New water soluble Pd-imidate complexes as highly efficient catalysts for the synthesis of C5-arylated pyrimidine nucleosides

Article abstract of DOI:10.1039/c4ra01326c

The direct reactions between the precursors trans-[Pd(imidate) ₂(SMe₂)₂] and 1,3,5-triaza-7-phosphaadamantane (PTA) yield new water-soluble palladium(ii) complexes trans-[Pd(imidate) ₂(PTA)₂](imidate

Full text of DOI:10.1039/c4ra01326c

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New water soluble Pd-imidate complexes as highly
efficient catalysts for the synthesis of C5-arylated
Cite this: RSC Adv., 2014, 4, 17567
pyrimidine nucleosides†
a
Anant Kapdi, Vijay Gayakhe,a Yogesh S. Sanghvi,b Joaquın Garcıa,c Pedro Lozano,d
*
´
´
e
f
f
*
Ivan da Silva, Jose Perez and J. Luis Serrano
´
´
The direct reactions between the precursors trans-[Pd(imidate)2(SMe2)2] and 1,3,5-triaza-7-
phosphaadamantane (PTA) yield new water-soluble palladium(II) complexes trans-
Received 14th February 2014
Accepted 31st March 2014
[Pd(imidate)2(PTA)2](imidate ¼ succinimidate (suc) 1, maleimidate (mal) 2, phthalimidate (phthal) 3 or
saccharinate (sacc) 4. The new complexes were revealed as excellent catalysts for environmentally
friendly, efficient Suzuki–Miyaura cross-coupling of synthetically challenging substrates like the antiviral
nucleoside analogue 5-iodo-20-deoxyuridine in water as solvent.
DOI: 10.1039/c4ra01326c
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strategies to perform Suzuki cross-coupling reactions in water
have been developed. The use of water-soluble palladium cata-
1. Introduction
lysts is one of those strategies that has attracted more atten-
tion,5,6 as might lead to an easy catalyst recovery by separating
the water phase and the organic coupled products.6h,7
Suzuki–Miyaura cross-coupling of aryl halides with aryl boronic
acids is one of the most important and industrially viable
reactions developed during the past century. This becomes
evident from the large amount of research devoted to it, which
has allowed the coupling of challenging substrates and
produced relevant building blocks in natural product synthesis
or pharmaceutical targets, among other elds.1 It was denitely
recognized when the shared 2010 Nobel Prize in Chemistry was
awarded to Suzuki for his contribution to the eld of C–C bond
formation using palladium catalysis.2 However, a major draw-
back from an environmental and economic perspective is the
use of toxic organic solvents in most of the aforementioned
catalytic transformations. Thus, Suzuki coupling has been fully
involved in the recent increasing interest of using water as a
solvent for many homogeneously catalyzed reactions.3 Since
Casalnuovo and Calabrese initial report in 1990,4 several
The use of water-soluble ligands to enhance the solubility in
water of transition metal complexes has been a common
approach to this eld. Among them, conveniently substituted
monodentated aryl phosphines or cage-like phosphines (as
phosphine, 1,3,5-triaza-7-phosphaadamantane: PTA that
enables the synthesis of water-soluble complexes without
introducing a charged species) have received continuous
attention.8 In fact, the coordination chemistry of PTA has been
mostly developed at the same time as the interest for environ-
mentally friendly catalysts. Halide complexes of the general
formula cis-[PdX2(PTA)2] (X ¼ Cl, Br, I) have played a relevant
role in the early development of Pd–TPA chemistry,8a,9,10 and
either themselves or used as precursors of new derivatives still
keep their relevance in this eld.8b,11–13 However to date there are
no reports on related complexes containing imidate ligands,
a variety of pseudohalides showing mixed s-donating and
p-accepting properties14 that in the course of our collaboration
with Fairlamb and co-workers have shown incredible potential
for cross-coupling reactions.15
aInstitute of Chemical Technology, Mumbai, Nathalal road, Matunga,
Mumbai-400019, India
bRasayan Inc. 2802, Crystal Ridge Road, Encinitas, California, 92024-6615, USA
c
´
´
Departamento de Quımic Inorganica, Regional Campus of International Excellence
“Campus Mare Nostrum” Universidad de Murcia, 30071 Murcia, Spain
Our most recent contribution to this eld has focused on the
use of trans-[Pd(PPh3)2(Saccharinate)2] as a general catalyst for
Suzuki–Miyaura, Negishi cross-coupling and C–H bond func-
tionalization of challenging substrates.16 The outstanding
performance of this complex encouraged us to synthesize the
water-soluble analogues of the type trans-[Pd(imidate)2(PTA)2]
reported here, that would allow us to explore the above
mentioned reactions in water. For this purpose we had available
the precursors trans-[Pd(imidate)2(SMe2)2]15i that provided a
straightforward route to the desired complexes. We present
d
´
´
´
Departamento de Bioquımica y Biologıa Molecular B eInmunologıa. Facultad de
´
Quımica, Regional Campus of International Excellence “Campus Mare Nostrum”,
Universidad de Murcia, 30071 Murcia, Spain
eISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK
fDepartamento de Ingenierıa Minera, Geologica
Politecnica de Cartagena. Area de Quımica Inorganica, Regional Campus of
International Excellence “Campus Mare Nostrum”, Universidad Politecnica de
´
´
´
y Cartograca. Universidad
´
´
´
´
´
Cartagena, 30203, Cartagena, Spain. E-mail: jose.serrano@upct.es
† Electronic supplementary information (ESI) available. CCDC 970233. For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4ra01326c
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here, together with the synthesis and characterization of the
new [Pd(imidate)2(PTA)2] complexes, a study of their ability/
recyclability to perform Suzuki–Miyaura cross-coupling reac-
tions of (hetero)aryl halides as well as 5-iodo-20-deoxyuridine
with differently substituted aryl boronic acids in water, under
milder conditions than previously reported.
2. Results and discussion
2.1. Synthesis and characterization
Fig. 1 ORTEP diagram of complex 4 with the atom numbering
scheme; thermal ellipsoids are drawn at the 50% probability level. H2O
found in the unit cell is not shown. Selected bond lengths (A˚) and
angles (ꢁ): Pd–N1: 2.027 A˚, Pd–N2: 2.048 A˚, Pd–P1: 2.320 A˚, Pd–P2:
2.290 A˚. Square planar coordination: N1–Pd–N2: 177.35ꢁ, P1–Pd–P2:
175.08ꢁ, N1–Pd–P1: 90.90ꢁ, N1–Pd–P2: 88.33ꢁ, N2–Pd–P1: 90.15ꢁ,
N2–Pd–P2: 90.42ꢁ.
The new complexes of general formula trans-[Pd(imida-
te)2(PTA)2] imidate ¼ succinimidate (suc) 1, maleimidate (mal)
2, phthalimidate (phthal) 3 or saccharinate (sacc) 4 are obtained
in high yields when PTA displaces the labile thioether ligands in
the precursors trans-[Pd(SMe2)2(imidate)2].15i,16 The insolubility
in water of such precursors prevented its use in this step,
although the use of the volatile SMe2 has been claimed to result
in cleaner products if compared with alternative routes.11 The
structures of the ligands employed, labelled with their abbre-
viations are shown in Scheme 1.
The new complexes have been fully characterized by
analytical and spectroscopic techniques, (Experimental
section) including a single crystal X-ray diffraction study of 4
that conrms the trans-geometry around the palladium centre.
The corresponding ORTEP drawing is shown in Fig. 1 with the
relevant bond lengths and angles. The structure around the
palladium atom may be described as nearly planar, and other
outstanding molecular features are the syn-conguration of
saccharinate ligands and the anti-conguration of TPA
ligands.
This conguration favours the most relevant supramolecular
interaction: C]O/H hydrogen bonds between both carbonyl
groups from one complex and hydrogen atoms in a saccharinate
ligand on the next molecule dening a R22 (11) ring (Fig. 2).
IR spectra displays characteristic strong carbonyl-imidato
absorptions nasim(C]O) in the 1675–1609 cmꢀ1 region, together
with weak bands at 1711–1724 cmꢀ1 attributed to nsim(C]O).
The incoming ligand PTA, that uncoordinated has infrared
absorptions at 452 and 405 cmꢀ1, displays typical bands that
appear shied downeld upon complexation.17 Good solubility
support for the proposed formula of the new complexes arises
from mass spectrometry, which shows fragments for the m/z
values corresponding to M+ and abundance of the signals
around the parent ions consistent with the natural isotopic
abundances.
2.2. Suzuki–Miyaura cross-coupling
At the outset of the initial studies, we tested several in situ and
preformed catalyst systems to optimise an efficient Suzuki–
Miyaura cross-coupling protocol for aryl bromides in water
(Scheme 2). It is worth mentioning that the precatalysts were
able to catalyse these transformations under mild conditions
in excellent yields (see ESI†). The water solubility of the
palladium catalyst offers an important advantage for catalyst
recycling,18 combined with the separation of the products
either by ltration or extraction with minimal amounts of
organic solvents. In order to explore the possibility of reusing
the aqueous solution containing the catalytically active
species, catalytic reactions between different aryl bromides
and aryl boronic acids were performed using precatalysts 4
(see ESI†).
The product obtained was isolated by extracting the
aqueous layer with ethyl acetate and then recharging the
reaction vessel containing the aqueous phase with fresh
substrates and base. Remarkably this catalytic solution was
1
of the new complexes in common solvents allowed its H- and
31P{1H}-NMR characterization (see Experimental section). The
latter singlet resonances of the complexes are shied to a higher
eld than those of the chloride derivatives and closer to previ-
ously reported thiolato Pd–PTA complexes.8,13 Additional
Scheme 1 Synthetic route for novel [Pd(imidate)2(PTA)2] complexes.
17568 | RSC Adv., 2014, 4, 17567–17572
Fig. 2 Crystal packing in 4.
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5-arylated product could be obtained in competitive reaction
times with the best result obtained at 80 ꢁC. Catalyst loading
experiments have also been performed on the catalytic system
with the catalyst 3 exhibiting good activity even at 0.1 mol%,
although longer reaction times were required. At 0.05 mol% the
reactivity reduced drastically, with similar trend observed at
0.01 mol% too. The isolation of the arylated nucleosides were
done by column chromatography using CH2Cl2–MeOH system.
However, given the toxic and the non-environmentally benign
nature of CH2Cl2, we decided to try other greener alternatives
for the chromatographic purication of nucleosides.23,24
Although, solvents such as methyl tert-butylether (MTBE),
2-methyl tetrahydrofuran (2-MeTHF) and ethyl acetate were
employed as the possible replacements, a poorer separation
coefficient (based on the Rf values in different solvents systems)
Scheme
2 Suzuki–Miyaura cross-coupling of aryl halides using
[Pd(imidate)2(PTA)2] complexes.
found to be active for ve consecutive runs without signicant suggest that CH2Cl2–MeOH system is best suited for the puri-
loss in activity. The EtOAc layer on extraction of products aer cation of these reactions.
1st, 4th and 5th recycle was analysed by Inductively Coupled
With the best conditions in hand we then explored the scope
Plasma Mass Spectrometry (ICP-MS) for any leaching of the for the Suzuki–Miyaura cross-coupling of 5-iodo-20-deoxyur-
palladium complex. No leaching of palladium complex was idine in water as solvent (Scheme 3). Electronic effects of the
observed (organic layer analysis aer 1st, 4th and 5th recycle) substituents on the aromatic ring played a crucial role in
even though there is drastic reduction in catalytic activity. deciding the reactivity of the catalytic system with the more
This could be attributed to the possible “salting out effect” of electron-rich coupling aryl boronic acids outperforming their
carbonate salts19 which reduces the water solubility of organic electron-poor counterparts. Synthetically challenging nucleo-
solutes also making the aqueous phase more viscous and less philic coupling partners such as naphthalene boronic acids
manageable for further use.
Nucleosides and their modication via metal-mediated
Table 1 Suzuki–Miyaura arylation of 5-iodo-20-deoxyuridinea,b
cross-coupling processes have attracted considerable attention
during the last decades due to their biological properties.
Palladium complexes have shown excellent reactivity towards
the modication of nucleosides containing purines or pyrimi-
dine series.20 Arylation of 5-halo-20-deoxyuridine has been
demonstrated consistently using palladium-catalysed Suzuki–
Miyaura or Stille cross-coupling reactions by several research
groups. However, most of these reactions have been performed
in organic solvents making the synthetic procedures environ-
mentally less attractive.21
Although some examples with water as the reaction solvent
for palladium-catalysed cross-coupling of 5-halo-20-deoxyur-
idine have been reported in literature, most of them however
suffer from less than satisfactory yields of the desired products,
and in certain cases higher reaction temperatures render the
conditions synthetically less feasible.22
Encouraged by the results mentioned above we decided to
employ the water soluble catalysts 1–4 towards developing an
efficient and environmentally feasible Suzuki–Miyaura protocol
for the synthesis of 5-arylated deoxyuridine analogs. It was
observed (Table 1) that complex 3 furnished the 5-arylated
nucleoside more efficiently than the rest of complexes in the
presence of triethylamine as base. The halide-containing
counterparts (entries 7–9, Table 1) of palladium complexes 1–4
as well as the in situ generated catalytic systems (entries 1 and 2,
Table 1) gave poor results towards the cross-coupling of 5-iodo-
2-deoxyuridine and aryl boronic acids. This result conrms the
ability of the water soluble palladium complexes to form the
product under mild conditions, although the reaction requires
longer time for completion. At elevated temperatures the
Temp.
(ꢁC)
Reaction time
(h)
%
Yield
No.
Complex
1
2
3
4
5
6
7
8
Pd(OAc)2
Pd(OAc)2/TPA
1
2
3
4
[PdCl2(TPA)2]
[PdBr2(TPA)2]
[PdI2(TPA)2]
3
3
3
3
3
3
3
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
60
80
100
80
80
80
48
48
48
48
48
48
48
48
48
8
6
4
15
24
48
48
29
40
66
68
75
72
35
48
21
78
92
82
72c
69d
51e
39f
9
10
11
12
13
14
15
16
80
a
Arylboronic acid (0.75 mmol), 5-iodo-20-deoxyuridine (0.5 mmol),
b
catalyst (1.0 mol%), 3 mL H2O, Et3N (1.0 mmol). Yields are isolated
c
yields. Instead of 1.0 mol% of catalyst, 0.5 mol% was employed.
d
e
Instead of 1.0 mol% of catalyst, 0.1 mol% was employed. Instead
f
of 1.0 mol% of catalyst, 0.05 mol% was employed. Instead of 1.0 mol
% of catalyst, 0.01 mol% was employed.
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3. Conclusions
The synthesis and characterization of new water soluble palla-
dium complexes 1–4 has been achieved. The precatalysts have
shown to efficiently catalyse Suzuki–Miyaura cross-coupling of
synthetically challenging substrates like the antiviral nucleoside
analogue 5-iodo-20-deoxyuridine and its cytidine analogue in
water as solvent under milder conditions and better yields that
previously reported. Catalyst loading could be reduced up to 0.1
mol% without any appreciable reduction in yields (although
reaction time increase drastically).
4. Experimental section
4.1. General remarks
C, H and N analyses were carried out with a Carlo Erba instru-
ment. IR spectra were recorded on a Perkin-Elmer spectropho-
tometer 16F PC FT-IR, using Nujol mulls between polyethylene
sheets. NMR data (1H or 31P) were recorded on BrukerAvance
300 or 400 spectrometers. HPCL-MS analyses were performed
on an Agilent VL mass spectrometer. The ionization mechanism
used was electrospray in positive and negative ion full scan
mode using acetonitrile as solvent and nitrogen gas for des-
olvation. ICP-MS analysis was performed on Thermo Fisher
Scientic, Germany (Model Element XR).
Imides and other commercially available chemicals were
Scheme 3 Scope study for Suzuki–Miyaura arylation of 5-iodo-20- purchased from Aldrich Chemical Co. and were used without
deoxyuridine. (a) Arylboronicacid (0.75 mmol), 5-iodo-20-deoxyuridine
(0.5 mmol), catalyst (1.0 mol%), 3 mL H2O, Et3N (1.0 mmol). (b) Yields
are isolated yields.
further purication, and all the solvents were dried by standard
methods before use.
4.2. Synthesis
furnished the 5-arylated nucleoside product in good yields,
however 2-methoxyphenyl boronic acid failed to give the desired
product in good yield probably due to steric factors. Several
other aryl boronic acids containing electron-withdrawing
groups also gave good yields of the 5-arylated 2-deoxyuridine
product.
Furthermore, to extend the scope of the developed protocol
we employed another synthetically important nucleoside, 5-
iodo-20-deoxycytidine towards cross-coupling with phenyl
boronic acid (Scheme 4). The solubility of this compound in
water is lower than that of the uridine analogue, and therefore
the reactivity towards cross-coupling with phenyl boronic acid
was found to be comparatively lower.
Preparation of complexes [trans-[Pd(imidate)2(PTA)2] imi-
date ¼ succinimidate (suc) 1, maleimidate (mal) 2, phthalimi-
date (phthal) 3 or saccharinate (sacc) 4. The complexes were
obtained by treating the appropriated precursor [Pd(imida-
te)2(SMe2)2] with neutral monodentated PTA (molar ratio 1 : 2)
in dichloromethane, according to the following general
method. To a dichloromethane (10 mL) solution of [Pd(imida-
te)2(SMe2)2] (0.100 g) was added the stoichiometric amount of
PTA (0.0736 g for 1; 0.0743 g for 2; 0.0601 g for 3; 0.0528 g for 4).
The solution was reuxed for 1 h, and then concentrated
until one third of the initial volume. The addition of diethyl
ether caused the precipitation of the title complexes, which
were isolated by ltration, washed with diethyl ether and
air-dried.
[Pd(succ)2(PTA)2] 1. Yield 0.129 g, 90%. Anal. calc. for
C
20H32N8O4P2Pd; C, 38.9; H, 5.2; N, 18.2. Found: C, 39.2; H, 5.3;
N, 18.3%. IR (Nujol) ꢀn ¼ 1711w, 1635vs, 1346s, 1234s, 1116s,
1102s, 974s, 943s, 669s, 526m, 452m, 390m cmꢀ1. HPLC-MS
(positive mode) m/z: 616 M+, 518 M+-succ, 361 M+-succ-PTA. 1H
NMR (300 MHz; CDCl3, 298 K, d): 4.42 (s, 12H, PTA); 4.14 (s,
12H, PTA); 2.71 (s, 8H, succ) ppm. 31P NMR (300 MHz; CDCl3,
298 K, d): ꢀ51.4 ppm.
Scheme 4 Scope study for Suzuki–Miyaura arylation of 5-iodo-20-
deoxycytidine. (a) Phenyl boronic acid (0.75 mmol), 5-iodo-20-deox-
ycytidine (0.5 mmol), catalyst (1.0 mol%), 3 mL H2O, Et3N (1.0 mmol).
(b) Yields are isolated yields.
[Pd(mal)2(PTA)2] 2. Yield 0.130 g, 90%. Anal. calc. for
C
20H28N8O4P2Pd; C, 39.2; H, 4.6; N, 18.3. Found: C, 39.3; H, 4.7;
N, 18.4%. IR (Nujol) ꢀn ¼ 1711w, 1635vs, 1340s, 1186s, 1097s,
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1012s, 970s, 942s, 694s, 526m, 455m, 392m cmꢀ1. HPLC-MS
(positive mode) m/z: 612 M+, 358 M+-mal-PTA. 1H NMR (300
MHz; CDCl3, 298 K, d): 6.68 (s, 4H, mal); 4.42 (s, 12H, PTA); 4.14
(s, 12H, PTA) ppm. 31P NMR (300 MHz; CDCl3, 298 K, d): ꢀ49.5
ppm.
4.4. Crystal structure determination of 4
Data collection for 4 were obtained at 100(2) K on a Bruker
Smart CCD diffractometer with a nominal crystal to detector
distance of 4.5 cm. Diffraction data were collected based on a u
scan run. A total of 2524 frames were collected at 0.3ꢁ intervals
and 10 s per frame. The diffraction frames were integrated using
the SAINT package25 and corrected for absorption with
SADABS.26 The structures were solved by direct methods27 and
rened by full-matrix least-squares techniques using aniso-
tropic thermal parameters for non-H atoms (Table 2).
[Pd(phthal)2(PTA)2] 3. Yield 0.117 g, 86%. Anal. calc. for
C
28H32N8O4P2Pd; C, 47.2; H, 4.5; N, 15.7. Found: C, 47.5; H, 4.6;
N, 15.9%. IR (Nujol) ꢀn ¼ 1724w, 1663vs, 1305s, 1183s, 1099s,
1013s, 971s, 943s, 681s, 457m, 392m cmꢀ1. HPLC-MS (positive
mode) m/z: 712 M+, 556 M+-phthal, 409 M+-phthal-PTA. 1H NMR
(300 MHz; CDCl3, 298 K, d): 7.74 (m, 4H, phthal); 7.61 (m, 4H,
phthal); 4.38 (s, 12H, PTA); 4.17 (s, 12H, PTA) ppm. 31P NMR
(300 MHz; CDCl3, 298 K, d): ꢀ49.7 ppm.
Acknowledgements
[Pd(sacc)2(PTA)2] 4. Yield 0.125 g, 95%. Anal. calc. for
´
´
We thank Fundacion Seneca (project 08670/PI/08) for nancial
support and Department of Science and Technology-India for
DST Inspire Faculty Award (IFA12-CH-22) for A. R. K. This work
was partially supported by CICYT-MICINN (CTQ 2011-28903-
C02).
C
26H32N8O6P2PdS2; C, 39.8; H, 4.1; N, 14.3. Found: C, 39.9; H,
4.3; N, 14.3%. IR (Nujol) ꢀn ¼ 1700w, 1675vs, 1593s, 1305s, 1252s,
1169s, 1014s, 972s, 942s, 679s, 526m, 456m, 392m cmꢀ1. HPLC-
MS (positive mode) m/z: 784 M+, 602 M+-sacc. 1H NMR (300
MHz; CDCl3, 298 K, d): 7.91 (m, 4H, sacc); 4.77 (m, 4H, sacc);
4.29–4.47 (m, 12H, PTA); 4.14 (s, 12H, PTA) ppm. 31P NMR (300
MHz; CDCl3, 298 K, d): ꢀ41.8 ppm.
Notes and references
1 (a) A. Suzuki, Angew. Chem., Int. Ed., 2011, 50, 6722; (b)
A. Suzuki and Y. Yamamoto, Chem. Lett., 2011, 40, 894; (c)
A. Fihri, M. Bouhrara, B. Nekoueishahraki, J.-M. Basset and
V. Polshettiwar, Chem. Soc. Rev., 2011, 40, 5181; (d)
A. Balanta, C. Godard and C. Claver, Chem. Soc. Rev., 2011,
40, 4973; (e) N. Miyaura and A. Suzuki, Chem. Rev., 1995,
95, 2457; (f) F. A. Littke and G. C. Fu, Angew. Chem., Int.
Ed., 2002, 41, 4176; (g) J. Dupont, C. S. Consorti and
J. Spencer, Chem. Rev., 2005, 105, 2527; (h) A. V. Gaikwad,
A. Holuigue, M. B. Thathagar, J. E. Elshof and
G. Rothenberg, Chem.–Eur. J., 2007, 13, 6908; (i)
J. D. Sellars and P. G. Steel, Chem. Soc. Rev., 2011, 40, 5170;
(j) A. Suzuki, in Metal-Catalyzed Cross-Coupling Reactions,
VCH, Weinheim, 1998; (k) A. Suzuki, J. Organomet. Chem.,
1999, 576, 147–168; (l) A. Zapf, in Transition Metals for
Organic Synthesis: Building Blocks and Fine Chemicals, Wiley-
VCH, Weinheim, 2004.
4.3. General procedure for Suzuki–Miyaura cross-coupling of
5-iodo-20-deoxyuridine or 5-iodo-20-deoxycytidinewith aryl
boronic acids
A solution of precatalyst 3 (0.005 mmol, 1.0 mol%) in
degassed H2O (1.0 mL) was stirred for 5 min at ambient
temperature under N2. Then, 5-iodo-20-deoxyuridine (177 mg,
0.5 mmol) was added and the solution stirred for 5 min at
80 ꢁC. Thereaer, phenyl boronic acid (90 mg, 0.75 mmol)
was added along with Et3N (1.0 mmol) and degassed ꢁwater
(2.0 mL). The resulting solution was then stirred at 80 C for
6.0 h. Aer the completion of reaction the solvent was
removed under vacuo and the resultant residue obtained was
puried using column chromatography in CH2Cl2–MeOH
solvent system (96 : 4) to afford the desired product as a white
solid (characterization of cross-coupled products is collected
as ESI†).
2 Nobel Prize official website, http://www.nobelprize.org/
nobel_prizes/chemistry/laureates/2010/.
Table 2 Crystal data and structure refinement for complex 4
3 (a) M.-O. Simon and C.-J. Li, Chem. Soc. Rev., 2012, 41, 1415;
(b) R. A. Sheldon, Chem. Soc. Rev., 2012, 41, 1437; (c)
M. Lamblin, L. Nassar-Hardy, J. C. Hierso, E. Fouquet and
F. X. Felpin, Adv. Synth. Catal., 2010, 352, 33; (d)
R. N. Butler and A. G. Coyne, Chem. Rev., 2010, 110, 6302;
(e) D. Dallinger and C. O. Kappe, Chem. Rev., 2007, 107,
2563; (f) R. A. Sheldon, Green Chem., 2005, 7, 267; (g)
D. Alonso and C. Najera, in Cross-Coupling and Heck
Reactions: Science of Synthesis: Water in organic Synthesis,
ed. S. Kobayashi, Thieme, Stuttgart, 2012.
4 A. L. Casalnuovo and J. C. Calabrese, J. Am. Chem. Soc., 1990,
112, 4324.
5 (a) N. Liu, Ch. Liu and Z. Jin, Green Chem., 2012, 14, 592; (b)
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references therein.
Formula
C26H32N8O6P2PdS2$1.5H2O
M
812.08
Hexagonal
P64
Crystal system
Space group
Z
6
˚
a/A
21.390(15)
12.812(13)
5077(6)
100
0.71073
0.823
˚
c/A
3
˚
V/A
T/K
˚
l/A
m/mmꢀ1
Reections collected
Independent reections
Goodness-of-t on F2
Final R indices [I > 2s(I)]
R indices (all data)
73 467
9152
0.890
0.0460
0.0617
1.407/ꢀ0.739
ꢀ3
˚
Max per min Dr [e A
]
This journal is © The Royal Society of Chemistry 2014
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17572 | RSC Adv., 2014, 4, 17567–17572
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