Exploring the scope of nitrogen acyclic carbenes (NACs) in gold-catalyzed reactions

Article abstract of DOI:10.1021/om100507r

The catalytic activity of the recently reported nitrogen acyclic carbene (NAC) complexes of gold(I) has been investigated and compared with the reported activity of other gold(I) and gold(III) complexes. The complexes studied, [AuCl{C(NEt₂)(NHTol-p)}], [AuCl{C(NEt₂)(NHXylyl)}], and [Au(NTf₂){C(NEt₂)(NHXylyl)}], are very active in processes such as the rearrangement of homopropargylsulfoxides, the intramolecular hydroamination of N-allenyl carbamates, the intramolecular hydroalkoxylation of allenes, the hydroarylation of acetylenecarboxylic acid ester, and the benzylation of anisole. Although the NAC ligands have not been optimized for the reactions tested, the yields obtained are usually similar and sometimes better than those reported with other catalysts, showing that the presence of N-H bonds and the wider N-C-N angle in the NAC (as compared to the NHC) complexes are not detrimental for the catalysis. For the hydroarylation reaction (where two competing products can be formed), the NAC complexes allow favoring one over the other. For the benzylation of anisole the selectivity is complementary to that obtained using H[AuCl₄] as catalyst, and depending on the substrate, the NAC gold(III) complexes outperform the activity of H[AuCl₄]. On average, the reactivity found suggests that the basicity of NACs toward gold(I) is very similar to that of NHCs and higher than that of phosphines.

Full text of DOI:10.1021/om100507r

Organometallics 2010, 29, 3589–3592 3589
DOI: 10.1021/om100507r
Exploring the Scope of Nitrogen Acyclic Carbenes (NACs) in
Gold-Catalyzed Reactions
ꢀ
Camino Bartolome, Domingo Garcıa-Cuadrado, Zoraida Ramiro, and Pablo Espinet*
´
ꢀ
IU CINQUIMA/Quımica Inorganica, Facultad de Ciencias, Universidad de Valladolid,
E-47071 Valladolid, Spain
Received May 24, 2010
The catalytic activity of the recently reported nitrogen acyclic carbene (NAC) complexes of gold(I)
has been investigated and compared with the reported activity of other gold(I) and gold(III)
complexes. The complexes studied, [AuCl{C(NEt2)(NHTol-p)}], [AuCl{C(NEt2)(NHXylyl)}], and
[Au(NTf2){C(NEt2)(NHXylyl)}], are very active in processes such as the rearrangement of homo-
propargylsulfoxides, the intramolecular hydroamination of N-allenyl carbamates, the intramole-
cular hydroalkoxylation of allenes, the hydroarylation of acetylenecarboxylic acid ester, and the
benzylation of anisole. Although the NAC ligands have not been optimized for the reactions tested,
the yields obtained are usually similar and sometimes better than those reported with other catalysts,
showing that the presence of N-H bonds and the wider N-C-N angle in the NAC (as compared to
the NHC) complexes are not detrimental for the catalysis. For the hydroarylation reaction (where
two competing products can be formed), the NAC complexes allow favoring one over the other. For
the benzylation of anisole the selectivity is complementary to that obtained using H[AuCl4] as
catalyst, and depending on the substrate, the NAC gold(III) complexes outperform the activity of
H[AuCl4]. On average, the reactivity found suggests that the basicity of NACs toward gold(I) is very
similar to that of NHCs and higher than that of phosphines.
Introduction
attention,2 because, as an advantage on phosphines, they
are not prone to oxidation. Moreover, recently, Bertrand
et al. have successfully used very interesting cationic gold(I)
complexes with five-membered cyclic (alkyl)(amino)-
carbene (CAAC) ligands as catalysts in some organic
transformations.3
In contrast to the scarce attention paid just twenty years
ago to gold complexes as catalysts, they are now recognized
as very active compounds in many organic transformations.1
Much research in the topic has been carried out on classical
complexes with phosphine ligands, but in the last years
nitrogen heterocyclic carbene ligands (NHCs) have gained
To the widely used NHC catalysts and the much less
exploited CAACs, we recently added two other carbene
types, the so-called hydrogen-bonded heterocyclic com-
plexes (HBHCs)4,5 and the nitrogen acyclic complexes
(NACs),6 both shown in Scheme 1. Although gold(I) com-
plexes of the NAC type have been long known,7-9 they had
never been applied in catalysis previous to our works show-
ing their high catalytic activity in the skeletal rearrangement
and in the alkoxycyclization of 1,6-enynes.5,6,10
*To whom correspondence should be addressed. E-mail: espinet@
qi.uva.es.
(1) Some recent reviews of gold-catalyzed reactions: (a) Hashmi,
A. S. K. Chem. Rev. 2007, 107, 3180–3211. (b) Jimenez-Nꢀunez, E.;
Echavarren, A. M. Chem. Commun. 2007, 333–346. (c) Gorin, D. J.; Toste,
F. D. Nature 2007, 446, 395–403. (d) Hashmi, A. S. K.; Hutchings, G. J.
Angew. Chem., Int. Ed. 2006, 45, 7896–7936. (e) Hashmi, A. S. K. Gold
Bull. 2004, 37, 1–2. (f) Li, Z.; Brouwer, C.; He, C. Chem. Rev. 2008, 108,
ꢀ
~
As we showed by NMR in our previous works,5,6 depend-
ing on the ability of the solvent to break the intramolecular
ꢀ
3239–3265. (g) Arcadi, A. Chem. Rev. 2008, 108, 3266–3325. (h) Jimenez-
Nꢀunez, E.; Echavarren, A. M. Chem. Rev. 2008, 108, 3326–3350. (i) Gorin,
~
D. J.; Sherry, B. D.; Toste, F. D. Chem. Rev. 2008, 108, 3351–3378. (j) Patil,
N. T.; Yamamoto, Y. Chem. Rev. 2008, 108, 3395–3442. (k) Shen, H. C.
Tetrahedron 2008, 64, 3885–3903. (l) Widenhoefer, R. A. Chem.;Eur. J.
2008, 14, 5382–5391. (m) Krause, N.; Belting, V.; Deutsch, C.; Erdsack, J.;
Fan, H. T.; Gockel, B.; Hoffmann-Roder, A.; Morita, N.; Volz, F. Pure Appl.
Chem. 2008, 80, 1063–1069.
ꢀ
(4) Bartolome, C.; Carrasco-Rando, M.; Coco, S.; Cordovilla, C.;
Martın-Alvarez, J. M.; Espinet, P. Inorg. Chem. 2008, 47, 1616–1624.
ꢀ
ꢀ
ꢀ
(5) Bartolome, C.; Ramiro, Z.; Perez-Galan, P.; Bour, C.; Raducan,
M.; Echavarren, A. M.; Espinet, P. Inorg. Chem. 2008, 47, 11391–11397.
ꢀ
ꢀ
ꢀ
ꢀ
(2) Dıez-Gonzalez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109,
(6) Bartolome, C.; Ramiro, Z.; Garcıa-Cuadrado, D.; Perez-Galan,
P.; Raducan, M.; Bour, C.; Echavarren, A. M.; Espinet, P. Organo-
metallics 2010, 29, 951–956.
3612–3676.
(3) (a) Lavallo, V.; Frey, G. D.; Donnadieu, B.; Soleilhavoup, M.;
Bertrand, G. Angew. Chem., Int. Ed. 2008, 47, 5224–5228. (b) Zeng, X.;
Frey, G. D.; Kousar, S.; Bertrand, G. Chem.;Eur. J. 2009, 15, 3056–3060.
(c) Lavallo, V.; Frey, G. D.; Kousar, S.; Donnadieu, B.; Bertrand, G. Proc.
Natl. Acad. Sci. U. S. A. 2007, 104, 13569–13573. (d) Zeng, X.; Frey, G. D.;
Kinjo, R.; Donnadieu, B.; Bertrand, G. J. Am. Chem. Soc. 2009, 131, 8690–
8696. (e) Xiaoming Zeng, X.; Soleilhavoup, M.; Bertrand, G. Org. Lett.
2009, 11, 3166–3169. (f) Zeng, X.; Kinjo, R.; Donnadieu, B.; Bertrand, G.
Angew. Chem., Int. Ed. 2010, 49, 942–945.
(7) Bonati, F; Minghetti, G. J. Organomet. Chem. 1973, 59, 403–410.
(8) Parks, J. E.; Balch, A. L. J. Organomet. Chem. 1974, 71, 453–463.
(9) Minghetti, G.; Bonati, F. Inorg. Chem. 1974, 13, 1600–1602.
(10) With the present manuscript finished, Hashmi et al. have pub-
lished following our previous papers the use of NAC gold carbenes in
phenol synthesis and in the hydration of alkynes: Hashmi., A. S. K.;
€
Hengst, T.; Lothschutz, C.; Rominger, F. Adv. Synth. Catal. 2010, 8,
1307–1314.
r
2010 American Chemical Society
Published on Web 07/22/2010
pubs.acs.org/Organometallics

ꢀ
Bartolome et al.
3590 Organometallics, Vol. 29, No. 16, 2010
Scheme 1. Types of Gold(I) Carbene Complexes
Table 1. NAC Gold-Catalyzed Rearrangement of
Homopropargylsulfoxide
entry
[Au]
AgX
yield [%]
1
2
3
4
5
6
1
1
2
2
3
AgSbF6
AgNTf2
AgNTf2
AgSbF6
62a
75a
82a
76a
60a
30a
(34b)
30a
25b
76a
(94b)
77a
93
[AuCl(PPh3)]
AgSbF6
Scheme 2. Types of Carbene Gold(I) Complexes
7
8
9
[AuCl(PPh3)]
[AuCl(P(p-CF3C6H4)3)]
[AuCl(IMes)]
AgNTf2
AgSbF6
AgSbF6
10
11
[AuCl(IMes)]
[AuCl2(N-O)]c
AgNTf2
a Our result, 1H NMR yield. b Literature, isolated yield, see ref 16.
c See ref 15.
hydrogen bond in HBHCs, these are structurally similar
(cyclic) to the NHC carbenes (in acetone or CH2Cl2) or
become similar to the NACs in solvents where the intra-
molecular hydrogen bond has been split (in MeOH). The fact
that the HBHC gold complexes were similarly active in
methoxycyclization of enynes, where their cyclic structure
is broken,5 and in cyclization reactions in CH2Cl2, where its
cyclic structure is preserved, suggested that, except for the
possible influence in the spatial arrangement of the substit-
uents, the cyclic or acyclic structure of the carbene is not a
crucial difference. In fact both types of gold complexes
(NACs and HBHCs) showed similar catalytic activity.5,6
The HBHC ligands require the cumbersome low-yield
synthesis of 2-pyridyl isocyanide, but the easy synthesis of
NAC metal complexes by simple nucleophilic attack of amines
to gold(I) isocyanide complexes (even from commercial iso-
cyanides and amines) (eq 1)11 makes NAC advantageous over
NHC complexes to produce a series of gold catalysts and easily
tune their electronic and steric characteristics.
This should give us information about the feasibility of
application of the NAC-type carbenes in gold catalysis and
about the actual nucleophilicity of this structural type of
carbenes compared to other ligands used in gold(I) catalysis.
Results and Discussion
Complexes 1 and 2 have been reported before6 and were
chosen for the tests because they had been found particularly
efficient and highly selective in the skeletal rearrangement
and methoxycyclization of 1,6-enynes (Scheme 2).6 Complex
3, with the weakly coordinated counteranion bis(trifluoro-
methanesulfonyl)imidate, was synthesized by reaction of the
neutral gold(I) carbene 2 with AgNTf2,13 affording in good
yield a white and fairly stable solid.
The catalytic reactions chosen to test the activity of the
NAC gold(I) complexes were carried out under the standard
conditions used for the reported references (this means that
the performance with NACs was not optimized) and, except
for [Au(NTf2){C(NEt2)(NHXylyl)}] (3), adding a silver salt
to extract the chloride in situ to allow for the coordination of
the substrate to the Au center.14
However, these NAC complexes (also the HBHCs) have
two peculiar features that make them different from the
NHCs: (i) In the absence of structural distortions by the
substituents, the N-C-N angle at the carbene atom should
be about 60°, compared to about 72° for the NHCs, which
means that, for similar electronic influences by the substit-
uents, the expected order of carbene basicity should be
NACs<NHCs.12 (ii) Due to the method of synthesis, the
coordinated carbenes have at least one (for secondary
amines) or two (for primary amines) active N-H hydrogen
atoms, which might interfere for some applications. These
two features could be detrimental for the activity of NACs
catalysts, so we decided to examine their scope of application
by examining their performance, compared to the best
results found in several reported gold-catalyzed processes.
1. Rearrangement of Homopropargylsulfoxides. Zhang
and Li have demonstrated that dichloro(pyridine-2-carboxy-
lato)gold(III) is active for this reaction in the absence of
a silver salt (Table 1, entry 11).15 With gold(I), Saphiro
and Toste have reported that phosphine complexes [AuClL]
(L = PPh3, P(p-CF3C6H4)3) are active catalysts for the re-
arrangement of the homopropargylsulfoxide 4 to 1-benzo-
thiepin-4-one 5 in the presence of AgSbF6.16 However, the
yield obtained with PPh3 was low (34%, Table 1, entry 6b),
and it was even worse with the poorer donor phosphine
P( p-CF3C6H4)3 (25%, Table 1, entry 8).16 In our hands (entries
6a and 7), similar poor results have been obtained by using
[AuCl(PPh3)] and AgNTf2 instead of AgSbF6 (Table 1, entry 7).
(13) Ricard, L.; Gagosz, F. Organometallics 2007, 26, 4704–4707.
(14) The reactions in the literature have been repeated in our lab, as
suggested by one reviewer, for better comparison. When there is a
significant difference, both results are given in the tables.
(15) Zhang, L.; Li, G. Angew. Chem., Int. Ed. 2007, 46, 5156–5159.
(16) Shapiro, N.; Toste, F. D. J. Am. Chem. Soc. 2007, 129, 4160–
4161.
(11) For other metal complexes with NACs, see: (a) Michelin, R. A.;
Pombeiro, A. J. L.; Guedes da Silva, M. F. C. Coord. Chem. Rev. 2001,
218, 75–112. (b) Vignolle, J.; Cattoe, X.; Bourissou, D. Chem. Rev. 2009,
109, 3333–3384.
(12) Magill, A. M.; Cavell, K. J.; Yates, B. F. J. Am. Chem. Soc. 2004,
126, 8717–8724.

Article
Organometallics, Vol. 29, No. 16, 2010 3591
Table 2. NAC Gold-Catalyzed Intramolecular exo-Hydro-
amination of N-Allenyl Carbamate
Table 3. NAC Gold-Catalyzed Intramolecular Hydroalkoxyla-
tion of 2,2-Diphenyl-4,5-hexadienol
entry
[Au]
AgX
yield [%]
entry
[Au]
AgX
Yield [%]
1
2
3
2
3
AgOTs
92a
78a
95b
1
2
3
4
2
3
AgOTs
94/<1a
45/<1a
48/37b
91c
[AuClP(t-Bu)2(o-biphenyl)]
AgOTf
[AuClP(t-Bu)2(o-biphenyl)]
[AuClP(t-Bu)2(o-biphenyl)]
AgOTf
AgOTs
a Our result, isolated yield. b Literature, ref 18.
The better donor NHC ligand IMes was reported by
Toste to afford 94% yield (Table 1, entry 9b);16 in the same
a Isolated yield. b Yield determined by GC analysis vs internal stan-
dard (see ref 18). c Isolated yield in ref 18.
1
reaction conditions, our yield calculated by H NMR was
not as high, whether with AgSbF6 or with AgNTf2 as chlo-
ride scavenger (entries 9a and 10). The results obtained with
1-3, shown in Table 1, are in the range of activity of their
analogous NHC (somewhat better or worse depending on
the experiment reference (our own or the data in the litera-
ture), which is consistent with the presumption that NACs
should be in the order of basicity of NHCs, maybe a bit less
basic than them. Under the same conditions NAC com-
plexes compare favorably with phosphines, as expected.17
Thus, the yields in this reaction seem to follow the order of
basicity of the ligand.
Table 4. NAC Gold-Catalyzed Hydroarylation of Acetylene-
carboxylic Acid Ester
entry
[Au]
AgX
Yield [%]
2. Intramolecular Hydroamination of N-Allenyl Carba-
mates. As nitrogen and oxygen heterocycles are a part of
the structure of a wide range of biologically active systems,
the design of new catalysts for the synthesis of heterocyclic
compounds is a very attractive field. The gold(I)-catalyzed
intramolecular hydroamination of N-allenyl carbamates
such as 6 (Table 2) has been reported with an equimolecular
mixture of [AuClP(t-Bu)2(o-biphenyl)] and AgOTf (Table 2,
entry 3) and is very selective toward exo-hydroamination.18
We find that the NAC gold(I) complexes 2 and 3 are also very
active catalysts for this exo-hydroamination. When a mix-
ture of 2 and AgOTs was used, the hydroamination of the
allenyl carbamate 6 led to isolation of 2-vinylpyrrolidine 7 in
92% yield (Table 2, entry 1), similar to the yield reported
using [AuClP(t-Bu)2(o-biphenyl)] as precatalyst and AgOTf.
The reaction carried out using 3 as catalyst with NTf2 as
ligand was about as effective (Table 2, entry 2).
3. Intramolecular exo-Hydroalkoxylation of Allenes. NAC
gold(I) complexes are also active catalysts in the intramole-
cular hydroalkoxylation of 2,2-diphenyl-4,5-hexadienol 8.
Widenhoefer et al. reported that the regioselectivity of this
reaction has a very strong dependence on the counterion.18
For instance, the reaction carried out using a mixture of
[AuClP(t-Bu)2(o-biphenyl)] and AgOTf had a very low
regioselectivity (Table 3, entry 3), producing a 1.3:1 mixture
of tetrahydrofuran 9 and dihydropyran 10 in 85% yield;
however, the same reaction using AgOTs instead of AgOTf
to extract the chloride was highly regioselective, again in
favor of the exo-hydroalkoxylation product 9 (Table 3,
entry 4). In the presence of AgOTs, the NAC complex 2
was not only very efficient for the hydroalkoxylation but
also highly selective toward 9 (Table 3, entry 1). The reaction
using 3, with the labile ligand NTf2, afforded lower yields,
1
2
3
4
2
3
AgNTf2
76/7a
78/7a
[AuCl(PEt3)]
[AuCl(PPh3)3)]
AgOTf
AgBF4
67/20b
63/6a
(57/16c)
77/7a
5
[AuCl(PPh3)3)]
AgSbF6
a Our results, 1H NMR yield. b Reaction run at 25 °C, 5% mol of
catalyst. Yield determined by GC analysis vs internal standard (see
ref 19.). c Reaction run at 60 °C with 5% mol of catalyst. Yield
determined by GC analysis vs internal standard (see ref 19).
but with high regioselectivity toward the exo-hydroalkoxy-
lation product 9.
4. Intermolecular Hydroarylation of Alkynes. The forma-
tion of C-C bonds as a result of the activation of an aromatic
C-H bond is an interesting alternative to the use of halo-
genated derivatives. Reetz and Sommer have reported that
[AuCl(PR3)] (R = Et, Ph) are active precatalysts in the
intermolecular hydroarylation of alkynes.19 The reactions
of mesitylene 11 with the electron-poor alkyne 12, catalyzed
with [AuCl(PR3)] and a silver salt (Table 4, entries 3-5),
produced the desired product 13 in moderate yields.
Although high Z-selectivity was obtained in both cases,
considerable percentages of the second alkyne addition
product 14 were also formed. In this case both the NAC
precatalyst 2 (with an equimolecular amount of AgNTf2)
and catalyst 3 were apparently more active and more che-
moselective than the phosphine complexes used in the origi-
nal paper, leading to the formation of 13 in better yields and
with a much lower percentage of 14 (Table 4, entries 1 and 2).
However, repeating the reactions with PPh3 and analyzing
the results by 1H NMR, we found that the results with both
types of ligand are very similar in our hands.
5. Benzylation of Arenes. Beller et al. have reported that H
[AuCl4] is active in the benzylation of arenes and heteroarenes.20
(17) Phosphines have been ranked as less basic than NHCs in ref 12.
(18) Zhang, Z.; Liu, C.; Kinder, R. E.; Han, X.; Qian, H.;
Widenhoefer, R. A. J. Am. Chem. Soc. 2006, 128, 9066–9073.
(19) Reetz, M. T.; Sommer, K. Eur. J. Org. Chem. 2003, 3485–3496.

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Bartolome et al.
3592 Organometallics, Vol. 29, No. 16, 2010
Table 5. NAC Gold-Catalyzed Benzylation of Anisole with
1-Phenylethyl Acetate
Conclusions
The scope of application of NACs as ligands for gold-
catalyzed reactions looks very large. The catalyzed reactions
are not disturbed by the presence of N-H bonds in the NAC
ligand. Considering that the ground properties of a ligand
can be tuned by changing substituents, the catalytic system
[AuX(NAC)] looks extremely flexible and interesting for
gold(I)-catalyzed processes: changes are particularly acces-
sible for NACs, as they are directly made from accessible
isocyanides and amines. In different reactions, these ligands
behave (as far as yields are concerned) as well as or better
than phosphines (even without optimization of the reaction)
and are comparable to NHCs. Furthermore, in the benzyla-
tion of arenes, reported in the literature with H[AuCl4], our
gold(I) ligands perform much better than the gold(III)
catalyst. Taking the yields as a rough indication of reactivity,
the trends observed do not contradict the expectations from
the calculated order of basicity of ligands PR3 <NACs<
NHCs,12 although practically there is no difference in beha-
vior between NACs and NHCs.
entry
[Au]
AgX
yield [%] (ratio)
1
2
3
4
5
6
1
1
3
3
AgNTf2
AgNTf2
95 (22/78)a,b
96 (19/81)a,c
94 (18/82)a,b
97 (23/77)a,c
82 (22/78)a,b
99 (13/87)d
H[AuCl4]
H[AuCl4]
a Our results, 1H NMR yield. b 10 mol %. c 5 mol %. d Reaction run
with 10% mol of catalyst. Yield determined by GC analysis vs internal
standard (see ref 20).
Table 6. NAC Gold-Catalyzed Benzylation of Anisole with
Benzyl Alcohol
Experimental Section
General Conditions. All reactions were carried out under dry
N2 atmosphere. The solvents were purified according to stan-
dard procedures. Complexes [AuCl{C(NEt2)(NHTol-p)}] (1),6
[AuCl{C(NEt2)(NHXylyl)}] (2),6 AgNTf2,21 4,16 6,18 8,18 and
1622 were prepared according to literature procedures. The rest
of the reactants are commercially available.
Infrared spectra were recorded in Perkin-Elmer 883 or 1720X
equipment. NMR spectra were recorded with Bruker AC300
and ARX 300 and Bruker Avance 400 Ultrashield instruments.
1H NMR spectra are referred to TMS.
entry
[Au]
AgX
yielda [%] (ratio)
1
2
3
4
5
1b
1c
3b
3c
AgNTf2
AgNTf2
96 (40/60)
91 (40/60)
94 (40/60)
66 (40/60)
15 (33/67)
[Au(NTf2){C(NEt2)(NHXylyl)}] (3). AgNTf2 (89 mg, 0.229
mmol) was added to a solution of [AuCl{C(NEt2)(NHXylyl)}]
(2) (100 mg, 0.229 mmol) in dry CH2Cl2 (15 mL). A white
precipitate appeared immediately. After stirring for 5 min, the
mixture was filtered (double HPLC Teflon filter). Addition of
Et2O (5 mL) led to the formation of the cationic complex as a
white solid, which was filtered, washed with Et2O (2 Â 5 mL), and
H[AuCl4]b
a 1H NMR yield. b 10 mol %. c 5 mol %.
We have also explored the activity of this process with our
gold(I) NACs. The benzylation of anisole 15 with 1-phenyl-
ethyl acetate 16 catalyzed with HAuCl4 was reported to give
the corresponding para-isomer 18 in very good yield. The
reaction is not regioselective, and ortho-isomer 17 is also
observed (Table 5, 99% yield determined by GC (o/p = 13/
87), entry 6,20 and 82% yield determined by 1H NMR (o/p =
22/78), entry 5, our result). Our gold(I) NAC complexes are
also active in this reaction, affording also excellent yields
(Table 5, entries 1-4). The regioselectivity is nearly the same
as with HAuCl4, and the major regioisomer in this case is still
18. The load of catalyst can be reduced, compared to the use
of HAuCl4, from 10 to 5 mol %, affording the same excellent
yields.
Additional experiments were performed using a different
benzylating agent (19, not reported in ref 20). The results
obtained for the gold-catalyzed benzylation of anisole with
benzyl alcohol are summarized in Table 6. The gold carbenes
1 and 3 catalyze this reaction (Table 6, entries 1-4). It is
remarkable that, in contrast with the reported related reac-
tion in Table 5, entry 6), the yields are here much better
(about 90% versus 15%) than those obtained using the
reported Au(III) system (Table 6, entry 5), even with lower
load of catalyst (entry 2).
1
vacuum-dried (122 mg, 78%). H NMR (300 MHz, CDCl3): δ
7.25-7.05 (m, 3 H, ArH), 6.76 (br s, 1 H, NH), 3.94 (q, J = 7.1 Hz,
2 H, NCH2CH3), 3.55 (q, J = 7.5 Hz, 2 H, NCH2CH3), 2.24 (s, 6
H, Ar-CH3), 1.41 (t, J = 7.5 Hz, 3 H, NCH2CH3), 1.40 (t, J = 7.1
Hz, 3 H, NCH2CH3). 19F NMR (282.5 MHz, CDCl3): δ -75.87
(s, N(SO2CF3)2, 6 F). Anal. Calcd for C15H20N3AuF6O4S2: C,
26.44; H, 2.96; N, 6.17. Found: C, 26.82; H, 2.66; N, 6.20.
Catalytic Procedures. The general procedures followed for the
rearrangement of homopropargylsulfoxide,16 intramolecular
exo-hydroamination of N-allenyl carbamate,18 intramolecular
hydroalkoxylation of 2,2-diphenyl-4,5-hexadienol,18 hydroaryl-
ation of acetylenecarboxylic acid ester,19 and benzylation of
anisole with 1-phenylethyl acetate20 are similar to those reported
(the procedure was also analogous when benzyl alcohol was
used as benzylating agent). The 1H NMR yields were obtained
by using 1,2-dichloroethane as an internal reference.
Acknowledgment. This work was supported by the
MICINN (CTQ2007-67411/BQU and Consolider Ingenio
2010, Grant CSD2006-0003; predoctoral fellowship to
Z.R.; and Juan de la Cierva Contract to D.G.-C.) and by
ꢀ
the Junta de Castilla y Leon (GR169).
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