Gold(III) iminophosphorane complexes as catalysts in C-C and C-O bond formations

Article abstract of DOI:10.1016/j.jorganchem.2008.09.058

The reaction of K[AuCl₄] with AgClO₄ and iminophosphorane ligands (N,N-IM) Ph₃P{double bond, long}NR [R = CH₂-2-NC₅H₄ (1), C(O)-2-NC₅H₄ (2)] or Ph₂PyP{double bond, long}NR [Py = -2-NC₅H₄; R = Ph (3), C(O)Ph (4)] (mol ratio 1:2.2:1) in acetonitrile affords complexes [AuCl₂(N,N-IM)]ClO₄ (5-8). These compounds are air- and moisture-stable and they have been evaluated in two types of catalytic processes. They have been found to be effective catalysts in the addition of 2-methylfuran or azulene to methyl vinyl ketone, as well as in the synthesis of 2,5-disubstituted oxazoles from N-propargylcarboxamides. The reactions proceed in mild conditions and with similar yields to those described for AuCl₃. Using this method, oxazoles bearing a thiophene functional group 2-(2′-thienyl)-5-methylthiazole can be prepared in excellent yields. In all cases the intermediate 5-methylene-4,5-dihydroxazole can be observed by ¹H NMR.

Full text of DOI:10.1016/j.jorganchem.2008.09.058

Journal of Organometallic Chemistry 694 (2009) 486–493
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Gold(III) iminophosphorane complexes as catalysts in C–C and C–O bond formations
a
c
a,
David Aguilar a, María Contel b, , Rafael Navarro , Tatiana Soler , Esteban P. Urriolabeitia
*
*
a Departamento de Compuestos Organometálicos, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-C.S.I.C., E-50009 Zaragoza, Spain
b Department of Chemistry, Broooklyn College and The Graduate Center, The City University of New York (CUNY), 2900 Bedford Avenue, Brooklyn, NY 11210, United States
c Servicios Técnicos de Investigación, Facultad de Ciencias Fase II, 03690, San Vicente de Raspeig, Alicante, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 April 2008
Received in revised form 28 August 2008
Accepted 30 September 2008
Available online 7 October 2008
The reaction of K[AuCl4] with AgClO4 and iminophosphorane ligands (N,N-IM) Ph3P@NR [R = CH2-2-
NC5H4 (1), C(O)-2-NC5H4 (2)] or Ph2PyP@NR [Py = -2-NC5H4; R = Ph (3), C(O)Ph (4)] (mol ratio 1:2.2:1)
in acetonitrile affords complexes [AuCl2(N,N-IM)]ClO4 (5–8). These compounds are air- and moisture-sta-
ble and they have been evaluated in two types of catalytic processes. They have been found to be effective
catalysts in the addition of 2-methylfuran or azulene to methyl vinyl ketone, as well as in the synthesis of
2,5-disubstituted oxazoles from N-propargylcarboxamides. The reactions proceed in mild conditions and
with similar yields to those described for AuCl3. Using this method, oxazoles bearing a thiophene func-
tional group 2-(20-thienyl)-5-methylthiazole can be prepared in excellent yields. In all cases the interme-
diate 5-methylene-4,5-dihydroxazole can be observed by 1H NMR.
Keywords:
Gold(III)
Iminophosphorane ligands
C–C coupling
2,5-Disubstituted oxazoles
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
(X = H, Me) resulted as efficient as AuCl3 in these processes and
even outperformed this salt in reactions with acid-sensitive elec-
The catalytic functionalizations of C–H bonds under mild condi-
tions are an example of atom economy and, therefore, of environ-
mentally friendly reactions. Much attention has been directed to
research in this area during the last ten years [1]. Gold compounds
have been successfully applied in C–H functionalization reactions
to form C–C and C-heteroatom bonds in the presence of different
electrophiles such as alkynes, alkenes or even nitrogen sources
[2]. The catalyst of choice for many of these transformations has
been the very hygroscopic and acidic AuCl3 salt. We and others
have focused in the search for gold(III) compounds as air- and
moisture-stable and molecularly well-defined alternatives to
AuCl3. In this context it has been reported that gold(III) coordina-
tion and organometallic compounds catalyze diverse processes like
the addition of nucleophiles to alkynes [3–5], the cycloisomeriza-
tion of allenones [5], the phenol synthesis [6], the 1,3-dipolar
cycloaddition to nitrones [7], or the addition of 2-methylfuran or
electron-rich arenes to methyl vinyl ketone [8]. Moreover, the
functionalization of ligands bonded to gold(III) centers has allowed
for their use in supported catalytic hydrogenations [9], hydrosily-
lations [10], or C–C bond forming reactions [11] with subsequent
recovery of the gold catalysts.
tron-rich arenes [8]. From NMR experiments we gathered that
the catalytically active species were cationic gold(III) compounds
stabilized by the C,N-backbone. However, Au(III) coordination
complexes of the type [AuCl3{Ph3P@NC(O)R}], with stabilized imi-
nophosphoranes as monodentate ligands, were not as efficient
even in combination with silver salts, and decomposed to metallic
gold during the reaction.
In this paper we report on the synthesis of new air- and mois-
ture-stable cationic gold(III) coordination complexes with N,N-
chelating iminophosphorane ligands. These compounds resulted
as efficient as the previously reported iminophosphorane cycloau-
rated derivatives in the addition reactions of 2-methylfuran or
electron-rich arenes to methylvinylketone. They were also evalu-
ated in the synthesis of 2,5-disubstituted oxazoles, compounds of
significant biological activity, from N-propargyl-carboxamides
[13]. The AuCl3 methodology has already been used by Merck as
a step in the synthesis of a pharmaceutically active substance [14].
2. Results and discussion
2.1. Synthesis of the coordination gold(III) compounds
We described recently that gold(III) compounds containing imi-
nophosphorane ligands [8] are efficient catalysts in the addition of
2-methylfuran or electron-rich arenes to methyl vinyl ketone [12].
The reaction of K[AuCl4] with AgClO4 and iminophosphorane li-
gands (N,N-IM) Ph3P@NR [R = CH2-2-NC5H4 (1), C(O)-2-NC5H4 (2)]
or Ph2PyP@NR [Py = -2-NC5H4; R = Ph (3), C(O)Ph (4)] (mol ratio
1:2.2:1) in acetonitrile at RT afforded complexes [AuCl2(N,N-IM)]-
ClO4 (5–8) (Scheme 1). Compounds 5–8 are obtained as air- and
moisture-stable yellow solids that are insoluble in chlorinated
Cycloaurated derivatives [Au{j
2-C,N-C6H4(PPh2@N(C6H4X))-2}Cl2]
* Corresponding authors.
E-mail address: esteban@unizar.es (E.P. Urriolabeitia).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.09.058

D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
487
R
PPh3
Cl
N
Au
R
PPh3
ClO4
N
N
N
Cl
CH3CN
R = CH2 (5); CO (6)
K[AuCl4] + 2.2 AgClO4
i) - 2 AgCl
ii) - KClO4
Ph2
Ph2
P
R
P
N
R
ClO4
N
Cl
Au
Cl
N
N
R =Ph(7); C(O)Ph (8)
Scheme 1. Syntheses of the gold(III) coordination iminophosphorane complexes.
solvents but soluble in highly polar solvents such as CH3CN. Spec-
Table 1
troscopic and analytical data are consistent with the proposed
structures.
Selected bond lengths (Å) and angles (°) for 8.
The crystal structure of 8 has been determined by X-ray diffrac-
tion methods. A drawing of the cationic metallic part is shown in
Fig. 1, and selected bond distances and angles are given in Table
1. The AuIII center is located in a slightly distorted square-planar
geometry, surrounded by two chlorine atoms and two nitrogen
atoms. The Au–N bond lengths are 2.030(3) Å and 2.049(3) Å.
These bond distances fall in the usual range found for this type
of bonds in cationic [15–24] or even neutral complexes [25] [rang-
ing from 2.018(10) to 2.055(11) Å]. The AuIII–Cl bond lengths are
2.2551(10) and 2.2636(10) Å, which are similar to those found in
the literature [15–25]. Other internal bond parameters are as ex-
pected and do not deserve additional comments.
Au(1)–N(2)
Au(1)–N(1)
Au(1)–Cl(2)
Au(1)–Cl(1)
N(1)–C(1)
N(1)–C(5)
N(2)–C(18)
N(2)–P(1)
P(1)–C(12)
P(1)–C(6)
2.030(3)
2.049(3)
2.2551(10)
2.2636(10)
1.342(4)
1.354(4)
1.407(4)
1.656(3)
1.784(3)
1.790(4)
1.809(4)
N(2)–Au(1)–N(1)
N(2)–Au(1)–Cl(2)
N(1)–Au(1)–Cl(2)
N(2)–Au(1)–Cl(1)
N(1)–Au(1)–Cl(1)
Cl(2)–Au(1)–Cl(1)
C(1)–N(1)–C(5)
C(1)–N(1)–Au(1)
C(5)–N(1)–Au(1)
C(18)–N(2)–P(1)
C(18)–N(2)–Au(1)
84.50(11)
93.41(8)
172.85(8)
177.83(8)
93.35(8)
88.77(4)
119.9(3)
123.7(2)
116.4(2)
115.6(2)
129.5(2)
P(1)–C(5)
Reactions were run at RT and examined after 6 or 18 h (Table 2).
The new gold coordination compounds are active in the absence of
silver salts (entries 1, 5 and 9) and, moreover, the addition of silver
salts does not increase the yields in a significant way. After the
reaction time, decomposition of the catalyst is evident, since a gold
mirror is formed. The comparison of complexes 5–8 as catalysts in
this reaction with the previously reported neutral cycloaurated
gold(III) compounds results in better conversions for the formers
in absence of silver salts and similar yields in presence of silver
salts. While 5–8 are air- and moisture-stable for months, even in
solution, their stability after consumption of the reactants in this
catalytic process is notably lower than that observed for the neu-
tral cycloaurated gold(III) compounds and is similar to that found
for [AuCl3{N(@PPh3)C(O)C6H4Me-2}] [8]. Clearly the chelating ef-
fect of the two N donor atoms in the iminophosphorane complexes
5–8 confers a certain degree of stability to the Au(III) center.
2.2. Catalytic studies of C–C and C–O bond formations
2.2.1. Addition of
a,b-unsaturated ketones with furans and
electron-rich arenes
Gold(III) compounds 5–8 have been evaluated in the addition of
2-methylfuran 9 to methyl vinyl ketone (MVK) 10 (Eq. (1))
O
O
[Au]
+
O
O
ð1Þ
9
10
11
Equation 1. Addition of MVK to 2-methyl furane
catalyzed by the new gold(III) coordination complexes.
Table 2
Results of the addition reactions of methyl vinyl ketone (10) to 2-methylfuran (9).a
Entry
Catalyst (1 mol%)
Silver salt (mol%)
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
5
5
5
5
6
6
6
6
8
8
8
8
0
18
18
6
18
18
18
6
18
18
18
6
63
59
62
75
76
73
75
84
60
71
70
79
AgOTf (1.1)
AgOTf (2.2)
AgOTf (2.2)
0
AgOTf (1.1)
AgOTf (2.2)
AgOTf (2.2)
0
9
10
11
12
AgOTf (1.1)
AgOTf (2.2)
AgOTf (2.2)
18
a
Reaction conditions: the reactions were performed at 25 °C in a kontex tube
using 2 mmol of 9, 2 mmol of 10, 0.02 mmol of gold complex and 0.044 mmol (or
0.022 mmol) of silver salt in 5 mL of CH3CN as solvent.
Fig. 1. Molecular drawing of the cation in [Au(Ph2PyP@NC(O)Ph)Cl2]ClO4 8.
Thermal ellipsoids are drawn at 50% probability.
b
Yields were obtained on isolated product. Details are given in Section 4.

488
D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
On the other hand, the addition of acid-sensitive azulene 12 to
fast equilibrium. Further addition of free ligand 4 to the mixture of
8, 9 and 10 does not change the appearance of the spectrum (a sin-
gle signal remains in the spectrum, although considerably broad-
ened) but the observed average chemical shift moves to the high
field region. This fact is in good agreement with an equilibrium
involving the non bonded iminophosphorane. The same behaviour
MVK (10) with compounds 5, 6 and 8 as catalysts (Eq. (2)) afforded
high yields of 13 (90 3% after 24 h). In this case the less acidic
character of all the gold(III) organometallic and coordination com-
plexes versus the acidic character of AuCl3 may be responsible for a
higher yield (with AuCl3, 55% yield after 3 days) [13]
O
O
O
[Au]
+
2
ð2Þ
12
10
13
Equation 2. Addition of MVK 10 to azulene 12 catalyzed by the new gold(III) complexes.
The reactions were performed at 25 oC in a kontex tube using 2 mmol of 10, 2 mmol of 12,
0.03 mmol of gold complex and 0.066 mmol of AgOTf in 5 mL of CH3CN as solvent.
Yields were obtained on isolated product. [Au] = 5, 6 or 8; time = 24 h; yield = 90 3%.
In order to detect some gold reaction intermediates we moni-
tored the reaction of 9 with 10 in CD3CN catalyzed by 8 by 1H and
31P NMR spectroscopy. The separate addition of 9 or 10 to CD3CN
solutions of 8 does not promote changes of the NMR parameters
immediately or even after 30 min. When 9 is reacted with 10 in
presence of stoichiometric amounts of 8 or substoichiometric
(20%) amounts we did not observe changes in the NMR signals
immediately after mixing, or after 30 min. After this period of time
some changes are evident: the formation of 11 by consumption of 9
and 10 is clear, and it is accompanied by a high field shift of the 31P
signal (from 57.8 ppm to 24.9 and 24.2 ppm) and also by a high field
shift of the peak due to the pyridinic ortho proton (from 9.70 ppm
to about 9.00 ppm) for 8. Similarly to what was observed in the cat-
alytic process, once the reagents were consumed and 11 was
formed, extensive decomposition to metallic gold was observed.
These observations are very similar to those reported for cycloa-
urated compounds, and also suggest that the limiting step of the
catalytic cycle is the coordination of the substrates to the metallic
center. Any other further steps should be very fast. To achieve the
bonding of the incoming substrates, vacant coordination sites
could be generated by, at least, two plausible ways: (i) dissociation
of the iminophosphorane ligand; (ii) dissociation of a chloride li-
gand. Both processes are possible under the experimental reaction
conditions. While we do not have evidence for halide dissociation,
is observed for the signal due to the Hortho of the pyridine fragment
in the 1H NMR spectrum, providing additional evidence. Therefore
the chelate is not preserved during the catalytic cycle, at least in
the NMR timescale. The data suggest that the iminophosphorane
ligand behaves as an ‘organic stabilizer’ for a reactive form of gold.
When the metal center is not involved in a catalytic cycle, the li-
gand confers a high stability to the complex, and 5–8 can be stored
at air without precautions, but the ‘organic wrapper’ can be re-
leased easily if necessary (for instance, in a catalytic cycle).
2.2.2. Synthesis of 2,5-disubstituted oxazoles
Although substituted oxazole fragments are structural motifs
that occur in a large number of natural products, a direct synthetic
path in mild conditions to obtain oxazoles had not been described
until 2004. Hashmi et al. reported that 2,5-disubstituted oxazoles
could be synthesized from the corresponding propargylcarboxa-
mides under mild reactions via homogeneous catalysis by AuCl3
[13]. Later, two different groups (Hashmi et al. and Echavarren
et al.) were able to identify a 5-methylene-4,5-dihydrooxazole
[26] intermediate. The new air- and moisture-stable complexes
5–8 catalyze these reactions by activation of the alkyne moiety.
The N-propargylcarboxamides (Eq. (3)) which have not been re-
ported so far are characterized in Section 4
O
N
O
CH2Cl2
NEt3
+
+
NH2
+
R
H
R
Cl
N
N
Cl
O
ð3Þ
S
N
R =
O
Cl
14
15
16
17
18
Equation 3. Synthesis of the different N-propargylcarboxamides (based on ref 13).
the iminophosphorane seems to leave the coordination sphere of
the gold center during the catalytic cycle. This is suggested from
the upfield shift of the P signal to a position intermediate between
8 (57.8 ppm) and the free ligand (14.8 ppm), probably indicating a
We found that 5–8 (5 mol%) were efficient catalysts in the
cycloisomerization of propargylic amides in CH2Cl2, at RT and at
air (Eq. (4)), and we did not observe decomposition after the reac-
tion time. The results are collected in Table 3. The yields were

D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
489
Table 3
Results of Au-catalyzed cycloisomerization of propargylic amides in CH2Cl2.
Entry
R
Catalyst (5 mol%)
Time (h)
15
Yield (%)a
93
Molar ratio final/intermediateb
1/2.44
O
O
O
O
O
O
O
S
S
S
S
S
S
S
1
AuCl3
2
AuCl3
48
72
15
72
72
72
15
30
48
15
72
72
72
15
95
90
100
90
86
87
95
95
85
95
90
80
85
97
1/0
1/0
3
5
1
4
6
4
5
6
1/0
1/0
1/0
1.26/1
1/0
1/0
2/1
1/0
1/0
1/0
2/1
6
7
7
8
8
AuCl3
9
AuCl3
10
11
12
13
14
15
5
6
6
7
8
Cl
Cl
Cl
Cl
Cl
Cl
AuCl3
Cl
Cl
Cl
Cl
Cl
Cl
16
17
18
19
20
AuCl3
30
15
48
48
48
90
97
85
81
78
1/0
5
5
6
7
1/6.5
1/0
1/0
1/0
(continued on next page)

490
D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
Table 3 (continued)
Entry
R
Catalyst (5 mol%)
Time (h)
48
Yield (%)a
80
Molar ratio final/intermediateb
1/0
Cl
21
22
23
24
25
26
27
8
Cl
AuCl3
AuCl3
5
24
48
48
15
30
30
94
94
80
0
1/4.8
1/4.8
0/1
–
N
N
N
AuCl3
AuCl3
5
O
O
O
0
–
0
–
a
Isolated product.
Determined by NMR.
b
equivalent to those described for AuCl3 (R = furane; Table 3, entry
2) although reaction times were longer (usually in a ratio 2:3). In
all the cases while monitoring the reaction by 1H NMR we could
observe the alkylidene-hydrooxazole intermediates (19, 20, 22
and 24)
tained in high yields with both AuCl3 or 5–8. This oxazole could be of
interest due to the possibility of further functionalization using the
halide groups, for instance, in Pd-catalysed CC coupling reactions
(Stille, Heck, Suzuki, etc.). In the case of R = vinyl, final product 25
only could be obtained with AuCl3 in a small yield (16%). Longer
reaction times did not improve the results. With compound 5 we
only got the intermediate product 24 and we did not find formation
of the oxazole 25 after 48 h (entry 24). With R = morpholyl there was
no conversion at all for either AuCl3 or compound 5 (entries 25–27)
showing the influence of electronic factors and intramolecular coor-
dinating functionalities close to the reaction center [13]. These re-
sults are important since air-stable cationic coordination Au(III)
complexes with chelating ligands have a catalytic efficiency in the
reported processes comparable to that of AuCl3. In addition, with
catalysts 5–8 the reactions can be performed at air while reactions
using AuCl3 were run under a N2 atmosphere.
O
N
N
[Au] 5%
N
R
R
R
H
O
O
CH2Cl2
R =
Final product
Intermediate
Cl
O
S
Cl
19 (18)
21 (20)
23 (22)
25 (24)
The PR3 fragment of the iminophosphorane motif has been used
as a ‘‘spectroscopic marker” to follow reactions by 31P NMR. We
run a stoichiometric reaction of 8 and 16 (R = 2,4-C6H3Cl2) in
CD2Cl2 at RT and monitored by 1H and 31P NMR. Interestingly we
found that the addition of the carboxamide 16 to a CD2Cl2 solution
of 8 promotes the immediate disappearance of the 31P peak at
Equation 4. Synthesis of the 2,5-Disubstituted oxazoles by
Au -homogeneous catalysis (based on ref 13).
ð4Þ
We tested the influence of different substituents in the cycloiso-
merization reaction. Reaction times were compared to those ob-
tained by us with AuCl3 (entries 1, 2, 8, 9, 15, 16, 22, 23, 25, 26). In
most cases the behaviour of 5–8 was similar to that of AuCl3 and they
resulted effective catalysts, although longer reaction times were
needed. In this manner 2-(20-thienyl)-5-methylthiazole 21 can be
prepared in good yields (entries 10–14). To the best of our knowl-
edge 21 (with potential medicinal applications) had been prepared
by a elimination reaction of a terminal b-oxy selenoxide in a two step
procedure and with H2O2/NaHCO3 as reagents [27]. This is a much
improved method to obtain this oxazole. The oxazole 23 can be ob-
56.8 ppm (pure 8) and
a singlet signal is seen instead at
d = 24.6 ppm. Further addition of free iminophosphorane
4
(14.8 ppm) gives an averaged broad signal shifted to high field.
This fact suggests, as previously described for the additions of
methyl-furan to MVK, the presence of a fast equilibrium. After
de-coordination of the iminophosphorane ligand and/or a chloride
ligand it seems sensible to assume the activation of the C–H bond
of the C„C–H motif from the N-propargylcarboxamide. Unfortu-
nately, we were not able to identify gold-alkyne or gold-vinylidene
intermediates [13].

D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
491
yellow solution was concentrated under vacuum to ca. 1–2 mL.
By addition of 15 mL of Et2O 5 is obtained as a yellow solid that
was filtered, washed with 10 mL of Et2O and dried under vacuum.
Yield: 0.283 g, 0.38 mmol, 70.9%. Complex 5 was recrystallized
from CH2Cl2/Et2O, affording crystals of 5 ꢂ CH2Cl2, which were
used for analytic and spectroscopic measurements. Anal. Calc.
for [C24H21AuCl3N2O4P]CH2Cl2 (735.75): C, 36.58; H, 2.82; N,
3.41. Found: C, 36.33; H, 2.71; N, 3.64%. MS (FAB+): 636 (75%)
3. Conclusion
We have prepared new air- and moisture-stable gold(III)
complexes with N,N-chelating iminophosphorane ligands that
are efficient catalysts in the addition of 2-methylfuran and azu-
lene to MVK in the presence of silver salts. These derivatives be-
have as efficient catalysts in the preparation of oxazoles by
cycloisomerization reactions of N-propargylcarboxamides at air.
The gold catalytically active species are formed by partial disso-
ciation of the iminophosphorane ligand and by dissociation of at
least one chloride ligand. Subsequent coordination of organic
substrates is fast and we have not observed these gold interme-
diates by NMR.
[MꢁClO4]+. IR:
t
(N@P) = 1275 cmꢁ1
.
31P{1H} NMR (CDCl3):
4
d = 43.54. 1H NMR (CDCl3): d = 4.92 (d, 2H, CH2, JHH = 4.3),
7.67–7.72 (m, 7H, H4, C6H4N + Hm, PPh3), 7.79–7.91 (m, 10H, H6,
3
C6H4N + Ho + Hp, PPh3), 8.19 (td, 1H, H5, C6H4N, JHH = 7.8,
3
4JHH = 0.9), 9.26 (d, 1H, H3, C6H4N, JHH = 7.3). 13C{1H} NMR
2
(CDCl3): d = 61.06 (d, CH2, JPC = 4.0), 122.29 (d, Ci, PPh3,
1JPC = 102.6), 124.16 (s, C4, C6H4N), 125.69 (s, C6, C6H4N), 129.94
3
2
4. Experimental
(d, Cm, PPh3, JPC = 13.2), 134.04 (d, Co, PPh3, JPC = 10.5), 134.92
4
(d, Cp, PPh3, JPC = 3.0), 143.73 (s, C5, C6H4N), 146.12 (s, C3,
General procedures are as reported elsewhere [8]. Iminophos-
phoranes 1–3 [28–30] and N-propargylcarboxamides 14 [13], 17
[31], and 18 [32] were prepared as previously described. Caution:
perchlorate salts of metal complexes with organic ligands are
potentially explosive. Only small amounts of material should be
prepared and all samples handled with great caution. Organic
azides are highly hazardous materials which can explode, and
whose preparation and manipulation must be carried out with
maximum caution. They must be stored at low T (ꢀ0 °C) and dis-
solved in an inert solvent.
C6H4N). Signals due to C1 (NC5H4) were not observed.
Compound 6 was obtained in the same way starting from
0.198 g (0.52 mmol) of K[AuCl4], AgClO4 (0.239 g, 1.15 mmol)
and ligand 2 (0.200 g, 0.52 mmol). Yield: 0.283 g, 0.38 mmol,
70.9%. Anal. Calc. for [C24H19AuCl3N2O5P] (749.41): C, 38.46; H,
2.55; N, 3.74. Found: C, 38.21; H, 2.56; N, 3.70%. MS (FAB+): 650
(80%) [MꢁClO4]+. IR:
t , t .
(C@O) = 1698 cmꢁ1 (N@P) = 1263 cmꢁ1
31P{1H} NMR (CDCl3): d = 39.00. 1H NMR (CDCl3): d = 7.64–7.77
(m, 9H, Hm, PPh3 + Hp, PPh3), 8.00–8.15 (m, 8H, H4 + H6,
3
4
C6H4N + Ho, PPh3), 8.37 (td, 1H, H5, C6H4N, JHH = 7.7, JHH = 1.1),
3
4
9.50 (dd, 1H, H3, C6H4N, JHH = 7.2, JHH = 1.0). 13C{1H} NMR
1
4.1. Syntheses
(CDCl3): d = 121.06 (d, Ci, PPh3, JPC = 109.8), 128.58 (s, C4,
C6H4N), 131.15 (s, C6, C6H4N), 129.73 (d, Cm, PPh3, JPC = 13.7),
134.09 (d, Co, PPh3, JPC = 11.4), 134.78 (d, Cp, PPh3, JPC = 2.9),
137.25 (s, C5, C6H4N), 144.53 (s, C3, C6H4N), 176.99 (s, CO). Signals
due to C1 (NC5H4) were not observed, even when long accumula-
tion times were used.
3
3
4
4.1.1. Syntheses of the iminophosphorane ligand [Ph2PyP@N-C(O)-Ph]
(4)
To a solution of benzoyl azide (0.615 g, 4.18 mmol) in CH2Cl2
(20 mL) a solution of PPh2Py (1.100 g, 4.18 mmol) in 20 mL of
CH2Cl2 was added dropwise. The reaction mixture was stirred at
RT until evolution of N2 gas was completed. The resulting yellow
solution was concentrated ca. 1–2 mL and by addition of 15 mL
of Et2O a white solid precipitated in the reaction media. The crude
(4) was filtered, washed with 10 mL of Et2O and vacuum dried.
Yield: 1.806 g, 2.84 mmol, 67.9%. Anal. Calc. for [C24H19N2OP]
(382.39): C, 75.38; H, 5.01; N, 7.32. Found: C, 75.21; H, 5.21; N,
4.1.2.2. Synthesis of [AuCl2(Ph2PyP@NR)]ClO4: R = Ph (7), C(O)-Ph
(8). Compound 7 was obtained in the same way starting from
0.192 g (0.51 mmol) of K[AuCl4], AgClO4 (0.232 g, 1.2 mmol) and li-
gand 3 (0.180 g, 0.51 mmol). Yield: 0.258 g, 0.36 mmol, 70.4%.
Anal. Calc. for [C23H19AuCl3N2O4P] (721.69): C, 38.24; H, 2.65; N,
3.88. Found: C, 38.30; H, 2.75; N, 3.86%. MS (FAB+): 622 (20%)
7.37%. MS (FAB+): 383 (85%) [M+H]+. IR:
t ;
(C@O) = 1592 cmꢁ1
[MꢁClO4]+. IR:
t
(N@P) = 1299 cmꢁ1
.
31P{1H} NMR (CDCl3):
(N@P) = 1349 cmꢁ1 31P{1H} NMR (CDCl3): d = 14.80. 1H NMR
.
d = 59.41. 1H NMR (CDCl3): d = 6.99–7.04 (m, 3H, Ho + Hp, Ph),
t
3
(CDCl3): d = 7.32–7.39 (m, 8H, Hm, PPh2 + Hm + Hp, PhCO + H4,
7.17 (t, 2H, Hm, Ph, JHH = 7.2), 7.62–7.71 (m, 5H, H6, C6H4N + Hm,
C6H4N), 7.44–7.47 (m, 2H, Hp, PPh2), 7.75 (tdd, 1H, H5, C6H4N,
PPh2), 7.77–7.82 (m, 2H, Hp, PPh2), 7.93–8.06 (m, 5H, H4,
3
4
4JHP = 7.7, JHH = 4.2, JHH = 1.4), 7.85–7.90 (m, 4H, Ho, PPh2), 8.29–
8.33 (m, 3H, H6, C6H4N + Ho, PhCO), 8.69 (d, 1H, H3, C6H4N,
3JHH = 4.5). 13C{1H} NMR (CDCl3): d = 125.48 (d, C4, C6H4N,
3
C6H4N + Ho, PPh3), 8.22 (t, 1H, H5, C6H4N, JHH = 6.7), 9.10 (d, 1H,
3
H3, C6H4N, JHH = 6.4). 13C{1H} NMR (CDCl3): d = 118.93 (d, Ci,
1
3
PPh2, JPC = 102.3), 120.30 (d, Co, Ph, JPC = 6.9), 124.15 (s, Cp, Ph),
1
4JPC = 3.2), 127.34 (s, Cm, PhCO), 127.74 (d, Ci, PPh2, JPC = 100.0),
4
128.19 (d, C4, C6H4N, JPC = 3.7), 129.67 (s, Cm, Ph), 130.16 (d, Cm,
3
128.43 (d, Cm, PPh2, JPC = 12.4), 129.58 (d, Co, PhCO,4JPC = 2.4),
3
3
PPh2, JPC = 13.6), 131.04 (d, C5, C6H4N, JPC = 23.0), 134.04 (d, Co,
2
2
4
129.75 (d, C6, C6H4N, JPC = 20.8), 130.86 (s, Cp, PhCO), 132.21 (d,
PPh2, JPC = 11.0), 135.56 (d, Cp, PPh2, JPC = 3.1), 137.50 (d, C1, Ph,
4
2
2JPC = 5.0), 138.22 (d, C6, C6H4N, JPC = 10.7), 145.92 (d, C1, C6H4N,
2
Cp, PPh2, JPC = 2.9), 133.50 (d, Co, PPh2, JPC = 9.6), 136.71 (d, C5,
3
3
1JPC = 130.1), 151.83 (d, C3, C6H4N, JPC = 21.2).
3
C6H4N, JPC = 9.3), 138.35 (d, C1, PhCO, JPC = 19.7), 150.36 (d, C3,
C6H4N, JPC = 19.4), 152.95 (d, C1, C6H4N, JPC = 129.0), 176.78 (d,
CO, JPC = 8.0).
3
1
Compound 8 was obtained in the same way starting from
0.239 g (0.52 mmol) of K[AuCl4], AgClO4 (0.239 g, 1.15 mmol)
and ligand 4 (0.200 g, 0.52 mmol). Yield: 0.245 g, 0.33 mmol,
62.5%. Anal. Calc. for [C24H19AuCl3N2PO5] (749.41): C, 38.46; H,
2.55; N, 3.74. Found: C, 39.22; H, 3.18; N, 3.39%. MS (FAB+):
2
4.1.2. Syntheses of gold(III) compounds [AuCl2(N,N-IM)]ClO4 (5–8)
4.1.2.1. Synthesis of [Au(Ph3P@NR)Cl2]ClO4: R = CH2-2-NC5H4 (5), CO-
2-NC5H4 (6). To a solution of K[AuCl4] (0.205 g; 0.54 mmol) in
CH3CN (20 ml), AgClO4 (0.247 g, 1.19 mmol) was added. The
resulting yellow reaction mixture was stirred at room tempera-
ture during 30 min and subsequently filtered through a celite
pad (to remove the AgCl formed). To the resulting yellow solution
1 (0.200 g, 0.54 mmol) was added. KClO4 precipitated immedi-
ately in the reaction media and after 1 h stirring at RT the reac-
tion mixture was filtered through a celite pad. The resulting
650 (25%) [MꢁClO4]+. IR:
t
(C@O) = 1637 cmꢁ1
;
t(N@P) =
1290 cmꢁ1
.
31P {1H} NMR (CD3CN): d = 56.20. 1H NMR (CD3CN):
3
d = 7.53 (t, 2H, Hm, PhCO, JHH = 8.0), 7.69 (t, 1H, Hp, PhCO,
3JHH = 8.0), 7.74–7.80 (m, 4H, Hm, PPh2), 7.93–8.05 (m, 6H, Ho + Hp,
PPh2), 8.15 (d, 2H, Ho, PhCO, 3JHH = 8.0), 8.20–8.29 (m, 2H, H4 + H6,
3
4
4
C6H4N), 8.55 (tdd, 1H, H5, C6H4N, JHH = 6.7, JHP = 3.8, JHH = 1.3),
3
9.67 (d, 1H, H3, C6H4N, JHH = 5.9). 13C{1H} NMR (CD3CN):
1
d = 118.35 (d, Ci, PPh2, JPC = 101.5), 128.71 (s, Cm, PhCO), 130.01

492
D. Aguilar et al. / Journal of Organometallic Chemistry 694 (2009) 486–493
3
(s, Co, PhCO), 130.45 (d, Cm, PPh2, JPC = 14.5), 132.39 (d, C4,
4.2.2. Synthesis of 2,5-disubstituted oxazoles and of compound 29
To solutions of 0.63 mmol of N-propargylcarboxamides 14–18
and 27 in dry CH2Cl2, 5 mol% of gold compound (either AuCl3 or
5–8) was added. In the case of 5–8 the reactions can be performed
at air. The reaction mixture was stirred at the temperature and
during the time specified in Table 3. The reaction mixture was fil-
tered through a celite pad to remove any gold source and the
resulting solutions were evaporated to dryness. Conversions
shown in Table 3 (and molar ratios intermediate/final product)
were obtained by 1H NMR analysis of the isolated products.
4
C6H4N, JPC = 2.2), 134.04 (C6, C6H4N, overlapped with Ci, PhCO),
134.09 (s, Cp, PhCO), 134.37 (d, Co, PPh2, JPC = 12.9), 136.89 (d,
Cp, PPh2, JPC = 3.1), 145.30 (d, C5, C6H4N, JPC = 9.8), 148.94 (d,
C1, C6H4N, JPC = 123.0), 151.75 (d, C3, C6H4N, JPC = 7.7), 174.83
2
4
3
1
3
(s, CO).
4.1.3. Syntheses of N-propargylcarboxamides 15 and 16
To a solution of propargylamine (1 mL, 14.5 mmol), NEt3 (2 mL,
14.5 mmol) and N,N-dimethylpyridine (0.035 g, 0.25 mmol) in
40 mL of CH2Cl2 at 0 °C a solution of 2-thiophenoyl chloride
(1.5 mL, 14.5 mmol) in 5 mL of CH2Cl2 was added dropwise. The
resulting yellow solution was stirred at 0 °C during 30 min and a
further 3 h at room temperature. The reaction mixture was then
washed with a saturated solution of NH4Cl (2 ꢃ 20 mL) and a sat-
urated solution of NaHCO3 (2 ꢃ 20 mL). The organic layer was
dried with anhydrous MgSO4, filtered and concentrated to ca. 1–
2 mL. The addition of 15 mL of Et2O afforded a white solid (15) that
was subsequently filtered, washed with 15 mL of Et2O and vacuum
dried. Yield: 1.425 g, 8.62 mmol, 59.4%. Anal. Calc. for [C8H7NOS]
(165.21): C, 58.16; H, 4.27; N, 8.47; S, 19.4. Found: C, 58.30; H,
4.39; N, 8.57; S, 19.5%. MS (ESI+): 188 (100%) [M+Na]+. 1H NMR
4.3. Crystal structure determination of 8
Single crystals of 8 were grown by diffusing Et2O into a NCMe
solution of complex [AuCl2(Ph2PyP@NC(O)Ph)]ClO4 (8). A yellow
prism of dimensions 0.16 ꢃ 0.11 ꢃ 0.07 mm3 was mounted at
the end of a quartz fiber in a random orientation, covered with
magic oil and placed under a cold stream of nitrogen. Data collec-
tion was performed at 150 K on a Oxford Diffraction Xcalibur2
diffractometer using graphite monochromated Mo K
(k = 0.71073 Å). An hemisphere of data was collected based on
three -scan and u-scan runs. The diffraction frames were inte-
a radiation
x
grated using CRYSALIS RED [33] and the integrated intensities were
corrected for absorption with SADABS [34].
4
(CDCl3): d = 2.22 (t, 1H, HC„C, JHH = 2.5), 4.17 (dd, 2H, CH2,
3JHH = 5.3, JHH = 2.5), 6.32 (br. s, 1H, NH), 7.01 (dd, H4, C4H3S,
4
3JH4–H3 = 3.7, JH4–H5 = 5.0), 7.43 (dd, H5, C4H3S, JHH = 5.0,
4
3
4.3.1. Crystal data and data collection parameters
4JHH = 1.1), 7.50 (dd, H3, C4H3S, JHH = 3.7, JHH = 1.1). 13C{1H} NMR
(CDCl3): d = 29.66 (s, CH2), 71.81 (s, C„C), 79.44 (s, HC„C),
127.75 (s, C4, C4H3S), 128.69 (s, C3, C4H3S), 130.49 (s, C5, C4H3S),
138.16 (s, C1, C4H3S), 161.82 (s, CO).
3
4
Compound 8: C24H19AuCl3N2O5P, M = 749.90, Triclinic, space
ꢀ
group P1, a = 8.5748(6) Å, b = 9.426(3) Å, c = 16.233(4) Å,
a =
88.13(2)°, b = 82.241(11)°,
c
= 79.843(12)°, V = 1279.6(5) Å3,
T = 150(2) K, Z = 2, Dcal = 1.946 mg mꢁ3, F(000) = 724,
l = 6.164
Compound 16 was obtained in the same way starting from
propargylamine (1 mL, 14.5 mmol); NEt3 (2 mL, 14.5 mmol) and
N,N-dimethylpyridine (0.035 g, 0.25 mmol) in 40 mL of CH2Cl2
and a solution of 2,6-dichlorobenzoylchloride (2.1 mL, 14.5 mmol)
in 5 mL of CH2Cl2 at 0 °C. Yield: 1.993 g, 8.74 mmol, 60.3%. Anal.
Calc. for [C10H7NOCl2] (228.07): C, 52.66; H, 3.09; N, 6.14. Found:
C, 52.64; H, 3.15; N, 6.16%. MS (ESI+): 250 (100%) [M+Na]+. 1H
mmꢁ1, h range 2.52–25.00°, 22771 reflections collected, 4498 inde-
pendent (Rint = 0.0377).
4.3.2. Structure solution and refinement
The structure was solved and developed by direct methods [35].
All non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were included in idealized
positions and treated as riding atoms. Each H atom was assigned
an isotropic displacement parameter equal to 1.2 times the equiv-
alent isotropic displacement parameter of the parent atom. The
structure was refined to F2o, and all reflections were used in the
least-squares calculations [36]. Refinement proceeded to:
R = 0.0197, wR = 0.0415 for 362 parameters, and R = 0.0256,
wR = 0.0421 for all data, residual electron density in the range
4
NMR (CDCl3): d = 2.30 (t, 1H, HC„C, JHH = 2.5), 4.28 (dd, 2H,
3
4
CH2, JHH = 5.3, JHH = 2.5), 6.02 (br. s, 1H, NH), 7.24–7.34 (m, 3H,
Ph). 13C{1H} NMR (CDCl3): d = 29.62 (s, CH2), 73.10 (s, C„C),
78.54 (s, HC„C), 128.00 (s, Cp, Ph), 130.82 (s, Cm, Ph), 132.29 (s,
Co, Ph), 135.20 (s, C1, Ph), 164.28 (s, CO).
4.2. Catalytic studies
1.002 and ꢁ0.533 e Åꢁ3
.
4.2.1. Addition of methyl vinyl ketone 10 with 2-methylfuran (9) or
azulene (12)
Acknowledgements
All catalytic reactions were performed at 25 °C in a Kontex tube
using distilled and degassed solvents and under Argon atmosphere.
Procedure for the addition of MVK (10) to 2-methylfuran (9):
2 mmol of 10, 2 mmol of 9, 0.02 mmol of the corresponding gold
complex and 0.044 mmol (or 0.022 mmol) of silver salt (when nec-
essary) were mixed in 5 mL of CH3CN, and this mixture was stirred
for a period of 6 or 18 h (Table 1). After the reaction time was com-
pleted, the resulting mixture was filtered through a short silica-gel
column using 20 mL of a Et2O/n-hexane (3/1) mixture as eluent.
The yellow solution was evaporated to dryness under vacuum,
affording pure 11. Procedure for the addition of MVK (9) to azulene
(12): 2 mmol of 12, 2 mmol of 9, 0.03 mmol of the corresponding
gold complex (0.02 mmol in the case of AuCl3) and 0.066 mmol
of silver salt (when necessary) were mixed in 5 mL of CH3CN,
and this mixture was stirred for 24 h (Table 2). After the reaction
time, the resulting mixture was filtered through a short silica-gel
column using 20 mL of a Et2O/n-hexane (3/1) mixture as eluent.
The yellow solution was evaporated to dryness under vacuum,
affording pure 13.
We thank the Spanish Ministry of Education and Science (MEC,
Project CTQ2005-01037) and Brooklyn College (CUNY) for financial
support. D.A. thanks the Diputación General de Aragón (Aragón,
Spain) for a Ph.D. grant (B021/2006).
Appendix A. Supplementary material
CCDC 684707 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. Supplementary data asso-
ciated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2008.09.058.
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