
(0.05 mmol), and LiCl (2 mmol) in AcOH (10 mL) at 25 C
for 20 h. b) Based on 2m; 1 mmol of 3am and 0.5 mmol of
biphenyl (4m) correspond to 100% yield, respectively. c) For
5 h.
Eventually, it was revealed that the salts of a Group 15 element
such as Sb2O3, BiCl3, Bi2O3, and Bi(NO3)3 5H2O were slight-
ꢂ
Scheme 2. Plausible reaction pathway

T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 7 (2003) 1427
Table 6. Hydrophenylation of Nitroalkenes Using Ar4Sn (2)
a)
Experimental
in the Presence of BiCl3
General. Melting points were determined on a Yanaco MP-J3
1
Isolated yield/%b)
micro melting point apparatus and are uncorrected. The H and
Entry
1
2
13C NMR spectra were recorded with JEOL JNM-AL300 spectro-
meter for solutions in CDCl3 with Me4Si as an internal standard.
Chemical shifts are reported in ꢂ ppm units downfield from
Me4Si. High resolution mass spectra (FAB HRMS) were obtained
with a JEOL JMX-SX 102A spectrometer. The isolation of a pure
product was carried out by column chromatography on SiO2
(Merck 60, 230–400 mesh, Merck KGaA.).
3
4
1
2
3
4
5
6
7
8
9
10
11
12
13
1a
1a
1b
1c
1d
1e
1f
1g
1h
1i
2m
2n
3am, 83 (52)
3an, 76 (67)
3bm, 82 (59)
3cm, 81 (50)
3dm, 88 (50)
3em, 85 (53)
3fm, 77 (37)
3gm, 55 (50)
3hm, 78 (68)
3im, 80 (54)
4m, 16 (39)
4n, 17 (19)
4m, 10 (31)
4m, 15 (33)
4m, 6 (43)
4m, 13 (35)
4m, 16 (36)
4m, 28 (47)
4m, 3 (13)
2m
2m
2m
2m
2m
2m
2m
2m
2m
2m
2m
Materials. Solvents except AcOH and EtOH were freshly
distilled under N2 prior to use; tetrahydrofuran (THF) was distill-
ed from sodium diphenylketyl; C6H6 and CH2Cl2 were distilled
from calcium hydride. Nitroalkenes such as 1b, 1c, 1d, 1e, 1f, 1h,
1i, 1j, and 7 were prepared from the corresponding carbonyl com-
pounds and nitromethane in the presence of NaOH, KOH, or
NaOMe in MeOH according to the literature procedure,13 typical
physical data being shown below. Other nitroalkenes such as 1a,
1g, 1k, 1l, 5, and 6 are commercial products. The palladium
complexes such as [PdCl2(PhCN)2]14a and [PdCl2(PPh3)2]14b
were prepared by the literature methods. The compound
[Rh3O(OAc)6(H2O)3]OAc was prepared by the literature method
4m,
1 (9)
1j
1k
1l
3jm,
3km, 25 (24)
3lm, (3)
5
(6)
4m, 70 (75)
4m, 39 (51)
4m, 21 (27)
7
a) Reaction conditions: 1 (1 mmol), 2 (0.25 mmol), PdCl2
(0.05 mmol), LiCl (2 mmol), and BiCl3 (0.1 mmol) in AcOH
(10 mL) at 25 ꢁC for 20 h. b) Based on 2: 1 mmol of 3 and 0.5
mmol of biaryl (4) correspond to 100% yield, respectively.
The yields obtained in the absence of BiCl3 are shown in
parentheses.
from RhCl3 3H2O and AgOAc in aqueous AcOH.14c Lithium
ꢂ
acetate was prepared from LiOH H2O and acetic anhydride under
ꢂ
reflux, followed by evaporation of unreacted acetic anhydride.
Commercially available chlorides such as MgCl2, SbCl3, and
BiCl3 were dehydrated by thionyl chloride and dried under vac-
uum prior to use. Arylating reagents such as 2m, 2p, 2q, 2r, 2s,
Ph4Ge, Ph3Sb, and PhB(OH)2 are commercial products. Tetraar-
yltins such as 2n and 2o were prepared from the corresponding
Grignard reagents and SnCl4 (as C6H6 solution) in THF, followed
by recrystallization.2;15 Triphenylbismuthine (Ph3Bi) was pre-
pared from phenylmagnesium bromide and BiCl3, followed
by recrystallization from petroleum ether.16 Bismuth triflate
[Bi(OTf)3] was prepared from trifluoromethanesulfonic acid and
Ph3Bi,17 and used without further purification. The compounds
11–13), showing that the addition of BiCl3 does not always
make the hydroarylation more efficient. No hydroarylation
occurred to 5 or 6 even in the presence of BiCl3 or SbCl3.
In the case of 7, a complex mixture was obtained whether
BiCl3 is present or not.
Plausible Reaction Scheme. Although the details are not
yet known, Scheme 2 is proposed for this catalytic Michael-
type addition reaction using organotin compounds as an
example. The transmetallation of Sn(d) moiety of aryltin(d)
compounds by Pd(b) (A) occurs to give an Ar–Pd(b)–X (X =
OAc or Cl) species (B), which adds to nitroalkenes to afford an
alkylpalladium(b) species (C).10 The Pd(b) species C might be
in equilibrium with a palladium(b) nitronate (D) to which the
other organotin(d) compound attacks to afford a tin(d) nitro-
nate (E), regenerating the Ar–Pd(b)–X species. The species
E is hydrolyzed (solvolyzed) to lead to the hydroarylated
product. A similar reaction scheme has already been proposed
in the reaction between the corresponding Rh enolate and
arylboron compounds.11 The role of metal chloride (mainly
LiCl) is to make a Pd(b) salt soluble and also to make the
transmetallation step more facile by coordination to aryltin(d)
compounds.12 In the presence of the salt of a Group 15
element, such as BiCl3, SbCl3, and Bi2O3 [abbreviated as
PnX3: it is assumed that Bi2O3 turns to Bi(OAc)3 or Bi(O)OAc
in AcOH], the salt may coordinate to the oxygen atom
of the nitro group of nitroalkenes. Then the carbopalladation
occurs to give the species F, from which a Pd(b) species is
eliminated to give a Group 15 nitronate (G). In the cases of 1j,
5, 6, and 7, the substituent at the carbon atom where a nitro
and/or alkyl group attaches might prevent the attack of the
species B to the alkenic part, although the exact reason is
not yet known. For the formation of biaryl, the second
transmetallation of Sn(d) moiety of aryltin(d) compounds
by the species B occurs to give Ar–Pd(b)–Ar species, followed
by the reductive elimination.
18
16
such as Ph3Sb(OAc)2 and Ph3Bi(OAc)2 were prepared by the
literature methods, using CH2Cl2 as solvent.
p-Methyl-ꢀ-nitrostyrene (1b): Recrystallized from hexane–
toluene, mp 101–102 ꢁC (lit. 102 ꢁC,19 103–103.5 ꢁC20); 1H NMR
(CDCl3, 300 MHz) ꢂ 2.41 (s, 3H), 7.24–7.27 (d, J ¼ 8:0 Hz, 2H),
7.43–7.46 (d, J ¼ 8:0 Hz, 2H), 7.54–7.59 (d, J ¼ 13:6 Hz, 1H),
7.96–8.02 (d, J ¼ 13:6 Hz, 1H); 13C NMR (CDCl3, 75 MHz)
ꢂ 21.66, 127.27, 129.18, 130.13, 136.29, 139.17, 143.09.
p-Methoxy-ꢀ-nitrostyrene (1c): Recrystallized from hex-
ane–benzene, mp 85.5–87.5 ꢁC (lit. 90 ꢁC,21 86 ꢁC,22 86–87
ꢁC,23;24); 1H NMR (CDCl3, 300 MHz) ꢂ 3.87 (s, 3H), 6.94–
6.98 (d, J ¼ 8:6 Hz, 2H), 7.49–7.55 (d, J ¼ 8:6 Hz, 2H and d,
J ¼ 13:7 Hz, 1H), 7.95–8.01 (d, J ¼ 13:7 Hz, 1H); 13C NMR
(CDCl3, 75 MHz) ꢂ 55.52, 114.91, 122.54, 131.15, 135.03,
139.01, 162.93.
p-Chloro-ꢀ-nitrostyrene (1d): Recrystallized from toluene,
mp 111–113 ꢁC (lit. 111–112 ꢁC,25 112–112.5 ꢁC,23 113–114
ꢁC26;27); 1H NMR (CDCl3, 300 MHz) ꢂ 7.41–7.51 (m, 4H),
7.53–7.59 (d, J ¼ 13:8 Hz, 1H), 7.94–7.99 (d, J ¼ 13:8 Hz,
1H); 13C NMR (CDCl3, 75 MHz) ꢂ 128.51, 129.76, 130.24,
137.40, 137.66, 138.31.
p-Bromo-ꢀ-nitrostyrene (1e): Recrystallized from toluene,
mp 151–153 ꢁC (lit. 150.5–151 ꢁC,27 156–158 ꢁC28); 1H NMR
(CDCl3, 300 MHz) ꢂ 7.39–7.44 (d, J ¼ 8:6 Hz, 2H), 7.55–7.63
(d, J ¼ 13:7 Hz, 1H and d, J ¼ 8:6 Hz, 2H), 7.92–7.97 (d, J ¼

1428 Bull. Chem. Soc. Jpn., 76, No. 7 (2003)
Michael-Type Hydroarylation of Nitroalkenes
13:7 Hz, 1H); 13C NMR (CDCl3, 75 MHz) ꢂ 126.77, 128.93,
130.37, 132.73, 137.45, 137.75.
Sb2O3 or Bi2O3 (for Example, Table 5, Entry 8). A mixture of
PdCl2 (0.009 g, 0.05 mmol), LiCl (0.085 g, 2.0 mmol), Bi2O3
(0.023 g, 0.049 mmol), and AcOH (1 mL) was stirred to give a
homogeneous red solution. To this solution, 1a (0.149 g, 0.999
mmol), 2m (0.107 g, 0.250 mmol), and AcOH (9 mL) were added.
After stirring for 20 h, the mixture was similarly treated as de-
scribed above to afford 4m (0.0118 g, 0.0765 mmol, 15.3% yield)
and 3am (0.193 g, 0.848 mmol, 84.8% yield).
General Procedure for Palladium(b)-Catalyzed Michael-
Type Addition Using Aryltin Compounds in the Presence of
Some Other Additive (for Example, Table 5, Entry 4). To a
homogeneous red solution which consisted of PdCl2 (0.009 g,
0.05 mmol), LiCl (0.085 g, 2.0 mmol), and AcOH (1 mL), 1a
(0.149 g, 0.999 mmol), 2m (0.107 g, 0.250 mmol), BiCl3 (0.032
g, 0.101 mmol), and AcOH (9 mL) were added successively and
the resulting mixture was stirred for 20 h. The mixture was then
treated as above to afford 4m (0.0122 g, 0.0791 mmol, 15.8%
yield) and 3am (0.188 g, 0.829 mmol, 82.9% yield).
The physical data of the produced hydroarylated compounds
are shown below in which 3em, 3en, 3fm, 3gm, 3hm, 3hn, 3im,
3in, 3jm, 3km, 3kn, 3lm, and 3ln are new compounds.
2-Nitro-1,1-diphenylethane (3am): Obtained as pale yellow
oil (lit. mp 68–70 ꢁC,34 69–70 ꢁC35); 1H NMR (CDCl3, 300 MHz)
ꢂ 4.81–4.91 (m, 3H), 7.16–7.28 (m, 10H); 13C NMR (CDCl3, 75
MHz) ꢂ 48.88, 79.16, 127.53, 127.60, 128.96, 139.15.
2-Nitro-1-phenyl-1-(p-tolyl)ethane (3an = 3bm): Obtained
as pale yellow oil (lit. mp 47–48 ꢁC35); 1H NMR (CDCl3, 300
MHz) ꢂ 2.27 (s, 3H), 4.79–4.91 (m, 3H), 7.08–7.10 (m, 4H),
7.14–7.29 (m, 5H); 13C NMR (CDCl3, 75 MHz) ꢂ 20.94, 48.57,
79.22, 127.43, 127.48, 127.57, 128.93, 129.64, 136.23, 137.20,
139.47.
m;ꢀ-Dinitrostyrene (1f): Recrystallized from ethyl acetate,
mp 124.5–126 ꢁC (lit. 124.5–125.5 ꢁC23); 1H NMR (CDCl3, 300
MHz) ꢂ 7.64–7.71 (t, J ¼ 8:0 Hz, 1H and d, J ¼ 13:8 Hz, 1H),
7.85–7.89 (d, J ¼ 8:0 Hz, 1H), 8.03–8.08 (d, J ¼ 13:8 Hz, 1H),
8.34–8.38 (d, J ¼ 8:0 Hz, 1H), 8.42 (s, 1H); 13C NMR (CDCl3, 75
MHz) ꢂ 123.47, 126.21, 130.61, 131.82, 134.41, 136.22,
139.28, 148.83.
1-Nitro-1-nonene (1h): Obtained as pale yellow oil, bp 150
ꢁC (bath temp., 5 mmHg, 1 mmHg = 133.322 Pa) (lit. 91–95 ꢁC/
0.2–0.3 mmHg29); 1H NMR (CDCl3, 300 MHz) ꢂ 0.86–0.92 (t,
J ¼ 6:7 Hz, 3H), 1.20–1.44 (m 8H), 1.46–1.55 (quartet-d,
J ¼ 7:3, 1.5 Hz, 2H), 2.23–2.31 (quartet, J ¼ 7:3 Hz, 2H),
6.95–7.01 (dt, J ¼ 13:4, 1.5 Hz, 1H), 7.23–7.33 (dt, J ¼ 13:4,
7.3 Hz, 1H); 13C NMR (CDCl3, 75 MHz) ꢂ 13.95, 22.51, 27.65,
28.37, 28.84, 28.98, 31.57, 139.47, 142.78.
(2-Nitroethenyl)cyclohexane (1i): Obtained as pale yellow
oil, bp 115–120 ꢁC (bath temp., 6 mmHg) (lit. 100 ꢁC/0.4
mmHg30); 1H NMR (CDCl3, 300 MHz) ꢂ 1.14–1.41 (m, 5H),
1.69–1.84 (m 5H), 2.21–2.32 (m, 1H), 6.91–6.96 (dd, J ¼ 13:5,
0.9 Hz, 2H), 7.18–7.29 (dd, J ¼ 13:5, 7.1 Hz, 1H); 13C NMR
(CDCl3, 75 MHz) ꢂ 25.20, 25.37, 31.16, 37.27, 138.02, 147.03.
3,3-Dimethyl-1-nitro-1-butene (1j): Obtaꢁined as pale yellow
ꢁ
1
oil, bp 70 C (bath temp., 7 mmHg) (lit. 40 C/2 mmHg31); H
NMR (CDCl3, 300 MHz) ꢂ 1.17 (s, 9H), 6.88–6.93 (d, J ¼ 13:6
Hz, 1H), 7.24–7.30 (d, J ¼ 13:6 Hz, 1H); 13C NMR (CDCl3, 75
MHz) ꢂ 28.21, 32.47, 137.01, 151.76.
(Nitromethylene)cyclohexane (7): Obtained as yellow oil, bp
100–130 ꢁC (bath temp., 6 mmHg) (lit. 50–52 ꢁC/0.2 mmHg,32 83
ꢁC/3 mmHg33); 1H NMR (CDCl3, 300 MHz) ꢂ 1.61–1.78 (m, 6H),
2.19–2.24 (t, J ¼ 6:0 Hz, 2H), 2.83–2.88 (t, J ¼ 6:0 Hz, 2H), 6.92
(s, 1H); 13C NMR (CDCl3, 75 MHz) ꢂ 25.59, 27.14, 28.05,
28.72, 34.18, 132.08, 155.65.
1-(4-Chlorophenyl)-2-nitro-1-phenylethane (3ao = 3dm):
Obtained as pale yellow oil (lit. mp 67–68 ꢁC35); 1H NMR
(CDCl3, 300 MHz) ꢂ 4.82–4.86 (m, 3H), 7.07–7.30 (m, 9H);
13C NMR (CDCl3, 75 MHz) ꢂ 48.01, 78.58, 127.32, 127.51,
128.84, 128.88, 133.10, 137.65, 138.57.
2-Nitro-1,1-di(p-tolyl)ethane (3bn): Obtained as pale yellow
oil (lit. bp 162 ꢁC/0.4 mmHg35); 1H NMR (CDCl3, 300 MHz)
ꢂ 2.22 (s, 6H), 4.74–4.83 (m, 3H), 7.03–7.06 (m, 8H); 13C NMR
(CDCl3, 75 MHz) ꢂ 20.78, 48.10, 79.15, 127.31, 129.47,
136.38, 136.93.
Tetra(p-tolyl)tin (2n):
Recrystallized from benzene–ethyl
acetate, mp 242–242.5 ꢁC (lit. 238 ꢁC15c); 1H NMR (CDCl3,
300 MHz) ꢂ 2.35 (s, 12H), 7.18–7.21 (d, J ¼ 7:8 Hz, 8H),
7.45–7.49 (d, J ¼ 7:8 Hz, 8H); 13C NMR (CDCl3, 75 MHz)
ꢂ 21.48, 129.38, 134.42, 137.15, 138.76.
Tetrakis(p-chlorophenyl)tin (2o): Recrystallized from ben-
ꢁ
ꢁ
1
zene–petroleum ether, mp 198–201 C (lit. 199 C15c); H NMR
(CDCl3, 300 MHz) ꢂ 7.36–7.58 (m, 16H); 13C NMR (CDCl3,
75 MHz) ꢂ 129.19, 134.62, 136.26, 138.09.
1-(p-Methoxyphenyl)-2-nitro-1-phenylethane (3cm):
Ob-
tained as yellow oil (lit. bp 166–168 C/0.4 mmHg35); H NMR
(CDCl3, 300 MHz) ꢂ 3.68 (s, 3H), 4.63–5.10 (m, 3H), 6.79–
6.82 (d, J ¼ 7:7 Hz, 2H), 7.09–7.12 (d, J ¼ 7:7 Hz, 2H), 7.16–
7.29 (m, 5H); 13C NMR (CDCl3, 75 MHz) ꢂ 48.04, 54.99,
79.17, 114.18, 127.26, 127.38, 128.55, 128.77, 131.09, 139.46,
158.72.
ꢁ
1
General Procedure for Palladium(b)-Catalyzed Michael-
Type Addition Using Aryltin Compounds (for Example,
Table 1, Entry 5). A mixture of PdCl2 (0.018 g, 0.10 mmol),
LiCl (0.170 g, 4.01 mmol), and AcOH (5 mL) was stirred to give a
homogeneous red solution. To this solution, ꢀ-nitrostyrene (1a,
0.298 g, 2.00 mmol), tetraphenyltin (2m, 0.214 g, 0.501 mmol),
and AcOH (15 mL) were added and the resulting mixture was
1-(p-Bromophenyl)-2-nitro-1-phenylethane (3em):
Ob-
tained as pale yellow oil; 1H NMR (CDCl3, 300 MHz)
ꢂ 4.76–4.87 (m, 3H), 7.03–7.06 (d, J ¼ 7:9 Hz, 2H), 7.13–7.31
(m, 5H), 7.34–7.38 (d, J ¼ 7:9 Hz, 2H); 13C NMR (CDCl3, 75
MHz) ꢂ 48.06, 78.51, 121.27, 127.32, 127.53, 128.89, 129.18,
131.84, 138.13, 138.45. Found: C, 55.04; H, 4.11; N, 4.38%.
Calcd for C14H12BrNO2: C, 54.92; H, 3.95; N, 4.58%.
ꢁ
stirred at 25 C. After stirring for 20 h, the mixture was poured
into brine (150 mL) and extracted with diethyl ether or ethyl
acetate (30 mL ꢃ 5). The organic layer was washed with dilute
HCl (ca. 3 mol dmꢄ3, 30 mL ꢃ 3), water (30 mL ꢃ 2), and
ꢂ
saturated NaHCO3 solution (usually 50 mL ꢃ 2) and then dried
over anhydrous MgSO4. After removal of the solvent under re-
duced pressure, the brownish yellow residue was subjected to
column chromatography to give biphenyl (4m, 0.061 g, 0.392
mmol, 39.1% yield) and 2-nitro-1,1-diphenylethane (3am, 0.239
g, 1.05 mmol, 52.4% yield).
1-(p-Bromophenyl)-2-nitro-1-(p-tolyl)ethane (3en):
Ob-
tained as pale yellow oil; 1H NMR (CDCl3, 300 MHz) ꢂ 2.22
(s, 3H), 4.57–4.82 (m, 3H), 7.00–7.05 (m, 6H), 7.32–7.35 (d, J ¼
7:3 Hz, 2H); 13C NMR (CDCl3, 75 MHz) ꢂ 20.81, 47.82, 78.67,
121.23, 127.25, 129.18, 129.62, 131.86, 135.51, 137.28, 138.45.
Found: C, 56.15; H, 4.42; N, 4.14%. Calcd for C15H14BrNO2: C,
56.27; H, 4.41; N, 4.37%.
General Procedure for Palladium(b)-Catalyzed Michael-
Type Addition Using Aryltin Compounds in the Presence of

T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 7 (2003) 1429
2-Nitro-1-(m-nitrophenyl)-1-phenylethane (3fm): Obtained
1
54.34, 77.21, 127.42, 128.13, 129.07, 137.58. Found: C, 69.38;
H, 8.17; N, 6.78%. Calcd for C12H17NO2: C, 69.54; H, 8.27; N,
6.76%.
2-(2-Nitro-1-phenylethyl)thiophene (3km): Obtained as pale
yellow oil; 1H NMR (CDCl3, 300 MHz) ꢂ 4.80–4.95 (m, 2H),
5.05–5.11 (t, J ¼ 7:9 Hz, 1H), 6.85–6.90 (m, 2H), 7.12–7.15 (d,
J ¼ 5:0 Hz, 1H), 7.20–7.44 (m, 5H); 13C NMR (CDCl3, 75 MHz)
ꢂ 44.46, 79.61, 124.94, 125.02, 126.86, 127.38, 127.87, 128.91,
138.63, 142.26. Found: C, 61.67; H, 4.74; N, 5.89%. Calcd for
C12H11NO2S: C, 61.78; H, 4.75; N, 6.00%.
as pale yellow viscous oil; H NMR (CDCl3, 300 MHz) ꢂ 5.03–
5.12 (m, 3H), 7.23–7.32 (m, 5H), 7.38–7.44 (t, J ¼ 7:8 Hz, 1H),
7.58–7.62 (d, J ¼ 7:5 Hz, 1H), 8.00–8.04 (d, J ¼ 7:7 Hz, 1H),
8.14 (s, 1H); 13C NMR (CDCl3, 75 MHz) ꢂ 48.45, 78.39,
122.60, 127.66, 128.08, 129.32, 130.09, 134.05, 138.01, 138.14,
141.58, 148.47. HRMS (FAB) found: 273.0880. Calcd for
C14H13N2O4 (M + Hþ): 273.0875.
2-Nitro-1-(o-nitrophenyl)-1-phenylethane (3gm): Obtained
1
as pale yellow viscous oil; H NMR (CDCl3, 300 MHz) ꢂ 4.94–
5.11 (dd + dd, J ¼ 7:9, 13.6 Hz, 2H), 5.58–5.65 (t, J ¼ 8:0 Hz,
1H), 7.20–7.32 (m, 5H), 7.34–7.43 (m, 2H), 7.50–7.56 (t, J ¼ 7:6
Hz, 1H), 7.81–7.85 (d, J ¼ 8:1 Hz, 1H); 13C NMR (CDCl3, 75
MHz) ꢂ 42.83, 77.76, 125.10, 127.64, 127.80, 128.45, 128.96,
129.00, 133.16, 133.32, 137.24, 149.29. HRMS (FAB) found:
273.0873. Calcd for C14H13N2O4 (M + Hþ): 273.0875.
1-Nitro-2-phenylnonane (3hm): Obtained as pale yellow oil;
1H NMR (CDCl3, 300 MHz) ꢂ 0.82–0.88 (t, J ¼ 6:7 Hz, 3H),
1.00–1.45 (m, 10H), 1.63–1.71 (quartet, J ¼ 7:1 Hz, 2H), 3.38–
3.49 (quintet, J ¼ 7:6 Hz, 1H), 4.48–4.60 (dd + dd, J ¼ 12:1, 7.5
Hz, 2H), 7.16–7.36 (m, 5H); 13C NMR (CDCl3, 75 MHz)
ꢂ 14.00, 22.54, 26.84, 28.96, 29.22, 31.68, 32.97, 44.34, 80.98,
127.47, 128.85, 139.54, 142.79. Found: C, 71.99; H, 9.58; N,
5.43%. Calcd for C15H23NO2: C, 72.25; H, 9.30; N, 5.62%.
1-Nitro-2-p-tolylnonane (3hn): Obtained as yellow oil, bp
195 ꢁC/1 mmHg (bath temp); 1H NMR (CDCl3, 300 MHz)
ꢂ 0.82–0.88 (t, J ¼ 6:8 Hz, 3H), 1.05–1.40 (m, 10H), 1.61–1.69
(quartet, J ¼ 7:2 Hz, 2H), 2.32 (s, 3H), 3.34–3.45 (quintet, J ¼
7:6 Hz, 1H), 4.45–4.58 (dd + dd, J ¼ 16:2, 7.7 Hz, 2H), 7.04–
7.08 (d, J ¼ 8:1 Hz, 2H), 7.12–7.15 (d, J ¼ 8:1 Hz, 2H); 13C
NMR (CDCl3, 75 MHz) ꢂ 14.01, 21.02, 22.56, 26.87, 28.98,
29.26, 31.70, 32.99, 44.00, 81.15, 127.33, 129.54, 136.46, 137.11.
Found: C, 73.20; H, 9.76; N, 5.03%. Calcd for C16H25NO2: C,
72.96; H, 9.57; N, 5.32%.
(2-Nitro-1-phenylethyl)cyclohexane (3im): Obtained as pale
yellow solid (from column chromatography), white crystal (re-
crystallized from hexane), mp 65–66.5 ꢁC; 1H NMR (CDCl3,
300 MHz) ꢂ 0.79–1.28 (m, 5H), 1.44–1.67 (m, 4H), 1.74–
1.83 (m, 2H), 3.22–3.31 (ddd, J ¼ 12:3, 9.9, 5.7 Hz, 1H), 4.57–
4.66 (dd, J ¼ 12:3, 9.9 Hz, 1H), 4.75–4.82 (dd, J ¼ 12:3, 5.7 Hz,
1H), 7.11–7.15 (d, J ¼ 8:1 Hz, 2H), 7.23–7.34 (m, 3H); 13C NMR
(CDCl3, 75 MHz) ꢂ 26.02, 26.03, 26.08, 30.50, 30.91, 40.83,
50.18, 78.79, 127.29, 128.09, 128.49, 138.75. Found: C, 72.12; H,
8.06; N, 5.94%. Calcd for C14H19NO2: C, 72.07; H, 8.21; N,
6.00%.
2-[2-Nitro-1-(p-tolyl)ethyl]thiophene (3kn):
Obtained as
pale yellow oil; 1H NMR (CDCl3, 300 MHz) ꢂ 2.31 (s, 3H),
4.83–4.98 (dd + dd, J ¼ 7:5, 12.6 Hz, 2H), 5.04–5.10 (t, J ¼ 7:9
Hz, 1H), 6.86–6.93 (m, 2H), 7.11–7.29 (m, 5H); 13C NMR
(CDCl3, 75 MHz) ꢂ 20.99, 44.29, 79.90, 124.91, 125.04,
126.92, 127.33, 129.70, 135.71, 137.77, 142.67. Found: C,
63.21; H, 5.32; N, 5.46%. Calcd for C13H13NO2S: C, 63.13; H,
5.30; N, 5.66%.
2-(2-Nitro-1-phenylethyl)furan (3lm): Obtained as pale yel-
1
low oil; H NMR (CDCl3, 300 MHz) ꢂ 4.76–4.82 (dd, J ¼ 6:9,
11.7 Hz, 1H), 4.89–4.94 (t, J ¼ 7:3 Hz, 1H), 4.97–5.04 (dd,
J ¼ 7:6, 11.7 Hz, 1H), 6.10–6.12 (d, J ¼ 3:0 Hz, 1H), 6.29–
6.32 (dd, J ¼ 1:8, 2.9 Hz, 1H), 7.23–7.36 (m, 6H); 13C NMR
(CDCl3, 75 MHz) ꢂ 43.49, 78.01, 107.40, 110.42, 127.83,
128.07, 129.03, 136.87, 142.52, 151.98. Found: C, 66.21; H,
5.10; N, 6.15%. Calcd for C12H11NO3: C, 66.35; H, 5.10; N,
6.45%.
2-[2-Nitro-1-(p-tolyl)ethyl]furan (3ln): Obtained as pale yel-
low oil; 1H NMR (CDCl3, 300 MHz) ꢂ 2.31 (s, 3H), 4.72–4.79
(dd, J ¼ 7:4, 11.1 Hz, 1H), 4.84–4.90 (t, J ¼ 7:4 Hz, 1H), 4.94–
5.01 (dd, J ¼ 7:4, 11.1 Hz, 1H), 6.08–6.10 (d, J ¼ 1:8 Hz, 1H),
6.27–6.30 (t, J ¼ 1:8 Hz, 1H), 7.11–7.17 (m, 4H), 7.33–7.35 (d,
J ¼ 1:8 Hz, 1H); 13C NMR (CDCl3, 75 MHz) ꢂ 20.99, 43.11,
78.06, 107.21, 110.35, 127.65, 129.64, 133.79, 137.80, 142.41,
152.20. Found: C, 67.24; H, 5.77; N, 5.57%. Calcd for
C13H13NO3: C, 67.52; H, 5.67; N, 6.06%.
The following three new compounds and a known 3dn,35 which
appeared in Scheme 1, but not in the Tables, were isolated. Their
physical data are also shown here.
1-(p-Methoxyphenyl)-2-nitro-1-(p-tolyl)ethane (3cn): Ob-
tained as yellow oil; 55% isolated yield; 1H NMR (CDCl3, 300
MHz) ꢂ 2.29 (s, 3H), 3.72 (s, 3H), 4.80–4.90 (m, 3H), 6.82–6.85
(d, J ¼ 8:1 Hz, 2H), 7.08–7.16 (m, 6H); 13C NMR (CDCl3, 75
MHz) ꢂ 20.87, 47.83, 55.08, 79.39, 114.24, 127.36, 127.60,
129.56, 131.46, 136.59, 137.02, 158.77. Found: C, 70.78; H,
6.16; N, 4.88%. Calcd for C16H17NO3: C, 70.83; H, 6.32; N,
5.16%.
(2-Nitro-1-p-tolylethyl)cyclohexane (3in): Obtained as pale
yellow viscous oil, bp 180 ꢁC/1 mmHg (bath temp); 1H NMR
(CDCl3, 300 MHz) ꢂ 0.82–1.28 (m, 5H), 1.44–1.67 (m, 4H),
1.72–1.81 (m, 2H), 2.31 (s, 3H), 3.17–3.26 (ddd, J ¼ 12:1, 10.1,
5.8 Hz, 1H), 4.54–4.63 (dd, J ¼ 12:1, 10.1 Hz, 1H), 4.72–4.79
(dd, J ¼ 12:1, 5.8 Hz, 1H), 6.99–7.03 (d, J ¼ 8:0 Hz, 2H), 7.08–
7.12 (d, J ¼ 8:0 Hz, 2H); 13C NMR (CDCl3, 75 MHz) ꢂ 20.88,
25.97, 25.99, 26.03, 30.39, 30.84, 40.75, 49.76, 78.80, 127.88,
129.10, 135.58, 136.73. Found: C, 72.92; H, 8.43; N, 5.48%.
Calcd for C15H21NO2: C, 72.84; H, 8.56; N, 5.66%.
1-(p-Chlorophenyl)-2-nitro-1-(p-tolyl)ethane (3dn):
Ob-
ꢁ
tained as pale yellow oil (lit. bp 174 C/0.5 mmHg35); 63% iso-
lated yield; 1H NMR (CDCl3, 300 MHz) ꢂ 2.26 (s, 3H), 4.79–
4.88 (m, 3H), 7.07–7.14 (m, 6H), 7.21–7.24 (d, J ¼ 7:0 Hz, 2H);
13C NMR (CDCl3, 75 MHz) ꢂ 20.76, 47.75, 78.76, 127.22,
128.82, 128.89, 129.60, 133.07, 135.59, 137.28, 137.92.
2-Nitro-1-(m-nitrophenyl)-1-(p-tolyl)ethane (3fn): Obtained
1
as pale yellow viscous oil; 62% isolated yield; H NMR (CDCl3,
3,3-Dimethyl-1-nitro-2-phenylbutane (3jm):36 Obtained as
pale yellow solid (from column chromatography), white crystal
300 MHz) ꢂ 2.31 (s, 3H), 4.94–5.10 (m, 3H), 7.10–7.13 (d, J ¼
8:2 Hz, 2H), 7.14–7.18 (d, J ¼ 8:2 Hz, 2H), 7.46–7.52 (t, J ¼ 7:8
Hz, 1H), 7.61–7.65 (d, J ¼ 9:2 Hz, 1H), 8.07–8.13 (m, 2H); 13C
NMR (CDCl3, 75 MHz) ꢂ 20.90, 48.10, 78.54, 122.50, 127.33,
129.96, 133.76, 134.72, 137.96, 141.62, 148.48. Found: C, 63.00;
H, 4.96; N, 9.76%. Calcd for C15H14N2O4: C, 62.93; H, 4.93; N,
9.79%.
ꢁ
1
(recrystallized from benzene–petroleum ether), mp 70–71 C; H
NMR (CDCl3, 300 MHz) ꢂ 0.95 (s, 9H), 3.32–3.38 (dd,
J ¼ 5:3, 10.6 Hz, 1H), 4.75–4.89 (dd + dd, J ¼ 5:3, 13.8 Hz
and 10.6, 13.8 Hz, 2H), 7.16–7.19 (d, J ¼ 7:3 Hz, 2H), 7.24–
7.31 (m, 3H); 13C NMR (CDCl3, 75 MHz) ꢂ 28.02, 33.68,

1430 Bull. Chem. Soc. Jpn., 76, No. 7 (2003)
Michael-Type Hydroarylation of Nitroalkenes
2-Nitro-1-(o-nitrophenyl)-1-(p-tolyl)ethane (3gn): Obtained
1
organopalladium(b) species.1b{d Actually, Pd(0) complex also
worked effectively as a catalyst in these reactions.1b{d On the
contrary, the present catalytic system does not contain any base,
and Pd(b) itself seems to work for transmetallation to afford the
organopalladium(b) species. In fact, we observed that the reaction
stopped when a black Pd(0) species appeared during the hydroar-
ylation.
as pale yellow viscous oil; 52% isolated yield; H NMR (CDCl3,
300 MHz) ꢂ 2.28 (s, 3H), 4.92–5.11 (dd + dd, J ¼ 8:0, 13.8 Hz,
2H), 5.55–5.62 (t, J ¼ 8:0 Hz, 1H), 7.08–7.14 (m, 4H), 7.36–7.43
(m, 2H), 7.52–7.59 (t, J ¼ 7:7 Hz, 1H), 7.83–7.87 (d, J ¼ 8:1 Hz,
1H); 13C NMR (CDCl3, 75 MHz) ꢂ 20.98, 42.73, 78.01, 125.27,
127.67, 128.52, 129.10, 129.82, 133.24, 133.75, 134.34, 137.82,
149.49. Found: C, 62.51; H, 4.93; N, 9.71%. Calcd for
C15H14N2O4: C, 62.93; H, 4.93; N, 9.79%.
11 M. Sakai, H. Hayashi, and N. Miyaura, Organometallics,
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5
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6
Preliminary results have already been reported in the form
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7
In the paper of Ref. 4a, a quite highly enantioselective
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8
In the case of Pd(b)-catalyzed hydroarylation of ꢁ; ꢀ-
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T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 7 (2003) 1431
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