Efficient One-Pot Synthesis of Unsymmetrical Gold ... - ACS Publications

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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-Universität 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 electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly.

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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 Here we report our findings on further exploration of the scope of that method for the preparation of gold(I) NHC complexes with donor- or acceptor-substituted phenyl groups and screening of their catalytic activity.

Scheme 1. Synthesis of the Gold(I) Aryl Isocyanide Complexes 3

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). Another very bulky substituent is the adamantyl group, which also gave a similarly reduced yield (74%, entry 7). The 1-naphthyl

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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 provided the isocyanides 2. From these and (tht)gold(I) chloride (tht = tetrahydrothiophene), the chlorogold(I) complexes 3 could be easily formed. 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 © 2012 American Chemical Society

Received: October 7, 2011 Published: January 25, 2012 895

dx.doi.org/10.1021/om2008919 | Organometallics 2012, 31, 895−904

Organometallics

Article

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). 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

Table 1. Synthesis of Unsymmetrically Substituted Au(I) NHC Complexes 5

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 goldcatalyzed 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.

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 a

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 phenylsubstituted 4b as the chloroammonium reagent. Here the 896


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Table 2. Gold Catalyst Loading in the Gold-Catalyzed Synthesis of Phenol 7

entry

cat.

loading (mol %)

solvent

time

conversion (%)

yield (%)a

TON

1 2 3 4 5

5a 5a 5a 5a 5a

1.0 0.5 0.1 0.05 0.05

CDCl3 CDCl3 CDCl3 CDCl3 CD2Cl2

6 7 8 9

5b 5b 5b 5b

0.5 0.5 0.1 0.1

CDCl3 CD2Cl2 CDCl3 CD2Cl2

67 154 670 1320 1140 1200 106 124

5c

0.5

CDCl3

69 72 71 74 71 69 54 53

730 720 710 740 710 730 108 106

11 12

5c 5c

0.1 0.1

CDCl3 CD2Cl2

13 14 15

5d 5d 5d

0.5 0.1 0.1

CDCl3 CDCl3 CD2Cl2

79 79 79 17

790 790 790 34

16 17 18

5e 5e 5e

0.5 0.1 0.1

CDCl3 CDCl3 CD2Cl2

80 73 76 8

800 730 760 16

19

5f

0.1

CD2Cl2

20 21 22 23 24 25 26 27 28 29

5g 5h 5i 5j 5k 5g 5h 5i 5k 5g

0.1 0.1 0.1 0.1 0.1 0.05 0.05 0.05 0.05 0.01

CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2 CD2Cl2

100 100 100 100 57 60 93 100 0 69 77 78 79 80 83 90 100 0 94 97 100 62 0 81 86 88 49 0 98 100 61 72 76 78 100 100 100 86 100 100 81 94 48 69 69

67 77 67 66 57 60 53 62

10

1h 1 day 5 days 7 days 3 days 5 days 10 days 1.5 h 7 days 1 day 3 days 4 days 5 days 6 days 7 days 6 days 7 days 7 days 10 h 1 day 2 days 7 days 7 days 10 h 1 day 2 days 7 days 7 days 10 h 1 day 1.5 h 1 days 2 days 3 days 10 h 1 day 10 h 1 day 1 day 1 day 1 day 1 day 1 day 3 days 4 days

79 79 60 70 73 78 90 96 97 76 95 90 68 84 32 55 55

790 790 600 700 730 780 900 960 970 760 950 1800 1360 1680 640 5500 5500

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).

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

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 897


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Table 3. Screening the New NHC Gold(I) Catalysts in the Synthesis of Oxazole 9

entry

cat.

loading (mol %)

1 2 3

5b 5b 5b

1.0 0.5 0.1

4

5g

0.1

5

5h

0.1

6

5i

0.1

7

5k

0.1

time 9 1 4 7 4 7 4 7 4 7 4 7

h day days days days days days days days days days days

conversion (%)a

yield of 9 (%)a

TON

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

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). 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). 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 dichloromethane 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 (naphthylsubstituted, 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

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%.

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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 complexes. A strong dependence on the electronic properties of the aryl group could not be observed in these test reactions.

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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 spectrometers. 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 898


Organometallics

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N-(2,4-Dimethoxyphenyl)formamide (1b). N-(2,4Dimethoxyphenyl)formamide (1b) was prepared according to GP 1

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. 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. Recrystallization from acetone/petroleum ether (1/1) afforded 1b as colorless crystals; yield 1.72 g (73%), mp 141 °C. IR (KBr): ν̃ 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. N-(2,6-Dimethoxyphenyl)formamide (1c). N-(2,6Dimethoxyphenyl)formamide (1c) was prepared according to GP 1

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. 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 151 °C. IR (KBr): ν̃ 3429, 3223, 2996, 2945, 2875, 2841, 1684, 1663, 1600, 1543, 1478, 1463, 1432, 1387, 1310, 1261, 1110, 1028, 770, 714 cm−1. 1H 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

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 literature procedure.9

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): ν̃ 3418, 3221, 3115, 3072, 1706, 1675, 1621, 1595, 1533, 1469, 1455, 1415, 1317, 1293, 1260, 1230, 810, 748, 636, 438 cm−1. 1H 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 according 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): ν̃ 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 colorless crystals. The 1H 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). 899


Organometallics

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751, 581, 559 cm−1. 1H 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. 2,4-Dimethoxyphenyl Isocyanide (2b). 2,4-Dimethoxyphenyl isocyanide (2b) was prepared according to GP 2 from 1.72 g (9.47 mmol)

H 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). ((2,4Dimethoxylphenyl)isocyano)gold(I) chloride (3b) was prepared 1

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): ν̃ 3440, 3091, 3053, 3019, 2968, 2930, 2832, 2222, 1687, 1602, 1582, 1500, 1465, 1454, 1430, 1419, 1315, 1301, 1264, 1212, 1203, 1161, 1122, 1036, 1017, 829 cm−1. 1H 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). ((2,6Dimethoxylphenyl)isocyano)gold(I) chloride (3c) was prepared

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 ether/ethyl acetate 15/1); mp 72 °C. IR (KBr): ν̃ 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): ν̃ 3442, 3098, 3014, 2940, 2840, 2570, 2351, 2218, 1629, 1595, 1486, 1453, 1435, 1306, 1268, 1115, 1023, 774, 718, 534 cm−1. 1 H 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. ((2-Fluorophenyl)isocyano)gold(I) Chloride (3d). ((2Fluorophenyl)isocyano)gold(I) chloride (3d) was prepared according

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 (dichloromethane); mp 101 °C. IR (KBr): ν̃ 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 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): ν̃ 3440, 2222, 1616, 1559, 1494, 1458, 1324, 1276, 1256, 1199, 1163, 1103, 1062, 952, 852, 759, 668, 568, 480 cm−1. 1H 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). ((4Nitrophenyl)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). 1 H 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). ((2Methoxylphenyl)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): ν̃ 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).

((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 (KBr): ν̃= 3431, 2969, 2941, 2838, 2228, 1636, 1595, 1495, 1466, 1438, 1303, 1287, 1262, 1180, 1166, 1111, 1041, 1016, 753, 531 cm−1. 900


Organometallics

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((2,6-Dimethylphenyl)isocyano)gold(I) Chloride (3f). ((2,6Dimethylphenyl)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-Methoxyphenyl)amino)(isopropylamino)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 prepared 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 chromatography on silica (dichloromethane); mp 230 °C. IR (KBr): ν̃ 3442, 2970, 1597, 1509, 1459, 1436, 1368, 1347, 1330, 1280, 1271, 1249, 1200, 1184, 1160, 1119, 1067, 1050, 1028, 762 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): [C13H18AuClN2O]+ calcd 450.0773, found 450.0781. [ ( ( 2, 4 - D i m e t h o x y p h e n y l ) a m in o)(isopro pylamino)imidazolidene]gold(I) Chloride (5b). [((2,4-Dimethoxyphenyl)-

50.0 mg (310 μmol) of 1-adamantyl isocyanide were employed. Evaporation of the solvent afforded 3g as a colorless solid (125 mg, >99%). 1H NMR (250 MHz, CDCl3): δ 1.66−1.77 (m, 6H), 2.12− 2.13 (m, 6H), 2.20 (m, 3H). All spectral data are in accordance with previous reports.9 ((2-Naphthyl)isocyano)gold(I) Chloride (3h). 3h was prepared according to GP 3, where 239 mg (750 μmol) of (tht)AuCl and

114 mg (750 μmol) of 2-naphthyl isocyanide were employed. Evaporation of the solvent afforded 3h as a colorless solid (292 mg, >99%). 1H NMR (250 MHz, CDCl3): δ 7.50−7.53 (m, 1H), 7.65− 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 prepared 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 (dichloromethane); mp 206 °C. IR (KBr): ν̃ 3431, 2968, 2935, 2837, 2052, 1611, 1518, 1456, 1418, 1368, 1328, 1274, 1209, 1161, 1129, 1063, 1029, 938, 833, 596 cm−1. 1H NMR (300 MHz, CDCl3): δ 1.29 (s, 3H), 1.31 (s, 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 - D i m e t h o x y p h e n y l ) a m in o)(isopro pylamino)imidazolidene]gold(I) Chloride (5c). [((2,6-Dimethoxyphenyl)amino)(isopropylamino)imidazolidene]gold(I) chloride (5c) was

34.0 mg (310 μmol) of cyclohexyl isocyanide were employed. Evaporation of the solvent afforded 3i as a colorless solid (110 mg, >99%). 1H NMR (250 MHz, CDCl3): δ 1.42−1.48 (m, 4H), 1.72− 1.81 (m, 4H), 1.97−1.99 (m, 2H), 3.87−3.91 (m, 1H). All spectral data are in accordance with previous reports.9 N-(2-Chloro-2-phenylethyl)isopropylammonium Chloride (4b). Under an atmosphere of nitrogen isopropylamine (2.00 g,

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 (3.64 g, 20.3 mmol, 60%). 1H 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, 13.2 mmol, 65%); mp >383 °C. IR (KBr): ν̃ 3453, 2945, 2753, 2687, 2440, 1580, 1496, 1471, 1450, 1408, 1391, 1376, 1287, 1152, 1135, 996, 765, 701, 669, 540 cm−1. 1H NMR (250 MHz, CDCl3): δ 1.51

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): ν̃ 3435, 2970, 2933, 2838, 1630, 1596, 1514, 1479, 1456, 1434, 1368, 1324, 1301, 1274, 1259, 1193, 1112, 780, 636, 591 cm−1. 1H 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. 901


Organometallics

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column chromatography on silica (DCM); mp: 217 °C dec. IR (KBr): ν̃ 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. [((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

[((2-Fluorophenyl)amino)(isopropylamino)imidazolidene]gold(I) Chloride (5d). [((2-Fluorophenyl)amino)(isopropylamino)-

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 chromatography on silica (dichloromethane); mp 207 °C. IR (KBr): ν̃ 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). 13 C 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): ν̃ 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. [(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

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 (KBr): ν̃ 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): ν̃ 3427, 2966, 2931, 2854, 1635, 1513, 1485, 1456, 1386, 1365, 1335, 1313, 1290, 1246, 1185, 1122, 993, 891, 607, 581 cm−1. 1H 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)-2phenylimidazolidene]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): ν̃ 3437, 2970, 2064, 1635, 1559, 1540, 1508, 1489, 1457, 1368, 1322, 1276, 1201, 1124, 1100, 1015, 788, 669, 608 cm−1. 1H 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): ν̃ 2959, 2928, 2858, 1733, 1629, 1598, 1506, 1465, 1417, 1370, 1315, 1256, 1177, 1127, 1033, 858, 811, 752, 698, 476 cm−1. 1 H 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


Organometallics

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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; WileyVCH: Weinheim, Germany, 2006. (b) Dröge, 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. (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 carbene ligand and also did not aim at catalysis: (c) Schrölkamp, S.; Völkl, A.; Lügger, 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, N.; Lügger, T.; Fehlhammer, W. P. Chem. Eur. J. 2003, 9, 704−712. (e) Hahn, F. E.; Plumed, C. G.; Münder, M.; Lügger, 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. (9) Hashmi, A. S. K.; Lothschütz, C.; Böhling, C.; Hengst, T.; Hubbert, C.; Rominger, F. Adv. Synth. Catal. 2010, 352, 3001−3012. (10) Hashmi, A. S. K.; Lothschütz, C.; Graf, K.; Hengst, T.; Schuster, A.; Rominger, F. Adv. Synth. Catal. 2011, 354, 1407−1412. (11) Hashmi, A. S. K.; Lothschütz, C.; Böhling, C.; Rominger, F. Organometallics 2011, 30, 2411−2417. (12) CCDC 832043 (5b) contains the supplementary crystallographic 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.; Wölfle, M.; Ata, F.; Hamzic, M.; Salathé, R.; Frey, W. Adv. Synth. Catal. 2006, 348, 2501− 2508. (f) Hashmi, A. S. K.; Salathé, 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.

(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)-2phenylimidazolidene]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

(53.3 mg, 77%) after column chromatography on silica (dichloromethane); mp 215 °C. IR (KBr): ν̃ 2960, 2929, 2860, 1734, 1597, 1507, 1463, 1424, 1370, 1321, 1302, 1249, 1201, 1178, 1125, 1076, 1024, 759, 699, 595 cm−1. 1H 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.

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S 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.

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AUTHOR INFORMATION

Corresponding Author

*Tel: +49(0)6221-548413. Fax: +49(0)6221-544205. E-mail: [email protected].

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ACKNOWLEDGMENTS Y. Yu is grateful to the CSC for a fellowship. Gold salts were generously donated by Umicore AG & Co., KG. REFERENCES

(1) For the discovery: (a) Ö fele, K. J. Organomet. Chem. 1968, 12, 42−43. (b) Wanzlick, H.-W.; Schönherr, H. J. Angew. Chem. 1968, 80, 154−155; Angew. Chem., Int. Ed. 1968, 7, 141−142. Medical applications: (c) Ö zdemir, I.̇ ; Temelli, N.; Günal, 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.; 903


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Efficient One-Pot Synthesis of Unsymmetrical Gold ... - ACS Publications

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