Gold catalysis: Alkyl migration in the addition of alcohols to nitriles

Article abstract of DOI:10.1002/adsc.201000779

Benzhydroles and nitriles upon gold-catalysed conversion deliver symmetrical ethers and/or N-substituted carboxylic amides. While with most phosphane ligands tested, the dominating product is always the ether, with the trimesitylene ligand the amides are the major products. The reaction conditions are much milder than those reported previously. Mechanistic control experiments with a chiral alcohol prove the intermediacy of carbenium ions, further studies with not readily ionisable alcohols indicate that for the benzhydroles the carbenium ions and gold(I)-hydroxy complexes are intermediates.

Full text of DOI:10.1002/adsc.201000779

FULL PAPERS
DOI: 10.1002/adsc.201000779
Gold Catalysis: Alkyl Migration in the Addition of Alcohols to
Nitriles
Nada Ibrahim,a A. Stephen K. Hashmi,a,b,* and Frank Romingerb
a
CaRLa – Catalysis Research Laboratory, Im Neuenheimer Feld 584, 69120 Heidelberg, Germany
Organisch-Chemisches Institut, Universitꢀt Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
b
Fax : (+49)-6221-544-205; e-mail: hashmi@hashmi.de
Received: October 14, 2010; Revised: December 2, 2010; Published online: February 16, 2011
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000779.
Abstract: Benzhydroles and nitriles upon gold-cata- cohol prove the intermediacy of carbenium ions, fur-
lysed conversion deliver symmetrical ethers and/or ther studies with not readily ionisable alcohols indi-
N-substituted carboxylic amides. While with most cate that for the benzhydroles the carbenium ions
phosphane ligands tested, the dominating product is and gold(I)-hydroxy complexes are intermediates.
always the ether, with the trimesitylene ligand the
amides are the major products. The reaction condi-
tions are much milder than those reported previous- Keywords: alcohols; amides; complexes; gold; ni-
ly. Mechanistic control experiments with a chiral al- triles
Introduction
the Lewis acidity of gold, previously observed in
other reactions such as, for example, the elimination
Interest in the catalytic chemistry of gold complexes of water from intermediates.[13] In addition, the unan-
has experienced an exponential growth in the last ticipated formation of N-tert-butylacetamide was ob-
decade.[1–6] The fundamental contributions of Utimoto served as a side reaction.[14] The latter product clearly
et al.[7] and Teles et al.[8,9] have demonstrated the utili- arose from the addition of the alcohol to the nitrile,
ty of gold complexes for the hydration of alkynes, this transformation resembles the Ritter reaction,[15]
gold(I) being superior to goldACTHNUGRTENUNG(III). Since 1986 Au(I) but while the Ritter reaction needs strongly acidic
species have been known to be very good catalysts in conditions, the conditions of the present gold catalysis
various reactions, including carbon-carbon as well as are mild and almost neutral.
several carbon-heteroatom bond forming reac-
The alternative methods available are the reaction
tions.[1,10] Gold has successfully been used in the addi- of alcohols with nitriles in the presence of transition
tion of primary and secondary alcohols and even metal compounds[16] or trifluoromethanesulfonic an-
weak O-nucleophiles such as phenols[11,12] to alkynes, hydride.[17] Recently, the conversions of primary and
however tertiary alcohols were unreactive.[8,9] Here secondary benzylic alcohols by Fe
ACTHNUTRGNEUNG(III)-montmorillon-
we report new findings regarding the reactivity of ni- ite K10,[18] iron trichloride[19] and iodine[20] catalysts
triles in gold-catalysed reactions, findings which were were reported. In addition, the Ritter reaction involv-
initiated when re-investigating the reactivity of these ing the activated tert-butyl acetate has been reported
tertiary alcohols.
to be catalysed by sulfuric acid[21] or bismuth tri-
flate.[22] Many of these methods suffer some limita-
tions, such as low yield, hygroscopicity of the reagent,
tedious work-up and competing side reactions.
Results and Discussion
Building on our initial observation, we have devel-
Our attempts to add tertiary alcohols like tert-butyl oped a new gold(I)-catalysed reaction in which the
alcohol to alkynes in the presence of gold(I) catalysts amide can be synthesised from an alcohol and a ni-
in MeCN as solvent led to the formation of ethers, a trile under mild and neutral conditions.
result of an SN1 type substitution, overall a dehydra-
tive dimerisation of the bulky alcohol. This stresses
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Figure 1. Gold complexes used in the catalyst screening.
Initially, benzhydrol has been used as a model sub- column chromatography. With regard to handling and
strate and acetonitrile as solvent to test the different yield of 11 the other two counter ions were inferior
conditions.
(entries 10 and 11). The biarylphosphane gold(I) com-
The screening of the complexes shown in Figure 1 plex 7 gave mainly the ether 12 (entry 12), with the
(after activation by silver salts with non-coordinating adamantylphosphane complex 8 only 27% of 11 was
counter ions) with substrate 10 and acetonitrile re- observed (entry 13). The phosphite complex
9
vealed that with the simple triphenylphosphane com- (entry 14) delivered mainly 12 (in all cases various
plex 1 and four different counter ions (Table 1, en- amounts of the corresponding ether 12 were detected
tries 1–4) the ether 12 is the dominating substrate. by GS/MS analysis). Overall, only complex 6 gave the
The IPr NHC complex 2 showed a similar behaviour amide as the major product, with many of the phos-
(entry 5). With the two phosphanes in 3 and 4 some phane ligands the reaction could be directed to the
of the product 11 was observed (entries 6, 7), but the symmetrical ether as the major product. The control
phosphane 5 again gave only 12 (entry 8). The use of experiment with AgNTf2 only did not show any prod-
the trimesitylphosphane gold(I) complex 6 (entry 9)[23] uct formation (entry 15).
ꢀ
with the NTf2 counter anion gave a good yield of 11,
The structures of both products were proven by X-
the amide was isolated in 70% yield after work-up by ray crystal structure analyses (Figure 2), which clearly
proved the connectivity of the products.[24]
All these reactions were carried out at 758C with
Table 1. Catalyst optimisation for the reaction of 10 with
5 mol% of catalyst, at room temperature the reaction
was never observed. However, these conditions are
still much milder than those traditionally used in the
Ritter reaction, especially the iron- and iodine-cata-
lysed variations, where the temperature used is 1508C
and the catalyst loading is 20 mol%. It is noteworthy
that under the latter conditions the authors men-
tioned the formation of a stable ether generated from
the alcohol, when the reaction was carried out at
708C. This observation stresses the superiority of our
approach, as the amides are generated from secon-
dary benzylic alcohols under mild and neutral condi-
tions. The gold(I) catalysts are active enough to oper-
ate at a much lower temperature (758C).
The conditions described in the Table 1, entry 9
were found to be suitable for the synthesis of various
other amides in very good yields as summarised in
Table 2.
These gold-catalysed reactions yielded the desired
amides in good to excellent yield (Table 2, entries 1,
3, 5, 9, 10). Both acetonitrile and propionitrile gave
comparable results (entries 1/5, entries 2/4 and en-
tries 8/9). When methoxyacetonitrile, which as an ad-
ditional activating functional group contains an ether
group, was used, the reaction still proceeded in excel-
lent yield (entry 10). Moderate yields only were ob-
acetonitrile with various gold(I) complexes from Figure 1.
Entry
Gold(I) complex
Silver salt
Yield[a]
12
11
1
2
3
4
5
6
7
8
1
AgBF4
1%
1%
0%
16%
0%
60%
19%
0%
64%
62%
62%
0%
27%
2%
–
87%
85%
89%
76%
0%
40%
74%
86%
29%
38%
38%
3%
AgNTf2
AgOTf
AgSbF6
AgNTf2
AgSbF6
AgSbF6
AgSbF6
AgNTf2
AgOTf
AgSbF6
AgNTf2
AgSbF6
AgSbF6
AgNTf2
2
3
4
5
6
9
10
11
12
13
14
15
7
8
9
–
67%
78%
–
[a]
Yields were determined by GS/MS.
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Gold Catalysis: Alkyl Migration in the Addition of Alcohols to Nitriles
Figure 2. Solid state molecular structures of the amide 11 (left) and the ether 12 (right).
Table 2. Gold-catalysed addition of alcohols to nitriles under the optimised conditions from Table 1 (5 mol% 6, 5 mol%
AgNTf2, 758C, nitrile).
Entry
Alcohol
Nitrile
Amide
Yield[a]
1
10
CH3CN
11
70%
2
3
4
13
15
17
CH3CN
14
16
18
40%
61%
44%
CH3CN
CH3CH2CN
5
6
19
21
CH3CH2CN
CH3CN
20
70%
22
10%
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Yield[a]
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Table 2. (Continued)
Entry
Alcohol
Nitrile
Amide
7
8
23
25
CH3CH2CN
24
26
50%
55%
CH3CN
9
27
29
CH3CH2CN
CH3OCH2CN
28
30
72%
84%
10
[a]
Isolated yields after column chromatography.
Scheme 1. Gold(I)-catalysed reaction of (S)-(ꢀ)-1-phenylethanol with acetonitrile.
served with benzylic alcohols bearing electron-with- starting from early publications often were used as a
drawing groups (entries 2 and 4). Only a very poor solvent,[27,28] their activation was first reported by
yield was obtained with alcohol 21 (entry 6), the re- Nolan et al.[26] in their investigation of the gold-cata-
sulting amide was accompanied by an unidentified lysed nitrile hydration. They proposed nitrile s- or p-
product (21%, an unsymmetrical dimer of the starting bonded to gold complexes as key intermediates for
material) as well as the corresponding ether. Cinnam- the hydration reaction. In order to gain some mecha-
yl alcohol, 1-ethynylcyclohexanol and di(cylohexyl)- nistic insight, we analysed then the stereochemical
carbinol did not give the Ritter-type reaction products outcome of the reaction to confirm the presence of
with MeCN under our conditions, which reveals that free carbocation species in the course of the reaction.
the strong resonance stabilisation of the carbocation For this purpose, we performed the reaction under
in the benzylic positions is crucial for a conversion identical conditions to the ones described above,
under the mild conditions of gold catalysis. Conse- using enantiomerically pure (S)-(ꢀ)-1-phenylethanol
quently, this observation led us to assume that the re- and acetonitrile (Scheme 1). We observed the forma-
action is initiated by an activation of the alcohol by tion of racemic amide, which confirms the contribu-
gold(I) as first step[25] rather than a nitrile activa- tion of carbocationic intermediates. Furthermore, the
tion[26] pathway. Although nitriles have always been corresponding symmetrical ether is formed as a mix-
considered to be inert in gold catalysis[27] and thus ture of two diastereomers (the GC/MS analysis shows
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Gold Catalysis: Alkyl Migration in the Addition of Alcohols to Nitriles
Scheme 2. The two possible reaction mechanisms.
proton rather than R’+, a subsequent proto-deaura-
tion would furnish an imidate product H (Scheme 3).
If the reaction were to follow the pathway via inter-
mediate A, with an alcohol, which does not afford
stable carbenium ions R’+, simply no reaction should
be observed. The experiments with cinnamyl alcohol
or benzyl alcohol show no consumption of the starting
material, no reaction is observed. This indicates that
the pathway including the intermediates A, B, C and
D is operating.
Scheme 3. Expected imidate product H if F would be an in-
termediate and the group R’ would not furnish stabilised
carbenium ions.
ratio of 57:31 with a difference of 10 s in the retention
Following the suggestion of one of the referees, we
time). If the same substrate is converted in the ab- conducted an experiment with 4-methoxyphenylisoni-
sence of acetonitrile (in THF as the solvent), an 88% trile instead of a nitrile, which might also afford the
yield of the symmetrical ether was obtained. In both intermediate C under the same catalysis conditions.
reactions the conversion of the starting material is The reaction partner again was 10 under the normal
complete.
catalysis conditions (from Table 2), but no amide
Possible mechanisms for the formation of the product was obtained. Furthermore, 98% of 10 could
amides are shown in Scheme 2. There are two funda- be re-isolated, by GC/MS only traces of the ether 12
mentally different pathways. On the one hand there is were detected. Since usually 12 is formed by the
activation of the nitrile group by the gold catalyst as active gold catalyst, this result indicates that the isoni-
discussed by Nolan et al. for the hydration reaction trile readily coordinates to the cationic gold complex,
(intermediate E). Then the alcohol could add and which thus suffers a substrate inhibition.
form intermediate F. The group R’+ migrates from O
to N (via intermediate G), a direct pathway of a
[1,3]sigmatropic rearrangement would be an uncom- Conclusions
mon pathway. On the other hand, there could be an
inital coordination of the alcohol to the cationic In summary, we have developed a new and very mild
gold(I) catalyst (intermediate A), followed by the gold(I)-catalysed reaction for the synthesis of amides
generation of a carbocation which then is trapped by from readily available benzohydric alcohols and ni-
the (weak nucleophile) nitrile to furnish intermediate triles. The neutral and mild character of the applied
C. Here an LAuOH species[29] B would be an inter- conditions for this transformation makes it a valuable
mediate, which then adds to C to afford D. Tautome- alternative to those previously described in the litera-
rization would furnish the amide product. This path- ture. Further mechanistic studies of an alcohol activa-
way would include a new and interesting reactivity of tion by cationic gold complexes are under investiga-
the gold(I) hydroxide species.
tion.
If the reaction were to follow the pathway via inter-
mediate F, in the case of alcohols which are still nu-
cleophilic (for example, do not possess additional
steric hindrance) but do not afford stable carbenium
ions R’+, the addition to the nitrile should still be pos-
Experimental Section
Commercially available reagents and solvents were used
sible. But then the intermediate F should eliminate a without further purification. Yields refer to isolated and pu-
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Nada Ibrahim et al.
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rified products. Column chromatography was performed on
silica gel (40.0–63.0 nm) from Macherey–Nagel. Mass spec-
tra were recorded on a Vacuum Generators ZAB-2F, Finni-
gan MAT TSQ 700 or JEOL JMS-700 spectrometer. GC-
MS were recorded on an Agilent 5890 Series II Plus with an
HP 5972 mass detector. IR spectra were recorded on a
Bruker Vector 22 FT-IR. Crystal structure analysis was ac-
complished on Bruker Smart CCD or Bruker APEX diffrac-
tometers. NMR spectra were recorded on Bruker Avance
500 or Bruker Avance 300 spectrometers. Chemical shifts of
1H NMR and 13C NMR are reported in ppm (d units) and
residual non deuterated solvent was used as internal refer-
ence. The following abbreviations were used to designate
the multiplicities: s=singlet, d=doublet, t=triplet, q=quar-
tet, bs=broad signal, m=multiplet.
1508C. 1H NMR (500 MHz, CDCl3): d=7.30–7.29 (d, J=
3 Hz, 4H), 7.13–7.12 (d, J=3 Hz, 4H), 6.19 (bs, 1H), 6.16
(d, J=6 Hz, 1H), 2.05 (s, 3H); 13C NMR (CDCl3, 125 MHz):
d=169.3 (1C), 139 .5 (2C), 133.6 (2C), 128.9 (4C), 128.7
(4C), 55.9 (1C), 23.2 (1C). MS (electrospray): m/z (%)=
611.06 (100) [2M+Na]+; HR-MS (ESI): m/z=294.04470,
˜
calcd. for C15H14Cl2NO: 294.04483; IR (KBr): n=3279,
2929, 1652, 1542, 1491, 1092, 1015, 853, 822, 551 cmꢀ1.
N-(1-Phenylethyl)acetamide (16)
Typical Procedure for the Addition Reaction of
Alcohols with Nitriles
The typical procedure was applied on 1-phenylethanol
(60.0 mg, 500 mmol), (Mes)3PAuCl (15.5 mg, 24.0 mmol) and
AgNTf2 (9.7 mg, 25 mmol) in anhydrous acetonitrile (1 mL).
The title compound was obtained as colourless oil; yield:
49 mg (61%). It was precipitated from pentane; mp 498C.
1H NMR (300 MHz, CDCl3): d=7.31–7.17 (m, 5H), 6.31 (d,
J=6 Hz, 1H), 5.04 (q, J=6 Hz, 1H), 1.90 (s, 3H), 1.42 (d,
J=6 Hz, 3H); 13C NMR (CDCl3, 75 MHz): d=169.6 (1C),
143.2 (1C), 128.6 (2C), 127.3 (1C), 126.2 (2C), 48.9 (1C),
23.2 (1C), 21.8 (1C); HR-MS (ESI): m/z=164.10701, calcd.
A
glass tube, purged with argon, was charged with
(Mes)3PAuCl (5 mol%), AgNTf2 (5 mol%) and the nitrile
(1 mL). The mixture was stirred at room temperature, and
then the alcohol (1 equiv.) was added. The tube was sealed
with a screw cap and heated in an oil bath at 758C for 24 h.
Then the reaction mixture was cooled down to room tem-
perature. The product was purified by column chromatogra-
phy on silica gel using a gradient of petrolium ether/EtOAc
(10: 0!2:8).
˜
for C10H14NO: 164.10699; IR (KBr): n=3263, 3066, 2976,
1642, 1555, 1450, 1376, 1199, 1137, 702 cmꢀ1
.
N-Benzhydrylacetamide (11)
N-[Bis(4-chlorophenyl)methyl]propionamide (18)
The typical procedure was applied on benzhydrol (184 mg,
1.00 mmol), (Mes)3PAuCl (31 mg, 50 mmol) and AgNTf2
(20 mg, 50 mmol) in anhydrous acetonitrile (1 mL). The title
compound was obtained as a white solid; yield: 162 mg
(70%). It was crystallised from petroleum ether/dichlorome-
The typical procedure was applied on 4,4’-dichlorobenzhy-
drol (100 mg, 400 mmol), (Mes)3AuCl (12 mg, 20 mmol) and
AgNTf2 (7.5 mg, 20 mmol) in propionitrile (1 mL). The com-
pound was obtained as a white solid; yield: 53 mg (44%)
and it was crystallised from petroleum ether/dichlorome-
1
thane; mp 1288C. H NMR (300 MHz, CDCl3): d=7.27–7.13
(m, 10H), 6.25 (bs, 1H), 6.15 (d, J=9 Hz, 1H), 1.59 (d,
3H); 13C NMR (CDCl3, 75 MHz) d=169.6 (1C), 141.8 (2C),
129.0 (5C), 127.8 (5C), 57.5 (1C), 23.6 (1C); MS (electro-
spray): m/z (%)=473.22 (100) [2M+Na]+; HR-MS (ESI):
m/z=226.12264, calcd. for C15H16NO:ꢀ2126.12274; IR (KBr):
1
thane; mp 1398C. H NMR (300 MHz, CDCl3): d=7.28 (d,
J=9 Hz, 4H), 7.13 (d, J=9 Hz, 4H), 6.17 (m, 2H), 2.27 (q,
J=9 Hz, 2H), 1.16 (t, J=6 Hz); 13C NMR (CDCl3,
75 MHz): d=173.4 (1C), 140.0 (2C), 133.9 (2C), 129.3 (4C),
129.2 (4C), 56.2 (1C), 30.0 (1C), 10.2 (1C); HR-MS (ESI):
m/z=308.06039, calcd. for C16H16Cl2NO: 308.06035; IR
˜
n=3258, 3061, 1646, 1545, 744, 698 cm .
˜
(KBr): n=3294, 3050, 2981, 2936, 1646, 1535, 1491, 1092,
N-[Bis(4-chlorophenyl)methyl]acetamide (14)
1015, 848, 824, 794 cmꢀ1.
N-Benzhydrylpropionamide (20)
The typical procedure was applied on benzhydrol (100 mg,
540 mmol), (Mes)3PAuCl (17 mg, 25 mmol) and AgNTf2
(10.4 mg, 25.0 mmol) in propionitrile (1 mL). The title com-
pound was obtained as a white solid; yield: 91 mg (70%). It
The typical procedure was applied on 4,4’-dichlorobenzhy-
drol (100 mg, 400 mmol), (Mes)3PAuCl (12 mg, 20 mmol) and
AgNTf2 (7.5 mg, 20 mmol) in anhydrous acetonitrile (1 mL).
The title compound was obtained as a white solid; yield:
47 mg (40%). It was crystallised from petroleum ether; mp
1
was crystallised from petroleum ether; mp 1108C. H NMR
(300 MHz, CDCl3): d=7.34–7.20 (m, 10H), 6.25 (m, 2H),
2.27 (q, J=6 Hz, J’=9 Hz, 2H), 1.16 (t, J=6 Hz, J’=9 Hz,
3H); 13C NMR (CDCl3, 75 MHz): d=173.3 (1C), 142.0
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Gold Catalysis: Alkyl Migration in the Addition of Alcohols to Nitriles
N-(Di-p-tolylmethyl)acetamide (26)
(2C), 129.0 (5C), 127.8 (5C), 57.2 (1C), 30.05 (1C), 10.27
(1C); HR-MS (ESI): m/z=240.13839, calcd. for C16H18NO:
The typical procedure was applied on 4,4’-dimethylbenzhy-
drol (100 mg, 490 mmol), (Mes)3AuCl (14.6 mg, 20.0 mmol)
and AgNTf2 (9.0 mg, 20 mmol) in propionitrile (1 mL). The
compound was obtained as a white solid; yield: 65 mg
(55%): mp 1498C. 1H NMR (300 MHz, CDCl3): d=7.15–
7.08 (m, 8H), 6.30 (d, J=9 Hz, 1H), 6.16 (d, J=9 Hz, 1H),
˜
240.13829; IR (KBr): n=3323, 3255, 3029, 1645, 1538, 1493,
739, 703 cmꢀ1.
N-[CyclopropylACHTUNGTRENNUNG(phenyl)methyl]acetamide (22)
1
2.32 (s, 6H), 2.04 (s, 3H); H NMR (75 MHz, CDCl3): d=
169.3 (1C), 138.6 (2C), 137.1 (2C), 129.3 (4C), 127.3 (4C),
56.6 (1C), 23.2 (1C), 21.0 (2C); HR-MS (ESI): m/z=
˜
254.15405, calcd. for C17H20NO: 254.15394; IR (KBr): n=
3293, 2919, 1646, 1546, 1512, 1370, 811, 762, 589, 546 cmꢀ1.
N-(Di-p-tolylmethyl)propionamide (28)
The typical procedure was applied on cyclopropyl-
ACHTUNGTRENNUNG(phenyl)methanol (100 mg, 670 mmol), (Mes)3PAuCl
(20.8 mg, 30.0 mmol) and AgNTf2 (13 mg, 30 mmol) in anhy-
drous acetonitrile (1 mL). The title compound was obtained
as a white solid; yield: 10 mg (10%); mp 2108C, decomposi-
tion. 1H NMR (300 MHz, CDCl3): d=7.37–7.20 (m, 5H),
6.45 (d, J=15 Hz, 1H), 6.17–6.10 (m, 1H), 5.54 (bs, 1H),
3.44–3.37 (m, 2H), 2.46–2.38 (qd, J=1 Hz, J’=6 Hz, 2H),
1.97 (s, 3H); 13C NMR (CDCl3, 75 MHz): d=170.0 (1C),
137.1 (1C), 132.4 (1C), 128.6 (1C), 127.4 (1C), 126.8 (1C),
126.0 (1C), 38.9 (2C), 33.05 (2C), 23.4 (1C); MS (EI+): m/z
(%)=105.01 (30) [C7H7N]+.
The typical procedure was applied on 4,4’-dimethylbenzhy-
drol (100 mg, 490 mmol), (Mes)3AuCl (14.6 mg, 20.0 mmol)
and AgNTf2 (9.0 mg, 20 mmol) in propionitrile (1 mL). The
compound was obtained as a white solid; yield: 90 mg
(72%); mp 1388C. 1H NMR (300 MHz, CDCl3): d=7.17–
7.11 (m, 8H), 6.28 (bs, 1H), 6.21 (d, J=9 Hz), 2.34 (s, 6H),
2.32–2.24 (q, J=9 Hz, J’=6 Hz, 2H), 1.21–1.16 (t, J=9 Hz,
J’=6 Hz, 3H); 13C NMR (75 MHz, CDCl3): d=172.9 (1C),
138.9 (2C), 136.9 (2C), 129.3 (4C), 127.3 (4C), 56.3 (1C),
29.7 (1C), 21.0 (2C), 9.9 (1C); HR-MS (ESI): m/z=
N-[CyclopropylACHTUNGTRENNUNG(phenyl)methyl]propionamide (24)
˜
268.16971, calcd. for C18H22NO: 268.16959; IR (KBr): n=
3304, 2967, 1648, 1540, 1513, 849 cmꢀ1.
N-(Di-p-tolylmethyl)-2-methoxyacetamide (30)
The typical procedure was applied on 1-phenylethanol
(100 mg, 810 mmol), (Mes)3PAuCl (25 mg, 40 mmol) and
AgNTf2 (16 mg, 40 mmol) in propionitrile (1 mL). The title
compound was obtained as a colourless oil; yield: 72 mg
1
(50%); mp 608C. H NMR (300 MHz, CDCl3): d=7.37–7.22
(m, 5H), 6.16 (bs, 1H), 5.17–5.08 (m, 1H), 2.24–2.16 (q, J=
6, 2H), 1.48 (d, J=6 Hz, 3H), 1.14 (t, J=9 Hz); 13C NMR
(CDCl3, 75 MHz) d=173.0 (1C), 143.4 (2C), 128.6 (2C),
127.2 (1C), 126.2 (2C), 48.6 (1C), 29.7 (1C), 21.82 (1C), 9.8
(1C); MS (EI+): m/z (%)=177.2 (96) [M]+, 106.1 (100)
[MꢀCH3CH2CONH]+; HR-MS (EI+): m/z=177.1155, calcd.
The typical procedure was applied on 4,4’-dimethylbenzhy-
drol (100 mg, 490 mmol), (Mes)3AuCl (14.6 mg, 20.0 mmol)
and AgNTf2 (9.0 mg, 20 mmol) in methoxyacetonitrile
(1 mL). The compound was obtained as a white solid; yield:
112 mg (80%); mp 808C.1H NMR (300 MHz, CDCl3): d=
7.12 (m, 9H), 6.23 (d, J=9 Hz, 1H), 3.95 (s, 2H), 3.40 (s,
3H), 3.32 (s, 6H); 13C NMR (75 MHz, CDCl3): d=168.9
(1C), 139.0, 137.5, 129.7, 127.8, 72.4 (1C), 59.6 (1C), 56.0
(1C), 21.4 (2C); MS: m/z (%)=283.3 (100) [M]+., 236.2
˜
for C11H15NO: 177.1154; IR (KBr): n=3329, 2973, 1650,
1534, 1495, 1245, 760, 703 cmꢀ1; NB: the same result was ob-
tained when 2 mL propionitrile were used.
Adv. Synth. Catal. 2011, 353, 461 – 468
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
467

Nada Ibrahim et al.
FULL PAPERS
(60) [MꢀCH3OCH3]+, 195.2 (68) [MꢀCH3OCH2CONH];
HR-MS (EI+): m/z=283.1587, calcd. for C18H21NO2:
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283.1572; IR (KBr): n3325, 2942, 1659, 1511, 1448, 1197,
1108, 813, 806, 600 cmꢀ1.
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The product was purified by column chromatography on
silica gel using a gradient of petrolium ether/EtOAc (10:0!
8:2). The product is obtained as a white solid and crystal-
1
lised from petroleum ether; mp 988C. H NMR (300 MHz,
CDCl3): d=7.31–7.15 (m, 20H), 5.32 (s, 2H); 13C NMR
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Acknowledgements
N. I. works at CaRLa of Heidelberg University, being co-fi-
nanced by University of Heidelberg, the State of Baden-Wꢀrt-
temberg and BASF SE. Support of these institutions is greatly
acknowledged.
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[24] CCDC 796517 (11), CCDC 796518 (12) and CCDC
796519 (N-tert-butylacetamide) contain the supplemen-
tary 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.
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468
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ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2011, 353, 461 – 468