Insights into the mechanism for gold catalysis: Behaviour of gold(i) amide complexes in solution

Article abstract of DOI:10.1039/c3dt33039g

We report the synthesis and activity of new mononuclear and dinuclear gold amide complexes 1-7. The dinuclear complexes 6b and 7 were characterised by single crystal X-ray analysis. We also report solution NMR and freezing point depression experiments to rationalise their behaviour in solution and question the de-ligation process invoked in gold catalysis.

Full text of DOI:10.1039/c3dt33039g

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Insights into the mechanism for gold catalysis:
behaviour of gold(I) amide complexes in solution†
Cite this: DOI: 10.1039/c3dt33039g
Mariusz Bobin, Iain J. Day, Stephen M. Roe and Eddy M. E. Viseux*
Received 19th December 2012,
Accepted 25th February 2013
We report the synthesis and activity of new mononuclear and dinuclear gold amide complexes 1–7. The
dinuclear complexes 6b and 7 were characterised by single crystal X-ray analysis. We also report solution
NMR and freezing point depression experiments to rationalise their behaviour in solution and question
the de-ligation process invoked in gold catalysis.
DOI: 10.1039/c3dt33039g
www.rsc.org/dalton
transformations catalysed by gold(I) and the proposed cationic
nature of the complex in these transformations, little experi-
Introduction
The applications of gold(I) catalysis in methodology and syn- mental information is available regarding the existence in
thesis have seen a remarkable growth in recent years1 follow- solution of a tricoordinate gold species and the general nature
ing Schwemberg’s perchlorination of naphthalene in 1935.2 of gold complexes in solution.
Most mechanisms have involved a cationic gold species
We describe herein our routes to catalytically active gold
usually from chlorine abstraction by a silver salt,3 protonolysis amide complexes LAuX featuring either modified L or X
of an alkyl gold4 or ligand dissociation in solution prior to ligands, as well as binuclear complexes. These results can
alkene complexation. The cationic nature was further demon- potentially be used to access structurally diverse gold amide or
strated by Widenhoefer who reported the results of X-ray diffr- peptide complexes. This opens up possibilities for structural
action experiments on cationic gold(I) complexes derived from modifications and drug design of organogold complexes, as
a series of alkynes.5 The loss of an X-ligand to generate an the routes are amenable to combinatorial chemistry and paral-
active gold intermediate combined with a limited coordination lel synthesis. We also examined the de-ligation process of such
sphere due to relativistic considerations and radial contraction amide complexes in the initial mechanistic step of gold cata-
on gold(I) complexes have also driven the development of lysed transformations. To this end, we report on the investi-
chiral gold(I) complexes LAuX with structural modification of gation of the behaviour of these complexes in solution with
the L-ligand and rare examples of chiral X-ligands; in the latter NMR and freezing point depression studies and contrast
case, the efficiency heavily relies on the nature of the the results with the standard mechanistic proposal involving a
solvent.1,6
Many tri- and tetra-coordinate gold complexes have been
cationic gold intermediate.
reported.2–4,7–21 Most notably, Hashmi reported the X-ray
crystallographic characterisation of a tri-coordinate gold(I)
complex L2AuX,5,9 and many polynuclear auracyclic complexes
featuring bidentate ligands have been described extensively
and such systems often include Au–Au interactions.8 For all
the evidence for complexes which, in the solid state, display
coordination numbers for gold that exceed two, the rationalis-
ation of gold catalysis in solution rarely invokes species with
coordination numbers that exceed two unless they are hypoth-
esised in transition states of complex-induced activation
reactions.5,7,8,22–24 Despite the ever-growing database of
Results and discussion
In our search for rapid routes to libraries of gold complexes,
we investigated the influence of the gold amide bond on the
catalytic activity of complexes that contain this moiety for
cycloisomerisation reactions in solution. Initial models
included chiral gold amides as described in Fig. 1.
Catalytic activities
The investigation of the connectivity of the gold–ligand complex
is a necessary step prior to the mechanistic investigation, and
notably rationalising the influence of the electronegative nature
of the N-derived X-ligands on both the reactivity and the stab-
ility of gold amide complexes is crucial. The initial design of 8,
featuring a gold N-alkyl triflic amide linkage, showed no cata-
lytic activity (Fig. 1) when evaluated in two model reactions, a
School of Life Sciences, Department of Chemistry, University of Sussex, Brighton,
BN1 9QJ, UK. E-mail: e.m.e.viseux@sussex.ac.uk; Tel: +44 (0) 1273 678621
†Electronic supplementary information (ESI) available: NMR spectra for all com-
pounds and X-ray crystallographic studies for compounds 6b and 7 are included.
CCDC 915634 and 916508. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c3dt33039g
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Scheme 2 Cycloisomerisation of enyne 13.
Table 2 Gold catalysed cycloisomerisation of an enyne
Fig. 1 General model for gold amide complexes (Tf = CF3SO2).
Cat.
Mol%
Solv.
Time [h]
T [C°]
Yield [%]
1
2
3
4
5
6
7
2
5
2
2.5
5
5
DCM
DCM
DCM
Benzene
DCM
168
48
168
120
120
120
RT
RT
RT
RT
RT
RT
55
67
/
63
78
46
5a/5b
3
3
4
5
DCM
Scheme 1 Cyclopentannulation of β-ketoester 11.
Table 1 Gold catalysed Conia-ene cyclopentannulation
Cat.
Mol%
Solv.
Time [h]
T [C°]
Yield [%]
1
2
3
4
5
6
7
8
2
2
2
7
7
7
2c
2
1
5
5
5
2.5
2.5
5
5
/
/
/
5
5
5
DCM
DCM
DCE
DCM
DCE
DCE
DCM
DCE
DCM
DCE
DCE
DCE
DCE
DCM
DCE
DCM
DCE
DCM
DCM
DCE
DCM
DCM
48
48
24
120
14
120
168
168
168
168
24
14
48
72
96
120
120
120
120
120
120
98
RT
RT
50
RT
70
70
RT
70
RT
70
50
70
80
RT
50
RT
70
RT
RT
50
RT
RT
73b
65b
58b
33b
75b
91a
a
5a/5b
5a/5b
6a/6b
6a/6b
/
/
/
/
52a
a
9
/
10
11
12
13
14
15
17
18
19
20
21
22
23
51a
8b
13b
Fig. 2 Summary of the gold amide complexes.
a
/
b
15
/
b
15
/
10d
10d
10e
/
b
b
5
5
/
b
/
b
10 + 15
10 + 15
3
5 + 20
5 + 5
5
5
/
b
/
96b
90b
4
Fig. 3 Potential decomplexation of complexes 2 and 7 to give the same cat-
ionic gold intermediate 2*.
a 12b: R1 = Ph, R2 = Et. b 12a: R1, R2 = Me. c 1 mol% was initially added,
d
followed by an extra 1 mol% after 24 h. L-Proline was added
(0.2 equiv.). e L-Proline was added (1 equiv.).
X-ligand prior to complexation with the substrate. Our design
of complexes 2 and 7 should generate the same cationic
species on dissociation of the X-ligand, as shown in Fig. 3. If
the standard mechanistic proposal holds, then cationic gold
2*, formed from either 2 or 7, should lead to identical results,
if 2* is the sole catalytic species.
The alkynyl substrate 13 was treated with two different com-
plexes 2 and 7 and both showed similar catalytic activities with
respect to the product, the yield and the rate. However, the
resulting cyclopentane 12 had opposite optical rotations ([α]D:
−3.2° with catalyst 2 and 3.2° with catalyst 7). Entries 11–13
show that the thermal cycloisomerisation is not favourable,
modified Conia-ene cyclopentannulation (Scheme 1, Table 1)25
and a phenol enyne cycloisomerisation (Scheme 2, Table 2).26
The influence of electron-withdrawing substituents on the nitro-
gen was found to have a critical impact on the outcome of these
reactions (Fig. 1). Switching to an N-triflic alkanamide 9 dra-
matically improved the reactivity and the yields were compar-
able to those obtained with bis-triflic amide complex
Ph3PAuNTf2 10 reported by Gagosz3 (Scheme 1, Table 1) (Fig. 2).
Cyclic gold complex vs. linear gold complexes vs. naked ligand
The standard mechanistic proposal for catalytic and stoichio- but proceeds in very poor yields to cyclopentane 12. To rule out
metric reactions of this type begins with dissociation of the any organocatalytic activity of the ligand, either via the
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corresponding iminium derived from the condensation of
Interestingly, no signals for free ligands are observed in any
ligand 15 with ketones 11 or through H-bonding to either car- of the experiments. The DOSY results for complex 5a/5b
bonyl, a test reaction was performed with the sole ligand 15 (Table 3, entry 3) are consistent with a potential monomer–
present. No cycloisomerisation was observed, even upon dimer equilibrium on the time scale of the diffusion measure-
heating (Table 1, entries 14 and 15). The role of ligand meta- ment (102 ms) given that this molecule shows a larger
thesis and the influence of the chiral coordination sphere of diffusion coefficient than that of dimer 7, but a smaller coeffi-
the gold complex were also investigated by treating the alkyne cient than that of monomer 6a (Table 3, entry 2). As expected,
with a mixture of triphenylphosphine bis-triflic amide gold the hydrodynamic radius of free ligand 15 (Scheme 5) is
complex 10 in the presence of either ligand 15 or L-proline smaller than that of dimeric complex 7. The radius of free
(Table 1, entries 17–21). Surprisingly, and despite similar reac- ligand 16 (Scheme 5) however is larger than its complexed
tivity between our chiral gold complexes and the standard bis- form 6a as 16 has more conformational flexibility than the
triflic amide complex, the reaction did not proceed and start- complex which has necessarily restricted bond rotations. This
ing material was recovered. This not only rules out any ligand clearly indicates the lack of decomplexation of the X-side of
metathesis, but also a potential weak interaction of the free the complex on the time-frame of the measurements, as the
ligand with any of the intermediates involved. These results subsequent cationic gold species would have a radius similar
also suggest that excess ligand suppresses any catalytic activity or greater to that of free ligand 16. Gold chlorides are stable in
of the gold(I) complex. Though they do not preclude the inter- solution and do not decomplex to form cationic gold unless a
vention of a different cationic gold species, they clearly indi- co-catalyst is used, usually silver(I) salts. Interestingly, gold
cate the involvement of multiple intermediates in the catalysis chloride 15 and gold bis-triflic amide 2 have a similar hydro-
of the isomerisation, including a possible tricoordinate gold dynamic radius and this confirms that 2 has a smaller radius
intermediate. These results have prompted us to investigate than the dimeric version in solution which does not dissociate
the dynamic equilibration of gold amides in solution by con- to a monomeric species. This also suggests that decomplexa-
trasting the covalent radii of the complexes in the solid state tion of the bis-triflic amide residue and subsequent dimerisa-
with those obtained in solution using DOSY and freezing tion to 7 were not observed at that concentration.
point depression experiments.
Freezing point depressions
DOSY methodology
Freezing point depression was chosen to examine and provide
Diffusion ordered spectroscopy (DOSY) is a powerful technique
for investigating the solution state assembly properties of
molecules.27–29 The technique relies upon measuring the
attenuation of an NMR signal, during the application of
pulsed magnetic field gradients, caused by incoherent sample
motion, such as translational diffusion. Fitting this signal
attenuation allows the transitional diffusion coefficient to be
determined, thereby accessing information on effective mole-
cular size in solution.30
Hydrodynamic radii were calculated from the Stokes–
Einstein equation: D = kT/(6πηr), where η represents the
viscosity of the solution (taken to be the same as CHCl3 at
25 °C).29 Strictly, the Stokes–Einstein equation assumes that
the diffusing particle is a hard sphere, and includes any
solvation effects, therefore the radii obtained are guides to the
true hydrodynamic size in solution. The results are compiled
in Table 1.
more evidence pertaining to the nature of gold amide com-
plexes in solution. Freezing point depression, ΔTf, can be used
to evaluate the number of the solute particles through the
van’t Hoff factor i (ΔTf = Kfmi), and to determine the oligo-
meric state of the complex from the colligative property of the
solution.
We found that complexes 6 and 7 were freely soluble in 1,2-
dibromoethane, which has a convenient freezing point and a
high cryoscopic constant (Kf = 12.5 K mol−1 kg−1]. The results
of the freezing point depressions are compiled in Table 4. Of
note, data could not be collected for complex 5a/5b as it could
not be dissolved in the required solvent.
The results of these colligative experiments are consistent
with the conclusions drawn from the DOSY experiments, in
spite of a different dielectric constant for both solvents
(Br2C2H4: εr = 10.5, CDCl3: εr = 4.8 at 293 K). In solution, the
complex mixture 6a/6b is predominantly a monomer contrary
to its solid state which is the dimeric form 6b. Complex 7 is
indeed dimeric in both solvent and in the solid state.
Table 3 Results for the DOSYexperiments
Diffusion coefficient D
Entry Compound [10−10 m2 s−1
Hydrodynamic radius
rH [Å]
]
Table 4 Freezing point depressions of gold amide complexes
1
2
3
4
5
6
7
7
3.2
4.4
3.7
4.4
3.6
3.5
3.5
12.6
9.0
10.9
9.2
11.2
11.5
11.5
Compounds
Expected ΔTf (°C)
Observed ΔTf (°C)
0.133
6a
5a/5b
15
16
1
7
Dimer: 0.138
Monomer: 0.275
Dimer 6b: 0.214
Monomer 6a: 0.428
6a
0.433
2
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Fig. 5 Single crystal X-ray structures of complexes 6b (top) and 7 (bottom).
Selected bond lengths (Å) and angles (°): 6b Au(1)–N(1) 2.094(8), Au(1)–P(1)
2.236(3), N(1)–Au(1)–P(1) 173.9(2), Au(2)–N(2) 2.091(7), Au(2)–P(2) 2.241(2),
N(2)–Au(2)–P(2) 177.4(2), Au–Au 6.613, longest dimension 18.803; 7 Au(1)–
N(1) 2.076(9), Au(1)–P(1) 2.232(2), N(1)–Au(1)–P(1) 176.1(4), Au(2)–N(2)
2.093(9), Au(2)–P(2) 2.238(3), N(2)–Au(2)–P(2) 174.1(4), Au–Au 9.077, longest
dimension 20.255.
Fig. 4 Comparative graphs between angles and distances around the Au(I)
centre.
X-ray diffraction studies
Synthesis of complexes 1–7
Compounds 6b and 7 both yielded crystals that were suitable
for X-ray diffraction studies to augment our solution-phase Complexes 3 and 4 were synthesised from protected amino
experiments (Fig. 4). In both cases, full structural data are acids Leucine and Tryptophan (Scheme 3). Carboxylic acids
included in the ESI.† The molecular structures of these com- 1731 and 18 were interconverted into the corresponding
plexes all contain a two-coordinate Au centre with un- N-triflic amide by treatment with EDC. Gold complexes 3
exceptional Au–N and Au–P distances and linear coordination and 4 were then subsequently obtained by treating triphenyl-
irrespective of the state of molecularity in the crystal (Fig. 5).
phosphine gold chloride with the corresponding silver amide
Amongst the 396 structures from the CCSD that have this salt generated in situ. The complexes were obtained as a
coordination sphere composition, all are linear, with conven- mixture of rotamers (3: [7 : 3], 4: [10 : 1]).
tional distances except those where the system is particularly
structurally constrained. Additionally, the amide nitrogen is Phosphine 19 was synthesised from prolinol 20 (Scheme 4).
invariably planar.
The aminol was activated as its cyclic sulfamidate 2132 and
Complexes 1, 2, 5–7 all feature the same proline core 19.
Interestingly the sequence of compounds 5, 6 and 7 treated with LiPPh2, followed by hydrolysis of the resulting sulf-
contains chains homologated by one CH2 unit sequentially. amic acid under oxygen free conditions to avoid any oxidation
6 and 7 are both dimers, presumably because the strain to the corresponding phosphine oxide. The ligands 15, 16 and
required to form a mononuclear linear-coordinate Au complex 22 were synthesised by nucleophilic substitution of the
from the corresponding bidentate ligands is too high. Interest- N-proline with the corresponding alkyl bromides (Scheme 5).
ingly, solution of poor data from a crystal of 5 showed that it is The acid obtained after saponification of the methyl ester was
polymeric in the solid state and subject to high levels of then converted to the corresponding N-triflic alkanamides 15,
disorder.
16 and 22. Ligand metathesis of the silver amide salt generated
Of note, the crystal structures are composed of the units in situ with dimethylsulfide gold chloride gave different com-
bound by F⋯H and O⋯H intermolecular bonds, leading to plexes depending on the length of the side chain. Both
highly porous, layered structures. There is also no metal–metal monomer 5a and 6a and dimer 6b were observed for n = 3,4
interaction present in the solid state.
(but solely the dimer in the solid state 6b, as mentioned
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Scheme 6 Synthesis of complexes 5–7.
Scheme 3 Synthesis of triphenylphosphine gold amides.
Scheme 7 Synthesis of complexes 1 and 2 with modified L-ligand 15.
Scheme 4 Synthesis of the core pyrrolidine precursor.
prior to the decomplexation of the X-ligand to give the for-
mation of a cationic gold species.
Experimental section
Methods and materials
Reagent grade solvents were dried by the standard procedures
and were freshly distilled prior to use. IR spectra were recorded
on a Perkin Elmer FT-IR Spectrum One spectrophotometer.
Mass spectra were recorded on VG Autospec Magnetic Sector
MS and Bruker Daltonic FT-ICR-MS Apex III instruments.
NMR spectra were recorded on either a Varian VNMRS 400 or a
VNMRS 500 instrument. Chemical shifts were referenced to
residual solvent resonances or external 85% H3PO4 in 1H
and 31P NMR spectra as appropriate. The units for the
reported [α]D values are: [α] = deg cm3 g−1 dm−1, c = cgd
m−3. Flash column chromatography was carried out using
Apollo Zeoprep 60 Hyd 35–70 micron silica gel. The freezing
point depressions were measured with an AutoTherm II Plus
thermometer in high-resolution mode (DIN standard). The
data were collected with the Metter Toledo program. A plati-
num resistance thermometer probe (no. 515–131) was used
with the following errors: 0.001 °C for 10.048 °C −0.004 °C
for 5.041 °C.
Scheme 5 Synthesis of the bidentate ligands.
earlier) (Scheme 6). In contrast, the sole dimer 7 was observed
for n = 2.
The introduction of L-ligand 15 was achieved by treating
dimethylsulfide gold chloride in the absence of Ag(I). The
corresponding complex 1 was then converted to its bis-triflic
amide complex 2 after ligand metathesis with silver bis-triflic
amide (Scheme 7).
Conclusions
It has been demonstrated that the catalytic activity of gold
amide complexes is highly dependent on the nature of the sub-
stitution around the N-linkage and that the widely accepted
cationic nature of organogold complexes in solution cannot be
generalized to N-triflic alkanamide gold complexes. We have
shown by DOSY NMR studies and freezing point depression
Syntheses
Methyl 3-{(2S)-2-[(diphenylphosphino)methyl]pyrrolidin-1-yl}-
studies that dimeric complex 6b in the solid state equilibrates propanoate. A solution of methyl-3-bromopropionate (1.55 g,
to monomer 6b in solution, suggesting that an amide X-ligand 9.28 mmol, 1.01 mL) in dichloromethane (8.0 mL) was added
is indeed labile in solution. We have also observed that com- dropwise to a solution of triethylamine (1.88 g, 18.57 mmol,
plexes 2 and 7 featuring the same L-ligand but different 2.61 mL) and (2S)-2-[(diphenylphosphino)methyl]pyrrolidine
X-ligands gave opposite optical rotations for the cycloisomeri- (2.50 g, 9.28 mmol) in dichloromethane (27 mL). The resultant
sation of alkynes. The fact that ligand 15 does not display any solution was stirred at 30 °C overnight. The reaction mixture
organocatalytic activity and that it inhibited complex 10 was poured into water–dichloromethane (1 : 1, 200 mL). The
suggests that the observed enantio-discrimination stems from organic phase was washed with water (100 mL), brine (100 mL)
the complexation of the alkynyl substrate with the gold amides and then dried over sodium sulfate, filtered and
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concentrated under reduced pressure. Purification by column Purification by column chromatography (methanol–dichloro-
chromatography (methanol–dichloromethane, [5 : 95]) afforded methane, [5 : 95]) afforded the title compound as a colourless
1
the title compound as a yellow viscous oil (1.57 g, 47%). solid (0.34 g, 49%). H NMR (500 MHz, DMSO) δ = 7.55–7.32
1H NMR (500 MHz, CDCl3) δ = 7.50–7.39 (4H, m, Ar), 7.37–7.28 (10H, m, Ar), 3.75–3.45 (2H, m, 5, 6-H), 3.22 (1H, s, 2-H),
(6H, m, Ar), 3.66 (3H, s, 9-H), 3.19–3.03 (2H, m, 5, 6-H), 2.54 3.11–2.89 (3H, m, 1, 5, 6-H), 2.55–2.45 (2H, m, 7-H), 2.28 (1H,
(1H, dt, J = 3.3, 13.3, 4-H), 2.49–2.29 (4H, m, 6, 7-H), 2.15–2.06 t, J = 12.1, 1-H), 2.15–2.03 (1H, m, 3-H), 1.94–1.77 (2H, m, 4-H),
(1H, m, 5-H), 2.06–1.91 (2H, m, 1, 3-H), 1.83–1.53 (3H, m, 3, 1.74–1.60 (1H, m, 3-H). 13C NMR (126 MHz, DMSO) δ = 174.3
4-H). 13C NMR (126 MHz, CDCl3) δ = 172.7 (s, 8-C), 139.3 (d, J = (s, 8-C), 137.3 (d, J = 12.2, Ar), 136.2 (d, J = 13.2, Ar), 132.7 (d,
12.1, Ar), 138.5 (d, J = 13.3, Ar), 133.0 (d, J = 19.3, Ar), 132.6 (d, J = 19.9, Ar), 132.4 (d, J = 19.6, Ar), 129.2 (d, J = 33.7, Ar), 128.8
J = 18.7, Ar), 128.7 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 128.4 (s, (d, J = 7.1, Ar), 128.6 (d, J = 7.0, Ar), 124.1 (s, 9-CF), 121.5 (s,
Ar), 128.3 (s, Ar), 128.3 (s, Ar), 62.1 (d, J = 19.3, 2-CH), 53.4 (d, 9-CF), 118.9 (s, 9-CF), 116.4 (s, 9-CF), 66.1 (d, J = 23.5, 2-CH),
J = 0.8, 5-CH2), 51.5 (s, 9-CH3), 49.1 (s, 6-CH2), 33.6 (d, J = 13.3, 52.8 (s, 5-CH2), 49.6 (s, 6-CH2), 34.3 (s, 7-CH2), 30.1 (s, 3-CH2),
1-CH2), 33.5 (s, 7-CH2), 31.7 (d, J = 7.8, 3-CH2), 22.1 (d, J = 0.6, 28.9 (d, J = 13.0, 1-CH2), 21.4 (s, 4-CH2). 31P NMR (162 MHz,
4-CH2). 31P NMR (162 MHz, CDCl3) δ = −21.20. IR (diamond, DMSO) δ = −21.76 (s). 19F NMR (376 MHz, DMSO) δ = −77.71
νMAX, cm−1) 2961, 2802 (CH3O st), 1735 (CvO st), 1433 (s). M.p.: 153–155 °C. IR (diamond, νMAX, cm−1) 3052, 2967
(H–C–H st as), 1175 (C–O st as). [α]2D6 = −78.2 (c = 1.0 in (NH st), 2192 (Ar comb), 1598 (CvO st amide), 1431 (H–C–H st
dichloromethane). Acc. Mass (FAB): C21H27NO2P Found: as), 1176 (S–O st as), 1123 (S–O st sy). [α]2D6 = −27.7 (c = 1.0 in
356.1778 error [ppm]: −1.28 Calculated: 356.1774.
dichloromethane). Acc. Mass (FAB): C21H24 F3N2NaO3PS
3-{(2S)-2-[(Diphenylphosphino)methyl]pyrrolidin-1-yl}propa- Found: 495.1117 m/z error [ppm]: −5.50 Calculated:
noic acid. A solution of 34.3 mL of the 1 N sodium hydroxide 495.1090 m/z.
was added to methyl 3-{(2S)-2-[(diphenylphosphino)methyl]- X-Ray: see the appendix for complex 15 (recrystallised from
pyrrolidin-1-yl}propanoate (0.50 g, 1.41 mmol) in methanol chloroform).
(22.85 mL, 0.062 M). After stirring for 20 h at room temp-
(3-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)-
erature the reaction mixture was neutralized with 32% hydro- propanoyl)((trifluoromethyl)sulfonyl)amide gold chloride
chloric acid (3.5 mL). The resulting solution was lyophilized to (1). (3-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-
yield the crude product which was then dissolved in methanol. yl)propanoyl)((trifluoromethyl)sulfonyl)amide (50 mg, 0.106
Any insoluble salts were removed by filtration. The resultant mmol) was dissolved in dry dichloromethane (1 mL)
solution was concentrated under reduced pressure to give the under an atmosphere of nitrogen. Dimethyl sulfide gold chlor-
corresponding compound as a yellow and cloudy viscous ide (31 mg, 0.106 mmol) was added to one portion and the
oil (0.57 g, quantitative). 1H NMR (500 MHz, CDCl3) δ = 8.07 (1H, resulting mixture was stirred for 3 h. Concentration of the reac-
br s, OH), 7.40 (10H, m, Ar), 3.70–3.80 (1H, m, 5-H), 3.61–3.49 tion mixture under reduced pressure afforded the title com-
1
(1H, m, 7-H), 3.06–2.72 (6H, m, 1, 6, 7, 5-H), 2.64 (1H, t, J = pound as a colourless solid (70 mg, 94%). H NMR (500 MHz,
12.1, 1-H), 2.24–1.82 (m, 4H, 3, 4-H). 13C NMR (126 MHz, CDCl3) δ = 7.92 (2H, dd, J = 7.1, 13.6, Ar), 7.80 (2H, dd, J = 7.1,
CDCl3) δ = 173.2 (s, 8-C), 136.8 (d, J = 11.3, Ar), 136.1 (d, J = 13.4, Ar), 7.59–7.42 (6H, m, Ar), 4.26 (1H, m, 5-H), 3.86–3.58
12.7, Ar), 133.0 (d, J = 20.2, Ar), 132.5 (d, J = 19.2, Ar), 129.6 (s, (2H, m, 6-H), 3.53–3.37 (2H, m, 1-H), 3.02–2.90 (2H, m, 5, 6-H),
Ar), 129.1 (s, Ar), 128.9 (d, J = 7.3, Ar), 128.7 (d, J = 6.9, Ar), 66.9 2.83–2.55 (2H, m, 7-H), 2.19–1.91 (3H, m, 3, 4-H), 1.80–1.67
(d, J = 23.2, 2-CH), 52.8 (s, 5-CH2), 49.4 (s, 7-CH2), 31.1 (s, (1H, m, 3-H). 13C NMR (126 MHz, CDCl3) δ = 175.6 (s, 8-C),
6-CH2), 30.5 (d, J = 7.4, 3-CH2), 29.6 (d, J = 16.2, 1-CH2), 21.7 (s, 134.1 (d, J = 14.3, Ar), 133.1 (d, J = 13.6, Ar), 132.6 (dd, J = 2.1,
4-CH2). 31P NMR (162 MHz, CDCl3) δ = −20.61 (s), 30.43 (s, 52.4, Ar), 129.5 (dd, J = 6.8, 12.1, Ar), 128.6 (d, J = 63.1, Ar),
PvO, 5%). IR (diamond, νMAX, cm−1) 2956, 2547 (HO st), 1720 127.9 (d, J = 61.7, Ar), 124.12 (s, 9-CF), 121.5 (s, 9-CF), 119.0 (s,
(CvO st), 1432 (H–C–H st as). [α]2D6 = −40.0 (c = 1.0 in dichloro- 9-CF), 116.4 (s, 9-CF), 67.7 (s, 2-CH), 54.6 (s, 5-CH2), 52.3 (s,
methane). Acc. Mass (FAB): C20H25NO2P Found: 342.1608 m/z 6-CH2), 34.5 (s, 7-CH2), 30.4 (s, 3-CH2), 29.1 (d, J = 38.9,
error [ppm]: 2.86 Calculated: 342.1617 m/z.
(3-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)- 26.38 (s). 19F NMR (376 MHz, CDCl3) δ = −78.34 (s). Com-
propanoyl)((trifluoromethyl)sulfonyl)amide
(15). 3-{(2S)-2- pound decomposed at 128–130 °C. IR (diamond, νMAX, cm−1
[(Diphenylphosphino)methyl]pyrrolidin-1-yl}propanoic acid 3055 (NH st), 2191 (Ar comb), 1610 (CvO st amide), 1437
(0.50 g, 1.46 mmol), triflic amine (0.218 g, 1.46 mmol) and (H–C–H st as), 1173 (S–O st as), 1124 (S–O st sy). [α]2D6 = −12.3
HOBt·H2O (0.224 g, 1.46 mmol) were dissolved in dichloro- (c 1.0 in dichloromethane). Acc. Mass (FAB): 21H24
1-CH2), 21.9 (s, 4-CH2). 31P NMR (162 MHz, CDCl3) δ =
)
=
C
methane (3.85 mL) and cooled to 0 °C. EDC (0.233 g, AuClF3N2NaO3PS Found: 727.0440 m/z error [ppm]: 0.48 Calcu-
1.50 mmol) was added and the mixture was stirred for 15 min lated: 727.0444 m/z.
at 0 °C and then at room temperature overnight. The precipi-
(3-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)-
tate was filtered off and the solvent was evaporated. The propanoyl)((trifluoromethyl)sulfonyl)amide gold bis-triflic
residue was dissolved in 20 mL of dichloromethane and amide (2). A solution of gold diphenylphosphine chloride
washed with 1 M citric acid (20 mL), saturated sodium (65.2 mg, 0.092 mmol) in dichloromethane (0.31 mL) was
bicarbonate (20 mL), brine (20 mL) and dried over anhydrous added to a premixed (5 min) solution of bis-triflic amide
magnesium sulfate; concentrated under reduced pressure. (26 mg, 0.092 mmol) and silver carbonate (25.5 mg,
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0.092 mmol) in dry dichloromethane (2 mL) under an inert concentrated under reduced pressure. Purification by column
atmosphere. The resulting mixture was stirred for 2 h exclud- chromatography (methanol–dichloromethane, [5 : 95]) afforded
ing light. The mixture was filtered through Celite and concen- the title compound as a colourless viscous oil (1.57 g, 65%).
trated under reduced pressure to give the title compound as an 1H NMR (500 MHz, CDCl3) δ = 7.55–7.27 (10H, m, Ar), 3.66
1
off white solid (70.5 mg, 80%). H NMR (500 MHz, CDCl3) δ = (3H, s, 11-H), 3.21 (1H, s, 5-H), 2.82 (1H, m, 5-H), 2.54 (1H, dt,
8.17–6.96 (10H, m, Ar), 4.33–2.89 (9H, m, 1, 5, 6, 7-H), J = 3.1, 13.2, 3-H), 2.40 (1H, s, 2-H), 2.33–2.27 (2H, m, 9-H),
2.22–1.75 (3H, m, 3, 4-H), 1.47–1.21 (1H, m, 3-H). 13C NMR 2.21–2.04 (3H, m, 3, 6-H), 2.04–1.96 (1H, m, 1-H), 1.83 (1H, m,
(126 MHz, CDCl3) δ = 174.8 (s, C-8), 134.9 (d, J = 14.0, Ar), 4-H), 1.74–1.45 (5H, m, 4, 7, 8-H). 13C NMR (126 MHz, CDCl3)
133.8 (s, Ar), 132.2 (s, Ar), 131.7 (d, J = 12.2, Ar), 130.0 (s, Ar), δ = 173.9 (s, 10-C), 133.09 (s, Ar), 132.94 (s, Ar), 132.62 (s, Ar),
129.6 (s, Ar), 129.4 (d, J = 11.7, Ar), 123.4 (s, CF), 120.9 (s, CF), 132.47 (s, Ar), 128.82 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 128.4 (s,
118.3 (s, CF), 115.7 (s, CF), 64.4 (s, 2-CH), 52.8 (s, 5-CH2), 44.9 Ar), 128.3 (s, Ar), 62.8 (s, 2-CH), 53.6 (s, 6-CH2), 53.5 (s, 5-CH2),
(s, 6-CH2), 29.5, 29.1 (s, 1, 3, 7-CH2), 20.8 (s, 4-CH2). 31P NMR 51.5 (s, 11-CH3), 33.8 (s, 9-CH2), 33.2 (s, 3-CH2), 31.6 (s,
(162 MHz, CDCl3) δ = 26.80 (s). 19F NMR (376 MHz, CDCl3) δ = 1-CH2), 27.6 (s, 7-CH2), 22.9 (s, 8-CH2), 22.1 (s, 4-CH2).
−76.56 (s), −78.68 (s). Compound decomposed at 109–111 °C. 31P NMR (162 MHz, CDCl3) δ = −20.82 (s). IR (diamond,
IR (diamond, νMAX, cm−1) 2178 (Ar comb), 1669 (CvO st νMAX, cm−1) 2945, 2788 (CH3O st), 1734 (CvO st), 1433
amide), 1439 (H–C–H st as), 1178 (S–O st as), 1128 (S–O st sy). (H–C–H st as), 1169 (C–O st as). [α]2D4 = −46.3 (c = 1.0 in
[α]2D6 = −23.6 (c = 1.0 in dichloromethane). Acc. Mass (FAB): dichloromethane). Acc. Mass (FAB): C23H31NO2P Found:
C23H24 AuF9N3O7PS3 Found: N/A Calculated: 949.5735.
384.2078 error [ppm]: 2.43 Calculated: 384.2087.
(S)-5-(2-((Diphenylphosphino)methyl)pyrrolidin-1-yl)pentanoic
acid. A solution of 27.5 mL of the 1 N sodium hydroxide was
Bidentate gold(I) complex (7)
(3-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)- added to methyl 3-{(2S)-2-[(diphenylphosphino)methyl]pyrroli-
propanoyl) ((trifluoromethyl)sulfonyl)amide. (100 mg, din-1-yl}pentanoate (0.41 g, 1.11 mmol) in methanol (18.5 mL,
0.212 mmol) was dissolved in dry dichloromethane (2.1 mL) in 0.062 M). After stirring for 20 h at room temperature the reac-
a flame dried flask, under nitrogen. The dimethyl sulfide gold tion mixture was neutralized with 32% hydrochloric acid
chloride (62 mg, 0.212 mmol) was added to one portion and (2.8 mL). The resulting solution was lyophilized to yield the
the mixture was stirred for 15 min. The silver carbonate crude product which was then dissolved in methanol. Any
(58 mg, 0.212 mmol) was added to one portion and the resul- insoluble salts were removed by filtration. The resultant
tant mixture stirred overnight. The reaction mixture was fil- solution was concentrated under reduced pressure to give the
tered through Celite and concentrated under reduced pressure corresponding compound as a colourless viscous oil (0.38 g,
to give the title compound as a yellow solid (139 mg, 98%). 93%). 1H NMR (500 MHz, CDCl3) δ = 11.94–11.20 (1H, br s, OH),
1H NMR (500 MHz, CDCl3) δ = 7.91–7.37 (10H m, Ar), 7.59–7.30 (10H, m, Ar), 3.84 (1H, s, 5-H), 3.26 (1H, s, 6-H),
3.36–1.23 (13H m, 1–7-H). 13C NMR (100 MHz, CDCl3) δ = 3.03–2.56 (5H, m, 1, 2, 5, 6-H), 2.34 (2 H, t, J = 6.7, 9-H), 2.20
176.6 (s, 8-C), 133.6 (s, Ar), 133.0 (s, Ar), 132.2 (s, Ar), 129.9 (s, (2 H, s, 3, 4-H), 2.04 (1 H, s, 3-H), 1.93 (2 H, s, 4, 7-H),
Ar), 129.4 (s, Ar), 129.3 (s, Ar), 125.4 (s, 9-CF), 122.1 (s, 9-CF), 1.74–1.52 (3 H, m, 7, 8-H). 13C NMR (126 MHz, CDCl3) δ =
118.7 (s, 9-CF), 115.5 (s, 9-CF), 61.8 (s, 2-CH), 53.4 (s, 5-CH2), 175.6 (s, 10-C), 136.4 (s, Ar), 133.2 (d, J = 14.26, Ar), 132.5 (s,
50.04 (s, 6-CH2), 37.4 (s, 7-CH2), 33.2 (s, 3-CH2), 31.9 (s, Ar), 129.7 (s, Ar), 129.1 (s, Ar), 128.9 (s, Ar), 128.7 (s, Ar), 67.1
1-CH2), 22.8 (s, 4-CH2). 31P NMR (162 MHz, CDCl3) δ = (s, 2-CH), 52.9 (s, 5, 6-CH2), 33.1 (s, 9-CH2), 30.6 (s, 3-CH2),
21.92 (s), 20.81 (s). Compound decomposed at 125–126 °C. IR 29.8 (s, 1-CH2), 24.4 (s, 7-CH2), 22.0 (s, 8-CH2), 21.7 (s, 4-CH2).
(diamond, νMAX, cm−1) 2962 (NH st), 2168 (Ar comb), 1683 IR (diamond, νMAX, cm−1) 2945, 2546 (HO st), 1720 (CvO st),
(CvO st amide), 1437 (H–C–H st as), 1177 (S–O st as), 1121 1432 (H–C–H st as), 1169 (C–O st as). [α]2D4 = −44.1 (c = 1.0 in
(S–O st sy). [α]2D4 = −21.2 (c = 1.0 in dichloromethane). Acc. dichloromethane). Acc. Mass (FAB): C22H29NO2P Found:
Mass (FAB): C42H47 Au2F6N4O6P2S2 Found: 1337.1704 m/z error 370.1921 error [ppm]: 2.57 Calculated: 370.1930.
[ppm]: −4.61 Calculated: 1337.1704 m/z.
X-Ray: available see the appendix (by slow diffusion of yl)pentanoyl)((trifluoromethyl)sulfonyl)amide
dichloromethane into benzene). ((Diphenylphosphino)methyl)pyrrolidin-1-yl)pentanoic
(5-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-
(16). (S)-5-(2-
acid
(S)-Methyl 5-(2-((diphenylphosphino)methyl)pyrrolidin-1-yl)- (0.300 g, 0.81 mmol), triflic amine (0.121 g, 0.81 mmol) and
pentanoate. A solution of methyl 5-bromopentanoate (0.36 g, HOBt·H2O (0.125 g, 0.14 mmol) were dissolved in dichloro-
1.86 mmol, 0.27 mL) in dichloromethane (1.64 mL) was added methane (2.15 mL) and cooled to 0 °C. EDC (0.140 g,
dropwise to a solution of triethylamine (0.38 g, 3.71 mmol, 0.83 mmol) was added and the mixture was stirred for 15 min
0.52 mL) and (2S)-2-[(diphenylphosphino)methyl]pyrrolidine at 0 °C and then at room temperature overnight. The precipi-
(0.500 g, 1.86 mmol) in dichloromethane (5.46 mL). The resul- tate was filtered off and the solvent was evaporated. The
tant solution was stirred at 30 °C overnight. The reaction residue was dissolved in 15 mL of dichloromethane and
mixture was poured into water–dichloromethane (1 : 1, 40 mL). washed with 1 M citric acid (15 mL), saturated sodium bicar-
The crude residue was extracted with dichloromethane bonate (15 mL), brine (15 mL) and dried over anhydrous
(20 mL), the organic phase was washed with water (20 mL), magnesium sulfate; concentrated under reduced pressure.
brine (20 mL) and then dried over sodium sulfate, filtered and Purification by column chromatography (methanol–
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dichloromethane, [5 : 95]) afforded the title compound as a 1.51 mmol) in dichloromethane (3.1 mL). The resultant solu-
white solid (0.268 g, 66%). 1H NMR (500 MHz, CDCl3) δ = tion was stirred at 30 °C overnight. The reaction mixture was
7.56–7.30 (10H, m, Ar), 3.98 (1H, s, 5-H), 3.40 (1H, s, 6-H), 2.95 poured into water–dichloromethane (1 : 1, 32 mL). The crude
(1 H, s, 2-H), 2.82 (2 H, m, 1, 5-H), 2.63–2.38 (4 H, m, 1, 6, 9- residue was extracted with dichloromethane (16 mL), the
H), 2.29–2.16 (2 H, m, 3, 4-H), 2.08–1.86 (2 H, m, 3, 4-H), 1.79 organic phase was washed with water (16 mL), brine (16 mL)
(1 H, s, 7-H), 1.71–1.52 (3 H, m, 7, 8H). 13C NMR (126 MHz, and then dried over sodium sulfate, filtered and concentrated
CDCl3) δ = 181.0 (s, 10-C), 136.7 (d, J = 11.4, Ar), 136.4 (d, J = under reduced pressure. Purification by column chromato-
10.9, Ar), 133.1 (d, J = 20.1, Ar), 132.4 (d, J = 19.1, Ar), 129.7 (s, graphy (methanol–dichloromethane, [5 : 95]) afforded the title
1
Ar), 129.1 (s, Ar), 129.0 (d, J = 7.2, Ar), 128.7 (d, J = 6.6, Ar), compound as a colourless viscous oil (0.264 g, 47%). H NMR
124.2 (s, 10-CF), 121.7 (s, 10-CF), 119.1 (s, 10-CF), 68.4 (d, J = (500 MHz, CDCl3) δ = 7.51–7.40 (4H, m, Ar), 7.38–7.28 (6H, m,
23.9, 2-CH), 54.8 (s, 6-CH2), 53.8 (s, 5-CH2), 37.5 (s, 9-CH2), Ar), 3.66 (3H, d, J = 1.3, 11-H), 3.19 (1H, s, 5-H), 2.80 (1 H, m,
30.6 (d, J = 7.1, 3-CH2), 29.8 (d, J = 15.1, 1-CH2), 24.7 (s, 7- 6-H), 2.51 (1 H, d, J = 13.1, 1-H), 2.46–2.22 (3H, m, 2, 8-H), 2.14
CH2), 22.6 (s, 8-CH2), 21.7 (s, 4-CH2). 31P NMR (162 MHz, (3H, s, 1, 5, 6-H), 2.03–1.94 (1H, m, 3-H), 1.86–1.57 (5H, m, 3,
CDCl3) δ = −20.38 (s). M.p.: 147–149 °C. IR (diamond, νMAX
cm−1) 2962 (NH st), 2192 (Ar comb), 1602 (CvO st amide), (s, Ar), 138.4 (s, Ar), 133.0 (d, J = 19.5, Ar), 132.6 (d, J = 18.7,
1431 (H–C–H st as), 1168 (S–O st as), 1126 (S–O st sy). [α]D24
Ar), 128.7 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 128.4 (s, Ar), 128.3
−21.3 (c 1.0 in dichloromethane). Acc. Mass (FAB): (s, Ar), 62.5 (s, 2-CH), 53.4 (s, 5-CH2), 53.1 (s, 6-CH2), 51.4 (s,
,
4, 7-H). 13C NMR (126 MHz, CDCl3) δ = 173.8 (s, 10-C), 139.2
=
=
C23H28F3N2NaO3PS Calculated: 523.1403 error [ppm]: 2.11 10-CH3), 33.5 (s, 1-CH2), 31.9 (s, 8-CH2), 31.7 (d, J = 7.4,
Found: 523.1392.
3-CH2), 23.6 (s, 7-CH2), 22.2 (s, 4-CH2). 31P NMR (162 MHz,
CDCl3) δ = −21.02 (s). IR (diamond, νMAX, cm−1) 2949, 2791
(CH3O st), 1733 (CvO st), 1433 (H–C–H st as), 1170 (C–O st
Complexes (6a)/(6b)
(5-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)- as). Acc. Mass (FAB): C22H29NO2P Found: 370.1913 error
pentanoyl)((trifluoromethyl)sulfonyl)amide (100 mg, 0.199 [ppm]: 4.76 Calculated: 370.1930.
mmol) was dissolved in dry dichloromethane (2.0 mL) in
(S)-4-(2-((Diphenylphosphino)methyl)pyrrolidin-1-yl)butanoic
a flame dried flask, under nitrogen. The dimethyl sulfide gold acid. A solution of 15.7 mL of the 1 N sodium hydroxide was
chloride (58.9 mg, 0.199 mmol) was added to one portion and added to methyl 3-{(2S)-2-[(diphenylphosphino)methyl]pyrrol-
the mixture was stirred for 15 min. The silver carbonate idin-1-yl}butanoate (0.237 g, 0.64 mmol) in methanol (10.4 mL,
(55.1 mg, 0.199 mmol) was added to one portion and the resul- 0.062 M). After stirring for 20 h at room temperature the reac-
tant mixture stirred overnight. The reaction mixture was fil- tion mixture was neutralized with 32% hydrochloric acid
tered through Celite and concentrated under reduced pressure (1.7 mL). The resulting solution was lyophilized to yield the
to give the title compound as a yellow solid (138.7 mg, quanti- crude product which was then dissolved in methanol. Any
tative). 1H NMR (500 MHz, CDCl3) δ = 7.83–7.69 (4H, m, Ar), insoluble salts were removed by filtration. The resultant solu-
7.57–7.45 (6H, m, Ar), 3.12–3.04 (1H, m, 6-H), 2.97–2.63 (5H, tion was concentrated under reduced pressure to give the corres-
m, 2, 3, 5, 9-H), 2.57–2.47 (1H, m, 9-H), 2.33–2.20 (2H, m, 6–8- ponding compound as a colourless oil (0.228 g, quantitative). 1H
H), 2.19–2.10 (1H, m, 5-H), 1.90–1.45 (6H, m, 1, 4, 8, 7-H), NMR (500 MHz, CD3OD) δ = 7.58–7.45 (4H, m, Ar), 7.44–7.35
1.35–1.24 (1H, m, 1-H). 13C NMR (126 MHz, CDCl3) δ = 178.8 (5H, m, Ar), 3.70–3.60 (1H, m, 5-H), 3.40–3.32 (1H, m, 6-H),
(s, 10-C), 133.1 (d, J = 12.9, Ar), 133.5 (d, J = 13.9, Ar), 132.1 (d, 3.25–3.14 (1H, m, 2-H), 3.13–3.02 (1H, m, 5-H), 3.00–2.90 (1H,
J = 22.7, Ar), 129.5 (s, Ar), 129.4 (s, Ar), 129.4 (s, Ar), 122.0 (s, m, 6-H), 2.84 (1H, dd, J = 3.4, 13.3, 1-H), 2.48–2.35 (3H, m, 1,
11-CF), 61.6 (s, 2-CH), 53.3 (s, 6-CH2), 51.6 (s, 5-CH2), 40.2 (s, 8-H), 2.32–2.23 (1H, m, 3-H), 2.10–1.80 (5H, m, 3, 4, 7-H). 13C
9-CH2), 32.3 (d, J = 40.9, 3-CH2), 31.3 (s, 1-CH2), 26.4 (s, NMR (126 MHz, CD3OD) δ = 181.3 (s, 9-C), 138.8 (d, J = 11.5,
7-CH2), 23.9 (s, 8-CH2), 22.3 (s, 4-CH2). 31P NMR (162 MHz, Ar), 137.9 (d, J = 12.4, Ar), 134.3 (d, J = 20.2, Ar), 133.8 (d, J =
CDCl3) δ = 16.41 (s) corresponding as monomer 6a. IR 19.5, Ar), 130.8 (s, Ar), 130.4 (s, Ar) 130.1 (d, J = 7.3, Ar), 129.9
(diamond, νMAX, cm−1) 2925, 2798 (NH st), 2168 (Ar comb), (d, J = 7.0, Ar), 67.4 (d, J = 21.9, 2-CH), 55.2 (s, 6-CH2), 54.4 (s,
1694 (CvO st amide), 1436 (H–C–H st as), 1176 (S–O st as), 5-CH2), 36.2 (s, 8-CH2), 32.0 (d, J = 7.8, 3-CH2), 31.5 (d, J = 15.8,
1123 (S–O st sy). Compound decomposed at 93–95 °C. [α]D24
=
1-CH2), 23.3 (s, 7-CH2), 22.9 (s, 4-CH2). 31P NMR (162 MHz,
−22.3 (c
=
1.0 in dichloromethane). Acc. Mass (FAB): CD3OD) δ = −21.13 (s). IR (diamond, νMAX, cm−1) 3307, 2541
C23H28AuF3N2NaO3PS Found: 719.0962 error [ppm]: 0.52 Cal- (HO st), 1586 (CvO st), 1432 (H–C–H st as) 1154 (C–O st as).
culated: 719.0966 Acc. Mass (FAB): C46H54Au2F6N4NaO6P2S2 [α]2D3 = −13.9 (c = 1.0 in methanol). Acc. Mass (FAB):
Found: 1415.2089 error [ppm]: −0.12 Calculated: 1415.2087.
C22H29NO2P Found: 356.1768 error [ppm]: 1.76 Calculated:
X-Ray: dimer 6b (recrystallised by slow diffusion of dichloro- 356.1774.
methane into n-heptane).
(4-((2S)-2-((Diphenylphosphino)methyl)pyrrolidin-1-ium-1-yl)-
(S)-Methyl 4-(2-((diphenylphosphino)methyl)pyrrolidin-1-yl)- butanoyl)((trifluoromethyl)sulfonyl)amide
butanoate. A solution of methyl 5-bromobutanoate (0.273 g, ((Diphenylphosphino)methyl)pyrrolidin-1-yl)butanoic
(22). (S)-5-(2-
acid
1.51 mmol) in dichloromethane (1.32 mL) was added dropwise (0.233 g, 0.65 mmol), triflic amine (0.098 g, 0.65 mmol)
to a solution of triethylamine (0.304 g, 3.01 mmol, 0.42 mL) and HOBt·H2O (0.100 g, 0.65 mmol) were dissolved in dichloro-
and (2S)-2-[(diphenylphosphino)methyl]pyrrolidine (0.405 g, methane (1.72 mL) and cooled to 0 °C. EDC (0.104 g,
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0.67 mmol) was added and the mixture was stirred for 15 min triflic amine (58.9 mg, 0.40 mmol) and HOBt·H2O (60.5 mg,
at 0 °C and then at room temperature overnight. The precipi- 0.40 mmol) were dissolved in dichloromethane (1.05 mL) at
tate was filtered off and the solvent was evaporated. The 0 °C. EDC (60.0 mg, 0.40 mmol) was added and the mixture
residue was dissolved in 10 mL of dichloromethane and stirred for 15 min and then at room temperature for a further
washed with 1 M citric acid (10 mL), saturated sodium bicar- 3 days. The precipitate was filtered off and the filtrate evapor-
bonate (10 mL), brine (10 mL) and dried over anhydrous ated under reduced pressure. The residue was dissolved in
magnesium sulfate; concentrated under reduced pressure. 5 mL of ethyl acetate and washed with 1 M citric acid, satu-
Purification by column chromatography (methanol–dichloro- rated sodium bicarbonate, brine, dried over anhydrous mag-
methane, [5 : 95], solid deposit) afforded the title compound as nesium sulphate, filtered and concentrated under reduced
a white solid (0.145 g, 46%). 1H NMR (500 MHz, DMSO) δ = pressure. Purification by column chromatography (diethyl
7.61–7.35 (10H, m, Ar), 3.58 (1H, s, 5-H), 3.45–3.37 (1H, m, ether) afforded the title compound as a white solid (0.149 g,
6-H), 3.20 (1H, s, 2-H), 3.09–3.02 (1H, m, 5-H), 2.99–2.84 (2H, 73%). 1H NMR (500 MHz, CDCl3) δ = 8.45 (1H, br s, NH),
m, 1, 6-H), 2.31–2.09 (4H, m, 1, 3, 8-H), 1.97–1.60 (5H, m, 3, 4, 7.37–6.82 (15H, m, Ar), 4.09–3.51 (6H, m, 12, 13, 3-H), 1.27
7-H). 13C NMR (126 MHz, DMSO) δ = 176.6 (s, 9-C), 137.3 (d, (1H, dd, J = 8.4, 15.0, 3-H). 13C NMR (126 MHz, CDCl3) δ =
J = 12.1, Ar), 136.0 (d, J = 13.1, Ar), 132.7 (d, J = 20.0, Ar), 132.4 171.9 (s, 1-C) 136.3 (s, Ar), 129.1 (d, J = 18.25 Ar), 126.5 (s, Ar),
(d, J = 19.5, Ar), 129.4 (s, Ar), 129.1 (s, Ar), 128.8 (d, J = 7.2, Ar), 123.8 (s, Ar), 122.3 (s, Ar), 121.4 (s, Ar), 119.6 (s, Ar), 118.9 (s,
128.6 (d, J = 6.9, Ar), 124.3 (s, 10-CF), 121.7 (s, 10-CF), 119.1 (s, Ar), 118.4 (s, Ar), 111.7 (s, Ar), 64.9 (s, 2-CH), 54.7 (s, 12,
10-CF), 116.5 (s, 10-CF), 65.7 (d, J = 21.9, 2-CH), 52.6 (s, 5-CH2), 13-CH2), 29.7 (s, 3-CH2). M.p.: 72–74 °C. IR (diamond, νMAX
,
52.3 (s, 6-CH2), 36.0 (s, 8-CH2), 30.0 (d, J = 8.3, 3-CH2), 28.7 (d, cm−1) 3403.21 (Ar NH st), 2919.69 (NH st), 2019.56 (Ar comb),
J = 14.3, 1-CH2), 21.5 (s, 7-CH2), 21.2 (s, 4-CH2). 31P NMR 1619.39 (CvO st amide), 1179.12, 1180.95 (S–O st as), 1125.62
(162 MHz, DMSO) δ = −25.11 (1s). M.p.: 158–160 °C. IR (S–O st sy). [α]2D1 = 39.3 (c = 1.0 in dichloromethane). Acc. Mass
(diamond, νMAX, cm−1) 2967, 2554 (NH st), 2192 (Ar comb), (FAB): C26H24F3N3O3SNa Found: 538.1398 m/z error [ppm]:
1645 (CvO st amide), 1434 (H–C–H st as), 1158 (S–O st as), −2.84 Calculated: 538.1383 m/z.
1134 (S–O st sy). [α]2D2 = −5.6 (c = 1.0 in dichloromethane). Acc.
Triphenyphosphine gold N,N-dibenzy-N[(trifluoromethyl)-
Mass (FAB): C22H26F3N2NaO3PS Calculated: 509.1246 error sulfonyl]-(D)-tryptophanamide (4). Silver carbonate (0.110 g,
[ppm]: 0.31 Found: 509.1244.
0.40 mmol) was added to a solution of N,N-dibenzyl-N-
[(trifluoromethyl)sulfonyl]-(D)-tryptophanamide (0.114 g,
0.22 mmol) in dichloromethane (2.52 mL) at 0 °C and stirred
min. Triphenylphosphine gold chloride (0.110 g,
4
Complexes (5a)/(5b)
The (4-((2S)-2-((diphenylphosphino)methyl)pyrrolidin-1-ium- for
5
1-yl)butanoyl)((trifluoromethyl)sulfonyl) amide (100 mg, 0.22 mmol) was added and the reaction mixture stirred for a
0.21 mmol) was dissolved in dry dichloromethane (2.1 mL) in further 2 days at 10 °C. The reaction mixture was filtered
a flame dried flask, under nitrogen. The dimethyl sulfide gold through Celite and the solvent evaporated under reduced
chloride (60.5 mg, 0.21 mmol) was added to one portion and pressure to give the corresponding compound as an olive
the mixture was stirred for 15 min. The silver carbonate coloured solid (0.238 g, quant.). 1H NMR (500 MHz, CDCl3) δ =
(56.7 mg, 0.21 mmol) was added to one portion and the resul- 7.61–6.67 (36H m, Ar), 4.26 (1H s, 2-H), 4.16 (2H d, J = 14.3, 12,
tant mixture stirred overnight. The reaction mixture was fil- 13-H), 3.80 (2H, d, J = 14.3, 12, 13-H), 3.57 (2 H, dd, J = 9.8,
tered through Celite and concentrated under reduced pressure 14.0, 3-H), 3.12 (2 H, dd, J = 4.5, 14.1, 3-H). 13C NMR
to afford the title compound as a yellow solid (122 mg, quanti- (126 MHz, CDCl3) δ = 178.9 (s, 1-C), 140.1 (s, Ar), 135.7 (s,
tative w/w (monomer or dimer)). 1H NMR (500 MHz, CDCl3) 11-C), 134.07 (d, J = 13.7, Ar), 131.9 (s, Ar), 129.1 (d, J = 12.1,
δ = 7.89–7.33 (10H m, Ar), 3.29–1.52 (15H m, 1–8-H). 13C NMR Ar), 128.9 (s, Ar), 128.1 (s, Ar), 128.0 (s, Ar), 127.5 (s, Ar), 127.3
(126 MHz, CDCl3) δ = 177.6 (s, 9-C), 133.5 (s, Ar), 133.0 (s, Ar), (s, Ar), 126.8 (s, 6-C), 123.2 (s, 5-CH), 121.7 (s, 9-CH), 119.3 (s,
132.2 (s, Ar), 132.0 (s, Ar), 131.0 (s, Ar), 129.9 (s, Ar), 129.4 (s, 8-CH), 118.9 (s, 7-CH), 112.2 (s, 10-CH), 110.7 (s, 4-CH), 67.2
Ar), 129.4 (s, Ar), 129.0 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 121.9 (s, 2-CH), 54.7 (s, 12, 13-CH2), 26.8 (s, 3-CH2). 31P NMR
(s, 10-CF), 119.3 (s, 10-CF), 116.6 (s, 10-CF), 62.1 (s, 2-CH), 53.6 (162 MHz, CDCl3) δ = 33.00 (s, 1), 29.92 (s, 11). IR (diamond,
(s, 5-CH2), 52.9 (s, 6-CH2), 33.7 (s, 1-CH2), 33.4 (s, 8-CH2), 32.0 νMAX, cm−1) 2920 (NH st), 2019.56 (Ar comb), 1685 (CvO st
(s, 3-CH2), 24.0 (s, 7-CH2), 22.7 (s, 4-CH2). 31P NMR (162 MHz, amide), 1437 (H–C–H st as) 1181 (S–O st as), 1101 (S–O st sy).
CDCl3) δ = 23.06 (s), 21.55 (br, s), 19.68 (s). Compound decom- [α]2D1 = 57.7 (c = 1.0 in dichloromethane). Acc. Mass (FAB):
posed at 109–111 °C. IR (diamond, νMAX, cm−1) 2935 (NH st), C44H39AuF3N3O3PSNa Found: 974.2110 m/z error [ppm]: −4.95
2168 (Ar comb), 1688 (CvO st amide), 1436 (H–C–H st as), Calculated: 974.2062 m/z.
1177 (S–O st as), 1121 (S–O st sy). [α]2D0 = −37.7 (c = 1.0 in
dichloromethane). Acc. Mass (FAB): C22H26AuF3N2O3PS Found: leucinamide. N-Benzoxycarbonyl-(L)-leucine
N2-[(Benzyloxy)carbonyl}-N1-[(trifluoromethyl)sulfonyl]-(L)-
(0.100 g,
683.1014 error [ppm]: −1.50 Calculated: 683.1014. Acc. Mass 0.377 mmol), triflic amine (56.2 mg, 0.377 mmol) and
(FAB): C44H51Au2F6N4O6P2S2 Found: 1365.1874 error [ppm]: HOBt·H2O (57.7 mg, 0.377 mmol) were dissolved in dichloro-
5.91 Calculated: 1365.1955.
methane and cooled to 0 °C. EDC (60.0 mg, 0.386 mmol) was
N,N-Dibenzyl-N[(trifluoromethyl)sulfonyl]-(D)-tryptophan- added and the mixture stirred for 15 min at 0 °C and then at
amide. N,N-Dibenzyl-(D)-tryptophan 18 (0.152 g, 0.40 mmol), room temperature for a further 3 days. The precipitate was
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filtered off and the filtrate concentrated under reduced dichloromethane) afforded the title compound as a colourless
1
pressure. The residue was dissolved in ethyl acetate (5 mL) and solid (1.648 g, 91%). H NMR (500 MHz, CDCl3) δ = 7.94–6.95
washed with 1 M citric acid (3 mL), a saturated solution of (10H, m, Ar), 3.76 (1H, s, 2-H), 3.32–2.80 (3H, m, 1, 5-H), 2.03
sodium carbonate (3 mL), brine (3 mL) and dried over anhy- (1H, s, 1-H), 1.77 (1H, s, 3-H), 1.52 (3H, s, 3, 4-H). 13C NMR
drous magnesium sulphate and filtered. The organic layer was (126 MHz, CDCl3) δ = 139.1 (s, Ar), 139.0 (s, Ar), 132.8 (s, Ar),
concentrated under reduced pressure. Purification by column 132.6 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 128.4 (s, Ar), 128.3 (s,
chromatography (diethyl ether) afforded the title compound as Ar), 128.3 (s, Ar), 58.8 (d, J = 21.0, 2-CH), 50.2 (s, 5-CH2), 35.6
1
a white solid (79.4 mg, 53%). H NMR (500 MHz, CDCl3) δ = (s, 1-CH2), 32.0 (s, 3-CH2), 24.3 (s, 4-CH2). 31P NMR (243 MHz,
7.33–7.16 (5H, m, Ar), 5.56 (1H, s, NH), 5.25–4.80 (2H m, 3-H), CDCl3) δ = −21.26 (s). M.p.: 120–121 °C. IR (diamond, νMAX
,
−
−
4.06 (1H, s, 1-H), 3.69 (1H, br s, NH), 1.63–1.32 (3H m, 3, 4-H), cm−1) 1433 (H–C–H st as), 1174 (–SO3 st as), 1041 (–SO3 st
0.81 (6H, s, 5, 6-H). 13C NMR (126 MHz, CDCl3) δ = 181.7 (2-C), sy). [α]2D2 = −50.4 (c = 1.0 in dichloromethane). Acc. Mass (FAB):
157.3 (9-C), 135.8 (11-C(Ar)), 128.4 (12, 14, 16-CH(Ar)), 128.1 C17H20NaNO3PS Found: 372.0803 m/z error [ppm]: −2.42 Cal-
(8-CF3), 127.8 (13, 15-CH(Ar)), 67.3 (10-CH2), 56.8 (1-CH), 40.8 culated: 372.0794 m/z.
(3-CH2), 24.6 (4-CH), 22.7 (6-CH3), 21.6 (5-CH3). M.p.:
(L)-(−)-2-[(Diphenylphosphino)methyl]pyrrolidine
(19).
51–53 °C. IR (diamond, νMAX, cm−1) 3393 (NH st), 2020 (Ar Deoxygenated 32% HCl (2 mL) was added to a round bottomed
comb), 1704, 1622 (CvO st amide), 1292 (CO–O st), 1181 (S–O flask containing (S)-2-((diphenylphosphino)methyl)pyrrol-
st as), 1124 (S–O st sy). [α]2D2 = 41.3 (c = 1.0 in dichloro- idine-1-sulfonic acid (100 mg, 0.30 mmol) under nitrogen and
methane). Acc. Mass (FAB): C15H19F3N2O5SNa Found: stirred for 16 h at 85 °C. After cooling, the reaction was neu-
419.0860 m/z error [ppm]: −0.26 Calculated: 419.0859 m/z.
tralized by a solution of potassium hydroxide to pH = 12 and
Triphenylphosphine gold N2-[(benzyloxy)carbonyl}-N1-[(tri- extracted with dichloromethane (3 × 7 mL). The reaction
fluoromethyl)sulfonyl]-(L)-leucinamide (3). Silver carbonate mixture was concentrated under reduced pressure to give the
(0.126 g, 0.46 mmol) was added to a solution of (S)-benzyl(4- title compound as a yellow oil (53 mg, 65%). All data are iden-
methyl-1-oxo-1-trifluoromethylsulfonamido)pentan-2-yl)carb- tical to those reported.33
amate (0.100 g, 0.25 mmol) in dichloromethane (C = 0.1 M,
2.52 mL) at 0 °C and stirred for 5 min. Triphenylphosphine-
gold chloride (0.125 g, 0.25 mmol) was added and the resul-
General procedure
tant mixture stirred for 2 days at 0 °C. The reaction mixture
5,8a-Dimethyl-7,8,8a,9,10,10a-hexahydroanthracen-1-ol (14).
was filtered through Celite and the solvent evaporated under (E)-2-(3-Methyloct-2-en-6-yn-1-yl)phenol (50 mg, 0.24 mmol)
reduced pressure to give the corresponding compound as a was placed in a flame dried round bottom flask under nitro-
pink solid (0.213 g, quantitative). 1H NMR (500 MHz, CDCl3) gen. The appropriate dry solvent (0.48 mL, 0.5 M) was added
δ = δ = 7.64–7.28 (20H, m, Ar), 5.16–4.97 (3H m, 10, 1-H), and the mixture stirred for around 2 minutes. The catalyst was
1.87–1.66 (2H m, 3, 4-H), 1.61–1.52 (1H m, 3-H), 0.86 (3H, d, added and the reaction mixture stirred for the appropriate
J = 6.5, 5-H), 0.73 (3H, d, J = 5.9, 6-H). 13C NMR (126 MHz, time at room temperature. The solvent was concentrated under
CDCl3) δ = 178.2 (2-C), 155.9 (9-C), 136.39 (s, Ar), 134.3 (s, Ar), reduced pressure. Purification by column chromatography
134.2 (s, Ar), 134.1 (s, Ar), 132.3 (s, Ar), 132.3 (s, Ar), 132.1 (s, ([99 : 1], cyclohexane–ethyl acetate) afforded the title com-
Ar), 132.0 (s, Ar), 131.9 (s, Ar), 131.9 (s, Ar), 131.57 (s, Ar), 129.5 pound as a pale yellow oil.
(s, Ar), 129.4 (s, Ar), 129.2 (s, Ar), 129.1 (s, Ar), 129.0 (s, Ar),
Methyl 1-acetyl-2-methylenecyclopentanecarboxylate (12a).
128.8 (s, Ar), 128.5 (s, Ar), 128.4 (s, Ar), 127.99 (s, Ar), 127.83 (s, Methyl 2-acetylhept-6-ynoate (50 mg, 0.27 mmol) was placed in
Ar), 127.48 (s, Ar), 127.35 (s, Ar), 124.29 (s, 8-CF), 121.71 (s, a dried round bottom flask under nitrogen. The appropriate
8-CF), 119.13 (s, 8-CF), 116.54 (s, 8-CF), 66.8 (10-CH2), 55.8 dry solvent (0.69 mL, 0.4 M) was added and the reaction
(1-CH), 43.0 (3-CH2), 24.7 (4-CH), 23.2 (6-CH3), 21.6 (5-CH3). mixture stirred for
2 minutes. The catalyst (16.5 mg,
31P NMR (161 MHz, CDCl3) δ = 31.1 (26%), 30.6 (74%). IR 0.014 mmol, 0.05 mol%) was added and the reaction mixture
(diamond, νMAX, cm−1) 3316 (NH st), 1982 (Ar comb), 1702 stirred for the appropriate time at the corresponding temp-
(CvO st amide), 1310 (CO–O st), 1180 (S–O st as), 1121 (S–O st erature. The solvent was concentrated under reduced pressure.
sy). [α]2D5 = 29.3 (c = 1.0 in dichloromethane). Acc. Mass (FAB): Purification by column chromatography ([99 : 1], cyclohexane–
C33H33AuF3N2O5PS Found: 877.1453 m/z error [ppm]: −10.85 ethyl acetate) afforded the title compound as a clear yellow oil.
Calculated: 877.1385 m/z.
Ethyl 1-benzoyl-2-methylenecyclopentanecarboxylate (12b).
(S)-2-((Diphenylphosphino)methyl)pyrrolidine-1-sulfonic acid. Ethyl 2-benzoylhept-6-ynoate (71 mg, 0.27 mmol) was placed
(S)-Hexahydropyrrolo[1,2-b]isothiazole 1,1-dioxide32 (0.850 g, in a flame dried round bottom flask under nitrogen. The ap-
5.21 mmol) was added to a solution of diphenylphosphine- propriate dry solvent (0.69 mL, 0.4 M) was added and the
lithium (5.21 mmol, C = 0.42 M) in dry tetrahydrofuran mixture stirred for 2 minutes. The catalyst was added and the
(12.4 mL). The reaction mixture was stirred for 3 h and reaction mixture stirred for the appropriate time at the corres-
quenched with 8 mL of water. The crude residue was extracted ponding temperature. The solvent was concentrated under
with dichloromethane (3 × 10 mL). The organic layers were reduced pressure. Purification by column chromatography
combined and concentrated under reduced pressure. Purifi- ([95 : 5], PET–ethyl acetate or diethyl ether) afforded the title
cation by column chromatography ([10 : 90], methanol– compound as a colourless oil (65 mg, 91%).
Dalton Trans.
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DOSY experiments
8 Modern Supramolecular Gold Chemistry: Gold-Metal Inter-
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600 equipped with an AutoX DB probe using the one-shot
sequence of Pelta et al. (M. D. Pelta, G. A. Morris,
M. J. Stchedroff and S. J. Hammond, A one-shot sequence for
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32 Transients were recorded per gradient point. The data were
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Gold complex 6a/6b (88.0 mg) was dissolved in 1,2-dibromo-
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experiments.
17 P. C. Healy, B. T. Loughrey, M. L. Williams and
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Gold complex 7 (58.5 mg) was dissolved in 1,2-dibromo-
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obtained (0.133 °C) was again taken as the average of three
experiments.
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Acknowledgements
22 D. Benitez, N. D. Shapiro, E. Tkatchouk, Y. Wang,
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23 B. N. Nguyen, L. A. Adrio, E. M. Barreiro, J. B. Brazier,
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Financial support from a Bader award is gratefully acknowl-
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Dr N. Tsoureas, Prof. M. Bagley and Prof. P.J. Parsons for
useful discussions, Prof. G. Cloke for providing access to a
high precision temperature probe and Dr Alaa Abdul Sadaa for
the Mass Spectrometry Service at the University of Sussex.
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This journal is © The Royal Society of Chemistry 2013
Dalton Trans.