Efficient one-pot synthesis of unsymmetrical gold(I) N-heterocyclic carbene complexes and their use as catalysts

Article abstract of DOI:10.1021/om2008919

Eleven different gold(I) complexes of new NHC ligands were prepared in excellent yield, demonstrating the versatility of the new route to NHC complexes. While the influence of electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly.

Full text of DOI:10.1021/om2008919

Article
pubs.acs.org/Organometallics
Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic
Carbene Complexes and Their Use as Catalysts
A. Stephen K. Hashmi,* Yang Yu, and Frank Rominger
Ruprecht-Karls-Universitat Heidelberg, Organisch-Chemisches Institut, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: Eleven different gold(I) complexes of new NHC
ligands were prepared in excellent yield, demonstrating the versatility
of the new route to NHC complexes. While the influence of electro-
nically different ligands on the synthesis of the catalysts was small, the
catalytic activities of the products differed significantly.
Scheme 1. Synthesis of the Gold(I) Aryl Isocyanide
Complexes 3
INTRODUCTION
■
NHC ligands have become a very important class of ligands for
transition metals, which, beyond other applications,1 is also true
for catalysis research.2 The use of NHC ligands in gold catalysis
has also been very successful,3 which includes the isolation of
important intermediates as alkene complexes4 and vinyl-,5a hetaryl-,5b
and alkylgold5c intermediates as well as elusive species such as gold
hydride6 and gold carbonyl complexes.7
In most cases the synthesis of a noncommercial NHC ligand
is troublesome and, in particular, for unsymmetrical or
structurally complex derivatives might be a multistep synthesis.
This makes the synthesis of a library of NHC complexes, for
example for a screening of catalytic activity, quite troublesome.
Thus, template syntheses, which allow the direct formation
of an NHC ligand directly on the metal center, have been
developed.8 Recently, we presented a very simple one-step
synthesis for gold(I) catalysts,9 which in addition used a
disconnection so far not covered by the preceding literature on
template synthesis for other metals and also allowed a one-step
access to NHOC (N-heterocyclic oxo-carbene) ligands.10 We
also could extend this method to the preparation of palladium
and platinum NHC complexes.9−11
corresponding NHC complex.9 Especially with the donor groups
in ortho positions of the aryl moieties (Table 1, entries 1−4) in
the isocyanide, the reaction had not been tried previously. The
influence of the ortho donor groups is still reflected by the yields;
we had to use 3 equiv of the amine. While the gold(I) complex 3a
with the 2-methoxy group then gave an excellent yield of 95% of
5a under these conditions (entry 1) and with the 2,4-dimethoxy
compound 3b even 97% of 5b was isolated (entry 2), the 2,
6-dimethoxy compound 3c provided only 80% of 5c (entry 3).
Only one fluoro substituent in 3d again gave an excellent yield of
98% of 5d (entry 4). A nitro group is an even stronger acceptor
than a fluoro substituent; entry 5 shows that now even 99% of
the NHC gold(I) complex 5e was isolated. The effect of two
methyl donors in substrate 3f once more is a reduced yield of 5f
(70%, entry 6).
Here we report our findings on further exploration of the
scope of that method for the preparation of gold(I) NHC com-
plexes with donor- or acceptor-substituted phenyl groups and
screening of their catalytic activity.
RESULTS AND DISCUSSION
■
The synthesis of the isocyanides followed the route shown in
Scheme 1. The formamides 1 were obtained by condensation of
the corresponding anilines and ethyl formate. A subsequent
dehydration with phosphoryl chloride and triethylamine pro-
vided the isocyanides 2. From these and (tht)gold(I) chloride
(tht = tetrahydrothiophene), the chlorogold(I) complexes 3
could be easily formed.
Another very bulky substituent is the adamantyl group, which
also gave a similarly reduced yield (74%, entry 7). The 1-naphthyl
In order to fully characterize the new isocyanide complexes,
we followed a stepwise strategy rather than a one-pot procedure
involving the in situ formation of the isocyanide complexes and
their direct reaction with chloroethylammonium salt to give the
Received: October 7, 2011
Published: January 25, 2012
© 2012 American Chemical Society
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reaction is more delicate. While with the aryl substituents
1-naphthyl and 2-methoxyphenyl the carbene compleses 5j,k
were obtained in decent yields (entries 10 and 11), the alkyl
substituents adamantyl and cyclohexyl could not be converted
to products of type 5; only an unspecific decomposition of the
starting material was observed (entries 12 and 13).
Table 1. Synthesis of Unsymmetrically Substituted Au(I)
NHC Complexes 5
All reactions readily proceeded at room temperature, but the
reaction times were shorter than in the previous examples (48 h
instead of 96 h).9
The results from Table 1 mainly indicate the strong steric
influence of substituents in ortho positions in the case of two ortho
substituents, reducing the yield. The overall electronic influence of
the donors or acceptors on the phenyl group is rather small.
Single crystals of 5b could be grown from DCM/hexane; the
molecular structure is shown in Figure 1.12 The gold−carbon
Figure 1. Solid-state molecular structure of two independent
molecules of 5b connected by an aurophilic interaction.
bond lengths are quite similar: Au11−C11 = 1.980(10) Å and
Au12−C12 = 1.974(11) Å. The same applies for the gold−
chloro bond lengths: Au11−Cl11 = 2.276(3) Å and Au12−
Cl12 = 2.281(3) Å. The bond angles are also in the normal
range: C11−Au11−Cl11 = 176.8(3)°, C12−Au12−Cl12 =
176.3(3)°, N21−C11−N51 = 109.4(8)°, N22−C12−N52 =
108.7(10)°, N21−C11−Au11 = 126.3(7)°, N22−C12−Au12 =
127.0(8)°, N51−C11−Au11 = 124.2(7)°, and N52−C12−
Au12 = 124.3(8)°. Two complexes are linked by an aurophilic
interaction. The aurophilic interaction is weak with a Au−Au
distance of 3.5181(6) Å.
The overall advantage of this simple route to gold(I) NHC
complexes is reflected by the fact that although the NHC
ligands in 5a−e are very simple, none of these NHCs have been
reported or been used in organometallic chemistry so far.
Having obtained these gold(I) NHC complexes 5, we next
investigated the influence of the donor or acceptor groups on
the catalytic activity. We turned to a substrate for the gold-
catalyzed phenol synthesis,13 the furan-yne 6 was used. Due to
the ether group in the tether the substrate preferentially assumes a
conformation unfavorable for the cyclization reaction. Thus, it is
a challenging task for gold catalysts, a good benchmark.14 The results
obtained with the new gold catalysts 5a−c are shown in Table 2.
a
General conditions: 132 μmol of (isonitrile)−Au(I) complex, 396 μmol
of 2-chloroethylammonium salt, 6.81 mmol of NEt3, DCM, room
temperature, 48 h.9
group is tolerated quite well (84%, entry 8); the cyclohexyl
substituent provided an excellent yield of 5i (95%, entry 9).
Now we switched from the unsubstituted 4a to the phenyl-
substituted 4b as the chloroammonium reagent. Here the
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Table 2. Gold Catalyst Loading in the Gold-Catalyzed Synthesis of Phenol 7
a
entry
cat.
loading (mol %)
solvent
time
1 h
conversion (%)
yield (%)
TON
1
2
3
4
5
5a
5a
5a
5a
5a
1.0
CDCl3
CDCl3
CDCl3
CDCl3
CD2Cl2
100
100
100
100
57
67
77
67
66
57
60
53
62
67
154
0.5
1 day
5 days
7 days
3 days
5 days
10 days
1.5 h
0.1
670
0.05
0.05
1320
1140
1200
106
60
6
7
8
9
5b
5b
5b
5b
0.5
0.5
0.1
0.1
CDCl3
CD2Cl2
CDCl3
CD2Cl2
93
100
0
124
7 days
1 day
3 days
4 days
5 days
6 days
7 days
6 days
7 days
7 days
10 h
69
69
72
71
74
71
69
54
53
730
720
710
740
710
730
108
106
77
78
79
80
83
10
5c
0.5
CDCl3
90
100
0
11
12
5c
5c
0.1
0.1
CDCl3
CD2Cl2
94
79
79
79
17
790
790
790
34
1 day
2 days
7 days
7 days
10 h
97
100
62
13
14
15
5d
5d
5d
0.5
0.1
0.1
CDCl3
CDCl3
CD2Cl2
0
81
80
73
76
8
800
730
760
16
1 day
2 days
7 days
7 days
10 h
86
88
16
17
18
5e
5e
5e
0.5
0.1
0.1
CDCl3
CDCl3
CD2Cl2
49
0
98
79
79
60
70
73
78
90
96
97
76
95
90
68
84
32
55
55
790
790
1 day
1.5 h
100
61
19
5f
0.1
CD2Cl2
600
1 days
2 days
3 days
10 h
72
700
76
730
78
780
20
21
22
23
24
25
26
27
28
29
5g
5h
5i
0.1
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
CD2Cl2
100
100
100
86
900
0.1
1 day
10 h
960
0.1
970
5j
0.1
1 day
1 day
1 day
1 day
1 day
1 day
3 days
4 days
760
5k
5g
5h
5i
0.1
100
100
81
950
0.05
0.05
0.05
0.05
0.01
1800
1360
1680
640
94
5k
5g
48
69
5500
5500
69
a
All catalyzed reactions were performed in NMR tubes. Before the catalyst was added, an NMR spectrum was measured. The conversion and the
yield were determined by integration and comparison with an internal standard (1,3,5-tri-tert-butylbenzene).
We started with 5a, and with this methoxy-substituted catalyst
at 1 mol % (entry 1), 0.5 mol % (entry 2), and even 0.1 mol %
(entry 3) catalyst loading a full conversion of the substrate
was observed; the isolated yields vary from 67 to 77%. With
0.05 mol % of 5a the yield was reduced to 57% after 3 days
and 60% after 5 days (entry 5; the switch of solvent was
suggested by observation of the results from entries 5/6 and
7/8, which demonstrated that dichloromethane gave a better
result). Nevertheless, this corresponds to an impressive TON
(=turnover number) of 1200, which is one of the best values
reported for that substrate so far. The best value for this
reaction of a TON of 3050 was observed with a gold(I) NAC
complex.14b
Switching to catalyst 5b, with two methoxy groups, gave an
incomplete conversion (93%) in chloroform after even 10 days
with 0.5 mol % catalyst (entry 6), while in dichloromethane in
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Table 3. Screening the New NHC Gold(I) Catalysts in the Synthesis of Oxazole 9
a
a
entry
cat.
loading (mol %)
time
9 h
conversion (%)
yield of 9 (%)
TON
1
2
3
5b
5b
5b
1.0
0.5
0.1
100
95
88
96
74
92
92
98
86
97
86
97
97
92
88
96
74
92
89
97
86
97
84
95
970
920
880
960
740
920
890
970
860
970
840
950
1 day
4 days
7 days
4 days
7 days
4 days
7 days
4 days
7 days
4 days
7 days
4
5
6
7
5g
5h
5i
0.1
0.1
0.1
0.1
5k
a
All catalyzed reactions were performed in NMR tubes. Before the catalyst was added, an NMR spectrum was measured. The conversion and the
yield were determined by integration and comparison with an internal standard (hexamethylbenzene).
1.5 h a full consumption of the substrate was detected (entry 7).
This solvent dependency was confirmed by the reactions with
0.1 mol % of catalyst. In chloroform after 7 days no conversion
could be detected (entry 8), while in dichloromethane after 1 day
already 69% conversion, slowly increasing to 83% during the next
6 days, was observed (entry 9).
was reached, but still, the 55% yield corresponds to 5500
turnovers.
Another interesting test reaction is the gold(I)-mediated
formation of alkylideneoxazolines.18 The conversion of 8 was
relatively insensitive to the choice of carbene catalyst. For 1 mol %
of catalyst 5b (which was the weakest catalyst with substrate 6),
after only 9 h a full conversion and 97% selectivity for the
product 9 was detected (Table 3, entry 1). Reducing the
catalyst amount to 0.5 mol % after 1 day gave 95% conversion
(entry 2). Even 0.1 mol % was active; after 7 days 96% of to led
to prolonged reaction times and reduced yields (entries 2
and 3). The other catalysts investigated, namely 5g−k (which
all gave quite good results with 6), in the reaction with 8 are
not superior to 5b (entries 4−7) and give quite similar results
with reaction times of 7 days for full conversion and yields of
92−97%.
With catalyst 5c, bearing two methoxy groups in ortho
positions, with 0.5 mol % of catalyst in chloroform full
conversion could only be reached after 1 week (entry 10). With
0.1 mol % no conversion was observed (entry 11). Switching to
dichloromethane again gave a full conversion after 2 days (entry 12).
The fluoro derivative 5d gave a lower conversion in CDCl3,
as with 0.5 mol % catalyst 62% conversion was observed after 7
days, but the reaction is not selective; the NMR demonstrated
only 17% of the desired product (entry 13). With 0.1 mol % of
catalyst no conversion was observed (entry 14). In CD2Cl2, the
reaction proceeded much more quickly and was more selective,
as after 10 h 81% conversion was observed and 80% of the
product could be obtained by NMR; with extended reaction
times the conversion increased slightly, but byproduct was
formed under these conditions at extended reaction times, and
the NMR yields dropped slightly (entry 15).
CONCLUSION
■
New NHC derivatives bearing donor or acceptor groups on the
aryl groups on the nitrogen atoms are readily accessible by the
template synthesis starting from gold(I) isocyanide complexes
and amines with a leaving group in the β-position. With two
donor groups a 3-fold excess of the nucleophilic component
was crucial, which shows the limits of the method. The
new gold(I) NHC complexes gave TONs of up to 5500 with a
furan-yne test substrate, which are very remarkable but do not
reach the values obtained with the best gold(I) NAC com-
plexes. A strong dependence on the electronic properties of the
aryl group could not be observed in these test reactions.
With the nitro compound 5e the observed trends are quite
similar to the previous case: low conversion and low selectivity
in chloroform (entries 16 and 17), much better results in
dichloromethane (entry 18).
The dimethyl derivative 5f was investigated in dichloro-
methane only and gave results comparable to those for the two
previous catalysts (entry 19). The adamantyl-substituted 5g
gave a good TON of 900 in only 10 h for a catalyst loading of
0.1 mol % (entry 20). The other catalysts, 5h (naphthyl-
substituted, entry 21) and 5i (cyclohexyl-substituted, entry 22)
as well as the catalysts with the phenyl group in the backbone
(5j,h, entries 23 and 24) needed significantly longer reaction
times but still gave good turnover numbers. Now the catalyst
loading was reduced to 0.05 mol % for 5g−k (entries 25−28).
With 1 day of reaction time and a TON of 1800 5g was the best
candidate. Thus, finally, as little as 0.01 mol % of 5g was used
(entry 29). With this low catalyst loading no full conversion
EXPERIMENTAL SECTION
■
General Methods. Chemicals (Aldrich, Fluka, Lancaster, and
Merck) were used without further purification. Dichloromethane was
dried by an MB SPS-800 apparatus with the aid of drying columns.
NMR spectra were recorded on Bruker ARX300 and AMX250 spectro-
meters. Chemical shifts were referenced to residual solvent protons.
Signal multiplicity is given as follows: s (singlet), d (doublet), t (triplet),
q (quartet), m (multiplet). 13C assignment was achieved via DEPT135
spectra. MS spectra were recorded on a Finnigan MAT 90 a Varian 711
or a micrOTOF-Q spectrometer. IR spectra were recorded on a Bruker
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Vector 22 instrument. Flash chromatography was performed with
Macherey-Nagel silica gel SiO2 (40.0 − 63.0 μm); thin-layer
chromatography (TLC) was performed on precoated polyester sheets
(POLYGRAM SIL/GUV254), and components were visualized by
observation under UV light or by treating the plates with p-anisaldehyde
followed by heating.
N-(2,4-Dimethoxyphenyl)formamide (1b). N-(2,4-
Dimethoxyphenyl)formamide (1b) was prepared according to GP 1
General Procedure 1 (GP 1): Preparation of the Formamides 1.
Formamides 1 were prepared in analogy to a literature procedure.
from 2.00 g (13.1 mmol) of 2,4-dimethoxybenzenamine. Recrystalliza-
tion from acetone/petroleum ether (1/1) afforded 1b as colorless
crystals; yield 1.72 g (73%), mp 141 °C. IR (KBr): ν 3250, 3134, 3100,
̃
3065, 3001, 2972, 2943, 2901, 2840, 2771, 1681, 1656, 1599, 1540,
1465, 1453, 1437, 1414, 1391, 1303, 1234, 1203, 1169, 1111, 1032,
932, 835, 828 cm−1. 1H NMR (300 MHz, CDCl3): δ 3.79 (s, 3H), 3.85
(s, 3H), 6.42−6.52 (m, 3H), 7.61 (bs, 1H), 8.39 (s, 1H). 13C NMR
(75 MHz, CDCl3): δ 55.5 (q), 55.7 (q), 110.0 (d), 120.5 (d), 121.1
(d), 124.3 (d), 125.2 (s), 147.7 (s), 158.6 (d). HRMS (EI (+), NBA):
[C9H11NO3]+ calcd 181.0739, found 181.0748.
The aniline derivative was dissolved in ethyl formate (15 mL). The
mixture was heated in an autoclave to 200 °C for 12 h as described in
the literature9 but for full conversion was finally heated to 250 °C for 4
h. Then the solid precipitate was filtered off and washed with pentane.
Recrystallization from acetone/petroleum ether furnished the pure
formamide compound.
N-(2,6-Dimethoxyphenyl)formamide (1c). N-(2,6-
Dimethoxyphenyl)formamide (1c) was prepared according to GP 1
General Procedure 2 (GP 2): Preparation of the Isocyanides
2. The isonitriles 2 were prepared according to a literature procedure.9
from 1.00 g (6.53 mmol) of 2,6-dimethoxybenzenamine. 1c was
obtained as a colorless solid (653 mg, 69%) after column
chromatography on silica (petroleum ether/ethyl acetate 5/1); mp
Instead of sublimation, the crude products were purified by column
chromatography on silica gel to afford the compounds 2.
General Procedure 3 (GP 3): Synthesis of the Au(I) Isocyanide
Complexes 3. The complexes 3 were prepared according to a litera-
ture procedure.9
̃
151 °C. IR (KBr): ν 3429, 3223, 2996, 2945, 2875, 2841, 1684, 1663,
1600, 1543, 1478, 1463, 1432, 1387, 1310, 1261, 1110, 1028, 770,
1
714 cm−1. H NMR (300 MHz, CDCl3): δ 3.85 (s, 6H), 6.61 (d, J =
8.4 Hz, 2H), 7.07 (t, J = 8.4 Hz, 1H), 8.83 (d, J = 11.4 Hz, 1H). 13C
NMR (75 MHz, CDCl3): δ 56.0 (q), 104.5 (d), 125.1 (d), 151.7 (s),
164.7 (s). HRMS (EI (+), NBA): [C9H11NO3]+ calcd 181.0739, found
181.0751.
N-(2-Fluorophenyl)formamide (1d). N-(2-Fluorophenyl)-
formamide (1d) was prepared according to GP 1 from 2.27 g
General Procedure 4 (GP 4): Synthesis of Unsymmetrically
Substituted Au(I) NHC Complexes 5. The gold(I) NHC chlorides
(20.4 mmol) of 2-fluorobenzenamine. 1d was obtained as a yellow
solid (2.37 g, 83%) after column chromatography on silica (petroleum
̃
ether/ethyl acetate 3/1). IR (KBr): ν 3418, 3221, 3115, 3072, 1706,
1675, 1621, 1595, 1533, 1469, 1455, 1415, 1317, 1293, 1260, 1230,
1
810, 748, 636, 438 cm−1. H NMR (300 MHz, CDCl3 ): δ 3.79 (s,
3H), 7.08−7.16 (m, 3H), 7.61−7.64 (bs, 1H), 8.30−8.71 (m, 1H),
8.47 (s, 1H). 13C NMR (75 MHz, CDCl3): δ 114.9 (d), 116.3 (d),
119.0 (d), 124.5 (s), 126.0 (d), 158.9 (s), 160.2 (s). HRMS (EI (+),
NBA): [C7H6FNO]+ calcd 139.0433, found 139.0430.
2-Methoxyphenyl Isocyanide (2a). 2-Methoxyphenyl isocyanide
(2a) was prepared according to GP 2 from 262 mg (1.73 mmol) of
5 were prepared in analogy to the literature procedure;9 the only
variation was a reaction time of 48 h instead of the previously
published 96 h.
N-(2-Methoxyphenyl)formamide (1a). 1a was prepared accord-
ing to GP 1 from 2.00 g (16.2 mmol) of 2-methoxybenzenamine.
N-(2-methoxyphenyl)formamide, 470 μL (5.19 mmol) of POCl3, and
1.40 g (13.8 mmol) of NEt3. 2a was obtained as an orange solid (182
mg, 78%) after column chromatography on silica (petroleum ether/
ethyl acetate 2/1). IR (film): ν 3013, 2971, 2945, 2841, 2126, 1596,
̃
1498, 1466, 1438, 1302, 1286, 1260, 1174, 1163, 1112, 1045, 1024,
Recrystallization from acetone/petroleum ether (1/3) afforded 1a as
1
colorless crystals. The H NMR data are in accordance with previous
reports;15 yield 1.30 g (53%). 1H NMR (250 MHz, CDCl3): δ 3.89 (s,
3H), 6.87−7.00 (m, 3H), 7.04−7.14 (m, 1H), 7.79 (bs, 1H).
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1
751, 581, 559 cm−1. H NMR (300 MHz, CDCl3 ): δ 3.93 (s, 3H),
6.90−6.97 (m, 2H), 7.32−7.37 (m, 2H); 13C NMR (75 MHz,
CDCl3): δ 56.0 (q), 111.7 (d), 120.5 (d), 127.7 (d), 130.4 (d), 155.0
(s). HRMS (EI (+), NBA): [C8H7NO]+ calcd 133.0528, found
133.0522.
1H NMR (300 MHz, CDCl3): δ 3.97 (s, 3H), 7.00−7.10 (m, 2H),
7.40−7.51 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 56.3 (q), 112.1
(d), 120.9 (d), 127.8 (d), 132.9 (d), 156.0 (s). HRMS (FAB (+),
NBA): [C8H7AuClNO]+ calcd 364.9882, found 365.9928.
((2,4-Dimethoxyphenyl)isocyano)gold(I) Chloride (3b). ((2,4-
Dimethoxylphenyl)isocyano)gold(I) chloride (3b) was prepared
2,4-Dimethoxyphenyl Isocyanide (2b). 2,4-Dimethoxyphenyl
isocyanide (2b) was prepared according to GP 2 from 1.72 g (9.47 mmol)
according to GP 3 from 0.10 g (0.31 mmol) of (tht)AuCl and
51 mg (0.31 mmol) of 2,4-dimethoxylphenyl isocyanide. Evaporation
of the solvent afforded 3b as a colorless solid (122 mg, >99%); mp:
̃
166 °C. IR (KBr): ν 3440, 3091, 3053, 3019, 2968, 2930, 2832, 2222,
of N-(2,4-dimethoxyphenyl)formamide, 2.59 mL (28.4 mmol) POCl3,
and 7.67 g (75.8 mmol) of NEt3. 2b was obtained as a yellow solid
(1.08 g, 70%) after column chromatography on silica (petroleum
1687, 1602, 1582, 1500, 1465, 1454, 1430, 1419, 1315, 1301, 1264,
1
1212, 1203, 1161, 1122, 1036, 1017, 829 cm−1. H NMR (300 MHz,
CDCl3): δ 3.86 (s, 3H), 3.93 (s, 3H), 6.47−6.53 (m, 2H), 7.37 (m,
1H). 13C NMR (75 MHz, CDCl3): δ 55.9 (q), 56.3 (q), 99.2 (d),
105.4 (d), 128.8 (d), 140.4 (s), 157.4 (s), 163.2 (s). HRMS (FAB (+),
NBA): [C9H9AuClNO2]+ calcd 394.9987, found 394.9956.
((2,6-Dimethoxyphenyl)isocyano)gold(I) Chloride (3c). ((2,6-
Dimethoxylphenyl)isocyano)gold(I) chloride (3c) was prepared
̃
ether/ethyl acetate 15/1); mp 72 °C. IR (KBr): ν 3080, 3015, 3005,
2976, 2957, 2886, 2845, 2128, 1603, 1507, 1477, 1457, 1448, 1437,
1419, 1324, 1290, 1273, 1214, 1202, 1183, 1172, 1108, 1028, 938, 840,
803 cm−1. 1H NMR (300 MHz, CDCl3): δ 3.75 (s, 3H), 3.82 (s, 3H),
6.31−6.42 (m, 2H), 7.18 (d, J = 8.5 Hz, 1H). 13C NMR (75 MHz,
CDCl3): δ 55.6 (q), 56.0 (q), 99.0 (d), 104.5 (d), 128.3 (d), 156.1 (s),
161.1 (s), 166.9 (s). HRMS (EI (+), NBA): [C9H9NO2]+ calcd
163.0633, found 163.0655.
2,6-Dimethoxyphenyl Isocyanide (2c). 2,6-Dimethoxylphenyl
isocyanide (2c) was prepared according to GP 2 from 407 mg (2.25 mmol)
according to GP 3 from 0.10 g (0.31 mmol) of (tht)AuCl and
51 mg (0.31 mmol) of 2,6-dimethoxylphenyl isocyanide. Evaporation of
the solvent afforded 3c as a colorless solid (121 mg, 99%); mp 196 °C.
̃
IR (KBr): ν 3442, 3098, 3014, 2940, 2840, 2570, 2351, 2218, 1629,
of N-(2,6-dimethoxyphenyl)formamide, 615 μL (6.75 mmol) of
POCl3, and 1.82 g (18.0 mmol) of NEt3. 2c was obtained as a yellow
solid (283 mg, 77%) after column chromatography on silica
1595, 1486, 1453, 1435, 1306, 1268, 1115, 1023, 774, 718, 534 cm−1.
1H NMR (300 MHz, CDCl3): δ 3.94 (s, 6H), 6.59 (d, J = 8.6 Hz, 2H),
7.41 (t, J = 8.6 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ 56.5 (q),
103.9 (d), 132.6 (d), 157.2 (s). HRMS (FAB (+), NBA):
[C9H9AuClNO2+H]+ calcd 396.0066, found 396.0081.
̃
(dichloromethane); mp 101 °C. IR (KBr): ν 3441, 3118, 3009,
2983, 2946, 2923, 2842, 2129, 1597, 1485, 1464, 1432, 1303, 1270,
1174, 1018, 778, 722, 692 cm−1. 1H NMR (300 MHz, CDCl3): δ 3.01
(s, 6H), 6.56 (d, J = 8.5 Hz, 2H), 7.25 (t, J = 8.5 Hz, 1H), 8.83 (d, J =
11.4 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ 56.2 (q), 103.7 (d),
129.9 (d), 156.3 (s). HRMS (EI (+), NBA): [C9H9NO2]+ calcd
163.0633, found 163.0648.
((2-Fluorophenyl)isocyano)gold(I) Chloride (3d). ((2-
Fluorophenyl)isocyano)gold(I) chloride (3d) was prepared according
2-Fluorophenyl Isocyanide (2d). 2-Fluorophenyl isocyanide
(2d) was prepared according to GP 2 from 1.00 g (7.19 mmol) of
to GP 3 from 0.10 g (0.31 mmol) of (tht)AuCl and 39 mg (0.31 mmol)
of 2-fluorophenyl isocyanide. Evaporation of the solvent afforded 3d as
̃
a colorless solid (116 mg, >99%); mp 153 °C. IR (KBr): ν 3440, 2222,
1616, 1559, 1494, 1458, 1324, 1276, 1256, 1199, 1163, 1103, 1062,
1
952, 852, 759, 668, 568, 480 cm−1. H NMR (300 MHz, CDCl3): δ
7.27−7.36 (m, 2H), 7.56−7.64 (m, 2H). 13C NMR (75 MHz, CDCl3):
δ 117.3 (d), 125.4 (d), 128.2 (d), 133.5 (d), 156.3 (s), 159.8 (s), 219.5
(s). HRMS (FAB (+), NBA): [C7H4AuClFN]+ calcd 352.9682, found
353.9753.
((4-Nitrophenyl)isocyano)gold(I) Chloride (3e). ((4-
Nitrophenyl)isocyano)gold(I) chloride (3e) was prepared according
2-fluorophenylformamide, 1.96 mL (21.6 mmol) of POCl3, and 5.82 g
(57.5 mmol) of NEt3. 2d was obtained as a brown oil (702 mg, 80%)
after column chromatography on silica (petroleum ether/EtOAc 1/1).
1H NMR (300 MHz, CDCl3): δ 7.15−7.22 (m, 1H), 7.36−7.43 (m,
1H). All spectral data are in accordance with previous reports.16
((2-Methoxyphenyl)isocyano)gold(I) Chloride (3a). ((2-
Methoxylphenyl)isocyano)gold(I) chloride (3a) was prepared according
to GP 3, where 0.10 g (0.31 mmol) of (tht)AuCl and 46 mg (0.31 mmol)
of 4-nitrophenyl isocyanide were employed. Evaporation of the solvent
afforded 3e as a colorless solid (117 mg, 99%); mp 260 °C. IR (KBr):
((2- to GP 3 from 100 mg (312 μmol) of (tht)AuCl and 42 mg
(0.31 mmol) of 2-methoxyphenyl isocyanide. Evaporation of the solvent
afforded 3a as a colorless solid (118 mg, >99%); mp 153 °C. IR
̃
ν 3428, 3104, 3069, 2222, 1609, 1590, 1526, 1485, 1345, 1311, 1294,
1206, 1166, 1108, 1013, 861, 799, 746, 677, 505 cm−1. 1H NMR (300 MHz,
THF-d8): δ 6.22−6.33 (m, 2H), 6.50−6.74 (m, 2H). 13C NMR (75 MHz,
THF-d8): δ 123.2 (d), 126.9 (d), 140.4 (q).
̃
(KBr): ν= 3431, 2969, 2941, 2838, 2228, 1636, 1595, 1495, 1466,
1438, 1303, 1287, 1262, 1180, 1166, 1111, 1041, 1016, 753, 531 cm−1.
900
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((2,6-Dimethylphenyl)isocyano)gold(I) Chloride (3f). ((2,6-
Dimethylphenyl)isocyano)gold(I) chloride (3f) was prepared according
(dd, J = 6.6 Hz, J = 13.7 Hz, 6H), 3.43−3.49 (m, 2H), 3.50−3.61 (m,
1H), 5.72−5.77 (m, 1H), 7.36−7.41 (m, 3H), 7.48−7.51 (m, 2H),
9.24 (bs, 1H), 10.38 (bs, 1H). 13C NMR (75 MHz, CDCl3): δ 18.8
(q), 19.1 (q), 51.1 (t), 51.3 (t), 57.8 (d), 127.2 (d), 129.2 (d), 129.5
(d), 137.4 (s). HRMS (EI (+), NBA): C11H17NCl[M-Cl−]]+ calcd
198.1044, found 198.1088.
[ ( ( 2 - M e t h o x y p h e n y l ) a m i n o ) ( i s o pr o p y l a m i n o ) -
imidazolidene]gold(I) Chloride (5a). [((2-Methoxyphenyl)amino)-
((2,6- to the literature procedure.14b The identity of the product was
confirmed by 1H NMR. 1H NMR (250 MHz, CDCl3): δ 2.44 (s, 6H),
7.18 (d, J = 7.1 Hz, 2H), 7.35 (t, J = 7.1 Hz, 1H).
((1-Adamantyl)isocyano)gold(I) Chloride (3g). 3g was pre-
pared according to GP 3, where 100 mg (310 μmol) of (tht)AuCl and
(isopropylamino)imidazolidene]gold(I) chloride (5a) was prepared
according to GP 4, where 48.3 mg (132 μmol) of 3a and 62.6 mg
(396 μmol) of 2-(chloroethyl)ammonium chloride (4a) were employed. 5a
was obtained as a white solid (56.0 mg, 95%) after column chromato-
50.0 mg (310 μmol) of 1-adamantyl isocyanide were employed.
Evaporation of the solvent afforded 3g as a colorless solid (125 mg,
1
>99%). H NMR (250 MHz, CDCl3): δ 1.66−1.77 (m, 6H), 2.12−
̃
graphy on silica (dichloromethane); mp 230 °C. IR (KBr): ν 3442,
2.13 (m, 6H), 2.20 (m, 3H). All spectral data are in accordance with
previous reports.9
2970, 1597, 1509, 1459, 1436, 1368, 1347, 1330, 1280, 1271, 1249,
1
1200, 1184, 1160, 1119, 1067, 1050, 1028, 762 cm−1. H NMR (300
((2-Naphthyl)isocyano)gold(I) Chloride (3h). 3h was prepared
according to GP 3, where 239 mg (750 μmol) of (tht)AuCl and
MHz, CDCl3): δ 1.35 (d, J = 6.8 Hz, 6H), 3.73−3.85 (m, 2H), 4.15−
4.42 (m, 2H), 4.93−5.11 (m, 1H), 7.85−7.95 (m, 2H), 8.20−8.31 (m,
2H). 13C NMR (75 MHz, CDCl3): δ 20.5 (q), 43.0 (t), 49.7 (t), 53.9
(d), 121.2 (d), 124.9 (d), 146.0 (s). HRMS (FAB (+), NBA):
[C13H18AuClN2O]+ calcd 450.0773, found 450.0781.
[((2,4-Dimethoxyphenyl)amino)(isopropylamino)-
imidazolidene]gold(I) Chloride (5b). [((2,4-Dimethoxyphenyl)-
114 mg (750 μmol) of 2-naphthyl isocyanide were employed.
Evaporation of the solvent afforded 3h as a colorless solid (292 mg,
>99%). H NMR (250 MHz, CDCl3): δ 7.50−7.53 (m, 1H), 7.65−
1
7.69 (m, 2H), 7.90−7.94 (m, 2H), 7.96−7.99 (m, 2H), 8.09−8.10 (m,
1H). All spectral data are in accordance with previous reports.9
(Cyclohexylisocyano)gold(I) Chloride (3i). 3i was prepared
according to GP 3, where 100 mg (310 μmol) of (tht)AuCl and
amino)(isopropylamino)imidazolidene]gold(I) chloride (5b) was pre-
pared according to GP 4, where 52.2 mg (132 μmol) of 3b and 62.6 mg
(396 μmol) of 4a were employed. 5b was obtained as a yellow solid
(61.0 mg, 97%) after column chromatography on silica (dichloro-
34.0 mg (310 μmol) of cyclohexyl isocyanide were employed.
Evaporation of the solvent afforded 3i as a colorless solid (110 mg,
1
>99%). H NMR (250 MHz, CDCl3): δ 1.42−1.48 (m, 4H), 1.72−
methane); mp 206 °C. IR (KBr): ν 3431, 2968, 2935, 2837, 2052, 1611,
̃
1.81 (m, 4H), 1.97−1.99 (m, 2H), 3.87−3.91 (m, 1H). All spectral
1518, 1456, 1418, 1368, 1328, 1274, 1209, 1161, 1129, 1063, 1029, 938,
data are in accordance with previous reports.9
833, 596 cm−1. H NMR (300 MHz, CDCl3): δ 1.29 (s, 3H), 1.31 (s,
1
N-(2-Chloro-2-phenylethyl)isopropylammonium Chloride
(4b). Under an atmosphere of nitrogen isopropylamine (2.00 g,
3H), 3.81 (s, 3H), 3.82 (s, 3H), 3.89−3.98 (m, 2H), 4.90−4.95 (m,
1H), 6.45−6.48 (m, 2H), 7.33−7.36 (m, 1H). 13C NMR (75 MHz,
CDCl3): δ 20.5 (q), 43.0 (t), 50.7 (t), 51.8 (q), 55.6 (d), 99.8 (d), 104.4
(d), 129.4 (d), 155.7 (s), 160.6 (s), 191.8 (s). HRMS (FAB (+), NBA):
[C14H20AuClN2O2]+ calcd 480.0873, found 480.0936.
[((2,6-Dimethoxyphenyl)amino)(isopropylamino)-
imidazolidene]gold(I) Chloride (5c). [((2,6-Dimethoxyphenyl)-
amino)(isopropylamino)imidazolidene]gold(I) chloride (5c) was
33.8 mmol) and styrene oxide (4.12 g, 34.3 mmol) were dissolved in
absolute EtOH (40.0 mL). The mixture was stirred at reflux for 48 h.
After this, the solvent was removed under reduced pressure and the
resulting colorless solid was recrystallized from EtOH/petroleum ether
(1/3) to yield 2-(isopropylamino)-1-phenylethanol as a colorless solid
1
(3.64 g, 20.3 mmol, 60%). H NMR (250 MHz, CDCl3): δ 1.07 (dd,
J = 1.0 Hz, J = 6.3 Hz, 6H), 2.62−2.69 (m, 1H), 2.81−2.85 (m, 1H),
2.91−2.96 (m, 1H), 4.64−4.68 (m, 1H), 7.23−7.30 (m, 1H), 7.32−
7.39 (m, 4H). All spectral data are in accordance with previous
reports.17
In the next step the alcohol was dissolved in absolute DCM (30.0 mL),
SOCl2 (4.40 mL, 60.0 mmol) was added, and the mixture was stirred
for 12 h at reflux. After this, all the volatiles were removed under
vacuum and the resulting crude product was washed several times with
diethyl ether to yield the title compound as a light gray solid (3.09 g,
prepared according to GP 4, where 52.2 mg (132 μmol) of 3c and
62.6 mg (396 μmol) of 4a were employed. 5c was obtained as a yellow
solid (50.0 mg, 80%) after column chromatography on silica
̃
(dichloromethane); mp 201 °C. IR (KBr): ν 3435, 2970, 2933,
2838, 1630, 1596, 1514, 1479, 1456, 1434, 1368, 1324, 1301, 1274,
1
1259, 1193, 1112, 780, 636, 591 cm−1. H NMR (300 MHz, CDCl3):
δ 1.31 (d, J = 6.8 Hz, 6H), 3.84 (s, 6H), 3.67−3.74 (m, 2H), 3.79−3.86
(m, 2H), 4.87−4.96 (m, 1H), 6.57 (d, J = 8.5 Hz, 2H), 7.25 (t, J =
8.4 Hz, 1H). 13C NMR (75 MHz, CDCl3): δ 20.6 (q), 42.9 (t), 49.7 (t),
51.5 (q), 56.1 (d), 104.7 (d), 117.9 (d), 129.7 (d), 156.9 (s), 193.7 (s).
HRMS (FAB (+), NBA): [C14H20AuClN2O2]+ calcd 480.0873, found
480.0863.
̃
13.2 mmol, 65%); mp >383 °C. IR (KBr): ν 3453, 2945, 2753, 2687,
2440, 1580, 1496, 1471, 1450, 1408, 1391, 1376, 1287, 1152, 1135,
1
996, 765, 701, 669, 540 cm−1. H NMR (250 MHz, CDCl3): δ 1.51
901
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[((2-Fluorophenyl)amino)(isopropylamino)imidazolidene]-
column chromatography on silica (DCM); mp: 217 °C dec. IR (KBr):
gold(I) Chloride (5d). [((2-Fluorophenyl)amino)(isopropylamino)-
̃
ν 3184, 2926, 2850, 2675, 1735, 1495, 1447, 1368, 1284, 1257, 1176,
1127, 1073, 1033, 988, 758, 676, 593, 553. 1H NMR (250 MHz,
CD2Cl2): δ 1.23 (d, J = 6.7 Hz, 6H), 1.70−1.72 (m, 6H), 2.16−2.19
(m, 3H), 2.34−2.35 (m, 6H), 3.40−3.44 (m, 2H), 3.66−3.69 (m, 2H),
4.89−4.94 (m, 1H). 13C NMR (75 MHz, CDCl3): δ 11.5 (q), 14.3
(q), 20.5 (t), 30.4 (t), 36.4 (d), 43.6 (t), 46.2 (d), 53.9 (t), 56.8 (s),
190.5 (s). HRMS (FAB (+), NBA): [C16H26AuClN2]+ calcd 478.145,
found 478.1440.
imidazolidene]gold(I) chloride (5d) was prepared according to GP 4,
where 46.7 mg (132 μmol) of 3d and 62.6 mg (396 μmol) of 4a were
employed. 5d was obtained as a yellow solid (57.0 mg, 98%) after column
[((2-Naphthyl)amino)(isopropylamino)imidazolidene]gold(I)
Chloride (5h). 5h was prepared according to GP 4, where 50.9 mg
(132 μmol) of 3h and 62.6 mg (396 μmol) of 4a were employed. 5h
was obtained as a yellow solid (52.8 mg, 85%) after column
chromatography on silica (dichloromethane); mp 207 °C. IR (KBr): ν
̃
3433, 2970, 2932, 1635, 1508, 1458, 1431, 1369, 1350, 1331, 1278, 1228,
1199, 1063, 760, 653, 608, 554 cm−1. 1H NMR (300 MHz, CDCl3): δ 1.33
(d, J = 6.8 Hz, 6H), 3.71−3.81 (m, 2H), 4.02−4.09 (m, 2H), 4.90−5.04
(m, 1H), 7.09−7.21 (m, 2H), 7.29−7.38 (m, 1H), 7.62−7.71 (m, 1H).
13C NMR (75 MHz, CDCl3): δ 20.5 (q), 43.3 (t), 50.7 (t), 52.4 (d), 116.8
(d), 124.9 (d), 128.7 (d), 129.5 (d), 191.8 (s). HRMS (FAB (+), NBA):
[C12H15AuClFN2]+ calcd 438.0568, found 438.0555.
[((4-Nitrophenyl)amino)(isopropylamino)imidazolidene]-
gold(I) Chloride (5e). [((4-Nitrophenyl)amino)(isopropylamino)-
̃
chromatography on silica (DCM); mp 232 °C. IR (KBr): ν 3435,
2961, 2929, 2859, 1734, 1631, 1599, 1506, 1480, 1449, 1326, 1305,
1273, 1243, 1213, 1127, 1033, 809, 757, 477 cm−1. 1H NMR (250 MHz,
CD2Cl2): δ 1.35 (d, J = 6.8 Hz, 6H), 3.74−3.81 (m, 2H), 4.02−4.24
(m, 2H), 4.95−5.04 (m, 1H), 7.48−7.55 (m, 2H), 7.84−7.88 (m, 2H),
7.91−7.96 (m, 3H). 13C NMR (75 MHz, CDCl3): δ 11.5 (q), 14.3
(q), 43.0 (d), 43.3 (t), 51.1 (t), 120.2 (d), 122.2 (d), 126.5 (d), 127.4
(d), 128.0 (d), 128.2 (d), 129.4 (d), 132.2 (s), 133.7 (s), 139.0 (s),
190.5 (s). HRMS (FAB (+), NBA): [C16H18AuClN2]+ calcd 470.0824,
found 470.0922.
imidazolidene]gold(I) chloride (5e) was prepared according to GP 4,
where 50.2 mg (132 μmol) of 3e and 62.6 mg (396 μmol) of 4a were
employed. 5e was obtained as a yellow solid (61.0 mg, 99%) after
column chromatography on silica (dichloromethane); mp 244 °C. IR
[(Cyclohexylamino)(isopropylamino)imidazolidene]gold(I)
Chloride (5i). 5i was prepared according to GP 4, where 45.1 mg
(132 μmol) of 3i and 62.6 mg (396 μmol) of 4a were employed. 5i
was obtained as a yellow solid (53.5 mg, 95%) after column
̃
(KBr): ν 3444, 2972, 1635, 1596, 1517, 1502, 1474, 1434, 1404, 1346,
1302, 1259, 1192, 1115, 1062, 846, 752, 691, 604, 573 cm−1. 1H NMR
(300 MHz, CDCl3): δ 1.35 (d, J = 6.8 Hz, 6H), 3.73−3.85 (m, 2H),
4.15−4.42 (m, 2H), 4.93−5.11 (m, 1H), 7.85−7.95 (m, 2H), 8.20−
8.31 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 20.5 (q), 43.0 (t), 49.7
(t), 53.9 (d), 121.2 (d), 124.9 (d), 146.0 (s). HRMS (FAB (+), NBA):
[C12H15N3O2]+ calcd 465.0513, found 465.0484.
[((2,6-Dimethylphenyl)amino)(isopropylamino)-
imidazolidene]gold(I) Chloride (5f). [((2,6-Dimethylphenyl)-
chromatography on silica (DCM); mp 213 °C dec. IR (KBr): ν
̃
3427, 2966, 2931, 2854, 1635, 1513, 1485, 1456, 1386, 1365, 1335,
1
1313, 1290, 1246, 1185, 1122, 993, 891, 607, 581 cm−1. H NMR
250 MHz, CD2Cl2): δ 1.06−1.16 (m, 1H), 1.20 (s, 3H), 1.23 (s, 3H),
1.35−1.53 (m, 5H), 1.63−1.63(m, 1H), 1.79−1.82 (m, 4H), 3.45−
3.59 (m, 4H), 4.59−4.75 (m, 1H). 13C NMR (75 MHz, CDCl3):
δ 19.5 (q), 24.4 (t), 24.6 (t), 30.4 (t), 41.5 (t), 42.9 (t), 51.1 (d), 58.8
(d), 189.4 (s). HRMS (FAB (+), NBA): C12H22AuN2 [M-Cl]+ calcd
391.1449, found 391.1443.
[1-((2-Naphthyl)amino)-5-(isopropylamino)-2-
phenylimidazolidene]gold(I) Chloride (5j). 5j was prepared
according to GP 4, where 50.9 mg (132 μmol) of 3h and 92.7 mg
(396 μmol) of 4b were employed. 5j was obtained as a yellow solid
amino)(isopropylamino)imidazolidene]gold(I) chloride (5f) was
prepared according to GP 4, where 48.0 mg (132 μmol) of 3f and
62.6 mg (396 μmol) of 4a were employed. 5f was obtained as a yellow
solid (41.0 mg, 70%) after column chromatography on silica
̃
(petroleum ether/ethyl acetate 5/1); mp 205 °C. IR (KBr): ν 3437,
2970, 2064, 1635, 1559, 1540, 1508, 1489, 1457, 1368, 1322, 1276,
1
1201, 1124, 1100, 1015, 788, 669, 608 cm−1. H NMR (300 MHz,
CDCl3): δ 1.33 (d, J = 6.8 Hz, 6H), 2.25 (s, 6H), 3.78 (s, 4H), 4.88−
4.96 (m, 1H), 7.09 (d, J = 7.6 Hz, 2H), 7.18 (t, J = 7.6 Hz, 1H). 13C
NMR (75 MHz, CDCl3): δ 18.1 (q), 20.6 (q), 42.9 (t), 50.0 (t), 51.6
(d), 128.9 (d), 129.0 (d), 136.0 (s), 137.6 (s), 192.7 (s). HRMS (FAB
(+), NBA): [C14H20AuClN2]+ calcd 448.0981, found 448.0943.
[((1-Adamantyl)amino)(isopropylamino)imidazolidene]-
gold(I) Chloride (5g). 5g was prepared according to GP 4, where
(43.7 mg, 61%) after column chromatography on silica (DCM); mp
̃
202 °C. IR (KBr): ν 2959, 2928, 2858, 1733, 1629, 1598, 1506, 1465,
1417, 1370, 1315, 1256, 1177, 1127, 1033, 858, 811, 752, 698, 476 cm−1.
1H NMR (250 MHz, CD2Cl2): δ 1.31 (d, J = 6.8 Hz, 6H), 3.60−
3.66 (m, 1H), 4.18−4.26 (m, 1H), 4.88−4.97 (m, 1H), 5.57−5.64 (m,
1H), 7.25−7.32 (m, 5H), 7.44−7.47 (m, 2H), 7.61−7.65 (m, 1H),
7.73−7.79 (m, 3H), 7.87−7.88 (m, 1H). 13C NMR (75 MHz, CDCl3):
δ 20.8 (q), 20.4 (q), 52.7 (t), 53.3 (d), 67.0 (d), 123.3 (d), 123.9 (d),
126.7 (d), 127.2 (d), 127.3 (d), 128.0 (d), 128.1 (d), 129.2 (d), 129.3
52.0 mg (132 μmol) of 3g and 62.6 mg (396 μmol) of 4a were
employed. 5g was obtained as a yellow solid (46.6 mg, 74%) after
902
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(d), 129.6 (d), 132.3 (s), 133.5 (s), 137.8 (s), 139.0 (s), 190.9 (s).
HRMS (FAB (+), NBA): [C22H22AuClN2]+ calcd 546.1137, found
546.1147.
[1-((2-Methoxyphenyl)amino)-5-(isopropylamino)-2-
phenylimidazolidene]gold(I) Chloride (5k). 5k was prepared
according to GP 4, where 48.3 mg (132 μmol) of 3a and 92.7 mg
(396 μmol) of 4b were employed. 5k was obtained as a white solid
Bielawski, C. W.; Cowley, A. H. J. Am. Chem. Soc. 2009, 131, 18232−
18233. Electronically active materials: (n) Schuster, O.; Mercsa, L.;
Albrecht, M. Chimia 2010, 64, 184−187.
(2) (a) Nolan, S. P., Ed. N-Heterocyclic Carbenes in Synthesis; Wiley-
VCH: Weinheim, Germany, 2006. (b) Droge, T.; Glorius, F. Angew.
̈
Chem. 2010, 122, 7094−7107; Angew. Chem., Int. Ed. 2010, 49, 6940−
6952.
(3) For early work on gold(I) NHC complexes in the context of
catalysis, see: (a) Teles, J. H.; Brode, S.; Chabanas, M. Angew. Chem.
1998, 110, 1475−1478; Angew. Chem., Int. Ed. 1998, 37, 1415−1418.
(b) Detlefs, M.; Raubenheimer, H. G.; Esterhuysen, M. W. Catal.
Today 2002, 72, 29−41. (c) Schneider, S. K.; Herrmann, W. A.;
Herdtweck, E. Z. Anorg. Allg. Chem. 2003, 629, 2363−2370.
(4) Dias, H. V. R.; Wu, J. Angew. Chem. 2007, 119, 7960−7962;
Angew. Chem., Int. Ed. 2007, 46, 7814−7816.
(5) (a) Hashmi, A. S. K.; Schuster, A.; Rominger, F. Angew. Chem.
2009, 121, 8396−8398; Angew. Chem., Int. Ed. 2009, 48, 8247−8249.
(b) Hashmi, A. S. K.; Ramamurthi, T. D.; Rominger, F. Adv. Synth.
Catal. 2010, 352, 971−975. (c) LaLonde, R. L.; Brenzovich, W. E. Jr.;
Benitez, D.; Tkatchouk, E.; Kelley, K.; Goddard, W. A. III; Toste, F. D.
Chem. Sci. 2010, 1, 226−233. For a highlight, see: (d) Hashmi, A. S.
K. Gold Bull. 2009, 42, 275−279.
(53.3 mg, 77%) after column chromatography on silica (dichloro-
̃
methane); mp 215 °C. IR (KBr): ν 2960, 2929, 2860, 1734, 1597,
1507, 1463, 1424, 1370, 1321, 1302, 1249, 1201, 1178, 1125, 1076,
1
1024, 759, 699, 595 cm−1. H NMR (500 MHz, CD2Cl2): δ 1.36 (d,
J = 6.8 Hz, 6H), 3.65−3.79 (m, 1H), 4.15−4.19 (m, 1H), 4.93−4.97
(m, 1H), 5.55−5.59 (m, 1H), 6.81−6.84 (m, 1H), 6.89−6.91 (m, 1H),
7.20−7.24 (m, 2H), 7.25−7.32 (m, 5H). 13C NMR (75 MHz, CDCl3):
δ 20.6 (q), 20.8 (q), 52.4 (t), 52.8 (q), 56.0 (d), 65.7 (d), 112.3 (d),
120.7 (d), 127.6 (d), 128.4 (d), 129.1 (d), 129.3 (d), 129.7 (d), 130.7
(d), 139.1 (s), 155.3 (s), 191.6 (s). HRMS (FAB (+), NBA):
[C19H22AuClN2O]+ calcd 526.1086, found 526.1119.
(6) Dias, H. V. R.; Wu, J. Angew. Chem. 2007, 119, 7960−7962;
Angew. Chem., Int. Ed. 2007, 46, 7814−7816.
(7) Dash, C.; Kroll, P.; Yousufuddin, M.; Dias, H. V. R. Chem.
Commun. 2011, 47, 4478−4480.
(8) All previous reports exclusively dealt with other metals, namely
Pd, Pt, Cr, Mo, and W, but to the best of our knowledge never with
gold. Two early reports on the addition of amines to coordinated
isonitriles did not address catalyst formation: (a) Burke, A.; Balch,
A. L.; Enemark, J. H. J. Am. Chem. Soc. 1970, 92, 2555−2557.
(b) Balch, A. L.; Parks, J. E. J. Am. Chem. Soc. 1974, 96, 4114−4121. A
recent report on the intramolecular cyclization of isocyanoacetate does
need a separate second alkylation step with another reagent to form a
ASSOCIATED CONTENT
* Supporting Information
Text and figures giving additional experimental details and
characterization data and a CIF file giving crystal data for 5b.
This material is available free of charge via the Internet
at http://pubs.acs.org.
■
S
carbene ligand and also did not aim at catalysis: (c) Schrolkamp, S.;
̈
AUTHOR INFORMATION
Volkl, A.; Lugger, T.; Hahn, F. E.; Beck, W.; Fehlhammer, W. P. Z.
̈
̈
■
Anorg. Allg. Chem. 2008, 634, 2940−2947. As in the preceding
reference, other examples of known template synthesis at the metal
center using isocyanides are based on entirely different disconnections
of the NHC framework and in addition do not lead to the NHCs with
oxo groups in the backbone: (d) Hahn, F. E.; Langenhahn, V.; Meier,
Corresponding Author
*Tel: +49(0)6221-548413. Fax: +49(0)6221-544205. E-mail:
hashmi@hashmi.de.
ACKNOWLEDGMENTS
■
N.; Lugger, T.; Fehlhammer, W. P. Chem. Eur. J. 2003, 9, 704−712.
̈
Y. Yu is grateful to the CSC for a fellowship. Gold salts were
generously donated by Umicore AG & Co., KG.
(e) Hahn, F. E.; Plumed, C. G.; Munder, M.; Lugger, T. Chem. Eur. J.
̈
̈
2004, 10, 6285−6293. For a review also covering such syntheses, see:
(f) (g) Hahn, F. E.; Jahnke, M. C. Angew. Chem. 2008, 120, 3166−
3216; Angew. Chem., Int. Ed. 2008, 47, 3122−3172.
REFERENCES
■
(9) Hashmi, A. S. K.; Lothschutz, C.; Bohling, C.; Hengst, T.;
̈
̈
̈
(1) For the discovery: (a) Ofele, K. J. Organomet. Chem. 1968, 12,
42−43. (b) Wanzlick, H.-W.; Schonherr, H. J. Angew. Chem. 1968,
Hubbert, C.; Rominger, F. Adv. Synth. Catal. 2010, 352, 3001−3012.
(10) Hashmi, A. S. K.; Lothschutz, C.; Graf, K.; Hengst, T.; Schuster,
A.; Rominger, F. Adv. Synth. Catal. 2011, 354, 1407−1412.
(11) Hashmi, A. S. K.; Lothschutz, C.; Bohling, C.; Rominger, F.
̈
̈
80, 154−155; Angew. Chem., Int. Ed. 1968, 7, 141−142. Medical
applications: (c) Ozdemir, I.; Temelli, N.; Gunal, S.; Demir, S.
̈
̇
̈
̈
̈
Molecules 2010, 15, 2203−2210. (d) Hindi, K. M.; Siciliano, T. J.;
Durmus, S.; Panzner, M. J.; Medvetz, D. A.; Reddy, D. V.; Hogue,
L. A.; Hovis, C. E.; Hilliard, J. K.; Mallet, R. J.; Tessier, C. A.; Cannon,
C. L.; Youngs, W. J. J. Med. Chem. 2008, 51, 1577−1583. (e) Hindi,
K. M.; Panzner, M. J.; Tessier, C. A.; Cannon, C. L.; Youngs, W. J.
Chem. Rev. 2009, 109, 3859−3884. Nanoparticles and supramolecular
chemistry: (f) Vignolle, J.; Tilley, T. D. Chem. Commun. 2009, 7230−
7232. (g) Chun, J.; Jung, I. G.; Kim, H. J.; Park, M.; Lah, M. S.; Son,
S. U. Inorg. Chem. 2009, 48, 6353−6355. Self-assembly: (h) Rit, A.;
Pape, T.; Hahn, F. E. J. Am. Chem. Soc. 2010, 132, 4572−4573.
Photochemistry: (i) Unger, Y.; Meyer, D.; Strassner, T. Dalton Trans.
2010, 39, 4295−4301. (j) Lin, J. C. Y.; Huang, R. T. W.; Lee, C. S.;
Bhattacharyya, A.; Hwang, W. S.; Lin, I. J. B. Chem. Rev. 2009, 109,
3561−3598. (k) Ampt, K. A. M.; Burling, S.; Donald, S. M. A.;
Douglas, S.; Duckett, S. B.; Macgregor, S. A.; Perutz, R. N.; Whittlesey,
M. K. J. Am. Chem. Soc. 2006, 128, 7452−7453. Liquid crystals:
(l) Huang, R. T. W.; Wang, W. C.; Yang, R. Y.; Lu, J. T.; Lin, I. J. B.
Dalton Trans. 2009, 7121−7131. Polymerization: (m) Powell, A. B.;
Organometallics 2011, 30, 2411−2417.
(12) CCDC 832043 (5b) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif
(13) For representative publications see: (a) Hashmi, A. S. K.; Frost,
T. M.; Bats, J. W. J. Am. Chem. Soc. 2000, 122, 11553−11554.
(b) Hashmi, A. S. K.; Frost, T. M.; Bats, J. W. Org. Lett. 2001, 3,
3769−3771. (c) Hashmi, A. S. K.; Weyrauch, J. P.; Rudolph, M.;
Kurpejovic, E. Angew. Chem. 2004, 116, 6707−6709; Angew. Chem.,
Int. Ed. 2004, 43, 6545−6547. (d) Hashmi, A. S. K.; Weyrauch, J. P.;
Kurpejovic, E.; Frost, T. M.; Miehlich, B.; Frey, W.; Bats, J. W. Chem.
Eur. J. 2006, 12, 5806−5814. (e) Hashmi, A. S. K.; Wolfle, M.; Ata, F.;
̈
Hamzic, M.; Salathe,
2508. (f) Hashmi, A. S. K.; Salathe,
́
R.; Frey, W. Adv. Synth. Catal. 2006, 348, 2501−
́
R.; Frey, W. Chem. Eur. J. 2006, 12,
6991−6996. (g) Hashmi, A. S. K.; Rudolph, M.; Bats, J. W.; Frey, W.;
Rominger, F.; Oeser, T. Chem. Eur. J. 2008, 14, 6672−6678.
903
dx.doi.org/10.1021/om2008919 | Organometallics 2012, 31, 895−904

Organometallics
Article
(h) Rudolph, M.; McCreery, M. Q.; Frey, W.; Hashmi, A. S. K.
Beilstein J. Org. Chem. 2011, 7, 794−801.
(14) (a) Hashmi, A. S. K.; Loos, A.; Littmann, A.; Braun, I.; Knight,
J.; Doherty, S.; Rominger, F. Adv. Synth. Catal. 2009, 351, 576−582.
(b) Hashmi, A. S. K.; Hengst, T.; Lothschutz, C.; Rominger, F. Adv.
̈
Synth. Catal. 2010, 352, 1315−1337. (c) Hashmi, A. S. K.; Loos, A.;
Doherty, S.; Knight, J. G.; Robson, K. J.; Rominger, F. Adv. Synth.
Catal. 2011, 353, 749−759.
(15) Dinunno, L.; Scilimati, A. Tetrahedron 1986, 42, 3913−3920.
(16) Kalinski, C.; Umkehrer, M.; Gonnard, S.; Jager, N.; Ross, G.;
̅
Hiller, W. Tetrahedron Lett. 2006, 47, 2041−2044.
(17) Solladie-
́
Cavallo, A.; Bencheqroun, M. Tetrahedron Lett. 1990,
31, 2157−2160.
(18) (a) Hashmi, A. S. K.; Weyrauch, J. P.; Frey, W.; Bats, J. W. Org.
Lett. 2004, 6, 4391−4394. (b) Hashmi, A. S. K.; Rudolph, M.;
Schymura, S.; Visus, J.; Frey, W. Eur. J. Org. Chem. 2006, 4905−4909.
(c) Doherty, S.; Knight, J. G.; Hashmi, A. S. K.; Smyth, C. H.; Ward,
N. A. B.; Robson, K. J.; Tweedley, S.; Harrington, R. W.; Clegg, W.
Organometallics 2010, 29, 4139−4147. (d) Weyrauch, J. P.; Hashmi,
A. S. K.; Schuster, A.; Hengst, T.; Schetter, S.; Littmann, A.; Rudolph,
M.; Hamzic, M.; Visus, J.; Rominger, F.; Frey, W.; Bats, J. W. Chem.
Eur. J. 2010, 16, 956−963. (e) Hashmi, A. S. K.; Schuster, A. M.;
Schmuck, M.; Rominger, F. Eur. J. Org. Chem. 2011, 4595−4602.
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