Pyridine- and Quinoline-Based Gold(III) Complexes: Synthesis, Characterization, and Application

Article abstract of DOI:10.1002/ejoc.202000139

Studies on gold(III) coordination of a series of prepared polydentate pyridine and quinoline based ligands are reported. Characterization (¹H, ¹³C, ¹⁵N NMR, and XRD) of the novel gold(III) complexes, prepared in 31–98 % yield, revealed different coordination ability of the pyridine and quinoline nitrogen atoms. Testing of catalytic activity in cyclopropanation of propargyl ester and styrene demonstrated that all the new ligated gold(III) complexes were catalytically active and outperformed KAuCl₄. The superior activity of the particular Au(III)-pyridine-oxazole complexes may indicate de-coordination of the pyridine-N ligand as a crucial step for efficient generation of catalytic activity.

Full text of DOI:10.1002/ejoc.202000139

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Accepted Article
Title: Pyridine- and quinoline-based gold(III) complexes: synthesis,
characterization and application.
Authors: Ann Christin Reiersølmoen and Anne Fiksdahl
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10.1002/ejoc.202000139
European Journal of Organic Chemistry
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Pyridine- and quinoline-based gold(III) complexes: synthesis,
characterization and application.
Ann Christin Reiersølmoen[a] and Anne Fiksdahl*[a]
[a]
A. C. Reiersølmoen, Prof. Dr. A. Fiksdahl
Department of Chemistry
Norwegian University of Science and Technology
Høgskoleringen 5, 7491, Trondheim, Norway
E-mail: anne.fiksdahl@ntnu.no
https://www.ntnu.edu/gold
Supporting information for this article is given via a link at the end of the document.
Abstract: Studies on gold(III) coordination of a series of prepared
polydentate pyridine and quinoline based ligands are reported.
Characterization (1H, 13C, 15N NMR and XRD) of the novel gold(III)
complexes, prepared in 31-98% yield, revealed different coordination
ability of the pyridine and quinoline nitrogens. Testing of catalytic
activity in cyclopropanation of propargyl ester and styrene
demonstrated that all the new ligated gold(III) complexes were
catalytic active and outperformed KAuCl4. The superior activity of the
particular Au(III)-pyridine-oxazole complexes may indicate de-
coordination of the pyridine-N ligand as a crucial step for efficient
generation of catalytic activity.
promising candidates for biological testing, such as antitumor
agents,[8] anticancer,[9] anti-parasitic agents,[10] antifungal,[11]
inhibition of DNA/RNA synthesis,[12] and aquaporin inhibition.[13]
The reported gold(III) complexes are often based on nitrogen
containing ligands, such as diamine, polyamine, cyclam, bipyridyl,
porphyrin, phenanthroline and terpyridine.
The limited experience and understanding of the chemistry
of gold(III)-ligand species, indicates that more knowledge is
needed for development of stable Au(III)-complexes and for
studies of their catalytic activity.
We have previously prepared gold(III) complexes based on
bisoxazoline and 2-pyridylmenthol ligands, and studied their
catalytic properties in cyclopropanation reactions.[14] We hereby
present further studies on the synthesis of a series of new pyridyl
and quinolinyl based polydentate ligands, along with gold(III)
coordination studies. The catalytic ability of the new gold(III)
complexes in cyclopropanation reaction is studied, as well.
Introduction
Homogeneous gold catalysis in organic synthesis has become a
rapidly growing field within the last decades.[1] However, gold
catalysis is still described as a new and young area compared to
the chemistry of the more utilized and developed neighbors in the
periodic table, e.g. Pt, Pd, Hg, Rh, Ru and Ir.[2] This is often
evidenced by the mechanism for gold catalysis being less
understood and explored compared to the other transition
metals.[3] The development of gold catalysis has mainly focused
on gold(I) species, as shown by a large number of reported ligated
gold(I) complexes utilized in various catalytic transformations.[4]
Also reaction mechanisms have been studied by characterization
of reactive intermediates and by corroboration of the experimental
data with computational studies.[4b, 4c, 5] Catalysis by gold(III) has,
on the other hand, been less developed and is still mainly
dominated by the inorganic gold(III) salts, such as AuCl3 and
KAuCl4.[6] However, compared to the linear gold(I) complexes, the
square planar coordination mode of gold(III) species may provide
advantages in order to obtain improved control around the
reaction center and, hence, influence the selectivity of the
catalytic reaction. A great variety of strategies for design of mono-
and polydentate ligands and their Au(III) complexes is
conceivable. It is also shown that the oxidation state of gold can
affect the reactivity and outcome for some organic
transformation.[4a]
Results and Discussion
Preparation of 2-(quinolin-2-yl)- and 2-(pyridin-2-yl)-4,5-
dihydrooxazole gold(III) complexes, 1-Au(III) and 2-Au(III).
Ligated gold(III) complexes based on bisoxazoline,[14-15] pyridinyl-
oxazolines[16] and 2,6-bisoxazoline-pyridine[17] have previously
been prepared with different counter ions. Given the affinity of
gold(III) to coordinate to such heterocyclic ligands, we initially
studied the coordination ability of gold(III) to (S)-4-isopropyl-2-
(quinolin-2-yl)-4,5-dihydrooxazole, 1a, and (S)-4-phenyl-2-
(quinolin-2-yl)-4,5-dihydrooxazole, 1b, (Scheme 1a). The
i
coordination of the alkyl substituted ligand (R= Pr) to AuCl3
seemed to give a mixture of two complexes (1H NMR). Addition of
NH4PF6 has been reported[18] to activate gold(III) for coordination.
This method allowed successful formation of the oxazole mono-
coordinated crystalline 1a-Au(III) complex as the only product
(74% yield, Scheme 1a). Addition of NH4PF6 was not required to
efficiently obtain the corresponding 1b-Au(III) complex (98%) with
the phenyl substituted ligand (R= Ph).
The crystal structure (XRD) of the 1a-Au(III) complex
confirmed the formation of a mono-coordinated Au(III) complex
through the oxazole-nitrogen, while no coordination of the
quinoline-nitrogen had taken place (Figure 1a).
However, in recent years, interesting ligated gold(III)
complexes are reported. Although some of the compounds are
studied as catalysts in organic transformations,[7] the Au(III)-
ligand concept was initially mainly developed for bioactive studies.
A number of stable Au(III)-ligand complexes were designed as
1
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10.1002/ejoc.202000139
European Journal of Organic Chemistry
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not observed for the more stable ligand 1a at the same
conditions (Table 1, entry 1). The ring opening reaction was also
observed by storage of the coordination solution of AuCl3 and the
1b ligand in dichloromethane for 2-3 days. Corresponding ring
opening of the oxazoline ring in the presence of water under weak
basic conditions[16] or during gold(III) coordination in aqueous
media[17] has been reported. In contrast to the presently observed
aminocarboxylate complex formed by cleavage of C=N bond by
water, we recently observed that oxazole ring opening by
nucleophilic attack of strongly coordinating anions on 2-Au(III)
-
complexes gave a different outcome, as the nucleophilic CF3CO2
or NO3- anions attack the oxazoline-CH2, to give cleavage of the
oxazoline CH2-O bond.[19]
a
Table 1. Attempted coordination of quinoline-nitrogen of ligands 1 to AuCl3
Entry
ligand
1a
Additive
Temp.
60 oC
r.t.
Observation c
1
2
3
4
5
6
7
n.r.
n.r.
n.r.
n.r.
n.r.
r.o.
n.r.
-
Scheme 1. Preparation of a) 1-Au(III), b) 2-Au(III) complexes[19] and c) Pyr-/Qu-
oxazoline ring opened product.
1a
1a
1a
NH4PF6
NH4PF6
AgSbF6
60 oC
r.t
It is expected that the 1-Au(III) complexes would be more
catalytic active if both N-heteroatoms of the bidentate ligands
were coordinated to gold(III). Different conditions were tested in
order to facilitate exchange of the second strongly coordinated
chlorine with the quinoline nitrogen (Table 1). However, none of
the experiments, including varied temperature, microwave
heating or addition of weakly coordinating anions, resulted in
coordination of the second nitrogen to gold(III). However, an
interesting difference between the quinoline ligands was identified,
1a-Au(III)b AgSbF6
r.t
1b
60 oC
80 oCd
1a
AgSbF6
[a] 1 equiv. AuCl3 was used. [b] AuCl3 was not added. [c] n.r.: no reaction; r.o.:
ring opening. [d] microwave heating in a closed vial.
As the unsuccessful coordination of the quinoline nitrogen
could be explained by insufficient electron density caused by
electron delocalization in the benzo-fused aromatic system, the
analogues pyridine ligand would be more promising for bidentate
coordination. In fact, initial treatment of the Pyridine-oxazoline
ligand 2 (Scheme 1b) with gold(III) (1 equiv. AuCl3) gave 50%
conversion of the ligand into a new product, which was initially
i
as the Pr-substituted ligand, 1a, had higher stability than the
phenyl analogue 1b. By heating (60 oC) the coordination solution
of AuCl3 and the ligand 1b, a ring opened and gold(III) reduction
minor product, the [(2-ammoniumquinoline carboxylate)(Au(I)Cl2)]
complex, was identified (XRD, Figure 1c, Scheme 1c, Table 1,
entry 6). The possible nucleophilic attack of water on the
oxazoline ring to afford ring opening, was however,
-
believed to be a Au(III) complex with AuCl4 as counter ion, as
reported for similar ligands.[16] However, a new minor product was
also selectively formed by reflux of ligand 2 and AuCl3 in
acetonitrile and was identified (XRD, Figure 1d) as the
ammonium-picolinate Au(I)Cl2 complex, which is the similar ring
opened product as described above (Figure 1c).
Figure 1. Crystal structures of a) 1a-Au(III); b) 2-Au(III)-SbF6; as well as ring
opened carboxylate Au(I)Cl2 products from c) ligand 1b and d) ligand 2
(determined by XRD).
It is previously reported that ligand coordination in the
presence of a silver salt of a weakly coordinating ion may give
more selective coordination to gold(III) and also prevent formation
-
16]
of AuCl4 complexes.[14,
This method successfully gave
crystalline 2-Au(III) complexes with the different counter ions
-
-
SbF6 , BF4 and Tf2N- (61-82%, Scheme 1b) by addition of the
appropriate silver salts.[19] Preparation of a 2-Au(III) complex by
BArF counter ion exchange with the NaBArF salt failed, possibly
due to the lack of driving force gained by the precipitation of AgCl,
using the silver salt of the counter ion.
The crystal structures of 2-Au(III) with SbF6 as the counter
ions were determined (XRD, Figure 1b). In contrast to the
quinoline ligands, the pyridine analogues coordinated efficiently
with both heterocyclic nitrogens in a bidentate Au(III) coordination
mode. Only the main structure with SbF6 as counter ion is shown.
However, X-ray analysis showed that the corresponding complex
with AuCl4 counter ion also was formed. However, selective
preparation of the 2-Au(III)-SbF6 complex was readily obtained by
increasing the amount of AgSbF6 from 1.2 to 2 equivalents in
2
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10.1002/ejoc.202000139
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order to suppress the formation of the unwanted AuCl4 counter
ion.
Δδ15Ncoord and stronger coordination of Au(III) to the oxazoline
nitrogen was observed for the mono-dentate quinoline based
complex (Δδ15Ncoord -76.2 ppm) than the di-coordinated pyridine
complex (Δδ15Ncoord -41.1 ppm). Additionally, 13C NMR clearly
showed that the aromatic carbons of quinoline ligands are less
affected by coordination (13C NMR spectra, see Figure S1, Supp.
Info.)
In order to increase the electron density of the quinoline
nitrogen to improve the coordination ability, the 4-methoxy
substituted analogues of ligands 1, ligands 3, were synthesized
according to the synthetic route described in Scheme 2.
The different coordination abilities of pyridine and quinoline
nitrogens to the gold(III), shown by XRD (Figures 1a,b), were also
clearly recognized by 1H NMR.
Monitoring of the gold
coordination experiments of quinoline and pyridine based ligands,
afforded a convenient method for identifying selective mono- or
di-dentate Au(III) coordination modes (Figure 2). Coordination of
pyridine-oxazoline ligand 2 to Au(III) and formation of the 2-Au(III)
complexes gave strong and significant deshielding effects and
large peak shifts (Δδ1Hcoord = δ1Hcomplex – δ1Hligand) of most pyridine
protons (Δδ1Hcoord up to 0.8 ppm, Figure 2a). Whereas pyridine
coordinates through its nitrogen, the delocalized aromatic
electron structure of the benzo-fused quinoline analogue prohibits
N-coordination to gold(III), as shown by the moderate deshielding
effect and peak shifts of the quinoline protons H3 and H4
(Δδ1Hcoord 0.2-0.6 ppm, Figure 2b). In particular, protons H5-8 in
the benzo-fused quinoline part were weakly affected by
coordination and experience minor deshielding (Δδ1Hcoord <0.2
1
ppm). The selective coordination effect was seen by H NMR for
both the complexes 1a-Au(III) and 1b-Au(III) and demonstrates
that no nitrogen-gold(III) coordination of quinoline takes place.
Scheme 2. Preparation of 4-methoxy substituted quinoline ligands 3a and 3b.
The 4-OMe quinoline substituted ligands 3a (iPr) and 3b (Ph)
were attempted coordinated to gold(III) by the same methods as
above, in the presence and absence of silver salt (Scheme 1).
However, no AgCl precipitate was observed by silver salt addition
and 1H NMR of the coordination solutions indicated unsuccessful
coordination of the quinoline nitrogen. Refluxing the reaction
mixtures in acetonitrile overnight had no further effect. These
observations were corroborated with 15N NMR of ligand 3b to
confirm the observed results. Mono-coordination of the ligand
through the oxazoline nitrogen was similarly seen by the
respective large and small NMR differences of the oxazoline and
quinoline nitrogen signals (Δδ15Ncoord,
Δδ15Ncoord,Qu -1.0 ppm).
-74.0 ppm and
oxaz
Figure 2. 1H NMR study ( 4-10 ppm) of AuCl3 coordination experiments of
ligands a) 2 and b) 1a.
Synthesis of potential pyridine and quinoline based
ligands for gold(III) coordination. To further explore the
selective quinoline and pyridine coordination patterns, a series of
new quinoline and pyridine based Au(III)-ligand complexes were
prepared, replacing the oxazoline ring with other heteroatom units.
The 10 new potential ligands for gold(III) coordination were
synthesized (4a-e and 5a-e, 47-99% yield) by two-step reductive
As 15N NMR chemical shifts have proven to give valuable
information on metal coordination,[20] the observed coordination
1
effect in H NMR was corroborated by the change in 15N NMR
shifts by coordination (Δδ15Ncoord = δ15Ncomplex – δ15Nligand). In a
recent study[19], we observed that both nitrogens in the 2-Au(III)
complexes were clearly affected by coordination, as shown by
large differences of both the pyridine nitrogen (Δδ15Ncoord -87.5
ppm) and the oxazoline nitrogen (Δδ15Ncoord -41.1ppm) by 1H,15N
HMBC in CD3CN, indicating bi-dentate Au(III) coordination of the
pyridine-oxazoline ligand 2. In contrast, similar studies of the 1a-
Au(III) complex, indicated that the quinoline nitrogen was hardly
affected by coordination, as shown by a minor NMR peak change
(Δδ15Ncoord 2.2 ppm). Mono-coordination of the oxazoline nitrogen
was demonstrated by the large difference of the oxazoline
nitrogen signal upon coordination (Δδ15Ncoord -76.2 ppm).
amination of quinolone-2-carbaldehyde
9
or 6-methyl-
picolinaldehyde 10, and the appropriate amine Ra-eNH2, (Scheme
3). Deprotection of N-Boc-compounds 4cꞌ and 5cꞌ yielded amines
4c and 5c (52-70%).
Gold(III) coordination studies of ligands 4a-e and 5a-e. All
ligands 4 and 5 readily coordinated to give Au(III) complexes (31-
92%, Table 2). Despite the polydentate nature of the ligands (N,N-
bi, N,N,N-tri; N,N,O-tri), no coordination of neither the quinoline
nor the pyridine nitrogens took place, as only amino, di-amino and
amino-alkoxylate complexes were formed. This was shown by full
characterization of all complexes and was also clearly recognized
by 1H NMR (Figure 3). Only small changes in H NMR chemical
shifts (0.1-0.2 ppm) of heteroaromatic protons were observed
1
Different impact on the oxazoline nitrogens by coordination of
the pyridine and the quinoline complexes was seen. Larger
3
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10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
upon coordination, indicating lack of coordination of the
heteroaromatic nitrogens, as discussed above (Figure 2).
Table 2. Formation of Au(III) complexes of quinoline and pyridine based ligands
4 and 5. Proposed structures of 4- and 5-Au(III) complexes.
4-Au(III) complexes:
5-Au(III) complexes:
Scheme 3. Preparation of quinoline and pyridine based ligands a) 4a-e and b)
5a-e through reductive amination.
Moderate to high yields of the monoamino-ligated Au(III)
complexes of N,N-ligands 4b and 5b (42-82%) were obtained.
Non-coordination of heterocyclic nitrogens was also seen by
formation of the respective N,N-diamino complexes (62-71%)
from the possible N,N,N-tridentate ligands 4c and 5c. Coordiation
of the analouge potential N,N,O-tridentate aminocyclohexanol
ligands 4e and 5e to gold(III) readly took place to afford the N,O-
bidentate complexes 4e-Au(III) and 5e-Au(III) (31-68%). No
coordination of the aromatic nitrogen was observed. The potential
N,N,O-tridentate aminoindenol ligands 4d and 5d showed similar
coordination behavior, affording the N,O-bidentate complexes 4d-
Au(III) and 5d-Au(III) (73-92%, Table 2).
It seems like one chloride is readily exchanged, while the
second requires more energy. When coordination of compound
5c was attempted, using AgSbF6 to facilitate chloride exchange
and coordination of the pyridine nitrogen, the compound seemed
to decompose, and a complex mixture was observed by 1H NMR.
Different stability of the quinoline and pyridine based
complexes was observed. Whereas the quinoline complex 4d-
Au(III) started to decompose in one day in acetonitrile, the
pyridine complex 5d-Au(III) remained stable. This trend was seen
for all complexes. The quinoline/pyridine benzylic CH2-group may
be a weak point, exposed for nucleophilic attack by traces of water
in the solvent. Specially coordination of 4a and 5a to Au(III)
resulted in complexes sensitive to water, hence these complexes
were not isolated, but complexed and used directly in situ in the
reaction. When suitable crystals for X-ray analysis were
attempted grown for 4c-Au(III) and 5c-Au(III), complex 4c-Au(III)
decomposed to give crystals of diaminocyclohexane
dihydrochloride, while 5c-Au(III) formed crystals, but not proper
quality for X-ray analysis.
1
Even though larger H NMR peak changes (Δδ1Hcoord) were
seen for the aromatic protons of compound 5c than of compound
4c upon coordination (Figure 3), 15N NMR of the 5c-Au(III)
complex indicated no coordination of the pyridine nitrogen
(Δδ15Ncoord -13.9 ppm) by addition of Au(III).
Figure 3. 1H NMR study of KAuCl4 coordination experiments of ligands 4c and
5c.
4
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Catalytic activity. The gold-catalyzed cyclopropanation of
propargyl 11 and alkene 12 was selected as the model reaction
for investigation of the catalytic ability of the new gold(III) catalyst
(Table 3). This reaction has previously been thoroughly
investigated (1H NMR) with similar gold(III) catalysts,[14] thus
providing a solid background for comparison. A difference in
catalytic activity was observed for the pyridine and quinoline
complexes (entries 1-5), as 2-Au(III) and 1-Au(III) gave full
conversion in 5 min and 12-24 hours, respectively. The Au(III)
complexes of the methoxy activated quinoline, 3-Au(III), afforded
faster conversion than the non-substituted complexes (entry 5 /
24 h; entry 7 /12 h). Comparable reactivity was observed in the
presence of the quinoline and pyridine complexes 4-Au(III) and 5-
Au(III), having the oxazoline ring replaced by other heteroatom
units (entries 8-17). Although they were less active than the
oxazoline based complexes above (entries 1-7), the catalytic
activity of 4-Au(III) and 5-Au(III) complexes were definitively larger
than the nearly non-catalytic KAuCl4 salt (entries 18-19). KAuCl4
seems to be to solvated in acetonitrile, blocking any catalyst
activity of the gold center. Even if the Au(III) complexes of ligands
4 and 5 proved to be unstable, they seem to be transformed into
new catalytic active species by ligand modification, as they
remained catalytic active. As discussed above, the ligand may
undergo benzylic cleavage, leaving gold coordinated to the
chlorides and the respective amine (Ra-fNH2). Hence,
decomposition of the complexes does not generate the highly
active AuCl3, which, in contrast, gave immediate conversion, even
by low catalyst loading (2 mol%, entry 21). The disadvantage of
AuCl3 is, however, instability and low reproducibility, as shown by
immediate decomposition into black precipitate. The large
reactivity difference of 4-Au(III) and 5-Au(III) complexes
compared to AuCl3, illustrates the deactivating effect of an
alkylamine ligand on the gold catalyst.
Table 3. Studies of catalytic activity of new gold(III) complexes in
cyclopropanation of propargyl ester 11 and styrene 12.
Entry
Au(III) cat.[a]
2-Au(III)-SbF6
2-Au(III)-BF4
2-Au(III)-Tf2N
Time
Conversion[b]
100 %
Cis:trans
ratio
1
2
3
5 min
12 h
60 : 40
14 : 86
56 : 44
26 : 74
5 min
12 h
100 %
5 min
24 h
100 %
54 : 46
27 : 73
4
1a-Au(III)
1b-Au(III)
3a-Au(III)
3b-Au(III)
4a-Au(III)
4b-Au(III)
4c-Au(III)
4d-Au(III)
4e-Au(III)
5a-Au(III)
5b-Au(III)
5c-Au(III)
5d-Au(III)
5e-Au(III)
K(AuCl4)
12 h
24 h
100 %
94 %
79 : 21
68 : 32
77 : 23
67 : 33
80 : 20
76 : 24
78 : 22
76 : 24
84 : 16
78 : 22
86 : 14
71 : 29
79 : 21
81 : 19
-
5
6
< 12 h
< 12 h
24 h
100 %
100 %
79 %
7
8
9
24 h
100 %
100 %
82 %
10
11
12
13
14
15
16
17
18
19
20
12 h
24 h
24 h
90 %
12 h
100 %
100 %
100 %
90 %
24 h
24 hd
24 h
<24 h
24 h
100 %
0 %
Our previous study on Box-Au(III) complexes proved their
strong catalytic effect both on cyclopropanation and subsequent
in situ cis-to-trans isomerization (90% trans in 12 h, entry 20).
Similar unique dual properties were identified for the present 2-
Au(III) N-pyridine coordinated complexes (up to 86% trans in 12
h; entries 1-3). The non-heterocycle-coordinated 1-Au(III), and 4-
Au(III) and 5-Au(III) complexes afforded less efficient conversions.
In a recent study, monitoring a different alkoxycyclization
K(AuCl4)[c]
Box-iPr-Au(III)[d]
24 h
< 5 %
100 %
<99 : >1
70 : 30
10 : 90
83 : 17
83 : 17
15 min
12 h
[e]
21
AuCl3
5 min
12 h
100 %
[a] 5 mol% catalyst was used unless stated otherwise. [b] percent conversion of
propargyl substrate (1H NMR). [c] 10 mol% of K(AuCl4) was used. [d] Previous
reported reaction repeated in d-ACN for comparison.[14] [d] 2 mol% of AuCl3 was
used.
reaction by 1H,15N HMBC, a large peak shift (Δδ15Nrx = δ15Ncoord
–
δ15Ndiss = + 83.3 ppm) of the pyridine nitrogen of the 2-Au(III)
complex was observed during the reaction.[19] This most likely
reflects dissociation of the pyridine nitrogen throughout the
reaction, which activates the complex for coordination to the
substrate. This correlates with the reactivity difference we
observe between the 2-Au(III) and 3-Au(III), 4-Au(III) and 5-Au(III)
complexes, which may indicate de-coordination of the pyridine-N
ligand as a crucial step for efficient generation of catalytic activity.
Despite the chiral nature of the applied Au(III) complexes, no
enantioselectivity was observed, and racemic cyclopropyl
products 13 were obtained (HPLC).
Conclusion
Our study on the coordination ability of new polydentate
pyridine- and quinoline-oxazoline based ligands to gold(III) (1H,
13C, 15N NMR and XRD) showed formation (61-98%) of N-
oxazoline Au(III) complexes, with selective coordination of
pyridine nitrogen, whereas quinoline nitrogens failed to undergo
complexation. Attempts to activate the quinoline nitrogen for
coordination (heat, microwave, silver salts additives, increased
quinoline electron density) were unsuccessful.
To further explore the selective quinoline and pyridine
coordination patterns, a series of new quinoline and pyridine
based Au(III)-ligand complexes were prepared (31-92%),
replacing the oxazoline ring with other heteroatom units. However,
the obtained complexes were formed by selective coordination of
5
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10.1002/ejoc.202000139
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The mixture was stirred for 15-60 minutes before white precipitate
from KCl was removed and the complex was dried under reduced
pressure. If the product needed additional treatment, it was done as
indicated for each compound.
the N,N- or N,O-heteroatom units, whereas pyridine and quinoline
nitrogen coordination was unsuccessful.
The catalytic ability of all of the described new gold(III)
complexes were screened in a cyclopropanation reaction pf
styrene using propargyl ester. While all complexes were catalytic
active, the pyridine coordinated 2-Au(III) complexes had similar
unique catalytic properties as our previously studied Box-Au(III)
complexes. Hence, the studies may indicate that pyridine-
nitrogen de-coordination ability is significant in order to generate
highly efficient catalytic activity.
General method 3: testing of catalytic ability in
cyclopropanation reaction. The propargyl ester 11 (5 mg, 1 equiv.)
and styrene 12 (4 equiv.) was dissolved in d‐ACN (0.6 mL) and
added the gold‐catalyst (5 mol‐%) dissolved in d‐ACN. The reaction
1
progress was monitored by H NMR at 5 min, 30 min, 1 h, 2 h, 5 h,
1
12 h, 24 h. The results are presented in Table 3. The H NMR shifts
are in accordance with characterized product previously
reported.[14]
(S)-N-(1-hydroxy-3-methylbutan-2-yl)-4-
methoxyquinoline-2-carboxamide (7a). 4-Methoxyquionoline-2-
carboxylic acid
6 (147 mg, 0.723 mmol) was dissolved in
Experimental Section
dichloromethane (15 mL) and added DIPEA (0.65 mL, 3.72 mmol)
and HATU (413 mg, 1.085 mmol). The reaction mixture was stirred
for 1 hour before (R)-2-amino-3-methylbutan-1-ol (230 mg, 2.23
mmol) dissolved in dichloromethane (2 mL) was added. The
solution was stirred for an additional hour, before the reaction
mixture was poured into aqueous HCl (0.1 M, 5 mL). The mixture
was extracted with dichloromethane (3 x 10 mL). The combined
organic phases were washed with conc. aqueous NaHCO3 solution
(10 mL) and water (10 mL). The aqueous phases were reextracted
with DCM before the combined organic phases were dried over
anhydrous sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was purified by silica gel
column chromatography (n-pentane:EtOAC, 1:1, Rf = 0.33) to give
120 mg (58%, 0.416 mmol) of the product, 7a, as a colorless oil1H
NMR (400 MHz, Chloroform-d) δ = 8.52 (d, J=8.5, 1H), 8.21 (ddd,
J=8.4, 1.6, 0.8, 1H), 8.07 – 8.00 (m, 1H), 7.73 (ddd, J=8.4, 6.8, 1.5, 1H),
7.69 (d, J=0.9, 1H), 7.56 (ddd, J=8.3, 6.9, 1.2, 1H), 4.12 (s, 3H), 3.96
(dtd, J=8.2, 6.6, 3.3, 1H), 3.87 (td, J=10.6, 10.0, 6.4, 2H), 2.89 (s, 1H),
2.19 – 2.02 (m, 1H), 1.07 (t, J=6.4, 6H). 13C NMR (101 MHz,
Chloroform-d) δ 165.7, 163.7, 151.0, 147.5, 130.3, 129.2, 126.9,
122.1, 122.0, 97.9, 64.4, 58.0, 56.2, 29.3, 19.7, 18.8; HRMS
(APCI/ASAP, m/z): 289.1553 (calcd. C16H21N2O3, 289.1552,
[M+H]+); HRMS (APCI/ASAP, m/z): 289.1553 (calcd. C16H21N2O3,
289.1552, [M+H]+).
General: Commercial grade reagents were used as received. Dry
solvents were collected from a solvent-purification system. All
reactions were monitored by thin-layer chromatography (TLC)
using silica gel 60 F254 (0.25-mm thickness) or by 1H-NMR. Flash
chromatography was carried out using silica gel 60 (0.040-0.063
mm). High Throughput Flash Purification (HPFP) was performed on
pre-packed cartridges. 1H and 13C NMR spectra were recorded using
1
a 400 or 600 MHz spectrometer, while H,15N HMBC was recorded
suing a 600 MHz spectrometer. Chemical shifts are reported in ppm
(δ) relative to tetramethylsilane (TMS) or d-ACN. Coupling
constants (J) are reported in Hertz (Hz). The attributions of the
chemical shifts were determined using COSY, HSQC and HMBC NMR
experiments. Accurate mass determination in either positive or
negative mode was performed with
a “Synapt G2-S” Q-TOF
instrument from Waters. Samples were ionized with an ASAP probe
(APCI) or ESI probe, and no chromatographic separation was used
before the mass analysis. Calculated exact mass and spectra
processing was done by Waters TM Software Masslynx V4.1
SCN871. Single crystal X-ray data was acquired using a Bruker D8
Venture diffractometer with the APEX3 suit, integrated with SAINT
V9.32B, solved with XT and refined with XL using Olex2 as GUI. The
cif files were edited with encipher 1.4 and molecular graphics were
produced with Mercury 3.8. ORTEP plots are shown in the thesis
and all metric data, including reflection data, are contained in the
respective cif files. This data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK. Fax: +44 1223 336 033; or deposit@ccdc.cam.ac.uk.
Propargyl ester 11[21] and 2-Au(III)-SbF6/BF4/NTf2 complexes39
were prepared according to literature procedures. The ligands (S)-
4-tert-butyl-2-(2-pyridyl)oxazoline, (S)-4-isopropyl-2-(quinolin-2-
yl)-4,5-dihydrooxazole and (R)-4-phenyl-2-(quinolin-2-yl)-4,5-
dihydrooxazole were commercial available. Crystal structures
(Figure 1a-d); CCDC ID: a) 1951650 1a-Au(III); b) 1951651 2-
Au(III)- SbF6; ring opened products: c) 1951652 and d) 1951653.
(S)-4-isopropyl-2-(4-methoxyquinolin-2-yl)-4,5-
dihydrooxazole (3a). (S)-N-(1-hydroxy-3-methylbutan-2-yl)-4-
methoxy-quinoline-2-carboxamide 7a (90 mg, 0.312 mmol) was
dissolved in dry THF (3 mL) and added thionylchloride (114 μL, 1.56
mmol). The reaction mixture was refluxed for 1.5 hours before the
reaction was quenched with sat. aqueous NaHCO3 solution and
extracted with dichloromethane (3 x 10 mL). The combined organic
phases were dried over anhydrous sodium sulphate, filtered and
concentrated under reduced pressure. The crude product, 8a, was
subsequently dissolved in dry ethanol (3 mL) and added sodium
hydroxide (37 mg, 0.925 mmol). The reaction mixture was refluxed
for one hour before water (10 mL) was added. The mixture was
extracted with dichloromethane (3 x 10 mL) and the combined
organic phases were washed with sat. aqueous sodium chloride
solution (20 mL), dried over anhydrous sodium sulphate and
concentrated under reduced pressure. Purification with silica gel
column chromatography (n-pentante: EtOAc, 1:1, Rf = 0.19) yielded
63 mg (63%, 0.233 mmol) of the ligand 3a as a white powder. 1H
NMR (400 MHz, Acetonitrile-d3) δ = 8.21 (dd, J=8.3, 1.5, 1H), 8.01
(dt, J=8.4, 0.9, 1H), 7.77 (ddd, J=8.4, 6.8, 1.5, 1H), 7.65 – 7.51 (m, 2H),
4.54 (dd, J=9.7, 8.4, 1H), 4.25 (t, J=8.4, 1H), 4.16 (ddd, J=9.8, 8.3, 6.5,
1H), 4.10 (s, 3H), 1.84 (dt, J=13.3, 6.7, 1H), 1.05 (d, J=6.7, 3H), 0.96
(d, J=6.7, 3H); 13C NMR (101 MHz, Acetonitrile-d3) δ 163.9, 163.5,
149.5, 149.4, 131.3, 130.3, 128.0, 122.6, 122.6, 100.8, 73.8, 71.7,
56.9, 33.8, 19.1, 18.7; HRMS (APCI/ASAP, m/z): 271.1445 (calcd.
C16H19N2O2, 271.1447, [M+H]+).
General method 1: synthesis of pyridine- and quinoline-
based
ligands.
Quinoline-2-carbaldehyde
9
or
6-
methylpicolinaldehyde 10 (1 equiv.) and the selected chiral amine
(1 equiv.) were dissolved in dry EtOH (0.15 molar solution) under a
nitrogen atmosphere. The reaction mixture was stirred until full
conversion into imine was observed by 1H NMR (around 1 hour),
before NaBH4 (3 equiv.) was added directly to the reaction mixture.
When 1H NMR showed full reduction to amine, the reaction was
quenched with HCl (1M). Aqueous NaOH solution (1M) was
subsequent added until basic solution, before the water phase was
extracted with DCM (3 x 30 mL). The combined organic phases were
dried over anhydrous Na2SO4, filtered and dried under reduced
pressure. If the product needed additional purification, it was done
as indicated for each compound.
(S)-N-(2-hydroxy-1-phenylethyl)-4-methoxyquinoline-2-
carboxamide (7b). 4-Methoxyquionoline-2-carboxylic acid 6 (145
mg, 0.714 mmol) was dissolved in dichloromethane (15 mL) and
General method 2: coordination of ligands to gold(III). Ligands
4a-e or 5a-e were dissolved in ACN and added KAuCl4 (1 equiv.).
6
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
added DIPEA (0.65 mL, 3.72 mmol) and HATU (413 mg, 1.085
mmol). The reaction mixture was stirred for 1 hour before (R)-2-
amino-2-phenylethan-1-ol (282 mg, 2.88 mmol) dissolved in
dichloromethane (2 mL) was added. The solution was stirred for an
additional hour, before the reaction mixture was poured into
aqueous HCl (0.1 M, 5 mL). The mixture was extracted with
dichloromethane (3 x 10 mL). The combined organic phases were
washed with conc. aqueous NaHCO3 solution (10 mL) and water (10
mL). The aqueous phases were reextracted with DCM before the
combined organic phases were dried over anhydrous sodium
sulphate, filtered and concentrated under reduced pressure. The
crude product was purified by silica gel column chromatography (n-
pentane:EtOAC, 1:1, Rf = 0.29) to give 147 mg (64%, 0.457 mmol)
of the product, 7b, as a colorless oil. . 1H NMR (400 MHz,
Chloroform-d) δ = 8.94 (d, J=7.5, 1H), 8.22 (ddd, J=8.4, 1.5, 0.7, 1H),
8.04 (ddd, J=8.6, 1.3, 0.7, 1H), 7.73 (ddd, J=8.5, 6.9, 1.5, 1H), 7.70 (s,
1H), 7.57 (ddd, J=8.2, 6.9, 1.2, 1H), 7.50 – 7.36 (m, 4H), 7.38 – 7.29
(m, 1H), 5.31 (td, J=6.6, 4.2, 1H), 4.12 (s, 3H), 4.13 – 4.01 (m, 2H),
2.78 (t, J=6.2, 1H); 13C NMR (100 MHz, Chloroform-d) δ: 165.3,
163.7, 150.8, 147.5, 138.9, 130.3, 129.3, 129.0 (2C), 128.0, 127.0,
126.9 (2C), 122.2, 122.0, 97.9, 67.0, 56.6, 56.2; HRMS (APCI/ASAP,
m/z): 323.1395 (calcd. C19H19N2O3, 323.1396, [M+H]+).
then added aq. NaOH solution (1 M) until basic solution and
extracted with diethyl ether (3 x 10 mL). The combined organic
phases were dried over anhydrous Na2SO4, filtered and dried under
reduced pressure. The procedure yielded 26 mg, (76 %, 0.099
mmol) of 4a as a colorless oil. 1H NMR (600 MHz, Chloroform-d) δ =
8.07 (d, J=8.4, 1H), 8.06 (d, J = 8.3, 1H), 7.78 (dd, J=8.1, 1.4, 1H), 7.69
(ddd, J=8.4, 6.8, 1.5, 1H), 7.50 (ddd, J=8.1, 6.7, 1.2, 1H), 7.44 – 7.38
(m, 2H), 7.36-7.33 (m, 3H), 7.27 – 7.24 (m, 1H), 3.95 (s, 2H), 3.91 (q,
J=6.6, 1H), 1.46 (d, J=6.6, 3H). 13C NMR (100 MHz, Chloroform-d) δ:
160.3, 147.8, 145.5, 136.3, 129.4, 129.1, 128.5 (2C), 127.5, 127.3,
127.0, 126.8 (2C), 126.0, 120.7, 58.3, 53.7, 24.5; HRMS (APCI/ASAP,
m/z): 263.1546 (calcd. C18H19N2, 263.1548, [M+H]+).
(E)-1-(quinolin-2-yl)-N-((4R)-1,7,7-
trimethylbicyclo[2.2.1]heptan-2-yl)methanimine
(4bꞌ).
Quinoline-2-carbaldehyde (27 mg, 0.172 mmol) was dissolved in
dry EtOH (5 mL) and added (R)-(+)-bornylamine b (26 mg, 0.172
mmol) dissolved in EtOH (2 mL). The reaction mixture was stirred
for 1.5 hours before solvent was removed under reduced pressure.
No purification was needed. Drying gave 48 mg (96 %, 0.164 mmol)
1
of the desired product as a pale yellow powder. H NMR (600 MHz,
Acetonitrile-d3) δ = 8.45 (s, 1H), 8.30 (d, J=8.6, 1H), 8.18 (d, J=8.5,
1H), 8.06 (d, J = 8.4, 1H), 7.95 (dd, J=8.2, 1.4, 1H), 7.77 (ddd, J=8.4,
6.8, 1.4, 1H), 7.62 (ddd, J=8.1, 6.9, 1.2, 1H), 3.68 (ddd, J=10.2, 4.3, 2.1,
1H), 2.31 – 2.22 (m, 2H), 1.85 (ddq, J=11.8, 7.8, 4.0, 1H), 1.76 (t,
J=4.5, 1H), 1.41 – 1.29 (m, 3H), 1.02 (s, 3H), 0.96 (s, 3H), 0.75 (s, 3H);
13C NMR (150 MHz, Acetonitrile-d3) δ: 161.5, 155.9, 148.4, 137.1,
130.4, 129.9, 129.2, 128.5, 127.9, 118.8, 75.5, 51.1, 48.9, 46.1, 37.8,
29.0, 28.7, 19.6, 18.7, 13.4; HRMS (APCI/ASAP, m/z): 293.2018
(calcd. C20H25N2, 293.2018, [M+H]+).
(S)-2-(4-methoxyquinolin-2-yl)-4-phenyl-4,5-
dihydrooxazole
(3b).
(S)-N-(2-hydroxy-1-phenylethyl)-4-
methoxyquinoline-2-carboxamide 7b (137 mg, 0.425 mmol) was
dissolved in dry THF (3 mL) and added thionylchloride (155 μL,
2.125 mmol). The reaction mixture was refluxed for 1.5 hours
before the reaction was quenched with sat. aqueous NaHCO3
solution and extracted with dichloromethane (3 x 10 mL). The
combined organic phases were dried over anhydrous sodium
sulphate, filtered and concentrated under reduced pressure. The
crude product, 8b, was subsequently dissolved in dry ethanol (3
mL) and added sodium hydroxide (46 mg, 1.150 mmol). The
reaction mixture was refluxed for one hour before water (10 mL)
was added. The mixture was extracted with dichloromethane (3 x
10 mL) and the combined organic phases were washed with sat.
aqueous sodium chloride solution (20 mL), dried over anhydrous
sodium sulphate and concentrated under reduced pressure. The
crude product was purified with silica gel column chromatography
(n-pentante: EtOAc, 1:1, Rf = 0.20), yielding 86 mg (67%, 0.283
mmol) of the ligand 3b as a white powder. 1H NMR (400 MHz,
Acetonitrile-d3) δ = 8.23 (dd, J=8.3, 1.5, 1H), 8.05 (d, J=8.4, 1H), 7.79
(ddd, J=8.4, 6.8, 1.5, 1H), 7.64 (s, 1H), 7.63 (ddd, J = 8.0, 6.9, 0.9, 1H),
7.40-7.32 (m, 5H), 5.49 (dd, J=10.3, 8.3, 1H), 4.94 (dd, J=10.3, 8.6,
1H), 4.36 (t, J=8.5, 1H), 4.10 (s, 3H).13C NMR (100 MHz, Acetonitrile-
d3) δ: 165.3, 163.6, 149.4, 149.3, 143.6, 131.4, 130.4, 129.7 (2C),
128.6, 128.2, 127.9 (2C), 122.7, 122.7, 101.0, 76.1, 71.0, 57.0; HRMS
(APCI/ASAP, m/z): 305.1293 (calcd. C19H17N2O2, 305.1290, [M+H]+).
(4R)-1,7,7-trimethyl-N-(quinolin-2-
ylmethyl)bicyclo[2.2.1]heptan-2-amine (4b). Compound 4bꞌ (31
mg, 0.106 mmol) was dissolved in dry EtOH (3 mL) under a nitrogen
atmosphere and added NaBH4 (12 mg, 0.318 mmol) in EtOH (2 mL).
The mixture was stirred over night before the reaction mixture was
quenched with HCl (2 M). The mixture was then added aq. NaOH
solution (1 M) until basic solution and extracted with diethyl ether
(3 x 10 mL). The combined organic phases were dried over
anhydrous Na2SO4, filtered and dried under reduced pressure. The
procedure yielded 21 mg, (67 %, 0.071 mmol) of 4b as a pale oil. 1H
NMR (600 MHz, Chloroform-d) δ = 8.10 (d, J=8.5, 1H), 8.05 (d, J=8.4,
1H), 7.79 (dd, J=8.2, 1.5, 1H), 7.69 (ddd, J=8.4, 6.8, 1.5, 1H), 7.54 –
7.48 (m, 2H), 4.11 (dd, J = 54.7, 13.8, 2H) 2.93 (ddd, J=10.0, 4.2, 2.0,
1H), 2.20 – 2.15 (m, 1H), 1.94 (ddd, J=13.2, 9.4, 4.3, 1H), 1.72 (ddq,
J=12.1, 8.0, 4.0, 1H), 1.63 (t, J=4.6, 1H), 1.32 (tdd, J=12.2, 4.6, 2.0, 1H),
1.24 (ddd, J=12.2, 9.4, 4.5, 1H), 0.96 – 0.93 (m, 1H), 0.91 (s, 3H), 0.87
(s, 3H), 0.84 (s, 3H). 13C NMR (150 MHz, Chloroform-d) δ: 161.3,
147.7, 136.2, 129.3, 129.0, 127.5, 127.3, 125.9, 120.7, 63.3, 55.2,
48.9, 48.4, 45.1, 38.0, 28.5, 27.5, 19.9, 18.7, 14.3; HRMS (APCI/ASAP,
m/z): 295.2173 (calcd. C20H27N2, 295.2174, [M+H]+).
(R,E)-N-(1-phenylethyl)-1-(quinolin-2-yl)methanimine
(4aꞌ). Quinoline-2-carbaldehyde 9 (39 mg, 0.248 mmol) was
dissolved in dry EtOH (5 mL) and added (R)-1-phenylethan-1-amine
a (32 μL, 0.248 mmol) dropwise. The reaction mixture was stirred
for 1.5 hours before solvent was removed under reduced pressure.
No purification was needed. Drying gave 63 mg (97 %, 0.241 mmol)
of the desired product 4a’ as a pale yellow powder. 1H NMR (600
MHz, Chloroform-d) δ = 8.64 (s, 1H), 8.26 (d, J=8.5, 1H), 8.19 (d,
J=8.5, 1H), 8.12 (d, J=8.5, 1H), 7.84 (d, J=8.6, 1H), 7.74 (dd, J=6.8, 1.4,
1H), 7.58 (dd, J=6.8, 1.4, 1H), 7.47 (d, J=7.6, 2H), 7.36 (t, J=7.6, 2H),
7.29-7.26 (m, 1H), 4.72 (q, J=6.7, 1H), 1.65 (d, J=6.7, 3H); 13C NMR
(150 MHz, Chloroform-d) δ: 161.0, 155.1, 147.8, 144.6, 136., 129.8,
129.6, 128.8, 128.5 (2C), 127.7, 127.4, 127.1, 126.8 (2C), 118.7, 69.6,
24.6; HRMS (APCI/ASAP, m/z): 261.1390 (calcd. C18H17N2,
261.1392, [M+H]+).
tert-Butyl((1S,2S)-2-((quinolin-2-ylmethyl)amino)-
cyclohexyl)carbamate (4cꞌ). The target compound was prepared
as described in General method 1 starting with quinoline-2-
carbaldehyde (84 mg, 0.532 mmol) and tert-butyl ((1S,2S)-2-
aminocyclohexyl)carbamate cꞌ (114 mg, 0.532 mmol). No
purification was necessary. The method yielded 166 mg (88%,
0.467 mmol) of the desired product as a pale white powder, mp.
110-112 oC. 1H NMR (600 MHz, Chloroform-d) δ: 8.32 (d, J = 8.2, 1H),
8.11(d, J = 8.2, 1H), 7.81 (d, J = 8.2, 1H), 7.70 (t, J = 6.9, 1H), 7.53 (t, J
= 7.6, 1H), 7.34 (d, J = 8.8, 1H), 4.18 (dd, J = 74.3, 17.0, 2H), 3.35 (br.s,
1H), 2.30 (dt, J = 20.4, 3.7, 2H), 2.14-2.11 (m, 1H), 1.71-1.69 (m, 1H),
1.65-1.63 (m, 1H), 1.53 (s, 9H), 1.33-1.29 (m, 1H), 1.24-1.20 (m, 1H),
1.16-1.11 (m, 1H), 1.05-0.99 (m, 1H); 13C NMR (150 MHz,
Chloroform-d) δ: 156.1, 147.7, 136.5, 129.8, 129.0, 127.6, 127.3,
126.1, 120.5, 79.0, 60.0, 54.8, 51.8, 32.9, 32.5, 28.6 (3C), 24.8, 24.6;
HRMS (APCI/ASAP, m/z): 356.2338 (calcd. C21H30N3O2, 356.2333,
[M+H]+).
(R)-1-phenyl-N-(quinolin-2-ylmethyl)ethan-1-amine
(4a).
Compound 4aꞌ (34 mg, 0.131 mmol) was dissolved in dry EtOH (3
mL) under a nitrogen atmosphere and added NaBH4 (15 mg, 0.392
mmol) in EtOH (2 mL). The mixture was stirred over night before
the reaction mixture was quenched with HCl (2 M). The mixture was
(1S,2S)-N1-(quinolin-2-ylmethyl)cyclohexane-1,2-diamine
(4c). Compound 4cꞌ (100 mg, 0.281 mmol) was dissolved in EtOH
7
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
(2 mL) and added cons. HCl (1mL). the reaction mixture was stirred
over night before NaOH was added until the solution was basic. The
water phase was extracted with diethyl ether (4 x30 mL). The
combined organic phases were dried over anhydrous Na2SO4,
filtered and dried under reduced pressure, yielding 50 mg (70 %,
0.196 mmol) of the deprotected product as a pale wax. 1H NMR (600
MHz, Chloroform-d) δ = 8.11 (d, J=8.4, 1H), 8.05 (d, J=8.5, 1H), 7.79
(d, J=8.1, 1H), 7.70 – 7.67 (m, 1H), 7.53 (dd, J=8.4, 1.3, 1H), 7.52 –
7.46 (m, 1H), 4.15 (dd, J=106.0, 14.6, 2H), 2.48 (dddd, J=10.9, 9.3,
4.2, 1.4, 1H), 2.20-2.14 (m, 2H), 1.91 – 1.89 (m, 1H), 1.75 – 1.67 (m,
3H), 1.30 – 1.21 (m, 3H), 1.16 – 1.07 (m, 2H).13C NMR (150 MHz,
Chloroform-d) δ: 161.2, 147.7, 136.3, 129.3, 129.0, 127.5, 127.3,
126.0, 120.7, 64.1, 55.5, 55.3, 36.0, 31.6, 25.32, 25.26; HRMS
(APCI/ASAP, m/z): 256.1809 (calcd. C16H22N3, 256.1814, [M+H]+).
27.5, 24.5, 19.9, 18.7, 14.3; HRMS (APCI/ASAP, m/z): 259.2177
(calcd. C17H27N2, 259.2174, [M+H]+).
tert-Butyl((1S,2S)-2-(((6-methylpyridin-2-
yl)methyl)amino)cyclohexyl)carbamate (5cꞌ). The target
compound was prepared as described in General method 1 starting
with 6-methylpicolinaldehyde (116 mg, 0.958 mmol) and tert-butyl
((1S,2S)-2-aminocyclohexyl)carbamate cꞌ (189 mg, 0.882 mmol).
Drying gave 262 mg (93%, 0.819 mmol) of the desired product as a
1
white powder. H NMR (600 MHz, Chloroform-d) δ: 7.51 (t, J = 7.6,
1H), 7.06 (d, J = 7.6, 1H), 7.01 (d, J = 7.6, 1H), 5.59 (br. s, 1H), 3.93
(dd, J = 76.5, 15.5, 2H), 3.30 (br. s, 1H), 2.59 (s, 3H), 2.25-2.21 (m,
2H), 2.11-2.08 (m, 1H), 1.70-1.63 (m, 2H), 1.46 (s, 9H), 1.35-1.23 (m,
2H), 1.89-1.13 (m, 2H), 1.07-1.03 (m, 1H); 13C NMR (150 MHz,
Chloroform-d) δ: 159.4, 158.0, 156.1, 136.7, 121.4, 119.3, 79.0, 60.0,
54.6, 51.2, 32.9, 32.0, 28.5 (3C), 24.7 (2C), 24.4; HRMS (APCI/ASAP,
m/z): 320.2332 (calcd. C18H30N3O2, 320.2338, [M+H]+).
(1S,2R)-1-((quinolin-2-ylmethyl)amino)-2,3-dihydro-1H-
inden-2-ol (4d). The target compound was prepared as described
in General method 1 starting with quinoline-2-carbaldehyde (62
mg, 0.394 mmol) and (1S,2R)-1-amino-2,3-dihydro-1H-inden-2-ol d
(58 mg, 0.389 mmol). Drying gave 99 mg (86%, 0.341 mmol) of the
desired product as a beige oil. 1H NMR (600 MHz, Chloroform-d) δ =
8.14 (d, J=8.4, 1H), 8.08 (d, J=8.5, 1H), 7.82 (dd, J=8.1, 1.4, 1H), 7.72
(ddd, J=8.4, 6.9, 1.4, 1H), 7.53 (ddd, J=8.1, 6.9, 1.2, 1H), 7.50 – 7.47
(m, 1H), 7.39 (d, J=8.4, 1H), 7.25 – 7.24 (m, 3H), .41 (dd, J = 69.5, 16.3,
2H), 4.36 (dt, J=5.0, 3.5, 1H), 4.19 (d, J=4.6, 1H), 3.02 (d, J=3.4, 2H);
13C NMR (150 MHz, Chloroform-d) δ: 160.5, 147.3, 132.7, 141.1,
136.9, 129.9, 128.6, 127.9, 127.6, 127.4, 126.6, 126.4, 125.4, 124.4,
120.2, 71.5, 67.8, 54.3, 39.2; HRMS (APCI/ASAP, m/z): 291.1492
(calcd. C19H19N2O, 291.1497, [M+H]+).
(1S,2S)-N1-((6-methylpyridin-2-yl)methyl)cyclohexane-1,2-
diamine (5c). Compound 5cꞌ (150 mg, 0.281 mmol) was dissolved
in EtOH (2 mL) and added cons. HCl (1mL). The reaction mixture
was stirred for 3 hours before NaOH was added until the solution
was basic. The water phase was extracted with diethyl ether (4 x30
mL). The combined organic phases were dried over anhydrous
Na2SO4, filtered and dried under reduced pressure, yielding 52 mg
(51 %, 0.237 mmol) of the deprotected product as a pale yellow oil.
1H NMR (600 MHz, Chloroform-d) δ: 7.52 (t, J = 7.6, 1H), 7.13 (d, J =
7.6, 1H), 7.01 (d, J = 7.6, 1H), 3.95 (dd, J = 105.3, 14.3, 2H), 2.58-2.56
(m, 1H), 2.55 (s, 3H), 2.26 (ddd, J=11.1, 9.7, 4.0, 1H), 2.12-2.10 (m,
1H), 2.01-1.99 (m, 1H), 1.75-1.69 (m, 2H), 1.29-1.22 (m, 3H), 1.13-
1.10 (m, 1H); 13C NMR (150 MHz, Chloroform-d) δ: 159.3, 157.9,
136.8, 121.5, 119.1, 63.0, 55.4, 52.0, 34.8, 31.4, 25.2, 25.0, 24.4;
HRMS (APCI/ASAP, m/z): 220.1816 (calcd. C13H22N3, 220.1814,
[M+H]+).
(1R,2R)-2-((quinolin-2-ylmethyl)amino)cyclohexan-1-ol
(4e). The target compound was prepared as described in General
method 1 starting with quinoline-2-carbaldehyde (32 mg, 0.204
mmol) and (1R,2R)-2-aminocyclohexan-1-ol e (23 mg, 0.200 mmol).
Drying gave 49 mg (94%, 0.191 mmol) of 4e as a pale powder, mp.
(1S,2R)-1-(((6-methylpyridin-2-yl)methyl)amino)-2,3-
dihydro-1H-inden-2-ol (5d). The target compound was prepared
o
90-92 C. 1H NMR (600 MHz, Methanol-d4) δ = 8.31 (d, J=8.4, 1H),
8.04 (dd, J=8.4, 1.2, 1H), 7.93 (dd, J=8.1, 1.4, 1H), 7.76 (ddd, J=8.4,
6.8, 1.5, 1H), 7.59 (ddd, J = 7.9, 6.8, 0.8, 1H), 7.58 (d, J = 8.5, 1H), 4.14
(dd, J=101.2, 14.6, 2H), 3.39 (ddd, J=10.4, 9.0, 4.4, 1H), 2.42 (ddd,
J=10.8, 9.2, 4.1, 1H), 2.18 – 2.15 (m, 1H), 2.00 – 1.97 (m, 1H), 1.74
(dt, J=11.7, 2.4, 2H), 1.35 – 1.17 (m, 4H); 13C NMR (150 MHz,
Methanol-d4) δ: 161.2, 148.6, 138.4, 131.0, 129.1, 129.0, 128.9,
127.6, 122.0, 74.7, 64.1, 52.9, 35.3, 31.0, 25.7, 25.6; HRMS (ESI, m/z):
257.1659 (calcd. C16H21N2O, 257.1654, [M+H]+).
as described in General method
1
starting with 6-
methylpicolinaldehyde (69 mg, 0.570 mmol) and (1S,2R)-1-amino-
2,3-dihydro-1H-inden-2-ol d (84 mg, 563 mmol). Drying gave 126
mg (87%, 0.495 mmol) of the desired product as a white powder,
mp. 107-109 oC(dec). 1H NMR (600 MHz, Chloroform-d) δ: 7.56 (t, J
= 7.7, 1H), 7.38-7.36 (m, 1H), 7.24-7.21 (m, 3H), 7.10 (d, J = 7.5, 1H),
7.06 (d, J = 7.7, 1H), 4.38-4.36 (m, 1H), 4.11 (dd, J = 43.2, 15.0, 2H),
4.14 (d, J = 4.6, 1H), 3.02-3.00 (m, 2H), 2.56 (s, 3H); 13C NMR (150
MHz, Chloroform-d) δ: 159.1, 158.2, 142.6, 141.1, 137.1, 127.8,
126.6, 125.4, 124.2, 121.9, 119.3, 71.1, 67.3, 52.6, 39.2, 24.2; HRMS
(APCI/ASAP, m/z): 255.1494 (calcd. C16H19N2O, 255.1497, [M+H]+).
(R)-N-((6-methylpyridin-2-yl)methyl)-1-phenylethan-1-
amine (5a). The target compound was prepared as described in
General method 1 starting with 6-methylpicolinaldehyde (78 mg,
0.647 mmol) and (R)-1-phenylethan-1-amine a (0.68 mL, 0.578
mmol). Drying gave 129 mg (99%, 0.570 mmol) of the desired
product as a colorless oil. 1H NMR (600 MHz, Chloroform-d) δ = 7.48
(dd, J=7.6, 1.0, 1H), 7.38 – 7.36 (m, 2H), 7.35 – 7.31 (m, 2H), 7.28 –
7.22 (m, 1H), 7.00 (dd, J=9.4, 7.7, 2H), 3.83 (q, J=6.6, 1H), 2.53 (s,
3H), 1.41 (d, J=6.6, 3H).13C NMR (150 MHz, Chloroform-d) δ: 159.1,
157.9, 145.6, 136.5, 128.4 (2C), 126.9, 126.8 (2C), 121.3, 119.2, 58.1,
53.2, 24.5 (2C); HRMS (APCI/ASAP, m/z): 227.1549 (calcd.
C15H19N2, 227.1548, [M+H]+).
(1R,2R)-2-(((6-methylpyridin-2-
yl)methyl)amino)cyclohexan-1-ol (5e). The target compound
was prepared as described in General method 1 starting with 6-
methylpicolinaldehyde (25 mg, 0.206 mmol) and (1R,2R)-2-
aminocyclohexan-1-ol e (23 mg, 0.200 mmol). Drying gave 43 mg
(98%, 0.195 mmol) of the desired product as a white powder, mp.
53-55 oC . 1H NMR (600 MHz, Acetonitrile-d3) δ: 7.57 (t, J = 7.8, 1H),
7.14 (d, J = 7.6, 1H), 7.06 (d, J = 7.6, 1H), 3.84 (dd, J = 109.0, 14.2, 2H),
3.17 (ddd, J=10.7, 9.1, 4.4, 1H), 2.46 (s, 3H), 2.21 (ddd, J=11.2, 9.1,
4.0, 1H), 2.03 (m, 1H), 1.91-1.87 (m, 1H), 1.67-1.64 (m, 2H), 1.28-
1.14 (m, 3H), 1.02 (tdd, J=12.7, 11.0, 3.4, 1H); 13C NMR (150 MHz,
Acetonitrile-d3) δ: 161.3, 158.6, 137.7, 122.0, 119.9, 74.6, 64.5, 52.8,
34.8, 31.5, 25.8, 25.3, 24.4; HRMS (ESI, m/z): 221.1652 (calcd.
C13H21N2, 221.1654, [M+H]+).
(4R)-1,7,7-trimethyl-N-((6-methylpyridin-2-
yl)methyl)bicyclo[2.2.1]heptan-2-amine (5b). The target
compound was prepared as described in General method 1 starting
with 6-methylpicolinaldehyde (58 mg, 0.480 mmol) and (R)-(+)-
bornylamine b (74 mg, 0.480 mmol). Drying gave 80 mg (65%,
1
0.310 mmol) of the desired product as a colorless oil. H NMR (600
1a-Au(III);
(S)-4-isopropyl-2-(quinolin-2-yl)-4,5-
MHz, Chloroform-d) δ = 7.51 (t, J=7.6, 1H), 7.15 (d, J=7.6, 1H), 6.99
(d, J=7.6, 1H), 3.87 (dd, J = 45.7, 14.4, 2H), 2.86 (ddd, J=10.0, 4.2, 2.0,
1H), 2.53 (s, 3H), 2.16 – 2.11 (m, 1H), 1.90 (ddd, J=13.2, 9.4, 4.3, 1H),
1.70 (tt, J=12.0, 3.9, 2H), 1.61 (t, J=4.6, 1H), 1.28 (tdd, J=12.1, 4.7, 2.0,
1H), 1.21 (ddd, J=12.3, 9.4, 4.6, 1H), 0.93-0.89 (m, 1H), 0.88 (s, 3H),
0.86 (s, 3H), 0.84 (s, 3H). 13C NMR (150 MHz, Chloroform-d) δ: 160.1,
157.7, 136.5, 121.2, 119.0, 63.0, 54.7, 48.8, 48.4, 45.1, 37.9, 28.5,
dihydrooxazole AuCl3 complex. NH4PF6 (4 mg, 0.025 mmol) and
AuCl3 (6 mg, 0.02 mmol) were dissolved in ACN and stirred for 15
min before (S)-4-isopropyl-2-(quinolin-2-yl)-4,5-dihydrooxazole (5
mg, 0.021 mmol) was added. The reaction mixture was stirred for
30 min before ACN was removed under reduced pressure. The
crude mixture was dissolved in DCM (5 mL) and extracted with
water (3 x 7 mL). The organic phase was dried over anhydrous
8
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
Na2SO4, filtered and removed under reduced pressure. Drying gave
10 mg (74 %, 0.015 mmol) of the gold(III) complex as a pale yellow
powder. 1H NMR (400 MHz, Acetonitrile-d3) δ: 8.62 (ap. d, J = 8.7,
1H), 8.44 (ap. d, J = 8.6, 1H), 8.13-8.09 (m, 2H), 8.00 (ddd, J=8.5, 6.9,
1.5, 1H), 7.85 (ddd, J=8.2, 6.9, 1.2, 1H), 5.09 (dd, J = 10.6, 9.4, 1H),
4.92 (dd, J=9.4, 8.2, 1H), 4.74 (ddd, J = 10.6, 8.1, 3.7, 1H), 2.55 (ddq,
J=10.5, 6.9, 3.4, 1H), 1.33 (dd, J = 7.9, 7.2, 6H); 13C NMR (100 MHz,
Acetonitrile-d3) δ: 167.8, 147.6, 141.3, 139.9, 133.1, 131.4, 131.0,
130.2, 129.4, 129.3, 121.9, 74.2, 71.6, 31.0, 19.0, 16.1; 15N NMR (61
MHz, Acetonitrile-d3) δ -66.5, -215.5; HRMS (ESI, m/z): found
503.0809 (calcd. C16H19N2O2ClAu, 503.0801, [M-Cl+MeOH]+). X-Ray:
CCDC ID 1951650.
Acetonitrile-d3) δ: 8.41 (d, J = 8.6, 1H), 8.08 (d, J = 8.6, 1H), 8.01 (d, J
= 8.2, 1H), 7.84 (t, J = 7.3, 1H), 7.68 (t, J = 7.3, 1H), 7.49 (d, J = 8.6,
1H), 4.60 (dd, J = 79.8, 16.6, 2H), 3.48-3.47 (m, 1H), 2.33-2.29 (m,
1H), 1.90-1.87 (m, 1H), 1.82-1.81 (m, 1H), 1.76-1.69 (m, 2H), 1.46-
1.44 (m, 1H), 1.33-1.30 (m, 1H), 1.15 (s, 3H), 0.94 (s, 3H), 0.80 (s,
3H); 13C NMR (150 MHz, Acetonitrile-d3) δ: 151.4, 147.2, 139.2,
131.7, 129.1, 129.1, 128.9, 128.4, 120.8, 66.3, 50.1, 50.0, 49.7, 45.1,
32.9, 28.2, 28.1, 19.5, 18.6, 13.9. HRMS; could not be detected, due
to low stability.
4c-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 4c (8 mg, 0.031 mmol) and
KAuCl4 (12 mg, 0.031 mmol). The complex precipitated immediately
after mixing in ACN and was filtered and washed with more ACN.
Drying gave 11 mg (67%, 0.021 mmol) of 4c-Au(III)-complex as a
1b-Au(III);
(R)-4-phenyl-2-(quinolin-2-yl)-4,5-
dihydrooxazole AuCl3 complex. AuCl3 (20 mg, 0.066 mmol) and
(R)-4-phenyl-2-(quinolin-2-yl)-4,5-dihydrooxazole (18 mg, 0.066
mmol) were dissolved in ACN (4 mL) and stirred over night before
ACN was removed under reduced pressure. Drying gave 37 mg (98
%, 0.064 mmol) of the gold(III) complex as a pale yellow powder. 1H
NMR (600 MHz, Acetonitrile-d3) δ: 8.66 ( ap. d, J = 8.4, 1H), 8.38 (ap.
d, J = 8.5, 1H), 8.21 (ap. d, J = 8.5, 1H), 8.14 (ap. d, J = 8.3, 1H), 7.99
(ddd, J=8.4, 6.9, 1.4, 1H), 7.86 (ddd, J=8.2, 6.9, 1.2, 1H), 7.70-7.69 (m,
2H), 7.54-7.52 (m, 3H), 5.87 (t, J = 10.8, 1H), 5.52 (dd, J = 10.6, 9.4,
1H), 5.06 (dd, J = 11.0, 9.4, 1H); 13C NMR (100 MHz, Acetonitrile-d3)
δ: 167.8, 147.7, 141.6, 139.9, 136.2, 133.1, 131.5, 131.1 (2C), 131.0,
130.7 (2C), 130.3, 130.1, 129.3, 122.1, 79.4, 70.4. HRMS; could not
be detected, due to low stability.
1
yellow powder. H NMR (600 MHz, Methanol-d4) δ: 8.42 (d, J = 8.1,
1H); 8.39 (d, J = 8.1, 1H), 7.98 (d, J = 8.1, 1H), 7.83 (ddd, J = 14.3, 7.2,
5.8, 1H), 7.66 (t, J = 7.2, 1H), 7.51 (d, J = 8.3, 1H), 5.10 (d, J = 17.2,
1H), 4.71 (d, J = 17.2, 1H), 3.22-3.18 (m, 1H), 3.04-2.98 (m, 1H), 2.54-
2.52 (m, 1H), 2.20 (m, 1H), 1.71-1.66 (m, 2H), 1.59-1.46 (m, 2H),
1.30-1.27 (m, 1H), 1.09-1.07 (m, 1H); 13C NMR (150 MHz, Methanol-
d4) δ: 154.0, 148.1, 139.2, 131.3, 130.0, 129.3, 129.0, 128.4, 121.6,
70.6, 66.0, 52.6, 33.9, 31.2, 25.6, 25.0; HRMS (ESI, m/z): 486.1014
(calcd. C16H20N3ClAu, 486.1011, [M-Cl]+).
4d-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 4d (8 mg, 0.028 mmol) and
KAuCl4 (10 mg, 0.028 mmol). Drying gave 11 mg (73%, 0.020 mmol)
of 4d-Au(III)-complex as a yellow solid. 1H NMR (600 MHz,
Acetonitrile-d3) δ: 8.39 (d, J = 8.2, 1H), 8.08 (d, J = 8.2, 1H), 7.99 (d, J
= 7.8, 1H), 7.83 8t, J = 7.8, 1H), 7.67 (d, J = 7.8, 1H), 7.64 (d, J = 7.8,
1H), 7.49 (d, J = 8.7, 1H), 7.41 (d, J = 7.8, 1H), 7.37 (d, J = 7.8, 1H),
7.34 (t, J = 7.6, 1H), 4.89 (q, J = 6.1, 1H), 4.83 (d, J = 6.1, 1H), 4.67 (d,
2H), 3.33 (dd, J = 16.6, 6.6), 3.10 (dd, J = 16.6, 5.8, 1H); 13C NMR (150
MHz, Acetonitrile-d3) δ: 152.1, 147.4, 143.2, 139.1, 135.1, 131.7,
131.6, 129.3, 129.1, 128.8, 128.4, 128.4, 127.2, 126.8, 120.7, 71.0,
65.4, 49.5, 39.8; HRMS (ESI, m/z): 557.0466 (calcd. C19H18N2OCl2Au,
557.0462, [M+H]+).
3a-Au(III); (S)-4-isopropyl-2-(4-methoxyquinolin-2-yl)-4,5-
dihydrooxazole AuCl3 complex. AuCl3 (11 mg, 0.035 mmol) and
(S)-4-isopropyl-2-(4-methoxyquinolin-2-yl)-4,5-dihydrooxazole
(10 mg, 0.035 mmol) were dissolved in ACN (2 mL) and stirred for
15 min before ACN was removed under reduced pressure. the
complex was purified by precipitation from DCM in n-pentane.
Drying gave18 mg (89 %, 0.031 mmol) of the gold(III) complex as a
yellow powder. 1H NMR (600 MHz, Acetonitrile-d3) δ: 8.36 (d, J =
8.5, 1H), 8.28 (dd, J = 8.4, 0.7, 1H), 7.95 (ddd, J = 8.4, 6.9, 1.4, 1H),
7.77 (ddd, J = 8.3, 6.9, 1.1, 1H), 7.48 (s, 1H), 5.08 (dd, J = 10.5, 9.4,
1H), 4.91 (dd, J=9.3, 8.2, 1H), 4.72 (ddd, J = 10.5, 8.2, 3.8, 1H), 4.15
(s, 3H), 1.14 (d, J = 7.0, 1H), 1.12 (d, J = 6.8, 1H); 13C NMR (100 MHz,
Acetonitrile-d3) δ: 168.0, 165.3, 148.4, 142.6, 133.1, 130.3, 129.9,
123.4, 123.1, 101.8, 74.2, 71.7, 57.7, 31.0, 19.0, 16.2. HRMS; could
not be detected, due to low stability.
4e-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 4e (8 mg, 0.031 mmol) and
KAuCl4 (12 mg, 0.031 mmol) in methanol. The complex was purified
by precipitation in acetonitrile, followed by filtration. Drying gave 5
mg (31% yield, 90% purity, 0.010 mmol) of 4e-Au(III)-complex as
pale crystals. 1H NMR (400 MHz, Methanol-d4) δ: 8.19 (d, J = 8.8, 1H),
7.90 (d, J = 8.1, 1H), 7.77 (d, J = 7.8, 1H), 7.60 (ddd, J = 8.3, 7.0, 1.3,
1H), 7.44 (ddd, J = 8..0, 7.0, 1.1, 1H), 7.33 (d, J = 8.4, 1H), 4.47 (dd, J
= 48.1, 15.7, 2H), 3.51-3.48 (m, 1H), 2.91-2.86 (m, 1H), 2.09-2.07 (m,
1H), 1.90-1.88 (m, 1H), 1.83-1.81 (m, 1H), 1.66-1.64 (m, 1H), 1.59-
1.57 (m, 1H), 1.34-1.32 (m, 1H), 1.21-1.15 (m, 2H); 13C NMR (100
MHz, Methanol-d4) δ:153.3, 148.4, 139.3, 131.6, 129.9, 129.3, 128.5,
121.0, 71.9, 64.6, 49.4, 35.6, 28.2, 25.4, 25.0. HRMS; could not be
detected, due to low stability.
3b-Au(III);
(S)-2-(4-methoxyquinolin-2-yl)-4-phenyl-4,5-
dihydrooxazole AuCl3 complex. AuCl3 (8 mg, 0.028 mmol) and (S)-
2-(4-methoxyquinolin-2-yl)-4-phenyl-4,5-dihydrooxazole (8 mg,
0.028 mmol) were dissolved in ACN (2 mL) and stirred for 15 min
before ACN was removed under reduced pressure. the complex was
purified by precipitation from DCM in n-pentane. Drying gave15mg
(89 %, 0.025 mmol) of the gold(III) complex as a yellow powder. 1H
NMR (600 MHz, Acetonitrile-d3) δ: 8.31-8.29 (m, 2H), 7.93 (ddd, J =
8.4, 6.9,1,3, 1H), 7.77 (ddd, J = 8.2, 7.3, 1.3, 1H), 7.69-7.67 (m, 2H),
7.60 (s, 1H), 7.53-7.52 (m, 3H), 5.86 (t, J = 10.8, 1H), 5.52 (dd, J =
10.5, 9.4, 1H), 5.05 (dd, J = 11.0, 9.4, 1H), 4.18 (s, 3H); 13C NMR (100
MHz, Acetonitrile-d3) δ: 168.0, 165.3, 148.8, 142.8, 136.2, 133.1,
131.0, 130.6 (2C), 130.4, 130.1 (2C), 130.0, 123.4, 123.1, 102.0, 79.3,
70.4, 57.8; 15N NMR (61 MHz, CD3CN) δ: -89.0, -211.6. HRMS; could
not be detected, due to low stability.
5b-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 5b (8 mg, 0.031 mmol) and
KAuCl4 (12 mg, 0.031 mmol). Drying gave 12 mg (71%, 0.022 mmol)
of 5b-Au(III)-complex as a yellow solid. 1H NMR (600 MHz,
Acetonitrile-d3) δ: 7.76 (t, J = 7.8, 1H), 7.28 (d, J = 7.8, 1H), 7.22 (d, J
= 7.4, 1H), 4.35 (dd, J = 90.5, 15.8, 2H), 3.32-3.30 (m, 1H), 2.54 (s,
1H), 2.27-2.25 (m, 1H), 1.87-1.86 (m, 1H), 1.80-1.79 (m, 1H), 1.66-
1.63 (m, 2H), 1.43-1.40 (m, 1H), 1.27-1.24 (dd, J = 13.7, 3.9, 1H), 1.04
(s, 3H), 0.92 (s, 3H), 0.81 (s, 3H); 13C NMR (150 MHz, Acetonitrile-
d3) δ: 159.0, 149.6, 139.3, 124.4, 120.8, 65.7, 50.0, 49.6, 45.1, 32.8,
28.2, 28.1, 26.5, 24.1, 19.5, 19.6, 13.7. HRMS; could not be detected,
due to low stability.
2-Au(III)-X,
X = SbF6, BF4, NTf2; (S)-4-tert-butyl-2-(2-
pyridyl)oxazoline AuCl2X complexes.
The pyridine-oxazoline 2-Au(III)- X complexes with X = SbF6, BF4 or
NTf2 anions, were prepared and characterized (NMR, HRMS)
according to literature.39 Crystals for X-ray analysis were grown for
2-Au(III)-SbF6 complex by slow diffusion of n-pentane into a
dichloromethane solution of the complex. X-Ray: CCDC ID 1951651.
5c-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 5c (8 mg, 0.035 mmol) and
KAuCl4 (13 mg, 0.035 mmol). The complex was purified by
crystallization in ACN. Filtration followed by drying gave 8 mg
(47%, 0.016 mmol) of 5c-Au(III)-complex as yellow crystals. 1H
4b-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 4b (8 mg, 0.027 mmol) and
KAuCl4 (10 mg, 0.027 mmol). Drying gave 10 mg (62%, 0.017 mmol)
of 4b-Au(III)-complex as
a
yellow oil. 1H NMR (600 MHz,
9
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
Schwarz, J.-H. Choi, T. M. Frost, Angew. Chem. Int. Ed.
2000, 39, 2285-2288; c) S. A. Shahzad, M. A. Sajid, Z. A.
Khan, D. Canseco-Gonzalez, Synth. Commun. 2017, 47,
735-755.
NMR (600 MHz, Methanol-d4) δ: 7.75 (t, J = 7.7, 1H), 7.32 (d, J = 7.7,
1H), 7.25 (d, J = 7.4, 1H), 4.90 (d, J = 14.0, 1H), 4.42 (d, J = 15.7, 1H),
3.12 (br. s, 1H), 2.73 (s, 3H), 2.45 (br. s, 1H), 2.15-2.14 (m , 1H), 1.71-
1.65 (m, 2H), 1.51-1.42 (m, 2H), 1.25-1.23 (m, 1H), 1.10-1.04 (m,
1H); 13C NMR (150 MHz, Methanol-d4) δ: 160.3, 151.8, 139.3, 124.6,
121.8, 70.1, 65.9, 52.2, 33.8, 30.9, 25.5, 24.9, 24.2; HRMS (ESI, m/z):
450.1017 (calcd. C13H20N3ClAu, 450.1011, [M-Cl]+).
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Daniliuc, F. Glorius, Chem. Eur. J. 2016, 22, 11587-
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5d-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 5d (8 mg, 0.031 mmol) and
KAuCl4 (12 mg, 0.031 mmol). Drying gave 15 mg (92%, 0.029 mmol)
of 5d-Au(III)-complex as a yellow solid. 1H NMR (600 MHz,
Acetonitrile-d3) δ: 7.77 (t, J = 7.6, 1H), 7.57 (d, J = 7.3, 1H), 7.44-7.43
(m, 1H), 7.40-7.35 (m, 2H), 7.29 (d, J = 7.6, 1H), 7.25 (d, J = 7.6, 1H),
4.87-4.85 (m, 1H), 4.73 (d, J = 5.7, 1H), 4.47-4.46 (m, 2H), 3.19 (ddd,
J = 147.3, 16.6, 6.8, 2H), 2.56 (s, 3H); 13C NMR (CD3CN, 150 MHz) δ:
159.1, 150.4, 143.1, 139.2, 135.2, 131.2, 128.4, 127.1, 126.8, 124.3,
120.7, 70.9, 65.2, 49.2, 39.7, 24.2. HRMS; could not be detected, due
to low stability.
[8]
5e-Au(III)-complex. The complex was prepared according to
General method 2, starting with ligand 5e (8 mg, 0.036 mmol) and
KAuCl4 (14 mg, 0.036 mmol). Drying gave 12 mg (68% yield, 92%
pyrity, 0.025 mmol) of 5e-Au(III)-complex as a yellow solid. 1H NMR
(600 MHz, Acetonitrile-d3) δ: 7.75 (t, J = 7.7, 1H), 7.27 (d, J = 7.7, 1H),
7.20 (d, J = 7.7, 1H), 4.35 (dd, J = 54.5, 15.3, 2H), 3.66-3.62 (m, 1H),
2.99-2.94 (m, 1H), 2.54 (s, 3H), 2.11-2.09 (m, 1H), 2.05-2.02 (m, 1H),
1.79-1.72 (m, 2H), 1.47-1.41 (m, 1H), 1.32-1.27 (m, 3H); 13C NMR
(150 MHz, Acetonitrile-d3) δ: 159.1, 150.4, 139.2, 124.3, 120.5, 71.1,
64.8, 48.3, 34.7, 27.4, 24.6, 24.3, 24.2; HRMS (ESI, m/z): 451.0857
(calcd. C13H19N2OClAu, 451.0851, [M-Cl]+).
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Acknowledgements
This work was partly supported by the Research Council of
Norway through the Norwegian NMR Platform, NNP
(226244/F50).
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Keywords: Ligands • Catalysis • Gold • Au(III) •
Cyclopropanation
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10
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000139
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
RESEARCH ARTICLE
Studies on gold(III) coordination of a
series of polydentate pyridine and
quinoline based ligands are reported.
Characterization of the novel gold(III)
complexes revealed different
coordination ability of the pyridine and
quinoline nitrogens. Evaluation of the
new ligated Au(III) complexes in
cyclopropanation of propargyl ester
and styrene demonstrated that all
were catalytic active and
Ann Christin Reiersølmoen and Anne
Fiksdahl*
Page No. – Page No.
Pyridine- and quinoline-based
gold(III) complexes: synthesis,
characterization and application.
outperformed KAuCl4 and that
pyridine-N decoordination may be a
crucial step for generation of catalytic
Key topics;
•
•
Au(III) coordination studies;
N,N- and N,O polydentate pyridine and quinoline based ligands
11
This article is protected by copyright. All rights reserved.