RhI-Catalyzed Stille-Type Coupling of Diazoesters with Aryl Trimethylstannanes

Article abstract of DOI:10.1071/CH15218

A Rh^I-catalyzed cross-coupling of diazoester with arylstannane was developed. This reaction represents the first Stille-type coupling that uses a diazo compound as the coupling partner. The reaction is operationally simple and can be carried out under mild conditions, thus providing an alternative approach for the synthesis of α-aryl esters. RhI-carbene migratory insertion process is suggested to be involved as the key step in this Stille-type coupling.

Full text of DOI:10.1071/CH15218

RESEARCH FRONT
CSIRO PUBLISHING
Aust. J. Chem. 2015, 68, 1379–1384
Full Paper
http://dx.doi.org/10.1071/CH15218
RhI-Catalyzed Stille-Type Coupling of Diazoesters with Aryl
Trimethylstannanes
A
A C
,
A
A
A
Zhen Liu, Ying Xia,
Sheng Feng, Shuai Wang, Di Qiu,
A
A B C
, ,
Yan Zhang, and Jianbo Wang
A
Beijing National Laboratory of Molecular Sciences (BNLMS), Key Laboratory of
Bioorganic Chemistry and Molecular Engineering of Ministry of Education,
College of Chemistry, Peking University, Beijing 100871, China.
State Key Laboratory of Organometallic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, China.
B
C
Corresponding authors. Email: xiayingbit@163.com; wangjb@pku.edu.cn
A RhI-catalyzed cross-coupling of diazoester with arylstannane was developed. This reaction represents the first Stille-
type coupling that uses a diazo compound as the coupling partner. The reaction is operationally simple and can be carried
out under mild conditions, thus providing an alternative approach for the synthesis of a-aryl esters. RhIꢀcarbene migratory
insertion process is suggested to be involved as the key step in this Stille-type coupling.
Manuscript received: 26 April 2015.
Manuscript accepted: 28 May 2015.
Published online: 17 June 2015.
(a) Suzuki-type coupling
Introduction
Transition metal-catalyzed cross-coupling reactions represent
one of the most important methods for the construction of
carbon–carbon bond in organic synthesis. Through the extensive
studies conducted over the past decades, various cross-coupling
partners have been explored. Recently, diazo compounds, as a
novel type of coupling partner, have drawn significant attention
since the seminal work of Van Vranken and coworkers.[1,2]
The distinct feature of these reactions is the formation of
metal–carbene intermediate and subsequent migratory insertion
process that are the basis of the development of a series of
novel cross-coupling reactions.[3] In addition to the palladium-
and copper-catalyzed reactions, rhodium-catalyzed coupling
reactions of diazo compounds have been investigated. In this
context, in 2011, Yu and coworkers reported a RhI-catalyzed
cross-coupling of aryl diazoesters with aryl boronates, followed
by in situ benzylation. The reaction afforded quaternary a,a-
diaryl carboxylic acid esters.[4] Subsequently, Ghorai and
Anbarasan reported the RhI-catalyzed cross-coupling of aryl
boronic acids with diazoacetates to give a-aryl carboxylic acid
esters (Scheme 1a).[5] Very recently, we have successfully
achieved the RhI-catalyzed Hiyama-type coupling of arylsi-
loxanes with a range of diazoesters, affording an alternative
methodology for the synthesis of a-aryl carboxylic acid esters
(Scheme 1b).[6]
Ar
Ј
Ar
Ј
Cat. [Rh]
Ref. [5]
ArB(OH)2
ϩ
N2
CO2R
CO2R
Ar
(b) Hiyama-type coupling
R
R
Cat. [Rh]
Ref. [6]
ϩ
Ar
ArSi(OMe)3
N2
CO2R
Ј
CO2R
Ј
(c) Stille-type coupling
R
R
Cat. [Rh]
ϩ
N2
Ar
ArSnMe3
This work
CO2R
Ј
CO2RЈ
Scheme 1. RhI-catalyzed cross-coupling reactions with diazo compounds.
study in carbene chemistry and the interest of developing new
transformation of aryl organotin regents,[10] we conceived that
aryl trimethylstannanes might couple with diazo compounds
under the catalysis of RhI complex. Herein, we report the RhI-
catalyzed cross-coupling reaction of aryl trimethylstannanes
with diazoesters (Scheme 1c). To the best of our knowledge,
this reaction represents the first example whereby diazo com-
pounds are used as coupling partners in Stille-type coupling.[11]
On the other hand, the Stille coupling represents a well-
established methodology for building C–C bond in modern
organic synthesis.[7] Due to the excellent functional group com-
patibility, the Stille coupling is widely used in total synthesis,
especially for later-stage C–C bond forming transformations.[8]
In addition, we have recently developed a Sandmeyer-type
stannylation reaction in which aryl trimethylstannanes can be
easily prepared from aryl amines.[9] As a continuation of our
Results and Discussion
At the beginning of this study, phenyl trimethylstannane (1a)
and phenyl diazoester (2a) were chosen as the model substrates
Journal compilation Ó CSIRO 2015
www.publish.csiro.au/journals/ajc

1380
Z. Liu et al.
[Rh(cod)OH]2 (2 mol-%)
XPhos (10 mol-%)
Table 1. Optimization of conditions of the RhI-catalyzed coupling
between 1a and 2aA
R1
R1
Ph
Ph
SnMe3
N2
ϩ
KF (1 equiv.)
THF/H2O (1:1)
70ЊC, 1 h
CO2R
CO2R
[Rh(cod)OH]2 (2 mol-%)
ligand (10 mol-%)
Ph
Ph
3a–r
1a
2a–r
Ph
Ph
SnMe3
ϩ
N2
base (1 equiv.)
THF (0.5 mL)
H2O (x µL), 70ЊC, 1 h
CO2Me
Ph
CO2Me
Ph
Ph
2a
1a
3a
Ph
t
CO2Et
Ph
Ph
3a, 96 %
CO2 Bu
CO2Me
3c, 35 %, 88 %A
3b, 92 %
Entry
Ligand
1a : 2a
H2O [mL]
Base
Yield [%]B
Ph
1
None
None
None
None
None
1 : 1
0
50
None
None
CsF
TBAFD
KF
N.R.C
,5
Trace
Trace
15
3d, X ϭ Me, R ϭ Me, 75 %
3e, X ϭ OMe, R ϭ Me, 84 %
3f, X ϭ Br, R ϭ Me, 84 %
3g, X ϭ Cl, R ϭ Me, 76 %
Ph
2
1 : 1
X
CO2Me
3
1 : 1
50
CO2R
4
1 : 1
50
X
3i, X ϭ OMe, 93 %
3j, X ϭ Cl, 85 %
5
1 : 1
50
3h, X ϭ Ac, R ϭ Et, 69 %
6
PCy3ꢁHBF4
XPhos
BINAPE
PPh3
1 : 1
50
KF
41
7
1 : 1
50
KF
48
Ph
X
Ph
CO2Me
Ph
Cl
8
1 : 1
1: 1
50
KF
19
Cl
Cl
CO2Me
9
50
KF
17
CO2Me
10
11
12
13
14
15F
16
XPhos
XPhos
XPhos
XPhos
XPhos
XPhos
XPhos
1.2 : 1
1 : 1.2
1.2 : 1
1.2 : 1
1.2 : 1
1.2 : 1
1.2 : 1
50
KF
60
Cl
50
KF
55
3k, X ϭ OMe, 77 %
3l, X ϭ F, 82 %
3m, 99 %
3n, 96 %
100
250
500
500
500
KF
75
KF
94
Ph
KF
96
Ph
Ph
KF
85
RO2C
CO2R
t
None
57
MeO2C
3r, 80 %A
CO2 Bu
Me
3o, 31 %A
CO2Bn
3p, R ϭ Et, 76 %
3q, R ϭ iPr, 83 %A
AThe reaction was carried out on a 0.1 mmol scale with 2 mol-% of [Rh(cod)
OH]2, 10 mol-% of ligand, and 1 equiv. of base at 708C for 1 h.
BYields correspond to isolated products by column chromatography.
CN.R.: no reaction.
DUsed as 1 M solution in THF.
EThe amount BINAP (2,20-bis(diphenylphosphino)-1,10-binaphthyl) used
Scheme 2. Reaction scope of diazoesters. Unless otherwise noted, the
reaction conditions are the same as those stated in entry 14 of Table 1. Yields
correspond to the products isolated by column chromatography. ATHF
(0.75 mL) and H2O (0.25 mL) were used as the mixed solvent.
was 5 mol-%.
FThe amounts of [Rh(cod)OH]2 and XPhos used were 1 mol-% and 5 mol-%,
respectively .
when the catalyst loading was reduced to 1 mol-%, and the
product could still be isolated in 85 % yield (entry 15). In
addition, when we removed KF from the reaction system, the
reaction yield was only 57 % (entry 16).
to optimize the reaction conditions (Table 1). Using the reaction
conditions of previously reported Hiyama-type coupling,[6] the
two substrates were first heated at 708C for 1 h in the presence of
2 mol-% [Rh(cod)OH]2 (cod ¼ 1,5-cyclooctadiene). However,
none of the target product 3a could be detected through gas
chromatography–mass spectrometry (GC–MS) analysis, and
both starting materials remained unreacted in large quantities
(entry 1). The addition of H2O to the reaction system was found
to slightly promote the reaction (entry 2). We considered that a
suitable base might accelerate the transmetalation of organotin
reagent to rhodium centre and thus promote the coupling
reaction. Then, a series of bases were screened; KF could afford
the target coupling product in 15 % isolated yield (entry 5),
whereas other stronger bases, such as CsF and TBAF (tetra-n-
butylammonium fluoride), were not effective (entries 3 and 4).
Similarly to our previously reported Hiyama-type coupling,[6]
the introduction of electron-rich ligand PCy3 (tricyclohex-
ylphosphine) to the reaction system significantly promoted the
reaction, and the yield could be improved to 41 % (entry 6).
By further screening the ligands, it was found that XPhos
(2-dicyclohexylphosphino-20,40,60-triisopropylbiphenyl) was
superior to PCy3 for the reaction, affording 3a in slightly
improved yields (entries 6–9). Adjusting the ratio of the two
substrates could further improve the yields (entries 10 and 11).
Finally, we found that the amount of H2O was crucial to this
transformation, and the yield was significantly improved by
increasing the amount of H2O (entries 12–14). Thus, the yield
could be improved to 96 % when a 1 : 1 ratio of the THF/H2O
was used as the solution (entry 14). The reaction worked well
With the optimized reaction conditions in hand, we then
inspected the reaction scope of this Stille-type coupling. The
diazoester component was first tested with phenyl trimethyl-
stannane (1a) under the established reaction conditions
(Scheme 2). The variation of the ester moiety on the diazo
compounds has some effects on the transformation (3a–c). For
both methyl and ethyl ester diazo compounds, the reactions are
efficient under the above reaction conditions (3a, 3b). For the
more hydrophobic tert-butyl ester diazo compound, the ratio of
H2O in the solution system should be reduced, and under the
modified conditions, the yield could be improved from 35 % to
88 % (3c). The position and electron property of the substituent
on the aryl diazo esters show marginal influence on this
transformation, and the corresponding products are obtained
in 69–99 % yields (3d–n). It should be noted that the ortho-
substituted diazo compounds work well in this reaction (3k–m),
and this RhI-catalyzed Stille-type coupling is well tolerated with
chloro (3g, 3j, 3m, 3n), bromo (3f), and ketone (3h) functional
groups.
Apart from aryl diazoesters, other types of diazo compounds
were investigated (Scheme 2, 3o–r). For alkyl diazoester, this
reaction is sluggish even under the modified reaction conditions,
and the product 3o was obtained in 31 % yield only. To our
delight, diazomalonates are good substrates for this reaction.
Both symmetric and asymmetric diazomalonates are converted
into the corresponding products (3p–r) in good yields.

Stille-Type Coupling with Diazoesters
1381
[Rh(cod)OH]2 (2 mol-%)
XPhos (10 mol-%)
Ph
accelerates the transmetalation step, probably via tin ate com-
plex formation.[7] Intermediate B then reacts with diazo sub-
strate to give rhodium–carbene species C with extrusion of a
molecule of N2 gas.[13,14] Subsequently, an oxa-p-allyl RhI
intermediate D is generated through migratory insertion of the
rhodium–carbene species.[14] Finally, protonation of the inter-
mediate D affords the coupling product and regenerates the
active rhodium species A, from which water is indispensable for
this transformation.
Ph
ϩ
N2
SnMe3
KF (1 equiv.)
THF/H2O (1:1)
70ЊC, 1 h
R
R
CO2Et
CO2Et
2b
1b–h
4a–g
Ph
CO2Et
Ph
Ph
CO2Et
EtO2C
CO2Et
Me
Br
4a, 79 %
Ph
CO2Et
4d, 72 %
4c, 71 %
4b, 61 %
Ph
CO2Et
Ph
R
Cl
Cl
Conclusions
CO2Et
4g, 58 %
O2N
In summary, we have developed a RhI-catalyzed Stille-type
cross-coupling of diazoester with aryl trimethylstannane. Aryl
organotin reagents are successfully applied in the coupling of
diazoesters under the catalytic action of RhI complex for the
construction of C–C bonds. Rhodium carbene migratory inser-
tion is proposed to be involved in this Stille-type coupling. This
reaction shows good functional group compatibility for both
coupling partners and the yields are generally good for most
examples, thus providing an alternative methodology for the
synthesis of a-aryl esters.[15]
4e, R ϭ OMe, 92 %
4f, R ϭ Me, 65 %
Scheme 3. Reaction scope of aryl trimethylstannane. The reaction condi-
tions are the same as those stated in entry 14 of Table 1. Yields correspond to
the products isolated by column chromatography.
[Rh(cod)OH]2
ligand
CO2Me
Ar
SnMe3
Experimental
Ar
Ph
Ϫ
Rh(OH)L
General Experimental Procedures
F
H2O
RhL
A
All solvents and reagents were purchased from commercial
suppliers and used without further purification. Column chro-
matography was performed on 200–300 mesh silica gal. 1H NMR
spectra were recorded on a Bruker ARX 400 (400 MHz) and
the data are referenced relative to tetramethylsilane (TMS) at
dH 0.00 ppm. The 1H NMR data are reported as follows:
chemical shift (d ppm), multiplicity (s ¼ singlet, d ¼ doublet,
t ¼ triplet, q ¼ quartet, m ¼ multiplet), coupling constant(s)
J (Hz), integration, and assignment. The 13C NMR spectra were
recorded on a Bruker ARX 400 MHz (100 MHz) and are refer-
enced relative to CDCl3 at dC 77.0 ppm. The infrared (IR)
spectra were recorded on a Thermo Electron Corporation
Nicolet AVATAR 300 FT-IR spectrometer; the data are repor-
ted in terms of frequency of absorption (cmꢀ1). Mass spectra
were recorded on a Bruker Apex IV FTMS spectrometer. The
high-resolution mass spectrometry (HRMS) measurements
were performed on a FT-ICR mass analyzer.
Protonation
Transmetalation
L ϭ XPhos
O
Ar
Ar RhL
B
Ph
OMe
D
N2
Migratory
insertion
Carbene
formation
Ph
CO2Me
Ar
N2
RhL
CO2Me
Ph
C
Scheme 4. Proposed reaction mechanism.
General Procedure for RhI-Catalyzed Stille Coupling
Next, the scope of aryl trimethylstannanes was inspected
with reaction of aryl diazoester 1b–h under the optimized
reaction conditions (Scheme 3). Aryl trimethylstannanes bear-
ing electron-rich (to give products 4a, 4e, 4f) and electron-
withdrawing (to give products 4b–d, 4g) groups are all suitable
substrates for this transformation, providing the corresponding
products in 58–92 % yields. Again, halogen substituents are
fully compatible under the current reaction conditions (4b, 4g),
thus affording the possibility for further transformations. Other
sensitive groups, such as ester and nitro moieties, could also
tolerate the reaction conditions (4c, 4d).
A mechanism is proposed for the RhI-catalyzed Stille-type
coupling reaction (Scheme 4). First, the active rhodium species
A is generated through ligand exchange, which then undergoes
base-assisted transmetalation with aryl trimethylstannane with
the aid of base to form aryl rhodium species B.[12] According to
our control experiment (Table 1, entry 16), KF could signifi-
cantly improve the reaction yield. One possibility was that KF
[Rh(cod)OH]2 (0.9 mg, 0.002 mmol, 2 mol-%), XPhos (4.8 mg,
0.01 mmol, 10 mol-%), and KF (5.8 mg, 0.1 mmol) were added
successively to a 10-mL Schlenk tube. The reaction tube was
degassed thrice with nitrogen gas, followed by the addition of
THF (0.5 mL) and deionized water (0.5 mL) using a syringe. The
diazoester substrates (0.1 mmol, 1.0 equiv.) and aryl trimethyl-
stannane (0.12 mmol, 1.2 equiv.) were then added successively
using a syringe. It should be noted that substrates in a solid form
were added to the reaction tube before adding the solvent. The
reaction tube was immediately immersed in an oil bath at 708C
with stirring for 1 h. Upon completion of the reaction, the
reaction mixture was diluted with petroleum ether (3 mL) and
filtered through a short plug of silica gel using petroleum
ether/ethyl acetate (5 : 1, 10 mL) as eluent. The solvent was then
removed under vacuum to leave a crude mixture, which was
purified by silica gel column chromatography to afford the
pure product.

1382
Z. Liu et al.
Methyl 2,2-Diphenylacetate (3a)[6]
Methyl 2-(2-Methoxyphenyl)-2-phenylacetate (3k)
Yield: 21.7 mg, 96 %. Colourless oil. dH (CDCl3, 400 MHz)
7.32–7.24 (m, 10H), 5.03 (s, 1H), 3.74 (s, 3H). dC (CDCl3,
100 MHz) 172.9, 138.6, 128.6, 128.6, 127.2, 57.0, 52.3.
Yield: 19.6 mg, 77 %. Colourless oil. nmax (film)/cmꢀ1 700, 756,
1245, 1730, 2921. dH (CDCl3, 400 MHz) 7.36–7.22 (m, 6H),
7.02 (dd, J 1.4, 7.7, 1H), 6.90–6.87 (m, 2H), 5.31 (s, 1H), 3.82
(s, 3H), 3.72 (s, 3H). dC (CDCl3, 100 MHz) 173.4, 156.7, 137.6,
129.1, 129.0, 128.5, 128.4, 127.6, 127.1, 120.4, 110.3, 55.5,
52.1, 50.7. HRMS (ESI (electrospray ionization) m/z 257.1170;
calcd for C16H17O3 257.1172. HRMS (ESI) m/z 279.0990; calcd
for C16H16NaO3 279.0992.
Ethyl 2,2-Diphenylacetate (3b)[6]
Yield: 22.1 mg, 92 %. Colourless oil. dH (CDCl3, 400 MHz)
7.32–7.23 (m, 10H), 5.01 (s, 1H), 4.20 (d, J 7.1, 2H), 1.24 (d, J
7.1, 3H). dC (CDCl3, 100 MHz) 172.4, 138.7, 128.5, 128.5,
127.2, 61.1, 57.1, 14.1.
Methyl 2-(2-Fluorophenyl)-2-phenylacetate (3l)[6]
tert-Butyl 2,2-Diphenylacetate (3c)[6]
Yield: 20.0 mg, 82 %. Colourless oil. dH (CDCl3, 400 MHz)
7.36–7.21 (m, 7H), 7.10–7.02 (m, 2H), 5.30 (s, 1H), 3.74 (s, 3H).
dC (CDCl3, 100 MHz) 172.3, 162.4 (d, J 246.6), 137.1, 129.9 (d,
J 3.5), 130.0 (d, J 8.2), 128.7, 127.5, 126.2 (d, J 14.2), 124.1 (d, J
3.5), 115.3 (d, J 22.1), 52.4, 49.7 (d, J 3.4).
Yield: 23.6 mg, 88 %. Colourless oil. dH (CDCl3, 400 MHz)
7.30–7.29 (m, 7H), 7.25–7.22 (m, 2H), 4.91 (s, 1H), 1.44 (s, 9H).
dC (CDCl3, 100 MHz) 171.6, 139.2, 128.6, 128.4, 127.0, 81.2,
58.0, 27.9.
Methyl 2-Phenyl-2-(p-tolyl)acetate (3d)[6]
Methyl 2-(2,4-Dichlorophenyl)-2-phenylacetate (3m)[6]
Yield: 18.0 mg, 75 %. Yellow oil. dH (CDCl3, 400 MHz)
7.30–7.24 (m, 5H), 7.19 (d, J 8.0, 2H), 7.12 (d, J 8.0, 2H), 4.99
(s, 1H), 3.72 (s, 3H), 2.31 (s, 3H). dC (CDCl3, 100 MHz) 173.1,
138.8, 136.9, 135.6, 129.3, 128.5, 128.5, 128.4, 127.2, 56.6,
52.2, 21.0.
Yield: 29.2 mg, 99 %. White solid. dH (CDCl3, 400 MHz) 7.40
(d, J 1.5, 1H), 7.37–7.24 (m, 5H), 7.19–7.14 (m, 2H), 5.42
(s, 1H), 3.74 (s, 3H). dC (CDCl3, 100 MHz) 172.0, 136.6,
135.2, 134.8, 133.8, 131.0, 129.3, 128.9, 128.7, 127.7, 127.2,
53.2, 52.6.
Methyl 2-(4-Methoxyphenyl)-2-phenylacetate (3e)[16]
Methyl 2-(3,4-Dichlorophenyl)-2-phenylacetate (3n)[6]
Yield: 21.6 mg, 84 %. Colourless oil. dH (CDCl3, 400 MHz)
7.34–7.22 (m, 7H), 6.89–6.84 (m, 2H), 4.98 (s, 1H), 3.78 (s, 3H),
3.73 (s, 3H). dC (CDCl3, 100 MHz) 173.2, 158.7, 138.9, 130.7,
129.6, 128.6, 128.4, 127.2, 114.0, 56.1, 55.2, 52.3.
Yield: 28.3 mg, 96 %. Colourless oil. dH (CDCl3, 400 MHz)
7.41–7.25 (m, 7H), 7.15 (dd, J 2.1, 8.4, 1H), 4.96 (s, 1H), 3.75
(s, 3H). dC (CDCl3, 100 MHz) 172.1, 138.7, 137.5, 132.6, 131.5,
130.6, 130.4, 128.9, 128.4, 128.0, 127.7, 56.0, 52.5.
Methyl 2-(4-Bromophenyl)-2-phenylacetate (3f)[6]
Benzyl 2-Phenylpropanoate (3o)[6]
Yield: 25.6 mg, 84 %. Colourless oil. dH (CDCl3, 400 MHz) 7.43
(d, J 8.5, 2H), 7.32–7.26 (m, 5H), 7.18 (d, J 8.5, 2H), 4.98
(s, 1H), 3.74 (s, 3H). dC (CDCl3, 100 MHz) 172.5, 138.0, 137.6,
131.7, 130.3, 128.7, 128.4, 127.5, 121.4, 56.3, 52.4.
Yield: 7.4 mg, 31 %. Colourless oil. dH (CDCl3, 400 MHz)
7.31–7.22 (m, 10H), 5.10 (AB quart, J 12.5, 2H), 3.77 (q, J 7.2,
1H), 1.52 (d, J 7.2, 3H). dC (CDCl3, 100 MHz) 174.3, 140.4,
136.0, 128.6, 128.4, 128.0, 127.8, 127.5, 127.1, 66.4, 45.5, 18.4.
Methyl 2-(4-Chlorophenyl)-2-phenylacetate (3g)[4]
Diethyl 2-Phenylmalonate (3p)[6]
Yield: 19.7 mg, 76 %. Colourless oil. dH (CDCl3, 400 MHz)
7.35–7.23 (m, 8H), 5.00 (s, 1H), 3.75 (s, 3H). dC (CDCl3,
100 MHz) 172.6, 138.1, 137.1, 133.2, 130.0, 128.7, 128.7,
128.4, 127.5, 56.3, 52.4.
Yield: 17.9 mg, 76 %. Colourless oil. dH (CDCl3, 400 MHz)
7.42–7.33 (m, 5H), 4.61 (s, 1H), 4.26–4.17 (m, 4H), 1.26 (t, J
7.1, 6H). dC (CDCl3, 100 MHz) 168.1, 132.8, 129.2, 128.6,
128.2, 61.8, 57.9, 14.0.
Ethyl 2-(4-Acetylphenyl)-2-phenylacetate (3h)[6]
Diisopropyl 2-Phenylmalonate (3q)[6]
Yield: 19.5 mg, 69 %. Yellow oil. dH (CDCl3, 400 MHz)
7.93–7.90 (m, 2H), 7.42 (d, J 8.2, 2H), 7.34–7.28 (m, 5H),
5.06 (s, 1H), 4.22 (d, J 7.1, 2H), 2.58 (s, 3H), 1.26 (d, J 7.1, 3H).
dC (CDCl3, 100 MHz) 197.6, 171.8, 144.0, 137.9, 136.0, 128.8,
128.7, 128.6, 128.5, 127.5, 61.4, 57.0, 26.6, 14.1.
Yield: 22.0 mg, 83 %. Colourless oil. dH (CDCl3, 400 MHz)
7.41–7.30 (m, 5H), 5.11–5.02 (m, 2H), 4.54 (s, 1H), 1.27–1.22
(m, 12H). dC (CDCl3, 100 MHz) 167.7, 133.0, 129.3, 128.5,
128.0, 69.3, 58.4, 21.5.
Methyl 2-(3-Methoxyphenyl)-2-phenylacetate (3i)[6]
1-tert-Butyl 3-Methyl 2-Phenylmalonate (3r)[6]
Yield: 23.8 mg, 93 %. Yellow oil. dH (CDCl3, 400 MHz)
7.32–7.23 (m, 6H), 6.90–6.86 (m, 2H), 6.81–6.79 (m, 1H), 5.00
(s, 1H), 3.76 (s, 3H), 3.74 (s, 3H). dC (CDCl3, 100 MHz) 172.8,
159.7, 140.0, 138.4, 129.5, 128.6, 128.5, 127.3, 120.9, 114.6,
112.5, 56.9, 55.2, 52.3.
Yield: 20.0 mg, 80 %. Colourless oil. dH (CDCl3, 400 MHz)
7.40–7.32 (m, 5H), 4.55 (s, 1H), 3.75 (s, 3H), 1.45 (s, 9H). dC
(CDCl3, 100 MHz) 169.0, 167.1, 133.1, 129.2, 128.5, 128.0,
82.4, 58.8, 52.6, 27.8.
Methyl 2-(3-Chlorophenyl)-2-phenylacetate (3j)[6]
Ethyl 2-Phenyl-2-(p-tolyl)acetate (4a)[17]
Yield: 22.1 mg, 85 %. Colourless oil. dH (CDCl3, 400 MHz)
7.34–7.18 (m, 9H), 4.99 (s, 1H), 3.75 (s, 3H). dC (CDCl3,
100 MHz) 172.4, 140.5, 137.9, 134.4, 129.8, 128.8, 128.5,
127.5, 127.5, 126.8, 56.6, 52.4.
Yield: 20.1 mg, 79 %. Yellow oil. dH (CDCl3, 400 MHz)
7.31–7.11 (m, 9H), 4.97 (s, 1H), 4.20 (d, J 7.1, 2H), 2.32 (s, 3H),
1.25 (t, J 7.1, 3H). dC (CDCl3, 100 MHz) 172.6, 138.9, 136.8,
135.7, 129.2, 128.5, 128.4, 127.0, 61.1, 56.7, 21.0, 14.1.

Stille-Type Coupling with Diazoesters
1383
Ethyl 2-(4-Bromophenyl)-2-phenylacetate (4b)
Acknowledgements
Yield: 19.4 mg, 61 %. White solid. nmax (film)/cmꢀ1 699, 1011,
1151, 1191, 1734. dH (CDCl3, 400 MHz) 7.45–7.18 (m, 9H),
4.95 (s, 1H), 4.20 (d, J 7.1, 2H), 1.25 (t, J 7.1, 3H). dC (CDCl3,
100 MHz) 172.0, 138.2, 137.7, 131.6, 130.3, 128.6, 128.4,
127.4, 121.3, 61.3, 56.4, 14.0. HRMS (ESI) m/z 319.0330; calcd
for C16H16BrO2 319.0328. HRMS (ESI) m/z 341.0150; calcd for
C16H15BrNaO2 341.0148.
The project is supported by the National Basic Research Program of China
(973 Program, No. 2012CB821600) and the Natural Science Foundation of
China (Grant Nos 21472004 and 21332002).
References
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1106, 1153, 1277, 1720. dH (CDCl3, 400 MHz) 8.01–7.99
(m, 2H), 7.40–7.27 (m, 7H), 5.06 (s, 1H), 4.36 (d, J 7.1, 2H), 4.22
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Yield: 20.4 mg, 72 %. Yellow oil. nmax (film)/cmꢀ1 703, 1153,
1348, 1521, 1734. dH (CDCl3, 400 MHz) 8.18–8.16 (m, 2H),
7.51–7.49 (m, 2H), 7.38–7.29 (m, 5H), 5.10 (s, 1H), 4.24 (d,
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7.32–7.21 (m, 6H), 6.91–6.87 (m, 2H), 6.81–6.78 (m, 1H), 4.98
(s, 1H), 4.20 (d, J 7.1, 2H), 3.76 (s, 3H), 1.25 (t, J 7.1, 3H). dC
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Ethyl 2-Phenyl-2-(m-tolyl)acetate (4f)
Yield: 16.6 mg, 65 %. Colourless oil. nmax (film)/cmꢀ1 700,
1028, 1147, 1735, 2921. dH (CDCl3, 400 MHz) 7.32–7.19 (m,
6H), 7.13–7.06 (m, 3H), 4.97 (s, 1H), 4.20 (d, J 7.1, 2H), 2.32 (s,
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C17H19O2 255.1380. HRMS (ESI) m/z 277.1197; calcd for
C17H18NaO2 277.1199.
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Yield: 17.9 mg, 58 %. Colourless oil. nmax (film)/cmꢀ1 699,
1011, 1151, 1191, 1734. dH (CDCl3, 400 MHz) 7.42–7.27 (m,
7H), 7.16 (dd, J 2.1, 8.3, 1H), 4.94 (s, 1H), 4.21 (d, J 7.1, 2H),
1.25 (t, J 7.1, 3H). dC (CDCl3, 100 MHz) 171.6, 138.8, 137.6,
132.5, 131.4, 130.6, 130.4, 128.8, 128.3, 128.0, 127.6, 61.5,
56.0. HRMS (ESI) m/z 309.0443; calcd for C16H15Cl2O2
309.0444. HRMS (ESI) m/z 331.0263; calcd for
C16H14Cl2NaO2 331.0263.
Supplementary Material
1
Copies of H and 13C NMR spectra for all new products are
available on the Journal’s website.

1384
Z. Liu et al.
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