Rhodium-catalyzed addition of arylstannanes to carbon-heteroatom double bond

Article abstract of DOI:10.1016/S0040-4020(03)00586-6

The addition of arylstannanes to the carbon-heteroatom double bond in the presence of a catalytic amount of a cationic rhodium complex ([Rh(cod)(MeCN)₂]BF₄) was examined. The reactions of aldehydes, α-dicarbonyl compounds, and N-substituted aldimines with the arylstannanes gave corresponding alcohols, α-hydroxy carbonyl compounds, and amines, respectively. An arylrhodium complex generated by the transmetalation with the arylstannane was probably the active catalytic species.

Full text of DOI:10.1016/S0040-4020(03)00586-6

Tetrahedron 59 (2003) 4351–4361
Rhodium-catalyzed addition of arylstannanes to
carbon–heteroatom double bond
*
Shuichi Oi, Mitsutoshi Moro, Hiroe Fukuhara, Takanori Kawanishi and Yoshio Inoue
*
Department of Materials Chemistry, Graduate School of Engineering, Tohoku University, 04 Aramaki-Aoba Aoba-ku,
Sendai 980-8579, Japan
Received 1 March 2003; revised 8 April 2003; accepted 10 April 2003
Abstract—The addition of arylstannanes to the carbon–heteroatom double bond in the presence of a catalytic amount of a cationic rhodium
complex ([Rh(cod)(MeCN)2]BF4) was examined. The reactions of aldehydes, a-dicarbonyl compounds, and N-substituted aldimines with the
arylstannanesgave corresponding alcohols, a-hydroxy carbonylcompounds, and amines, respectively. Anarylrhodium complex generatedby the
transmetalation with the arylstannane was probably the active catalytic species. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
rhodium,12 palladium and platinum,13 and applied success-
fully in organic synthesis. We reported the arylation of
aldehydes with arylstannanes catalyzed by rhodium com-
plexes.3a In this paper, we report on the scope and limitation
of the rhodium-catalyzed addition reaction of aryltin
compounds to the carbon–heteroatom double bonds in
such as carbonyl compounds and imines. Aldehydes,
a-dicarbonyl compounds, and N-substituted aldimines
successfully underwent the addition of arylstannanes
under mild and neutral conditions, affording corresponding
alcohols, a-hydroxy carbonyl compounds, and amines,
respectively.
Transition metal-catalyzed transformations using organo-
metallic reagents are of great importance in modern organic
chemistry.1 One of the recent topics of such transformations
is the rhodium-catalyzed addition of the organometallic
reagents to the carbon–heteroatom double bonds in such as
aldehydes or imines as well as the 1,4-addition to a,b-
unsaturated carbonyl compounds.2 These reactions com-
monly involve organorhodium complexes as active species
generated by the transmetalation with the organometallic
reagents such as tin (Sn),3 boron (B),4 silicon (Si),5 lead
(Pb),6 bismuth (Bi),7 titanium (Ti),8 and zirconium (Zr).9 In
most cases, they occur chemo- and regioselectively
rendering them useful in organic synthesis. They can also
be developed for asymmetric reactions induced by chiral
catalyst.10
2. Results and discussion
2.1. Addition of arylstannanes to aldehydes
The addition of organometallic reagents to aldehydes is the
general method to synthesize secondary alcohols. Organo-
lithium and organomagnesium (Grignard reagent) com-
pounds are recognized to be most versatile. However, their
extraordinary reactivities as nucleophiles and bases some-
times give rise to the limitations in the synthesis of
multifunctional compounds such as natural products.
Organotin compounds are the promissing reagents for
chemoselective reactions. The allylation of aldehydes with
allylstannanes was reported to be promoted by Lewis
acids11 or catalyzed by transition metal complexes such as
ð1Þ
The addition of arylstannanes to aldehydes was studied
using a rhodium complex as a catalyst (Eq. (1)). Initially, the
addition of trimethylphenylstannane (1a) to benzaldehyde
(2a) was examined in the presence of various transition
metal catalysts. The results are summarized in Table 1. All
reactions were carried out in THF at room temperature for
20 h with 2 mol% of the catalyst. Among the transition
metal complexes of Pd, Rh, Ir, and Ru with chloride and
cyclooctadiene ligands (entries 1–4), [RhCl(cod)]2 was
found to exhibit catalytic activity, although the yield was
low (entry 2). Compared with the neutral chloride complex,
cationic Rh complexes, [Rh(cod)(MeCN)2]BF4 and
[Rh(cod)2]BF4, showed much higher catalytic activity
affording the product in 54 and 58% yield, respectively
Keywords: arylation; carbonyl compounds; imines; organotin compounds;
rhodium catalyst.
*
Corresponding authors. Tel.: þ81-22-217-5876; fax: þ81-22-217-5873;
e-mail: oishu@aporg.che.tohoku.ac.jp
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00586-6

4352
S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 1. Transition metal-catalyzed addition of trimethylphenylstannane
(1a) to benzaldehyde (2a)
still gave the product in good yield (entry 9), which is
evidence that the reaction was not hindered by water. This
point is in strong contrast to the reaction of organolithium or
organomagnesium reagent.
With the optimized reaction conditions (Table 2, entry 6),
reactions of various arylstannanes with aldehydes were
examined. The results are listed in Table 3. The reaction of
tributylphenylstannane (1b), instead of trimethylphenyl-
stannane (1a), with benzaldehyde (2a) gave the product
alcohol 3aa in a lower yield of 65% (entry 2), that would be
caused by steric hindrance of the butyl group in the
transmetalation step (vide infra). Tetraphenylstannane (1c)
was much less reactive to give the product in only 17%
yield (entry 3). Substituted phenylstannanes, p-methoxy-
phenyltrimethylstannane (1d) and p-fluorophenyltrimethyl-
stannane (1e), also reacted with benzaldehyde affording
the corresponding diarylcarbinol (3da and 3ea) in good
yield (entries 4 and 5). However, pyridyltrimethylstannane
(1f) was found not to react with benzaldehyde.
Entry
Catalyst
Yield (%)a
1
2
3
4
5
6
7
8
PdCl2(cod)
[RhCl(cod)]2
[IrCl(cod)]2
[RuCl2(cod)]n
[Rh(cod)2]BF4
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4þ2PPh3
[Rh(cod)(MeCN)2]BF4þdppe
RhCl(PPh3)3
RhCl(CO)(PPh3)2
RhH(PPh3)4
0
10
Trace
0
54
58
Trace
26
2
9
10
11
9
0
Common reaction conditions: 1a (1.2 mmol), 2a (1.0 mmol), catalyst
(0.02 mmol or 0.01 mmol for dimer complex), THF (1.0 mL), rt, 20 h, N2
atmosphere.
a
Isolated yield.
A wide range of aldehydes were employed in the present
rhodium-catalyzed addition of arylstannanes. Almost all of
the substituted benzaldehydes examined, bearing electron-
donating or -withdrawing groups on either ortho or para
position, reacted readily with trimethylphenylstannane (1a)
to give the corresponding alcohols in high yields (entries
7–23). It is noted that the reaction was highly chemo-
selective, in that other electrophilic functional groups than
the aldehyde moiety in 2, such as methoxycarbonyl (2m),
acetyl (2n), nitro (2o and 2p), and cyano (2q) groups
remained intact. Halogen substituted benzaldehydes (2h–l)
were also compatible with the catalytic system. Other
aromatic aldehydes, 3-pyridinecarboxaldehyde (2s), fur-
fural (2t), and 1- and 2-naphthaldehydes (2u and 2v) were
also phenylated with 1a, affording the corresponding
diarylcarbinol in good yields (entries 24–27). The yield of
the alcohol in the reactions of trimethylphenylstannane (1a)
with aliphatic aldehydes, hexanal (2w), was lower (34%,
entry 28) than those with aromatic aldehydes. In the reaction
of 2w, 28% (0.14 mmol) of ester 4aw was obtained as a by-
product, which would be formed by the further reaction of
the rhodium or tin alkoxide produced (vide infra) with the
starting aldehyde 2w. To immediately decompose the
rhodium or tin alkoxide to alcohol 3aw, the reaction was
performed in the presence of 1 mmol of water. This
approach gave the product in an improved yield of 60%
(entry 29). Other aliphatic aldehydes with primary,
secondary, and tertiary alkyl groups (2x–2z and 2a) were
also phenylated by 1a in the presence of water affording the
product alcohol (3ax–3az and 3aa) in relatively good yield
(entries 30–33). On the contrary, the rhodium-catalyzed
reaction of trimethylphenylstannane (1a) with ketones was
found to be very sluggish. The reaction with cyclohexanone
(2b) gave the corresponding alcohol (3ab) in 29% yield
(entry 34), however, the reaction with acetophenone did not
take place under the same reaction conditions (entry 35). To
ensure the chemoselectivity of the reaction toward aldehyde
(entries 5 and 6). Addition of phosphine ligands such as
PPh3 or dppe to [Rh(cod)(MeCN)2]BF4 inhibited the
reaction (entries 7 and 8). Other Rh complexes,
RhCl(PPh3)3, RhCl(CO)(PPh3)2, and RhH(PPh3)4 did not
show good catalytic activity (entries 9–11).
Other conditions in the reaction of 1a with 2a were then
examined using 2 mol% of [Rh(cod)(MeCN)2]BF4 as a
catalyst (Table 2). THF was the most suitable solvent, while
CHCl3 and toluene decreased the yield and acetonitrile
completely inhibited the reaction (entries 1–4). The yield
increased to 84% when the reaction temperature was raised
to 608C (entry 5), and the reaction appeared to be complete
within 5 h at this temperature (entry 6). When the amount of
catalyst was decreased to 1 mol%, the yield slightly
decreased to 73% (entry 7). Changing the counter anion of
the Rh complex from BF42 to PF26 did not affect the yield
(entry 8). The reaction in THF containing 1 mmol of water
Table 2. Rh-catalyzed addition of trimethylphenylstannane (1a) to
benzaldehyde (2a)
Entry
Solvent
Temp. (8C)/time (h)
Yield (%)a
1
2
3
4
5
6
THF
rt/20
rt/20
rt/20
rt/20
60/20
60/5
60/5
60/5
60/5
58
24
20
Trace
84
87
73
83
CHCl3
Toluene
MeCN
THF
THF
THF
7b
8c
9d
THF
THF
84
Common reaction conditions: 1a (1.2 mmol), 2a (1.0 mmol),
[Rh(cod)(MeCN)2]BF4 (0.02 mmol), solvent (1.0 mL), N2 atmosphere.
a
Isolated yield.
0.01 mmol of catalyst was loaded.
[Rh(cod)(MeCN)2]PF6 was used as the catalyst.
1.0 mmol of water was added.
b
c
d

S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 3. Rhodium-catalyzed addition of arylstannanes 1 to aldehyde 2
4353
Entry
Arylstannane 1
Aldehyde 2
Time (h)
Product
Yield (%)a
1
2
3
4
PhSnMe3 (1a)
PhSnBu3 (1b)
Ph4Sn (1c)
PhCHO (2a)
5
5
20
2
3aa
3aa
3aa
3da
87
65
17
91
2a
2a
2a
5
2a
2a
2
3ea
88
6
20
24
5
–
3ab (¼3da)
3ac
0
7
PhSnMe3 (1a)
85
94
84
87
83
78
90
91
96
91
72
96
8
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
9
5
3ad
10
11
12
13
14
15
16
17
18
24
20
20
5
3ae
3af
3ag
3ah (¼3ea)
3ai
5
5
3aj
5
3ak
5
3al
5
3am
19
20
1a
1a
5
5
3an
3ao
96
94
(continued on next page)

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S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 3 (continued)
Entry
Arylstannane 1
Aldehyde 2
Time (h)
Product
Yield (%)a
92
21
22
23
24
PhSnMe3 (1a)
5
3ap
1a
1a
1a
5
3aq
3ar
3as
90
31
54
20
20
25
26
1a
1a
5
5
3at
91
84
3au
27
1a
5
3av
84
28
1a
1a
1a
1a
1a
n-C5H11CHO (2w)
2w
n-C9H19CHO (2x)
PhCH2CH2CHO (2y)
20
24
24
24
24
3aw
3aw
3ax
3ay
3az
34
60
48
57
45
29b
30b
31b
32b
33b
34
1a
1a
tert-C4H9CHO (2a)
20
24
3aa
3ab
54
29
35
1a
24
–
0
Common reaction conditions: 1 (1.2 mmol), 2 (1.0 mmol), [Rh(cod)(MeCN)2]BF4 (0.02 mmol), THF (1.0 mL), 608C, N2 atmosphere.
Isolated yield.
a
b
1 mmol of water was added.
and ketone, a competitive reaction of benzaldehyde (2a,
1 mmol) and cyclohexanone (2b, 1 mmol) with 1a
(1 mmol) was carried out at 608C for 5 h. In result, 79%
yield of the product alcohol (3aa) from benzaldehyde was
obtained preferentially, and only a trace amount of the
product alcohol (3ab) from cyclohexanone was formed
(Scheme 1).
phenylstannane (1a) was studied. When 0.1 mmol of
[Rh(cod)(MeCN)2]BF4 was treated with equimolar amount
of 1a and D2O in THF at 258C for 20 h, the stannane 1a was
completely consumed and deuterized benzene (44% yield,
78%-d) was formed. A control experiment confirmed that
the stannane 1a was inert to water. Considering these
results, it is probable that the generation of a water-labile
species was formed from [Rh(cod)(MeCN)2]BF4 and the
stannane 1a, which we attribute to an unstable phenyl-
rhodium species that should decompose rapidly to give
benzene. Interestingly, the present addition reaction can be
carried out in the presence of water indicating that the
unstable phenylrhodium species reacted with aldehydes
faster than with water. Unfortunately, peaks corresponding
to the phenylrhodium species by 1H and 13C NMR
measurements could not be detected, that would be caused
by the instability of the species. However, Hartwig’s group
reported the generation and characterization of the phos-
phine-coordinated phenylrhodium complexes, which
reacted with aldehydes to give rhodium alkoxides.14
To gain information on the reaction mechanism, the
reactivity of [Rh(cod)(MeCN)2]BF4 toward trimethyl-
Scheme 1.

S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
4355
The rhodium-catalyzed addition of arylstanannes was
applied to a-dicarbonyl compounds. As stated above, the
reaction was very sluggish with ketones, however, con-
jugate a-diketones were found to undergo the addition of
arylstannanes (Eq. (2)). An advantage of the reaction is that
the arylation takes place only at one carbonyl group and the
diarylation never occurs even when an excess amount of the
arylstannane was used.
The reactions were carried out under the same conditions
optimized for the reaction of aldehydes. Results are listed in
Table 4. When benzil (8a) was treated with 1.2 equiv. of
trimethylphenylstannane (1a) in the presence of 2 mol% of
[Rh(cod)(MeCN)2]BF4, almost quantitative yield of mono-
phenylated ketoalcohol 9aa was obtained (entry 1). The
reaction using 2.0 equiv. of stannane 1a gave the same
result. Substituted phenylstannanes 1d and 1e also added to
benzil to give the monoarylated ketoalcohol 9da and 9ea
(entries 2 and 3). A symmetric aliphatic diketone 8b reacted
with 1a affording the product 9ab in a moderate yield of
62% (entry 4). The reaction of an asymmetric diketone 8c
gave 82% yield of a mixture of regioisomers, the adduct on
its methyl ketone moiety 9ac and the adduct on its ethyl
ketone moiety 9ac0, in a ratio of 65:35 (entry 5). The ratio of
regioisomers was affected by the difference of bulkiness of
two carbonyl groups and the addition took place preferen-
tially on the less hindered carbonyl carbon. A diketone 8d
having a methyl group and a propyl group on each carbonyl
carbon gave an improved ratio of regioisomers, 9ad and
9ad0, in a ratio of 76:24 (entry 6). A diketone 8e having a
methyl group and a phenyl group on each carbonyl carbon
gave a similar ratio of 77:23 (entry 7). To determine the
electronic effect on the regioselectivity, the reactions of
benzil derivatives having a functional group on one phenyl
group 8f–8j were then performed. As a result, the
regioselectivity was strongly affected by the electronic
nature of the functional groups and the addition took place
preferentially on the relatively electron deficient carbonyl
carbon. For benzil derivatives having a methoxyl group 8f
and a methyl group 8g, the addition occurred opposite
carbonyl carbons to those with the substituted phenyl
groups in ratios of 36:64 and 47:53, respectively (entries 8
and 9). For benzil derivatives having a fluoro group 8h
and an acetyl group 8g, the regioselectivity reversed to give
9ah and 9ai preferentially (entries 10 and 11). The
reaction of benzil derivatives having a nitro group 8j was
completely regioselective affording 9aj as a sole product
(entry 12).
Scheme 2.
Evidence for the formation of phenylrhodium species was
also found by the treatment of [Rh(cod)(MeCN)2]BF4
(0.1 mmol) with 1.0 equiv. of 1a in the presence of
2.0 equiv. of styrene in THF (1 mL) at room temperature
for 20 h that gave trans-stilbene in 49% yield. The trans-
stilbene should be formed by the Heck-type reaction
between the phenylrhodium species and the styrene. The
presumed reaction pathway for the arylation reaction of
aldehydes 2 with arylstannanes 1 is shown in Scheme 2. The
transmetalation between the cationic rhodium complex and
1 would produce the arylrhodium intermediate 5, which
adds to an aldehyde to give a rhodium alkoxide 6. Then, the
rhodium alkoxide 6 would afford the stannyl ether 7 and
regenerate the cationic rhodium complex. From the result
that the addition of phosphine ligands inhibited the reaction,
a phosphine-free phenylrhodium species is probably more
reactive than that with phosphine ligands. The mechanism
for the formation of the ester 4 would involve the insertion
of another aldehyde 2 to the Rh–O bond of 6 followed by
b-H elimination (Scheme 3). A similar mechanism was
proposed by Slough’s group in their report on Tishchenko-
type disproportionation of aldehydes catalyzed by rhodium
complexes15 and by Hartwig’s group in their report on
reactivity of aryl- and alkoxy-rhodium complexes.14
The reactions of glyoxylic acid esters and a-ketoesters were
then examined. In these cases, the addition occurred
selectively at the formyl group on the glyoxylic acid esters
and at the acyl group on the a-ketoesters. As shown in
Table 5, the reactions of trimethylphenylstannane (1a) with
ethyl and isopropyl glyoxylate (10a and 10b) gave
corresponding a-phenylated a-hydroxyesters, 11aa and
11ab, in 69% and 62% yield, respectively (entries 1 and
2). Ethyl pyruvate (10c) and methyl and ethyl benzoylfor-
mate (10d and 10e) also underwent the phenylation to give
the a-hydroxyesters in good yield. The reaction with
dimethyl oxalate (10f) did not take place showing that the
ester groups did not undergo the addition even though they
were conjugated.
Scheme 3.
2.2. Addition of arylstannanes to a-dicarbonyl
compounds
ð2Þ

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S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 4. Rhodium-catalyzed addition of arylstannanes 1 to a-diketones 8
Entry
1
Arylstannane 1
PhSnMe3 (1a)
a-Diketone 8
Product
Yield (%)a
99
2
8a
8a
51
3
4
72
62
PhSnMe3 (1a)
5
1a
82
6
7
1a
1a
70
93
8
1a
1a
1a
1a
89
84
98
84
9
10
11
12
1a
82
Common reaction conditions: 1 (1.2 mmol), 8 (1.0 mmol), [Rh(cod)(MeCN)2]BF4 (0.02 mmol), THF (1.0 mL), 608C, 20 h, N2 atmosphere.
Isolated yield.
a
2.3. Addition of arylstannanes to aldimines
N-benzylideneaniline (12a) with trimethylphenylstannane
(1a), but no arylation occurred (entry 1). This is probably
due to the low electrophilicity of the imine 12a. Then,
N-tosylbenzylideneamine (12b), which are activated by the
electron-withdrawing sulfonyl group on the nitrogen atom,
was examined as a substrate. The reaction of 12b with 1a
proceeded well under the same reaction conditions
optimized for the reaction of aldehydes, affording N-tosyl-
diphenylmethylamine (13ab) in 98% isolated yield (entry
ð3Þ
The rhodium-catalyzed addition of organotin compounds
was then applied to aldimines (Eq. (3)).3c–e,g The results are
listed in Table 6. At first, we examined the arylation of

S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 5. Rhodium-catalyzed addition of arylstannanes 1 to a-ketoesters 10
4357
Entry
1
Arylstannane 1
PhSnMe3 (1a)
a-Ketoester 10
Product
Yield (%)a
69
2
3
4
5
1a
1a
1a
1a
62
71
60
77
6
1a
–
0
Common reaction conditions: 1 (1.2 mmol), 10 (1.0 mmol), [Rh(cod)(MeCN)2]BF4 (0.02 mmol), THF (1.0 mL), 608C, 20 h, N2 atmosphere.
Isolated yield.
a
2). Other electron-withdrawing groups were examined as
the activating group of the aldimines. The reaction of
N-(diethoxyphosphoryl)benzylideneamine (12c) with 1a
gave N-(diethoxyphosphoryl)diphenylmethylamine (13ac)
in 84% yield (entry 3). Acyl and alkoxycarbonyl groups can
also be employed as the activating group. N-Benzoyl-
benzylideneamine (12d) and N-(tert-butoxycarbonyl)-
benzylideneamine (12e) reacted with 1a under the same
reaction conditions, affording N-benzoyl- and N-(tert-
butoxycarbonyl)diphenylmethylamine (13ad and 13ae) in
48% and 74% yield, respectively (entries 4 and 5).
amines in good yield. In the reaction of a-diketones,
monoarylated products were obtained selectively and the
predominant addition was observed for less hindered and
more electron deficient carbonyl group. The reaction of
a-ketoesters gave a-arylated a-hydroxy esters selectively.
4. Experimental
4.1. General information
All reactions were carried out in a Schlenk tube under N2.
THF was dried over sodium/benzophenone ketyl, and
distilled before use. NMR spectra were recorded using
CDCl3 as the solvent. Elemental analyses were performed
by the Microanalytical Laboratory of the Institute for
Chemical Reaction Science, Tohoku University. Spherical
silica gel (40–100 mm, Kanto Chemical) was used for flash
chromatography.
Ortho- or para-substituted N-tosylbenzylideneamines with
either an electron-withdrawing or -donating group (12f–
12k) also reacted with 1a, affording the corresponding
N-tosyldiarylmethylamines (13af–13ak) in good isolated
yields (entries 7–12). The reaction of N-tosylfurylidene-
amine (12l) with 1a gave the product 13al in 72% yield
(entry 13). The reaction of a N-tosylaldimine derived from
cinnamaldehyde (12m) gave not a conjugate adduct but the
1,2-adduct 13am in 39% yield (entry 14). Ethyl tosyl-
iminoacetate (12n), having three electrophilic moieties,
ester, imino, and sulfonyl groups, was phenylated selec-
tively at the imino group, affording N-tosylphenylglycine
ethyl ester (13an) in 65% isolated yield (entry 15).
4.2. Materials
The organotin compounds 2d–2f were prepared from the
corresponding Grignard reagents and trimethylstannyl
chloride.16 Aromatic a-diketones 8f–8j were prepared as
described in the literature17 from corresponding diaryl-
acetylenes.18 Aldimines 12b and 12f–12m,19 12c,20 12d,21
12e,22 and 12n23 were prepared as described in the
literature.
3. Conclusion
Rhodium-catalyzed additions of arylstannanes to carbon–
heteroatom double bonds were presented. The reaction of
arylstannanes with aldehydes gave arylated secondary
alcohols and N-tosyl-, -phosphoryl-, -acyl-, and -alkoxy-
carbonyl-aldimines gave arylated protected secondary
4.2.1. Rh(cod)(MeCN)2]BF4.24 To
[RhCl(cod)]2 (0.8 g, 1.6 mmol) in CH2Cl2 (20 mL) and
acetonitrile (3.0 mL) was added a solution of AgBF4 (0.7 g,
3.8 mmol) in acetonitrile (3.0 mL) and the mixture was
a
solution of

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S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
Table 6. Rhodium-catalyzed addition of phenyltrimethylstannane (1a) to imines 12
Entry
1
Arylstannane 1
PhSnMe3 (1a)
Imine 12
Product
Yield (%)a
0
–
2
3
1a
1a
13ab
13ac
98
84
4
5
7
1a
1a
1a
13ad
13ae
13af
48
74
76
8
1a
1a
1a
1a
1a
13ag
13ah
13ai
13aj
13ak
13al
75
60
78
79
83
9
10
11
12
13
14
1a
1a
72
39
15
1a
65
Common reaction conditions: 1 (1.2 mmol), 10 (1.0 mmol), [Rh(cod)(MeCN)2]BF4 (0.02 mmol), THF (1.0 mL), 608C, 20 h, N2 atmosphere.
Isolated yield.
a
stirred at room temperature for 2 h under N2 with shielding
the light. After the precipitated AgCl was filtered off, the
solution volume was reduced in vacuo to ca. 5 mL and
20 mL of Et2O was then added slowly. Precipitated yellow
powder was collected by filtration and dried in vacuo to give
[Rh(cod)(MeCN)2]BF4 in 85% yield.
give the product. Known compounds were identified by
comparing the spectroscopic data with those reported in the
literature (Table 7).
4.3.1. (4-Isobutylphenyl)phenylmethanol (3ag). IR (KBr)
3314, 2952, 2868, 1453, 1035, 1017, 774, 749, 700 cm21
.
1H NMR (400 MHz, CDCl3) d 7.36–7.29 (m, 4H), 7.25–
7.21 (m, 3H), 7.09 (d, J¼7.8 Hz, 2H), 5.76 (s, 1H), 2.44 (d,
J¼6.8 Hz, 2H), 2.32 (s, 1H), 1.83 (nonet, J¼6.8 Hz, 1H),
0.88 (d, J¼6.8 Hz, 6H). 13C NMR (100 MHz, CDCl3) d
143.9, 141.2, 141.1, 129.2, 128.4, 127.4, 126.5, 126.4, 76.1,
45.1, 30.2, 22.4. Anal. calcd for C17H20O: C, 84.96; H, 8.39.
Found: C, 84.84; H, 8.45.
4.3. Rhodium-catalyzed addition of arylstannanes
The general procedure was as follows. To a mixture of the
substrate (2, 8, 10, or 12, 1.0 mmol) and
[Rh(cod)(MeCN)2]BF4 (7.4 mg, 0.02 mmol) in THF
(1 mL) was added the arylstannane (1, 1.2 mmol) and
stirred at 608C for the appropriate time. The reaction was
quenched by adding a small amount of water and then
stirred for 1 h. Et2O (20 mL) was added to the reaction
mixture and the resulting precipitate was removed by
filtration. The solvent was removed in vacuo and the residue
was purified by flash chromatography (hexane/AcOEt) to
4.3.2. (2-Bromophenyl)phenylmethanol (3al). IR (neat)
3360, 3062, 1494, 1454, 1183, 1015, 750, 699, 644,
.
601 cm21 1H NMR (400 MHz, CDCl3) d 7.54 (dd,
J¼16.2, 7.8 Hz, 2H), 7.39–7.23 (m, 6H), 7.12 (t,
J¼7.6 Hz, 1H), 6.17 (s, 1H), 2.44 (s, 1H). 13C NMR

S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
4359
Table 7. References for known compounds
d 7.34–7.26 (m, 5H), 5.73 (dd, J¼7.7, 6.2 Hz, 1H), 2.31 (dt,
J¼7.5, 2.3 Hz, 2H), 1.95–1.80 (m, 2H) 1.62 (qui, J¼7.5 Hz,
2H), 1.38–1.18 (m, 10H), 0.87 (t, J¼7.0 Hz, 3H), 0.86 (t,
J¼7.0 Hz, 3H). 13C NMR (100 MHz, CDCl3) d 173.2,
141.1, 128.4, 127.7, 126.5, 75.9, 36.4, 34.6, 31.5, 31.3, 25.2,
24.7, 22.5, 22.3, 14.0, 13.9. Anal. calcd for C18H28O2: C,
78.21; H, 10.21. Found: C, 77.88; H, 9.95.
Compound
Reference
Compound
Reference
3aa
25
25
26
27
28
25
25
25
29
26
30
31
32
33
34
35
36
37
38
39
40
41
42
9aa
43
44
44
45
45
45
46
47
48
49
44
44
44
50
50
51
52
53
3e
3e
54
55
56
3da (¼3ab)
3ea (¼3ah)
3ac
3ad
3ae
3af
3ai
3aj
3ak
3ao
3aq
3ar
3as
3at
3au
3av
9da (¼9af)
9ea (¼9ah)
9ab
9ac
9ac0
9ad
4.3.7. A mixture of 2-hydroxy-2-phenylhexan-3-one
(9ad) and 3-Hydroxy-3-phenylhexan-2-one (9ad0). p
Peaks for 9ad0. IR (neat) 3459, 3060, 2965, 2874, 1709,
1447, 1364, 760, 700 cm21. 1H NMR (400 MHz, CDCl3) d
7.48–7.30 (m, 5H), 4.61 (s, 1H), 4.51p (s, 1H), 2.41–2.28
(m, 2H), 2.16–2.13p (m, 2H), 2.08p (s, 3H), 1.77 (s, 3H)
1.55–1.45 (m, 2H), 0.99p (t, J¼7.3 Hz, 3H) 0.75 (t,
J¼7.4 Hz, 3H). 13C NMR (100 MHz, CDCl3) d 211.6,
209.5p, 141.0, 129.3, 128.6, 128.0, 127.9, 126.2, 126.1,
119.6, 82.6p, 79.7, 38.7p, 34.4, 24.0, 23.6p, 17.4p, 16.6,
14.4p, 13.4. Anal. calcd for C12H16O2: C, 74.97; H, 8.39.
Found: C, 74.68; H, 8.37.
9ae
9ae0
9af0
9ag
9ag0
9ah0
11aa
11ab
11ac
11ad
11ae
13ab
13ad
13ae
13al
3aw
3ax
3ay
3az
3aa
3ab
4.3.8. A mixture of 2-(4-acetylphenyl)-2-hydroxy-1,2-
diphenylethan-1-one (9ai) and 1-(4-acetylphenyl)-2-
hydroxy-2,2-diphenylethan-1-one (9ai0). p Peaks for
9ai0. IR (neat) 3443, 3059, 3014, 2924, 1681, 1604, 1268,
13am
1
1058, 818, 764, 700 cm21. H NMR (400 MHz, CDCl3) d
(100 MHz, CDCl3) d 142.5, 142.2, 132.8, 129.1, 128.5,
128.4, 127.8, 127.7, 127.0, 122.8, 74.8. Anal. calcd for
C13H11BrO: C, 59.34; H, 4.21; Br, 30.37. Found: C, 59.798;
H, 4.478, Br, 30.60.
7.92–7.26 (m, 14H), 4.99 (s, 1H), 4.65p (s, 1H), 2.58 (s,
3H), 2.56p (s, 3H). 13C NMR (100 MHz, CDCl3) d 200.5,
200.1, 197.6p, 146.8, 141.56, 141.47, 139.6, 136.6, 134.8,
133.2, 130.8, 128.57, 128.53, 128.50, 128.44, 128.35,
128.25, 128.10, 128.07, 127.8, 85.4p, 85.0, 26.7p, 26.6.
Anal. calcd for C22H18O3: C, 79.98; H, 5.49. Found: C,
79.82; H, 5.61.
4.3.3. (4-Methoxycarbonylphenyl)phenylmethanol
(3am). Mp 62–638C. IR (neat) 3440, 2950, 1720, 1612,
1435, 1280, 1110, 1018, 754, 705 cm21
.
1H NMR
(400 MHz, CDCl3) d 7.97 (d, J¼8.3 Hz, 2H), 7.44 (d,
J¼8.3 Hz, 2H), 7.34–7.25 (m, 5H), 5.84 (s, 1H), 3.87 (s,
3H), 2.64 (s, 1H). 13C NMR (100 MHz, CDCl3) d 166.9,
148.7, 143.3, 129.7, 129.2, 128.6, 127.9, 126.6, 126.3, 75.8,
52.1. Anal. calcd for C15H14O3: C, 74.36; H, 5.82. Found: C,
74.02; H, 5.91.
4.3.9. 2-(4-Nitrophenyl)-2-hydroxy-1,2-diphenylethan-1-
one (9aj). Mp 88–898C. IR (neat) 3457, 3063, 2983, 2855,
1
1681, 1347, 1236, 1181, 1060, 852, 748, 697 cm21. H
NMR (400 MHz, CDCl3) d 8.17 (d, J¼9.0 Hz, 2H), 7.98 (d,
J¼7.8 Hz, 2H), 7.63 (d, J¼9.0 Hz, 2H), 7.49 (t, J¼7.5 Hz,
1H), 7.41–7.35 (m, 5H), 7.32 (dd, J¼7.8, 7.5 Hz, 2H), 4.93
(s, 1H). 13C NMR (100 MHz, CDCl3) d 199.6, 148.8, 147.5,
141.2, 134.5, 133.5, 130.7, 129.3, 128.84, 128.77, 128.4,
127.8, 123.3, 84.8. Anal. calcd for C20H15NO4: C, 72.06; H,
4.54; N, 4.20. Found: C, 71.80; H, 4.67; N, 4.27.
4.3.4. (4-Acetylphenyl)phenylmethanol (3an). IR (neat)
3420, 3030, 1675, 1608, 1498, 1452, 1412, 1360, 1270,
1
1190, 1042, 1018, 801, 699 cm21. H NMR (400 MHz,
CDCl3) d 7.87 (d, J¼8.3 Hz, 2H), 7.46 (d, J¼8.3 Hz, 2H),
7.34–7.23 (m, 5H), 5.83 (d, J¼2.6 Hz, 1H), 2.86 (d,
J¼2.6 Hz, 1H), 2.53 (s, 3H). 13C NMR (100 MHz, CDCl3) d
198.0, 149.0, 143.2, 136.1, 128.6, 128.5, 127.9, 126.5,
126.5, 75.7, 26.5. Anal. calcd for C15H14O2: C, 79.62;
H,6.24. Found: C, 79.156; H, 6.085.
4.3.10. N-(Diethoxyphosphoryl)diphenylmethylamine
(13ac). Mp 111–1128C. IR (KBr) 3221, 2989, 2902,
1496, 1467, 1226, 1121, 1027, 961, 752, 710, 541 cm21
.
1H NMR (500 MHz, CDCl3) d 7.33–7.23 (m, 10H), 5.41 (t,
J¼9.8 Hz, JH–P¼9.8 Hz, 1H), 4.02–3.95 (m, 2H), 3.87–
3.81 (m, 2H), 3.46 (dd, J¼9.8 Hz, JH–P¼10.3 Hz, 1H), 1.17
(t, J¼7.3 Hz, 6H). 13C NMR (125 MHz, CDCl3) d 143.3 (d,
JC–P¼5.1 Hz), 128.5, 127.3, 127.2, 62.4 (d, JC–P¼5.1 Hz),
59.2, 16.0 (d, JC–P¼7.5 Hz). Anal. calcd for C17H22NO3P:
C, 63.94; H, 6.94; N, 4.39. Found: C, 64.08; H, 6.99; N,
4.43.
4.3.5. (2-Nitrophenyl)phenylmethanol (3ap). IR (neat)
3417, 3032, 1607, 1577, 1538, 1454, 1359, 1178, 1019, 737,
1
701, 601 cm21. H NMR (500 MHz, CDCl3) d 7.91 (dd,
J¼7.9, 1.2 Hz, 1H), 7.73 (dd, J¼7.9, 1.2 Hz, 1H), 7.62 (dt,
J¼7.9, 1.2 Hz, 1H), 7.44 (dt, J¼7.9, 1.2 Hz, 1H), 7.36–7.30
(m, 4H), 7.29–7.26 (m, 1H), 6.41 (d, J¼3.5 Hz, 1H), 2.88
(d, J¼3.5 Hz, 1H). 13C NMR (125 MHz, CDCl3) d 148.5,
141.6, 138.5, 133.4, 129.5, 128.6, 128.5, 128.1, 127.0,
124.7, 71.5. Anal. calcd for C13H11NO3: C, 68.11; H, 4.84;
N, 6.11. Found: C, 68.277; H, 4.979; N, 6.049.
4.3.11. N-Tosyl-(4-methoxylphenyl)phenylmethylamine
(13af). Mp 146.0–147.08C. IR (KBr) 3239, 2950, 1609,
1509, 1432, 1321, 1251, 1159, 1048, 842, 673, 559 cm21
.
1H NMR (500 MHz, CDCl3) d 7.55 (d, J¼8.30 Hz, 2H),
7.21–7.00 (m, 7H), 6.99 (d, J¼8.65 Hz, 2H), 6.73 (d,
J¼8.65 Hz, 2H), 5.52 (d, J¼6.90 Hz, 1H), 5.00 (d,
4.3.6. Hexanoic acid 1-phenylhexyl ester (4aw). IR (neat)
2910, 2845, 1730, 1165 cm21. 1H NMR (400 MHz, CDCl3)

4360
S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
J¼6.90 Hz, 1H), 3.75 (s, 3H), 2.37 (s, 3H). 13C NMR
(125 MHz, CDCl3) d 159.0, 143.1, 140.7, 137.4, 132.7,
129.3, 128.6, 128.5, 127.4, 127.28, 127.22, 113.9, 60.8,
55.2, 21.4. Anal. calcd for C21H21NO3S: C, 68.64; H,5.76;
N,3.81; S,8.73. Found: C, 68.67; H, 5.84; N, 3.80; S, 8.74.
123.6, 60.9, 21.5. Anal. calcd for C20H18N2O4S: C, 62.81;
H, 4.74; N, 7.33; S, 8.38. Found: C, 62.87; H, 4.85; N, 7.32;
S, 8.47.
4.3.17. 2-Phenyl-2-(tosylamino)ethanoic acid ethyl ester
(13an). Mp 85–868C. IR (KBr) 3267, 3031, 2988, 1726,
1388, 1160, 1090, 696 cm21. 1H NMR (500 MHz, CDCl3) d
7.63 (d, J¼7.9 Hz, 2H), 7.26–7.22 (m, 5H), 7.19 (d,
J¼7.9 Hz, 2H), 5.77 (d, J¼8.1 Hz, 1H), 5.04 (d, J¼8.1 Hz,
1H), 4.06–3.94 (m, 2H), 2.38 (s, 3H), 1.09 (t, J¼7.1 Hz,
3H). 13C NMR (125 MHz, CDCl3) d 170.0, 143.4, 136.9,
135.4, 129.4, 128.7, 128.4, 127.2, 127.0, 62.2, 59.3, 21.4,
13.8. Anal. calcd for C17H19NO4S: C, 61.24; H, 5.74; N,
4.20; S, 9.62. Found: C, 61.28; H, 5.68; N, 4.33; S, 9.68.
4.3.12. N-Tosyl-(2-methoxylphenyl)phenylmethylamine
(13ag). Mp 126.6–127.88C. IR (KBr) 3302, 1599, 1493,
1455, 1333, 1242, 1159, 1094, 1064, 1024, 817, 755, 699,
547 cm21
.
1H NMR (250 MHz, CDCl3) d 7.51 (d,
J¼8.22 Hz, 1H), 7.25–6.95 (m, 10H), 6.79 (t, J¼7.39 Hz,
1H), 6.67 (d, J¼3.20 Hz, 1H), 5.76 (d, J¼9.13 Hz, 1H), 5.64
(d, J¼9.13 Hz, 1H), 3.59 (s, 3H), 2.42 (s, 3H). 13C NMR
(100 MHz, CDCl3) d 156.3, 142.6, 140.6, 137.5, 129.4,
128.9, 128.8, 128.0, 127.7, 126.95, 126.93, 126.7, 120.5,
111.0, 58.7, 55.1, 21.3. Anal. calcd for C21H21NO3S: C,
68.64; H, 5.76; N, 3.81; S, 8.73. Found: C, 68.68; H, 5.83;
N, 3.81; S, 8.84.
References
4.3.13. N-Tosyl-(4-dimethylaminopheny)phenylmethyl-
amine (13ah). Mp 128.2–128.78C. IR (KBr) 3311, 1613,
1524, 1324, 1158, 1047, 806, 701, 669, 568, 541 cm21. 1H
NMR (500 MHz, CDCl3) d 7.60–7.56 (m, 2H), 7.33–7.15
(m, 7H), 6.92 (d, J¼8.45 Hz, 2H), 6.57 (d, J¼8.45 Hz, 2H),
5.51 (d, J¼5.95 Hz, 1H), 5.00 (d, J¼5.95 Hz, 1H), 2.92 (s,
6H), 2.40 (s, 3H). 13C NMR (125 MHz, CDCl3) d 149.9,
142.8, 141.0, 137.5, 129.2, 128.33, 128.30, 128.2, 127.27,
127.23, 127.1, 112.3, 60.9, 40.4, 21.4. Anal. calcd for
C22H24N2O2S: C, 69.44; H, 6.36; N, 7.36; S, 8.43. Found: C,
69.23; H, 6.42; N, 7.28; S, 8.31.
1. Knight, D. W. Comprehensive Organic Synthesis; Trost, B. M.,
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4.3.14. N-Tosyl-(4-chlorophenyl)phenylmethylamine
(13ai). Mp 119.0–120.08C. IR (KBr) 3238, 1490, 1432,
1321, 1159, 1091, 1048, 836, 803, 745, 700, 668, 572 cm21
.
1H NMR (250 MHz, CDCl3) d 7.54 (d, J¼8.18 Hz, 2H),
7.25–7.03 (m, 11H), 5.53 (d, J¼7.07 Hz, 1H), 5.22 (d,
J¼7.07 Hz, 1H), 2.38 (s, 3H). 13C NMR (62.5 MHz, CDCl3)
d 143.4, 140.0, 138.9, 137.1, 133.4, 129.4, 128.77, 128.72,
128.6, 127.8, 127.2, 127.1, 60.7, 21.4. Anal. calcd for
C20H18ClNO2S: C, 64.59; H, 4.88; Cl, 9.53; N, 3.77; S, 8.62.
Found: C, 64.59; H, 4.96; Cl, 9.64; N, 3.71; S, 8.59.
4.3.15. N-Tosyl-(2-chlorophenyl)phenylmethylamine
(13aj). Mp 172.0–173.28C. IR (KBr) 3296, 1597, 1494,
1431, 1333, 1155, 1082, 942, 759, 693, 665, 572, 547 cm21
.
1H NMR (250 MHz, CDCl3) d 7.62 (d, J¼8.29 Hz, 2H),
7.33–7.06 (m, 11H), 5.94 (d, J¼7.28 Hz, 1H), 5.34 (d,
J¼7.28 Hz, 1H), 2.38 (s, 3H). 13C NMR (62.5 MHz, CDCl3)
d 143.3, 139.2, 137.5, 132.7, 129.8, 129.3, 128.7, 128.6,
128.5, 127.8, 127.5, 127.2, 127.1, 126.9, 58.6, 21.4. Anal.
calcd for C20H18ClNO2S: C, 64.59; H, 4.88; Cl, 9.53; N,
3.77; S, 8.62. Found: C, 64.56; H, 4.88; Cl, 9.69; N, 3.80; S,
8.92.
4.3.16. N-Tosyl-(4-nitrophenyl)phenylmethylamine
(13ak). Mp 128.5–129.58C. IR (KBr) 3243, 3065, 1598,
1517, 1447, 1346, 1158, 1094, 1051, 906, 838, 741, 696,
665, 572, 557 cm21. 1H NMR (250 MHz, CDCl3) d 8.02 (d,
J¼8.71 Hz, 2H), 7.52 (d, J¼8.27 Hz, 2H), 7.32 (d,
J¼8.71 Hz, 2H), 7.20–7.10 (m, 5H), 6.96–6.92 (m, 2H),
5.56 (d, J¼6.75 Hz, 1H), 5.20 (d, J¼6.75 Hz, 1H), 2.34 (s,
3H). 13C NMR (100 MHz, CDCl3) d 147.7, 147.2, 143.8,
139.2, 136.9, 129.5, 129.1, 128.4, 128.2, 127.3, 127.2,

S. Oi et al. / Tetrahedron 59 (2003) 4351–4361
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