Monooxychlorophosphine as a novel and efficient ligand for palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl chlorides

Article abstract of DOI:10.1055/s-2007-985567

A new sterically hindered monooxychlorophosphine was synthesized and the complex generated in situ from its reaction with Pd₂(dba)₃ promoted the Suzuki-Miyaura reactions of arylboronic acids with aryl chlorides in good yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-985567

LETTER
2247
Monooxychlorophosphine as a Novel and Efficient Ligand for Palladium-
Catalyzed Suzuki–Miyaura Cross-Coupling of Aryl Chlorides
M
onooxychlorophosphi
e
ne
a
s
a
N
ov
n
el and
E
ffici
p
e
nt Ligand eng Mai, Guanghua Lv, Lianxun Gao*
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Graduate School of Chinese Academy of Sciences, Changchun 130022, P. R. of China
Fax +86(431)85685653; E-mail: lxgao@ciac.jl.cn
Received 16 May 2007
Suzuki reactions and Buchwald–Hartwig amination.9
Abstract: A new sterically hindered monooxychlorophosphine was
Wolf also reported Stille cross-coupling reactions using
synthesized and the complex generated in situ from its reaction with
Pd2(dba)3 promoted the Suzuki–Miyaura reactions of arylboronic
PXPd (X = Cl) as the catalyst.10 Although chloro-
phosphine compounds are comparatively unstable in
moist air, they possess higher activities because oxidative
addition of chlorophosphine to low-valent palladium
species could give a phosphenium cation,9 which is
isolobal to N-heterocyclic singlet carbenes.11
acids with aryl chlorides in good yields.
Key words: Suzuki reaction, monooxychlorophosphine, aryl chlo-
rides
Herein, we wish to report a new, comparatively air-stable
monooxychlorophosphine 1 as a novel and efficient
ligand for palladium-catalyzed Suzuki reactions of aryl
chlorides as part of our continuous work in cross-coupling
reactions.12 As shown in Scheme 1, through path A, we
obtained monooxydichlorophosphine 213 in 70% yield
and then obtained 114 as a white solid in 83% yield
through path C. It was interesting that proleptic com-
pounds 3 or 4 were not generated under the reaction con-
ditions and only the unexpected compound 1 was formed.
We speculated that both path B and path D were not viable
because of the steric bulkiness around the P center of
compound 1. Compound 1 is very stable and can be stored
in a desiccator for up to two months without any notable
hydrolysis.
The Suzuki–Miyaura cross-coupling reaction is an ex-
tremely powerful and widely utilized method for the con-
struction of C–C bonds.1 The reaction has been applied to
many areas,2 including natural product synthesis.3 Some
of the recent progress in this reaction has been focused on
the use of aryl chlorides as substrates due to their low cost
and easily availability.4 It has been well recognized that
the properties of ligands have significant impact on the
outcome of the coupling reaction.5 Buchwald,6 Fu7 and
Beller8 have demonstrated that palladium complexes
derived from electron-rich and bulky phosphines such as
P(t-Bu)3, dialkyl biphenylphosphines and dialkyl hetero-
aromatic phosphines are very efficient catalytic systems
in Suzuki coupling with unactivated aryl chlorides.
Recently, Ackermann and co-workers reported a diamino-
chlorophosphine as a new and highly efficient ligand in
a
b
O
P(Cl)2
OH
O P
path A
path B
2
3
path C
b
c
O
P
O
P
O
H
path D
Cl
1
4
(stable white solid)
Scheme 1 Reagents and conditions: (a) PCl3, Et3N, toluene, 0–100 °C, 70%; (b) t-BuMgCl (2.5 equiv), Et2O, r.t.–reflux, 83%.; (c) washed
with aq NaHCO3 solution.
SYNLETT 2007, No. 14, pp 2247–2251
0
3
.0
9
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0
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Advanced online publication: 13.08.2007
DOI: 10.1055/s-2007-985567; Art ID: W09607ST
© Georg Thieme Verlag Stuttgart · New York

2248
W. Mai et al.
LETTER
Table 1 Screening of Reaction Conditionsa
gave the coupling product in high yield (92%) in THF
(Table 1, entry 6). The reason that t-BuOK was the best
choice as base for the coupling reaction may be that it
could react with 1 to form a new and sterically more
hindered dioxyphosphine ligand in situ.9
Pd2(dba)3/1 (1:2)
B(OH)2
Cl +
base, solvent
65 °C, 8 h
5a
6a
7
Entry
Pd (mol%) Base
Solvent
Yield (%)b
On the basis of the optimized reaction conditions, the
coupling reactions between a variety of aryl chlorides and
several arylboronic acids were carried out and the results
are summarized in Table 2. Under standard conditions
[THF as solvent, t-BuOK as base, and with Pd2(dba)3/1
(1:2, 1 mol%) as catalyst] various aryl chlorides 5a–j were
coupled with several arylboronic acids 6a–c in moderate
to high yields (66–93%).15 For electron-rich aryl chlo-
rides, the corresponding biaryl products were obtained in
moderate to good yields (Table 2, entries 3, 4, 9 and 10).
On the other hand, higher yields were obtained for the bi-
aryl products obtained from the electron-deficient aryl
chlorides (Table 2, entries 5, 6, 8 and 11). The hetero-
cyclic chloride 3-chloropyridine (5g) was likewise con-
verted efficiently into the biaryl products with arylboronic
acids 6a and 6b in 92% and 92% yields, respectively
(Table 2, entries 7 and 12). It is worth noting that the new
catalytic system is tolerant to some sensitive functional
groups, such as COMe, CHO and CN without needing any
protection (Table 2, entries 5, 6, 8, 11 and 13). But for
ortho substituents on the aromatic rings, the yields of the
coupling products were slightly lower under our condi-
tions. For example, 2-chlorotoluene (5b) with phenyl-
boronic acid (6a) gave 8 in 70% yield (Table 2, entry 2)
and the more activated 4-chloroacetophenone (5e) with 2-
methoxyphenylboronic acid (6c) gave 19 in 66% yield
(Table 2, entry 13). Unfortunately, more hindered biaryl
product was not obtained when 5b reacted with 6c in
the new catalytic system under our conditions (Table 2,
entry 14).
1
2
3
4
5
6
7
8
9c
1
2
1
2
1
2
1
2
2
K2CO3
THF
47
K2CO3
K2CO3
K2CO3
t-BuOK
t-BuOK
Cs2CO3
Cs2CO3
t-BuOK
THF
55
i-PrOH
i-PrOH
THF
68
69
83
THF
92
THF
72
THF
77
THF
none
a Reaction conditions: Pd2(dba)3/1 (1:2), chlorobenzene (1.5 mmol),
phenylboronic acid (1.7 mmol), base (3 mmol), solvent (5 mL), 65 °C,
8 h.
b Isolated yield.
c Prepared without 1.
To evaluate the effectiveness of Pd2(dba)3/1 in the Suzuki
coupling, we first tested the reaction between chloroben-
zene (5a) and phenylboronic acid (6a) to explore the opti-
mal reaction conditions (Table 1). Moderate to high yields
were observed for the coupling reaction when 1 was used
as the ligand under mild conditions. Pd loadings, base,
ligand and solvent played very important roles in deter-
mining the catalytic activity. In the absence of 1, no
product was observed (Table 1, entry 9). When mild bases
such as K2CO3 and Cs2CO3 were used, the product yield
was slightly low (Table 1, entries 1–4, 7 and 8). The
strong base t-BuOK was the most effective choice and
Table 2 Pd-Catalyzed Suzuki–Miyaura Coupling of Aryl Chloridesa
Pd2(dba)3 (1)
Cl
+
B(OH)2
THF, t-BuOK, 65 °C
R
R'
R'
R
Entry
RArCl
R¢ArB(OH)2
Products
Yield (%)b
92
Cl
B(OH)2
1
2
6a
6a
5a
5b
5c
7
8
Cl
Cl
70
85
3
6a
9
Synlett 2007, No. 14, 2247–2251 © Thieme Stuttgart · New York

LETTER
Monooxychlorophosphine as a Novel and Efficient Ligand
2249
Table 2 Pd-Catalyzed Suzuki–Miyaura Coupling of Aryl Chloridesa (continued)
Pd2(dba)3 (1)
Cl
+
B(OH)2
THF, t-BuOK, 65 °C
R
R'
R'
R
Entry
RArCl
R¢ArB(OH)2
Products
Yield (%)b
Cl
B(OH)2
4
5
86
93
90
92
91
79
75
92
92
5d
O
6b
6b
10
O
Cl
Cl
5e
NC
5f
11
NC
12
6
6b
6b
6a
6a
6a
6a
6a
Cl
7
N
N
5g
13
OHC
5h
Cl
OHC
14
8
MeO
5i
Cl
MeO
15
9
Cl
10
11
12
16
5j
O
5e
17
5g
5e
N
18
O
B(OH)2
OMe
13
66
MeO
6c
6c
19
MeO
14c
5b
trace
20
a Reaction conditions: Pd2(dba)3/1 (1:2), aryl chlorides (1.5 mmol), arylboronic acid (1.7 mmol), base (3 mmol), THF (5 mL), 65 °C, 8 h.
b Isolated yield.
c Reaction time was 18 h.
In summary, we have synthesized a new and efficient
monooxychlorophosphine with interesting properties as a
ligand for Suzuki reactions of aryl chlorides. A variety of
aryl chlorides including electron-deficient and electron-
rich chlorides were coupled with arylboronic acids in
short reaction times under mild conditions. The detailed
study of the properties and potential of the ligand is in
progress in our laboratory.
References and Notes
(1) Selected recent reviews: (a) Miyaura, N. Top. Curr. Chem.
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2002, 58, 9633. (c) Bellina, F.; Carpita, A.; Rossi, R.
Synthesis 2004, 2419. (d) Hassan, J.; Sevignon, M.; Gozzi,
C.; Schulz, E.; Lemaire, M. Chem. Rev. 2002, 102, 1359.
(e) Corbet, J.-P.; Mignani, G. Chem. Rev. 2006, 106, 2651.
Synlett 2007, No. 14, 2247–2251 © Thieme Stuttgart · New York

2250
W. Mai et al.
LETTER
To a flame-dried three-necked flask equipped with an
(2) (a) Wang, W.; Xiong, C.; Yang, J.; Hruby, V. J. Tetrahedron
Lett. 2001, 42, 7717. (b) Vaz, B.; Rosana, R.; Nieto, M.;
Paniello, A. I.; de Lera, A. R. Tetrahedron Lett. 2001, 42,
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66, 7125. (d) Wong, K.-T.; Huang, T. S.; Lin, Y.; Wu, C.-C.;
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T.; Daimon, A.; Uemura, M. Tetrahedron 2000, 56, 2325.
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Am. Chem. Soc. 2003, 125, 2856. (c) Zapf, A.; Beller, M.
Chem. Commun. 2005, 431. (d) Liu, D.; Gao, W.; Dai, Q.;
Zhang, X. Org. Lett. 2005, 7, 4907. (e) Dai, Q.; Gao, W.;
Liu, D.; Kapes, L. M.; Zhang, X. J. Org. Chem. 2006, 71,
3928. (f) Li, G. Y. Angew. Chem. Int. Ed. 2001, 40, 1513.
(g) Billingsley, K.; Buchwald, S. L. J. Am. Chem. Soc. 2007,
129, 3358. (h) Botella, L.; Nájera, C. Angew. Chem. Int. Ed.
2002, 41, 179. (i) Ohta, H.; Tokunaga, M.; Obora, Y.; Iwai,
T.; Iwasawa, T.; Fujihara, T.; Tsuji, Y. Org. Lett. 2007, 9,
89. (j) Gong, J. F.; Liu, G. Y.; Du, C. X.; Zhu, Y.; Wu, Y. J.
J. Organomet. Chem. 2005, 690, 3963.
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Chem. Int. Ed. 2004, 43, 2201. (c) Littke, A. F.; Fu, G. C.
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Soc. 1998, 120, 9722. (b) Wolfe, J. P.; Buchwald, S. L.
Angew. Chem. Int. Ed. 1999, 38, 2413. (c) Yin, J.; Rainka,
M. P.; Zhang, X. X.; Buchwald, S. L. J. Am. Chem. Soc.
2002, 124, 1162. (d) Barder, T. E.; Walker, S. D.; Martinelli,
J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 4685.
(e) Wolfe, J. P.; Singer, R. A.; Yang, B. H.; Buchwald, S. L.
J. Am. Chem. Soc. 1999, 121, 9550.
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3387. (b) Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem. Soc.
2000, 122, 4020. (c) Netherton, M. R.; Dai, C.; Neuschütz,
K.; Fu, G. C. J. Am. Chem. Soc. 2001, 123, 10099.
(d) Kirchhoff, J. H.; Netherton, M. R.; Hills, I. D.; Fu, G. C.
J. Am. Chem. Soc. 2002, 124, 13662. (e) Zhou, J.; Fu, G. C.
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1282.
(8) (a) Zapf, A.; Jackstell, R.; Rataboul, F.; Reirmeier, T.;
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Rataboul, F.; Zapf, A.; Fuhrmann, C.; Riermeier, T.;
Monsees, A.; Beller, M. Adv. Synth. Catal. 2004, 346, 1742.
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Althammer, A. Angew. Chem. Int. Ed. 2006, 45, 7627.
(b) Ackermann, L.; Born, R. Angew. Chem. Int. Ed. 2005,
44, 2444.
addition funnel were added anhyd Et3N (27 mL, 200 mmol),
freshly distilled PCl3 (26 mL, 300 mmol) and anhyd toluene
(200 mL). 2,6-Di-tert-butyl-4-methylphenol (22 g, 100
mmol) dissolved in anhyd toluene (100 mL) was transferred
into an addition funnel and was added dropwise to the
solution of PCl3 at 0 °C within one hour. The reaction
mixture was stirred for 2 h at r.t. and then for 8 h at 100 °C,
after which time the Et3N·HCl precipitate was isolated by
filtration over a celite frit and washed with toluene (3 × 50
mL). The solvent was removed under reduced pressure, and
the residual mixture was distilled at 120 °C/0.1 Torr giving
2 as a colorless liquid (70%). 1H NMR (600 MHz, CDCl3):
d = 1.46 (s, 18 H), 2.30 (s, 3 H), 7.10 (s, 2 H). 31P NMR
(242.9 MHz, CDCl3): d = 201.9 (s). Anal. Calcd for
C15H23OPCl2: C, 56.09; H, 7.22; P, 9.64. Found: C, 56.02; H,
7.06; P, 9.10
(14) Synthesis of (2,6-t-Bu2-4-MeC6H2O)P(Cl)t-Bu (1):
To a flame-dried two-necked flask equipped with an
addition funnel were added 2 (1.6 g, 5 mmol) and anhyd
Et2O (50 mL) at 0 °C. t-BuMgCl [7.4 mL (1.7 M/L in THF
solution), 12.5 mmol] was transferred into an addition funnel
and was added dropwise to the stirred solution within 0.5 h.
The ice bath was removed and the stirring was continued at
r.t. for 20 h and then the mixture was refluxed for 2 h. The
solvent was removed under reduced pressure and the
residual mixture was extracted with Et2O, washed with aq
NaHCO3 (3 × 30 mL) and dried over Na2SO4. The solution
was filtered and Et2O was removed and then the residue was
recrystallized from absolute ethanol to give 1 as a white solid
(83%). 1H NMR (600 MHz, CDCl3): d = 1.32 (d, J = 12 Hz,
9 H), 1.43 (s, 18 H), 2.27 (s, 3 H), 7.03 (s, 2 H). 31P NMR
(242.9 MHz, CDCl3): d = 217.2 (s). Anal. Calcd for
C19H32OPCl: C, 66.55; H, 9.41. Found: C, 66.31; H, 8.72.
GC–MS: m/z = 342 [M+].
(15) General Procedure for the Suzuki Reaction:
A mixture of aryl chlorides 5a–j (1.5 mmol), arylboronic
acid 6a–c (1.7 mmol), Pd2(dba)3 (0.0075 mmol), 1 (0.015
mmol), t-BuOK (3 mmol), and THF (5 mL) was added to a
flask and stirred at 65 °C under N2 for the desired time until
complete consumption of the starting substrates was
observed (as judged by TLC). The solvent was removed
under reduced pressure, and the residue was purified by flash
column chromatography (PE–EtOAc) to afford the desired
coupled products.
Compound 7:4a 1H NMR (400 MHz, CDCl3): d = 7.61 (d,
J = 8.0 Hz, 4 H), 7.44 (t, J = 7.2 Hz, 4 H), 7.34 (tt, J = 7.2
Hz, J¢ = 1.2 Hz, 2 H). 13C NMR (150 MHz, CDCl3): d =
141.2, 128.7, 127.2, 127.1.
Compound 8:9b 1H NMR (600 MHz, CDCl3): d = 7.39 (t, J =
7.2 Hz, 2 H), 7.32 (t, J = 7.2 Hz, 3 H), 7.22–7.25 (m, 4 H),
2.26 (s, 3 H). 13C NMR (150 MHz, CDCl3): d = 141.9, 135.2,
130.2, 129.7, 129.1, 128.0, 127.2, 126.7, 125.7, 20.4.
Compound 9:9b 1H NMR (600 MHz, CDCl3): d = 7.58 (d,
J = 7.2 Hz, 2 H), 7.38–7.44 (m, 4 H), 7.34 (t, J = 7.2 Hz,
2 H), 7.17 (d, J = 7.8 Hz, 1 H), 2.42 (s, 3 H). 13C NMR
(150 MHz, CDCl3): d = 141.3, 141.2, 138.2, 128.6, 127.9,
127.1, 124.2, 21.5.
Compound 10:16a 1H NMR (400 MHz, CDCl3): d = 7.48 (d,
(10) Lerebours, R.; Soto, A. C.; Wolf, C. J. Org. Chem. 2005, 70,
8601.
(11) (a) Gudat, D. Coord. Chem. Rev. 1997, 163, 71.
(b) Nakazawa, H. Adv. Organomet. Chem. 2004, 50, 107.
(12) Mai, W. P.; Gao, L. X. Synlett 2006, 2553.
J = 8.0 Hz, 4 H), 7.24 (d, J = 8.0 Hz, 4 H), 2.39 (s, 6 H). 13
NMR (150 MHz, CDCl3): d = 138.2, 136.6, 129.4, 126.8,
21.1.
C
Compound 11:16b 1H NMR (300 MHz, CDCl3): d = 8.07 (d,
J = 6.6 Hz, 2 H), 7.72 (d, J = 6.6 Hz, 2 H), 7.58 (d, J = 6.0
Hz, 2 H), 7.33 (d, J = 9.0 Hz, 2 H), 2.67 (s, 3 H), 2.45 (s, 3
H). 13C NMR (150 MHz, CDCl3): d = 197.7, 145.7, 138.2,
137.0, 135.6, 129.6, 128.9, 127.1, 126.9, 26.6, 21.1.
(13) Heinrich, L.; Michael, L.; Laszlo, Z. J. Organomet. Chem.
1990, 386, 349.
Synthesis of (2,6-t-Bu2-4-MeC6H2O)PCl2 (2):
Synlett 2007, No. 14, 2247–2251 © Thieme Stuttgart · New York

LETTER
Monooxychlorophosphine as a Novel and Efficient Ligand
2251
Compound 12:16c 1H NMR (600 MHz, CDCl3): d = 7.71 (dd,
Compound 17:6e 1H NMR (400 MHz, CDCl3): d = 8.05 (d,
J = 8.4 Hz, 2 H), 7.70 (d, J = 8.4 Hz, 2 H), 7.64 (d, J = 7.2
Hz, 2 H), 7.48 (t, J = 7.2 Hz, 2 H), 7.40 (t, J = 7.2 Hz, 1 H),
2.64 (s, 3 H). 13C NMR (150 MHz, CDCl3): d = 197.7, 145.8,
139.9, 135.8, 128.94, 128.9, 128.2, 127.26, 127.21, 26.7.
Compound 18:7f,9b 1H NMR (400 MHz, CDCl3): d = 8.86 (d,
J = 0.8 Hz, 1 H), 8.60 (d, J = 4.8 Hz, 1 H), 7.88 (dt, J = 8.0
Hz, J¢ = 2.0 Hz, 1 H), 7.59 (d, J = 7.2 Hz, 2 H), 7.48 (t, J =
7.2 Hz, 2 H), 7.42 (d, J = 7.2 Hz, 1 H), 7.34–7.36 (m, 1 H).
13C NMR (150 MHz, CDCl3): d = 148.4, 148.22, 137.7,
136.6, 134.3, 129.0, 128.0, 127.0, 123.5.
J = 8.4 Hz, J¢ = 16.2 Hz, 4 H), 7.5 (d, J = 8.4 Hz, 2 H), 7.29
(d, J = 8.4 Hz, 2 H), 2.41 (s, 3 H). 13C NMR (150 MHz,
CDCl3): d = 145.6, 138.7, 136.3, 132.5, 129.8, 127.4, 127.0,
119.0, 110.5, 21.1.
Compound 13:16d 1H NMR (400 MHz, CDCl3): d = 8.84 (d,
J = 2.0 Hz, 1 H), 8.57 (d, J = 3.6 Hz, 1 H), 7.87 (dt, J = 8.0
Hz, J¢ = 2.0 Hz, 1 H), 7.49 (d, J = 8.0 Hz, 2 H), 7.37 (dd, J =
4.8 Hz, J¢ = 3.2 Hz, 1 H), 7.30 (d, J = 8.0 Hz, 2 H), 2.41 (s,
3 H). 13C NMR (150 MHz, CDCl3): d = 148.1, 148.0, 138.0,
136.6, 134.8, 134.2, 129.8, 126.9, 123.5, 21.1.
Compound 14:16b 1H NMR (400 MHz, CDCl3): d = 10.1 (s,
1 H), 7.97 (d, J = 8.4 Hz, 2 H), 7.77 (d, J = 8.4 Hz, 2 H), 7.65
(d, J = 7.2 Hz, 2 H), 7.50 (t, J = 7.2 Hz, 2 H), 7.40–7.43 (m,
1 H). 13C NMR (150 MHz, CDCl3): d = 191.9, 147.1, 139.7,
135.1, 130.2, 129.0, 128.4, 127.6, 127.3.
Compound 19:16f 1H NMR (400 MHz, CDCl3): d = 8.01 (d,
J = 8.0 Hz, 2 H), 7.64 (d, J = 8.0 Hz, 2 H), 7.32–7.39 (m, 2
H), 7.00–7.07 (m, 2 H), 3.85 (s, 3 H), 2.63 (s, 3 H). 13C NMR
(150 MHz, CDCl3): d = 197.8, 156.4, 143.6, 135.5, 130.7,
129.7, 129.4, 128.0, 120.9, 111.3, 55.5, 26.6.
Compound 15:4a,9b 1H NMR (400 MHz, CDCl3): d = 7.54 (t,
J = 8.0 Hz, 4 H), 7.41 (t, J = 7.6 Hz, 2 H), 7.30 (t, J = 7.2 Hz,
(16) (a) Tang, Z. Y.; Hu, Q. S. J. Am. Chem. Soc. 2004, 126,
3058. (b) Zeng, F. L.; Yu, Z. K. J. Org. Chem. 2006, 71,
5274. (c) Nishimura, M.; Ueda, M.; Miyaura, N.
1 H), 6.99 (dt, J = 8.8 Hz, J¢ = 2.0 Hz, 2 H), 3.85 (s, 3 H). 13
NMR (150 MHz, CDCl3): d = 159.1, 140.8, 133.8, 128.7,
128.1, 126.7, 126.6, 114.2, 55.3.
C
Tetrahedron 2002, 58, 5779. (d) Iwasawa, T.; Ajami, D.;
Rebek, J. Jr. Org. Lett. 2006, 8, 2925. (e) Mino, T.; Shirae,
Y.; Sakamoto, M.; Fujita, T. J. Org. Chem. 2005, 70, 2191.
(f) McNulty, J.; Capretta, A.; Wilson, J.; Dyck, J.; Adjabeng,
G.; Robertson, A. Chem. Commun. 2002, 1986.
Compound 16:16e 1H NMR (300 MHz, CDCl3): d = 7.72 (t,
J = 7.2 Hz, 8 H), 7.52 (t, J = 7.2 Hz, 4 H), 7.47 (t, J = 7.2 Hz,
2 H). 13C NMR (150 MHz, CDCl3): d = 140.7, 140.1, 128.8,
127.5, 127.3, 127.0.
Synlett 2007, No. 14, 2247–2251 © Thieme Stuttgart · New York

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