Chiral wide-bite-angle diphosphine ligands: Synthesis, coordination chemistry, and application in Pd-catalyzed allylic alkylation

Article abstract of DOI:10.1021/om5008055

A series of diphosphine ligands bearing ester- and ether-modified diphenylether backbones have been prepared. The introduction of carboxylic acid or ether auxiliaries in the ortho-positions relative to the diphenylphosphine groups was achieved via straigh

Full text of DOI:10.1021/om5008055

Article
pubs.acs.org/Organometallics
Chiral Wide-Bite-Angle Diphosphine Ligands: Synthesis,
Coordination Chemistry, and Application in Pd-Catalyzed Allylic
Alkylation
†
†
†
†
†
Christine F. Czauderna, Amanda G. Jarvis, Frank J. L. Heutz, David B. Cordes,
‡
,†
Alexandra M. Z. Slawin, Jarl Ivar van der Vlugt, and Paul C. J. Kamer*
†
EASTCHEM, School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9ST, United Kingdom
‡
van’t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
*
S Supporting Information
ABSTRACT: A series of diphosphine ligands bearing ester- and ether-
modified diphenylether backbones have been prepared. The introduc-
tion of carboxylic acid or ether auxiliaries in the ortho-positions relative
to the diphenylphosphine groups was achieved via straightforward four-
step synthetic protocols, prior to introduction of the phosphines. The
electronic properties of these backbone-modified DPEPhos ligands were
evaluated by probing the relevant carbonyl stretching frequencies (νCO
)
of Ni(CO) (PP) species (PP = diphosphine) using IR spectroscopy and
2
by determining the phosphorus−selenium coupling constant J
of
Se−P
3
1
1
phosphine selenide derivatives using P{ H} NMR spectroscopy. Also,
the X-ray structure for the bis(carbonyl)nickel(0) species with one of
3
the ligands is reported. The [Pd(η -allyl)(PP)] complexes were
characterized by multinuclear NMR spectroscopy and applied in the
asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate and
cyclohex-2-enyl acetate with dimethyl malonate in order to benchmark their catalytic potential. The enantioselectivity (ranging
from 3 to 70%) was found to depend on the size of the chiral auxiliary introduced within the diphenyl ether backbone and its
proximity to the phosphorus donor groups and hence to the active metal center.
INTRODUCTION
chiral auxiliary modification, as the backbone is more easily
subjected to alterations by organic transformations and displays
more flexibility compared to 9,9-dimethylxanthene. DPEPhos,
with a calculated natural bite angle of 102.9°, has displayed high
selectivity in a variety of reactions, including rhodium-catalyzed
■
Achiral diphosphorus ligands with a natural bite angle between
00 and 110° (i.e., wide-bite-angle ligands) have been found to
have a significant impact on the reactivity of various transition-
metal-catalyzed reactions, including Rh-catalyzed hydroformy-
lation and Pd-catalyzed allylic substitution. The correlation
between bite angle and selectivity has been studied systemati-
1
6
7
1
hydroformylation, palladium-catalyzed cross-couplings, and
2
allylic alkylation. The only chiral diphosphorus ligands based
on diphenyl ether as backbone carry either chiral auxiliaries at
cally using a specific series of the Xantphos ligand family (1−4,
8
,9
2
phosphorus
(7−9 in Figure 2) or possess stereogenic
Figure 1).
10
phosphorus atoms (10). The former systems have been
successfully applied in a number of asymmetric catalytic
transformations, including conjugate addition of arylboronic
acids, hydrogenation, allylic alkylation, hydrocyanation, and
Also in asymmetric catalysis, wide-bite-angle ligands such as
Duxantphos 5 have shown encouraging results with respect to
chemo-, regio-, and enantioselectivity. Chirality has been
introduced in wide-bite-angle diphosphine ligands mainly
through the use of chiral substituents on the phosphorus
3
,4
9
,11−13
hydroformylation.
Recent years have shown a growing interest in combining the
reactivity of transition metal complexes with the unrivalled
donors (5) and via the introduction of P-stereogenic centers
5
(
6). We herein discuss an unexplored approach to develop
14
selectivity of enzymes. So far, focus has mainly been on
anchoring strategies and genetic optimization, whereas rational
ligand design could also contribute to novel unnatural enzymes.
Lu et al. have shown that dual anchoring of artificial cofactors
could be very beneficial to the induced selectivity of a catalytic
new chiral wide-bite-angle diphosphine ligands, using chiral
backbones, with the aim to disclose potential new ligand classes
for asymmetric catalysis.
Concerning the choice of wide-bite-angle backbone, it can be
anticipated that chiral substituents have a higher impact toward
the active center of the catalyst when they are located at a
flexible backbone instead of a rigid backbone. Diphenyl ether
was selected as a promising candidate to assess this approach of
Received: August 5, 2014
©
XXXX American Chemical Society
A
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Figure 1. Examples of wide-bite-angle diphosphine ligands.
Figure 2. Chiral DPEPhos ligand 7, hybrid analogues 8 and 9 and P-stereogenic derivative 10.
1
5
reaction. Flexible wide-bite-angle ligands such as DPEPhos
are promising candidates for such an approach. Therefore, we
wanted to explore the effect and impact of dual chiral entities in
close proximity to wide-bite-angle bidentate phosphorus donor
centers in model structures.
Synthesis of DPEPhos Derivatives Bearing Chiral
Ether Side Groups. To install a chiral ether entity in the
backbone of DPEPhos, thereby generating novel chiral
diphosphines, the diphenyl ether skeleton could be coupled
with a chiral alcohol. (L)-Menthol was used as an example as it
is a cheap and commercially available reagent. 3,3′-Difluor-
odiphenyl ether 11F, obtained by Cu-catalyzed coupling of 3-
fluorophenol and 3-bromofluorobenzene as a colorless oil, was
reacted with L-menthol in the presence of NaH in
dimethylformamide (DMF) at 120 °C to yield product 12 as
an oil (see Scheme 1).
Altogether, the above considerations have resulted in a
modular design concept that is depicted in Figure 3. For the
Subsequent selective lithiation of both phenyl rings followed
by phosphorylation and in situ protection with BH gave the
3
air-stable diphosphine borane 13 after recrystallization from an
acetone/methanol mixture in high yield. Slow diffusion of
hexane into a concentrated diethyl ether solution of 13 resulted
in single crystals suitable for X-ray crystallographic analysis. The
molecular structure is shown in Figure 4, including relevant
bond distances and angles, and the absolute configuration of
the ligand was confirmed (Flack parameter 0.05(17)). As
expected from the free rotation of the C−O−C bond, the two
phenyl rings are not in one plane. The phosphorus atoms are
close to ideal tetrahedral geometry. The P−C bond lengths are
similar to those of other wide-bite-angle ligands such as
Figure 3. (Top) Schematic representation of the potentially modular
approach with modified chiral DPEPhos backbone through the
introduction of chiral carboxylic acid or alcohol auxiliaries in the
backbone.
6
Xantphos. The two BH3 groups are positioned inward,
modification of the diphenyl ether with chiral auxiliaries, alkoxy
as well as ester functionalities have been considered as chiral
entities. These groups have the advantage that they are easily
accessible from the chiral pool, starting from commercial chiral
carboxylic acids and alcohols. The novel wide-bite-angle
diphosphorus ligands have been evaluated in Pd-catalyzed
asymmetric allylic substition reactions. The influence of the
chiral auxiliaries on various transition metal complexes was
studied.
resulting in a large intramolecular distance between the two
phosphorus atoms (5.34 Å), which is larger than a P···P
16
distance of 4.876 Å in unprotected DPEPhos. The average
intramolecular P···O distance of 3.089 Å suggests that the
menthol substituents are too far away to show direct interaction
with the diphenylphosphine group, although this situation may
change upon coordination to a transition metal. Free
diphosphine 14 was obtained as a white solid on removal of
the BH protecting group by treatment of 13 with DABCO.
3
B
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Scheme 1. Synthetic Route to Ligand 14 Bearing Chiral Ether Auxiliaries in the DPE Backbone
(
Scheme 2). Subsequent selective lithiation of both phenyl
rings (ortho of the two oxygen substituents) followed by
phosphorylation by chlorodiphenylphosphine resulted in
compound 15 in 78% yield.
After slow addition of an excess of BBr to a solution of
3
3
1
1
species 15 in CH Cl and subsequent hydrolysis, the P{ H}
2
2
NMR spectrum indicated full conversion of the starting
material after 6 h of reaction. However, isolation of this
species, presumably structure 16, in pure form proved to be
very difficult, and as a consequence, this compound was used
without further purification for the introduction of chiral ester
fragments. After careful optimization of the reaction conditions,
and by using different commercially available carboxylic acids, a
prototypical achiral (17a) and three chiral ligands (17b−d)
were accessible. The products were obtained in good yields
after crystallization from methanol or by flash filtration over
silica gel.
Figure 4. ORTEP representation of compound 13. Displacement
ellipsoids are drawn at the 50% probability level. All hydrogen atoms
and carbon atoms of the phenyl rings at the phosphorus atoms are
omitted for clarity. Selected bond lengths (Å) and angles (deg): P −
1
C
1.829(10); P −C 1.812(10); P −B 1.940(18); P −B
1
2
31
1
1
2
31
1
.917(19); P ···P 5.34; P ···O1 3.132(8); P ···O3 3.045(8); C −
1
1
2
1
2
13
P −B 105.0(6); C −P −B 103.6(6); C −P −C 106.4(5); C −
P −C 107.1(5); C −O −C 117.4(7).
1
43
2
31
1
1
7
31
Electronic Properties of the Ligands. The σ-donation
can be assessed by measuring the coupling constant of the
corresponding phosphine selenide species, observable by
2
37
6
2
32
Synthesis of DPEPhos Derivatives Bearing Chiral Ester
31
1
17,18
P{ H} NMR spectroscopy.
To estimate the σ-donation
Auxiliaries. As an alternative to the ether functionalization, a
chiral ester entity can also be introduced in the backbone of
DPEPhos. Cheap and commercially available carboxylic acids
give access to a series of different new chiral ligands. As the
starting point, the same diphenyl ether backbone bearing two
methoxy groups (11OMe) (vide supra) was employed
abilities of the new ligands, the corresponding diselenides were
synthesized by treating the diphosphines with elemental
selenium in refluxing chloroform. For the chiral-ether-modified
1
backbones, the phosphorus−selenium coupling constant J
P−Se
was 740 Hz, while for the ester derivatives, a value of 750 Hz
Scheme 2. Synthetic Route to Members of the New Chiral DPEPhos Ligand Family (17a−d)
C
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Table 2. IR and 31P{ H} NMR Data of [Ni(L)(CO) ] of
1
was found (Table 1). These values are only slightly higher than
that for the parent DPEPhos system ( JP−Se 734 Hz).
2
1
19
a
Selected Modified DPEPhos Ligands and Parent DPEPhos
Table 1. Corresponding Diselenides of the Modified
a
DPEPhos Ligands and Parent DPEPhos
a
31
1
P{ H} NMR: 161 MHz, CDCl , 297 K
3
a
31
1
P{ H} NMR: 161 MHz, CDCl , 297 K
3
Therefore, comparable σ-donation abilities of the modified
ligands can be expected compared to DPEPhos.
The degree of ligand π-acceptor character can be probed by
measuring the carbonyl stretching frequencies of Ni(L )-
x
20
(
CO)4−x complexes with IR spectroscopy. This methodology
has primarily been utilized to assess the electronic properties of
monodentate phosphorus ligands, although also some
2
1
Ni(L)(CO) complexes with diphosphine systems have been
2
2
0
reported. The nickel−carbonyl complexes are easily prepared
by reaction of the respective ligand with [Ni(CO) (PPh ) ].
2
3 2
The corresponding DPEPhos-derived Ni complex was also
investigated for comparison as no literature data for this
compound were available. The carbonyl frequencies (νCO) are
summarized in Table 2. It is evident that chiral modification of
the ligand skeleton infers significant electronic differences (of
Figure 5. ORTEP representation of complex 21, Ni(15)(CO) .
2
Displacement ellipsoids are drawn at the 50% probability level. All
hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Ni −P 2.253(2); Ni −P 2.254(2); P −C 1.848(6);
1
1
1
2
1
13
P −C 1.844(7); Ni −C 1.856(8); Ni −C 1.819(9); P ···P 3.67;
2
20
1
41
1
40
1
2
P −Ni −P 109.32(8); P −Ni −C 107.3(2); P −Ni −C
−1
21
1
1
2
1
1
41
2
1
40
up to 25 cm ) in the frameworks compared to DPEPhos.
1
05.06(3); Ni −C −O 176.0(8); Ni −C −O 173.9(8).
1
40
40
1
41
41
Besides the information gathered from the IR spectroscopic
study on these nickel−carbonyl complexes, an X-ray crystallo-
graphic analysis of single crystals of complex 21, Ni(15)(CO) ,
The cationic Pd allyl complex of 15 (22) was prepared by
2
3
obtained by slow diffusion of diethyl ether into a CH Cl2
reaction with [Pd(η -allyl)(Cl)] using 2 molar equiv of 15,
2
2
solution, provided the molecular structure depicted in Figure 5.
The Ni center has a tetrahedral geometry, as expected, with a
followed by chloride abstraction using NH PF . Single crystals
4
6
0
3
of complex 22 ([Pd(η -allyl)(15)]PF ) were obtained by slow
6
P −Ni −P bite angle of 109.32(8)°.
diffusion of hexane into a saturated dichloromethane (DCM)
solution (see Figure 6 for molecular structure). Both intra- and
intermolecular π−π interactions between the phenyl rings
1
1
2
Coordination Behavior to Pt and Pd. The natural bite
6
angle of PdCl (DPEPhos) was calculated to be 102.9°, and the
2
1
platinum−phosphorus coupling constant J
of 3795 Hz,
(both from the backbone and PPh fragments) are observed in
Pt−P
2
observable by 31P{ H} NMR spectroscopy, for the related
1
the unit cell. The bite angle P −Pd−P (β of 106.62(9)°) is
1
2
square-planar species PtCl (DPEPhos) indicates cis-coordina-
slightly larger than that in the complex [(DPEPhos)Pd(1,1-
2
7
3
22
tion of the diphosphine ligand. To assess the structural
(CH ) -η -allyl)] (β = 103.93°). The Pd−P bond lengths are
3
2
similarity with the modified diphenyl ether ligands, the
in the same range as found previously for [(DPEPhos)Pd(1,1-
3
23 24
corresponding [PtCl (L)] complexes were synthesized by
(CH ) -η -allyl)] and [(tcne)Pd(DPEPhos)]. The allyl
2
3 2
reaction of PtCl (MeCN) with the chiral diphosphines. All
moiety is coordinated in almost symmetric fashion to the Pd
2
2
1
complexes showed similar large coupling constants J
center, as reflected by the Pd−C bond lengths (Pd −C
Pt−P
1
39
(
(
between 3858 and 3877 Hz), comparable with DPEPhos
Table 3). These coupling constants indicate cis-coordination
2.191(16); Pd −C 2.09(2); Pd −C 2.206(14) Å) similar
1
40
1
41
3
25
to the Pd−C distances reported for [Pd(η -allyl)(μ-Cl)] .
2
of the ligands in the square-planar Pt complex. In the case of
5, the trans-compound was also observed.
There are two independent molecules in the monoclinic
1
asymmetric unit cell (space group P1 /1).
n
D
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Table 3. 31P{ H} NMR Data of PtCl (L) Complexes Using
1
and II in Figure 7) interconvert via either a formal π-rotation or
22
2
a
3
1
3
Selected DPEPhos Analogues
a π−σ isomerization involving an η −η −η process.
Alternatively, the chemical shifts of the anti and syn protons
may overlap. Ligand 17b only bears a small stereogenic group,
that is, the (S)-methylpropyl moiety, compared to the larger
groups on the other chiral ligands, which may account for the
difference if an isomerization process is expected.
Catalysis. The palladium-catalyzed asymmetric allylic
26
substitution is a widely studied benchmark reaction, which
provides a good indication for ligand performance with respect
to chiral induction. The novel chiral ligands were studied in the
asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate
and cyclohexyl-2-enyl acetate with dimethyl malonate as
nucleophile. The catalysis was carried out in CH Cl at room
2
2
temperature for 20 h (full conversion) under argon atmosphere
and in the presence of bis(trimethylsilyl)acetamide (BSA) as
27
base. The results are summarized in Figure 8.
In the case of the chiral-ester-modified DPEPhos, the
enantioselectivity for both substrates increased with increasing
steric bulk of the chiral auxiliary. Ligand 17dwith naproxen
as the chiral moietyshowed the highest enantioselectivity of
the ester-modified DPEPhos class of ligands. Small chiral
groups, such as found in 17b, induced only low levels of
enantioselectivity. When comparing the ester- and ether-
modified DPEPhos systems, the menthol-derived ether
derivative (14) led to the highest enantioselectivity for both
substrates. This is likely due to closer proximity of the chiral
auxiliary group to the phosphorus atoms, hence giving more
chiral induction onto the catalytic metal center. Although state-
of-the-art asymmetric induction for this reaction provides
a
Reactions performed at room temperature in dichloromethane/
MeCN overnight. 3 P{ H} NMR: 161 MHz, CDCl , 297 K.
1
1
3
28
enantioselectivities over 95%, the levels of enantioselectivity
achieved under standard conditions with the novel ligand
systems were promising. Further optimization of the catalytic
efficiency was undertaken, and decreasing the reaction
temperature to 10 °C led to 68% ee, while performing the
reaction at 4 °C even resulted in 70% ee, albeit at the expense
of a lower conversion (33% after 20 h). The choice of reaction
medium had little effect on the enantioselectivity, as polar
solvents like MeCN, tetrahydrofuran (THF), DMF, or 1,4-
dioxane gave comparable results to DCM (64−68% ee) at 20
Figure 6. ORTEP representation for one of the two molecules in the
3
asymmetric unit cell of complex 22, [Pd(η -allyl)(15)]PF . Displace-
6
ment ellipsoids are drawn at the 50% probability level. The PF anion
6
is omitted for clarity. Selected approximate bond lengths (Å) and
°
C.
angles (deg): Pd −P 2.321(3); Pd −P 2.349(3); Pd −C
1
1
1
2
1
39
2
1
.191(16); Pd −C 2.09(2); Pd −C 2.206(14); P −Pd −P
1
40
1
41
1
1
2
SUMMARY AND CONCLUSION
06.62(9); C −Pd −C 67.4(6); P −Pd −C 90.6(5); P −Pd −
39
1
41
1
1
39
2
1
■
C3 161.8(5).
9
By introduction of chiral ether or ester substituents in the 3,3′-
positions of diphenyl ether and subsequent phosphorylation at
the 2,2′-positions using tailor-made synthetic procedures, a
small series of new wide-bite-angle ligands related to DPEPhos
have been realized. The chiral ether needed to be installed
before phosphorylation, in contrast to the ester groups. The
latter could be introduced in the final step, which might prove
more powerful for the construction of larger ligand libraries,
using commercially available chiral carboxylic acids. NMR and
IR spectroscopic investigations on Ni-carbonyl and selenide
derivatives of these compounds showed little influence on the
electronic character of the P donor atoms compared to
nonsubstituted (parent) DPEPhos. Coordination to Pt(II)
occurred in a cis-fashion, according to the large coupling
The coordination behavior of the related ligands to Pd was
3
+
also probed via the corresponding cationic [Pd(η -allyl)(L)]
1
31
1
species. The reactions were followed by H NMR and P{ H}
NMR spectroscopy, and the results are summarized in Table 4.
In the case of achiral ligands 15 and 17a, the NMR analysis
of the Pd complexes is as expected, showing singlets in the
3
1
1
P{ H} NMR and one signal for each of the allyl-related
protons (H , H , and H ). The Pd allyl complexes of the chiral
1
2
3
ligands 14, 17b, 17c, and 17d display an AB system in the
3
1
1
P{ H} NMR, indicating magnetic inequivalence of the two
phosphorus atoms, due to the C -symmetry of the phosphine.
2
The inequivalence of the phosphorus atoms leads to the
observation of two sets of signals for the terminal (H and H )
constants of PtCl L complexes (between 3858 and 3877 Hz).
In Pd-allyl complexes, larger substituents on the ligand
1
3
2
1
allylic protons in the H NMR spectrum, giving five signals
overall for all of the chiral ligands except ligand 17b. In this
case, the H and H protons appear as a single signal each,
backbone result in larger chemical shift differences for the
3
allyl protons in [Pd(η -allyl)(L)]X complexes. The molecular
1
3
which can be attributed to flipping of the allyl fragment, which
can adopt two orientations. The resulting isomers (species I
structures of complex 21, Ni(15)(CO) , revealed no
interaction of the substituents with the metal center.
2
E
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Table 4. NMR Spectroscopic Data for Selected [PdCl (L)] Complexes of the Modified DPEPhos Ligands
Article
+
a
2
a
1
31
1
Reactions were carried out at room temperature in CH Cl /MeCN overnight. H NMR: 400 MHz, CDCl , 297 K. P{ H} NMR: 161 MHz,
2
2
3
CDCl , 297 K.
3
3
Figure 7. Interconversion of the [Pd(η -allyl)(L)]X isomers I and II.
Application of these novel ligands in Pd-catalyzed asymmetric
allylic substitution reactions showed a dependency of the
enantioselectivity on the size of the stereogenic center and its
proximity to the phosphorus moiety. For future applications,
we envision the use of these functionalized ligand backbone
structures in enantioselective catalysis via noncovalent secon-
dary interactions of ligands and substrates, mimicking the
behavior of enzymes. Although the enantioselectivity
displayed by these novel ligands is still modest, the effect of
small changes in sterics is such that the combination of ligand
design and protein interactions seems really promising.
analysis was performed using silica F254 TLC plates from VWR.
Silica gel 60 (0.063−0.2 mm; Fluka) was used for flash
chromatography. Melting points were determined on a Gallenkamp
1
13
31
MF-370 melting point apparatus in open capillaries. H, C, and
spectra were measured on a Bruker Advance II 400, a Bruker Advance
00, or a Bruker Ascend 500 NMR spectrometer. CDCl was distilled
P
3
3
over CaH and stored over K CO under argon. Other deuterated
2
2
3
solvents were degassed by three freeze−pump−thaw cycles. Mass
spectra were collected using a Micromass GC mass spectrometer or a
Thermo Scientific DSQ II single quadrupole GC/MS spectrometer. IR
spectra were taken on an AVATAR E.S.P. 360 FTIR spectrometer.
1
4
29
Propionyl chloride was prepared according to a literature procedure.
The esterification was carried out under conditions similar to those
3
0
described in literature.
General Procedure for Copper-Catalyzed C−O Coupling To
Form Diphenylethers 11X (X = OMe, F). Cs CO (2 equiv) was
EXPERIMENTAL SECTION
General Methods. All reactions were carried out using standard
Schlenk techniques under an atmosphere of purified argon. Toluene
■
2
3
added to a solution of phenol (1 equiv) in NMP in a Schlenk flask that
was subsequently evacuated and backfilled with argon three times. Aryl
halide (1 equiv), ligand (5 mol %), and metal precursor (2.5 mol %)
were added successively. The flask was evacuated and backfilled with
argon three times again. Then the reaction mixture was heated to 120
°C under argon. The reaction was monitored by GC/MS and TLC.
After complete conversion of aryl halide, the reaction mixture was
allowed to cool to room temperature and diluted with methyl-tert-
butyl ether (MTBE). The solution was filtered (glass frit, Por. 3), and
was distilled from sodium, THF, and Et O from sodium/
2
benzophenone, hexane from sodium/benzophenone/triglyme, meth-
anol and ethanol from magnesium, and DCM from CaH under an
2
argon atmosphere. N-Methyl-2-pyrrolidone (NMP) over molecular
sieves was purchased from Fluka. Chemicals were purchased from
Acros Organics, Sigma-Aldrich, and Alfa Aesar. For the phosphine
synthesis, the washing solutions (water, brine) were degassed by three
freeze−pump−thaw cycles. Thin-layer chromatography (TLC)
F
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Figure 8. Palladium-catalyzed allylic alkylation of rac-l,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate in CH Cl . Reaction conditions:
2
2
3
L/Pd(η -allyl)Cl ] = 2:1, [S]/[C] = 100, 0.1 mmol substrate (rac-l,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate), 1 mL of CH Cl ,
2
2
2
2
20 °C, 0.3 mmol of dimethyl malonate, 0.3 mmol of N,O-bis(trimethylsilyl)acetamide (BSA) and a catalytic amount of KOAc.
the filter cake was washed with MTBE. The combined organic phases
were washed with 2 M HCl, 0.6 M HCl, 2 M NaOH, and brine. After
the organic phase was dried over MgSO4 and evaporated under
reduced pressure (rotary evaporator), the crude product was purified
by crystallization, distillation, or column chromatography.
solution of (L)-menthol (16.68 g, 106.8 mmol) in DMF (70 mL, dry)
(strong effervescence). The reaction mixture was slowly warmed to
room temperature and stirred for 30 min. The conversion was checked
by a deuterium exchange in the GC/MS. After full deprotonation, 11F
(5.5 g, 26.69 mmol) in DMF (20 mL) was slowly added to the
reaction via a cannula. The reaction mixture was stirred at 120 °C for
48 h. The reaction mixture was cooled to room temperature, diluted
with dichloromethane (100 mL), and washed with water and brine.
Di(3-methoxyphenyl)ether 11OMe. Modified literature proce-
31
dure: 3-iodoanisole (1.78 mL, 15 mmol), 3-methoxyphenol (3.29
mL, 30 mmol), Cs CO (9.77 g, 30 mmol), 2,2,6,6,-tetramethylhepta-
2
3
3,5-dione (0.276 g, 1.5 mmol), and CuCl (0.074 g, 0.75 mmol) in
The organic phase was dried with MgSO , and the solvent was
4
NMP (50 mL) were used. The crude product was purified by column
evaporated at reduced pressure. Compound 12 was purified by column
chromatography (silica gel, eluent from 100% PE to 97.5% PE + 2.5%
AcOEt). 11OMe was obtained as colorless oil (2.934 g, 85%). H
chromatography (silica gel, hexane/ethyl acetate (2%)) and obtained
1
1
as highly viscous clear oil (8.71 g, 68%). H NMR (400 MHz, CD
Cl
,
2
2
3
NMR (400 MHz, CD Cl , 295 K): δ (ppm) 7.22−7.20 (m, 2H),
296 K): δ (ppm) 7.19 (t, 2H; JHH = 8.1 Hz), 6.66−6.53 (6H, m), 4.02
2
2
13
1
6
(
.68−6.65 (m, 2H), 6.60−6.58 (m, 4H), 3.76 (s, 6H). C{ H} NMR
75 MHz, CD Cl , 297 K): δ (ppm) 161.49, 158.67, 130.52, 111.38,
(m, 2H), 2.20−2.13 (m, 4H), 1.73−1.68 (m, 4H), 1.53−1.43 (m, 4H),
3
13
1
1.17−1.04 (m, 18H), 0.76 (d, 6H, JHH = 6.96 Hz). C{ H} NMR
2
2
1
09.36, 105.38, 55.71. GC-MS (m/z (EI), rel. intensity): 230. Mass
(101 MHz, CD
110.91, 106.89, 77.91, 48.46, 40.60, 34.83, 31.70, 26.51, 24.05, 22.26,
20.8, 16.73. Mass (TOF-MS ESI+) m/z calcd for [C32
+ Na]+
501.3345 (M + Na) , observed 501.3329 (M + Na) . GC/MS: m/z
2 2
Cl , 295 K): δ (ppm) 160.2, 158.6, 130.4, 110.98,
+
+
(
TOF MS ESI+) m/z calcd for [C H O + H] 231.1021 [M + H] ,
14 14
+
observed 231.1023 [M + H] .
H O
46 3
3
2
+
+
Di(3-fluorophenyl)ether 11F. Modified literature procedure: 1-
+
bromo-3-fluorobenzene (30.8 mL, 0.276 mol), 3-fluorophenol (50 mL,
calcd for [C32H O ] 478.7 (M) , observed 478.2 (9.38 min, 50−320
46 3
0
.552 mol), Cs CO (180 g, 0.552 mol), 2,2,6,6,-tetramethylhepta-3,5-
°C, flow = 20, helium).
2
3
dione (5.75 mL, 27 mmol), and CuCl (1.36 g, 13.8 mmol) in NMP
200 mL) were used. The crude product was purified by column
chromatography (silica gel, eluent from 100% PE to 97.5% PE + 2.5%
Bis(2-diphenylphosphino-3-menthoxy)phenyl)ether 13.
TMEDA (0.83 g, 1.1 mL, 7.18 mmol) was added to a solution of
12 (1.560 g, 3.26 mmol) in diethyl ether (50 mL) via syringe. The
solution was stirred for 15 min at room temperature and cooled to
(
AcOEt). 11F was obtained as a colorless oil (36.56 g, 64%) that was
1
n
used without further purification. H NMR (500 MHz, CD Cl , 296
−78 °C. A 1.6 M BuLi hexane solution (2.9 mL, 7.2 mmol) was
2
2
13
1
K): δ (ppm) 7.35−7.27 (m, 2H), 6.89−6.74 (m, 6H). C{ H} NMR
126 MHz, CD Cl , 295 K): δ (ppm) 163.9 (d, J = 246 Hz), 158.3
d, J = 10.5 Hz), 131.2 (d, J = 9.9 Hz), 115.1 (d, J = 3.1 Hz),
11.0 (d, J = 21.3 Hz), 107.1 (d, J = 24.4 Hz). F{ H} NMR
added slowly while maintaining the temperature at −78 °C. The
1
(
(
1
reaction mixture was allowed to warm to room temperature over 8 h.
2
2
CF
3
2
3
The reaction was followed by GC/MS of a sample quenched by D O
CF
CF
CF
19 1
2
1
1
in THF. Chlorodiphenylphosphine (1.17 mL, 6.52 mmol) was added
dropwise to the reaction mixture at −78 °C, and the reaction mixture
was allowed to warm slowly to room temperature over 20 h. A white
precipitate was formed. The reaction mixture was quenched with 5 mL
of methanol and evaporated to dryness. The precipitate was
azeotropically dried with toluene (2 × 3 mL) and suspended in 50
mL of THF. BH ·SMe in THF (2.5 M, 2.5 mL, 5 mmol) was added
CF
CF
(
282 MHz, CD Cl , 295 K): δ (ppm) 111.2 (s). Mass (TOF MS CI+)
2 2
+
+
m/z calcd for [C H F O + H] 207.0621 (M + H) , observed
1
2
8 2
+
2
07.0624 (M + H) .
S, S , R ) - 3 , 3 ′ -O x yb i s(( (1 S , 2 R , 5S ) - 2 - i s o p r o p y l - 5 -
methylcyclohexyl)oxy)benzene) 12. A suspension of NaH (3.2 g,
33.3 mmol) in DMF (30 mL, dry) was added slowly at 0 °C to a
(
1
3
2
G
DOI: 10.1021/om5008055
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
107.10, 55.78. 31P{ H} NMR (161 MHz, CD Cl , 296 K): δ (ppm)
1
to the suspension. The reaction mixture was stirred overnight before
the solvent was removed under high vacuum. The resulting precipitate
was dissolved in dichloromethane (50 mL) and washed with water (50
mL). The aqueous layer was extracted three times with dichloro-
methane. The combined organic layers were washed with brine and
2 2
−23.82. Mp: 177 °C (decomp.). Mass (FD MS+) m/z calcd for
+
+
[C H O P + H] 599.1894 [M + H] , observed 599.1899 [M +
3
8
32
3 2
+
−1
H] . FT-IR (ATR mode, solid, selected peaks) ν (cm ) 3064−2933
(C−H), 1582, 1561, 1481, 1457, 1424, 1264, 1235, 1179, 1087 (C−
O−C), 1067, 1052, 1026, 798, 776, 737, 721, 692. Anal. Calcd for
C H O P : C, 76.25; H, 5.39. Found: C, 76.10; H, 5.47.
dried over MgSO , and the solvent was evaporated under vacuum. The
4
resulting white precipitate was purified by column chromatography
38
32
3 2
(
silica gel, diethyl ether/hexane (1:20 to 1:10, crude product was
impregnated on silica gel, diameter = 5 cm, length = 25 cm). Yield of
3: 1.74 g = 61%. Alternatively, the crude reaction mixture was
Bis(2-diphenylphosphino-3-hydroxy)phenyl)ether 16. A sol-
ution of BBr (1.927 mL, 20 mmol) in dry DCM (8 mL) was added
3
1
dropwise to a solution of 15 (962 mg, 2 mmol) in dry DCM (25 mL)
at −78 °C. The reaction mixture was allowed to warm to room
temperature and was stirred for 20 h. After full conversion of the
1
purified by or precipitation from methanol/acetone in good yields. H
NMR (400 MHz, CD Cl , 296 K): δ (ppm) 7.56−7.23 (m, 18H),
7
2
2
.12−7.08 (m, 4H), 6.63−6.69 (m, 2H), 6.43−6.40 (m, 2H), 3.98−
.89 (m, 2H), 1.82−1.79 (m, 2H), 1.55−0.47 (m, 38H), 0.18 (q, 2H;
starting material, the excess BBr and DCM were evaporated and the
3
3
solid was co-evaporated with toluene (3 × 2 mL). The mixture was
quenched with ice-cold water (20 mL), and after phase separation, the
aqueous phase was extracted with DCM (3 × 20 mL). The combined
organic phases were subsequently washed with water (30 mL) and
3
13
1
J
= 11.24 Hz). C{ H} NMR (101 MHz, CD Cl , 296 K): δ
HH
2 2
(
3
(
ppm) 162.21, 160.64, 133.91−128.07, 113.47, 107.39, 77.07, 46.48,
7.84, 34.53, 31.55, 24.64, 22.82, 22.06, 20.96, 15.29. 31P{ H} NMR
161 MHz, CD Cl , 296 K): δ (ppm) 12.28 (s). Mass (TOF-MS ESI
1
brine (30 mL) and dried over MgSO . Compound 16 was obtained in
2
2
4
10
+
+
31
1
+
) m/z calcd for [C H B O P + NH ] 890.5402 (M + NH ) ,
quantitative yield and was used without further purification. P{ H}
56
70
2
3
2
4
4
+
observed 890.5397 (M + NH ) . Mp 153 °C (decomp.). Anal. Calcd
for C H B O P : C, 76.89; H, 8.07. Found: C, 76.84; H, 8.14.
NMR (400 MHz, CDCl , 294.8 K): δ (ppm) −34.79 (s).
4
3
Bis(2-diphenylphosphino-3-propionyl)phenyl)ether 17a. A
solution of 16 (3.06 g, 5.3 mmol), propionic acid (0.830 mL, 11.13
mmol), and 4-dimethylaminopyridine (DMAP) (0.123 g, 1.0 mmol)
in DCM (3 mL) was added to a solution of EDC·HCl (2.84 g, 14.8
mmol) and N,N-diisopropylethylamine (0.2.59 mL, 14.8 mmol) in
DCM (150 mL) at 0 °C. The reaction was allowed to warm to room
56
70
2
3 2
Removal of BH from 3 with DABCO To Yield 14. DABCO
3
(
1.00 g, 8.9 mmol) in toluene was added to a solution of 13 (1.560 g,
3
.26 mmol) in toluene (50 mL) via cannula at room temperature. The
solution was stirred at 50 °C overnight. The reaction mixture was
followed by phosphorus NMR for completion. After complete
reaction, the solvent was evaporated under vacuum. The white
precipitate was purified by a short filtration over silica gel (100%
DCM) to give a crude product that was used directly in subsequent
3
1
1
temperature, stirred for 20 h, and monitored by P{ H} NMR
spectroscopy. After complete reaction, the reaction mixture was
diluted with DCM and extracted with 10% aqueous HCl and water.
The organic layer was dried over Na SO , concentrated, and purified
1
steps without further purification. H NMR (400 MHz, CD Cl , 296
2
2
2
4
3
1
K): δ (ppm) 7.34−7.13 (m, 22H), 6.59 (d, 2H; J = 8.4 Hz), 6.19
by crystallization from methanol (1.88 g, 56%). H NMR (400 MHz,
HH
3
3
3
3
(
dd, 2H; J = 8.0 Hz, J = 3.1 Hz), 3.92 (td, 2H, J = 10.4, 4.0
CD Cl , 297 K): δ (ppm) 7.28−7.15 (m, 22H), 6.76 (ddd, 2H; J
=
HH
HP
HH
2
2
HH
4
4
3
4
Hz), 1.83−1.76 (m, 2H), 1.64−1.40 (m, 6H), 1.34−1.21 (m, 2H),
1
8.1, J = 1.75 J = 1.05 Hz), 6.16 (ddd, 2H; J = 8.1, J = 2.5,
HP HH HH HP
3
4
3
3
.03−0.82 (m, 4H), 0.76 (d, 6H, J = 6.5 Hz), 0.72−0.62 (m, 2H),
JHH = 0.9 Hz), 2.09 (q, 4H; J = 7.4 Hz), 0.98 (t, 6 H, J = 7.4
HH HH
HH
3
3
13
1
0
.60 (d, 6H, J = 7.0 Hz), 0.56 (d, 6H, J = 6.9 Hz), 0.17−0.05
Hz). C{ H} NMR (100 MHz, CD Cl , 297 K): δ (ppm) 171.77,
HH
HH
2 2
13
1
3
3
3
(
m, 2H). C{ H} NMR (101 MHz, CD Cl , 296 K): δ (ppm) 162.64
161.51 (d, J = 11.1 Hz), 155.07 (d, J = 8.79 Hz), 136.31 (d, J
CP CP CP
2
2
3
3
3
3
(
d, J = 16.70 Hz), 161.75, 139.19 (d, J = 13.6 Hz), 136.63 (d,
= 11.66 Hz), 133.16 (d, J = 20.48 Hz), 131.81, 128.57 (d, J = 7.0
CP
CP
CP CP
3
3
3
3
JCP = 11.6 Hz), 133.26 (d, J = 10.3 Hz), 132.7 (d, J = 10.6 Hz),
Hz), 128.3, 120.80 (d, J = 26.9 Hz), 118.92, 116.88, 27.27, 8.79.
P{ H} NMR (161 MHz, CD Cl , 296 K): δ (ppm) −22.28. Mp: 93
C. FT-IR (ATR mode, solid, selected peaks) ν (cm ) 3051 (CH),
CP
CP
CP
3
3
31
1
1
1
2
−
28.07, 127.57 (d, J = 26.1 Hz), 115.63 (d, J = 26.2 Hz), 110.99,
CP
CP
2
2
−
1
07.70, 76.92, 46.87, 46.58, 38.76, 34.68, 31.55, 24.822, 23.03, 22.09,
°
0.89, 15.56. 31P{ H} NMR (161 MHz, CD Cl , 296 K): δ (ppm)
1
2
2
2982 (CH), 2940 (CH), 1758 (CO), 1587, 1569, 1479, 1433, 1383,
+
23.66 (s). Mass (TOF-MS ESI+) m/z calcd for [C H O P + H]
56 64 3 2
1359, 1252, 1214, 1182, 1124, 1076, 1060, 1026, 863, 807, 779, 741,
+
+
8
47.4384 (M + H) , observed 847.4403 (M + H) . Mp 94 °C. FT-IR
1
7
7
26, 692. Anal. Calcd for C H O P : C, 73.89; H, 5.32. Found: C,
42 36 5 2
−
(
ATR mode, solid, selected peaks) ν (cm ) 3064 (C−H), 2998 (C−
3.74; H, 5.38.
S,S)-Bis(2-diphenylphosphino(3-(2-methylbutyroyl))-
H), 2960 (C−H), 2933 (C−H), 2833 (C−H), 1582, 1561, 1481,
(
1
457, 1424, 1264, 1235, 1179, 1087 (C−O−C), 1067, 1052, 1026,
98, 776, 737, 721, 692.
Bis(2-diphenylphosphino(3-methoxy)phenyl)ether 15.
phenyl)ether 17b. A solution of 16 (2.57 g, 4.5 mmol), (S)-2-
methylbutyric acid (1.03 mL, 9.45 mmol), and DMAP (0.123 g, 1.0
mmol) in DCM (3 mL) was added to a solution of EDC·HCl (2.68 g,
14 mmol) and N,N-diisopropylethylamine (2.43 mL, 14 mmol) in
DCM (10 mL) at 0 °C. The reaction was allowed to warm to room
temperature and stirred for 20 h. The reaction mixture was worked up
as for 17a and purified by filtration over silica gel, using CH Cl as
7
TMEDA (1.201 g, 1.54 mL, 10.34 mmol) was added to a solution
of 8 (1.081 g, 4.7 mmol) in THF (5 mL) via syringe. The solution was
stirred for 15 min at room temperature and cooled to −78 °C. A 2.5 M
n
BuLi hexane solution (4.14 mL, 10.34 mmol) was added slowly while
2
2
1
maintaining the temperature at −78 °C. The reaction mixture was
slowly warmed to room temperature. After 20 h, the deprotonation
was checked by GC/MS after quenching a sample with D O in THF.
eluent (yield: 1.92 g, 58%). H NMR (400 MHz, CD Cl , 297 K): δ
(ppm) 7.29−7.08 (br m, 22H), 6.77 (br d, 2H; J = 8.2 Hz), 6.13
(br d, 2H; J = 8.2 Hz), 2.03 (m, 2H), 1.63 (m, 2H), 1.42 (m, 2H),
1.04 (d, 6H; J = 7.00 Hz, (CH )), 0.87 (t, 6H; J = 7.41 Hz,
(CH )). C{ H} NMR (100 MHz, CD Cl , 297 K): δ (ppm) 175.14,
2 2
3
HH
3
2
HH
3
3
The reaction mixture was diluted with THF (20 mL), and
chlorodiphenylphosphine (1.856 mL, 10.34 mmol) dissolved in
hexane (3 mL) was added dropwise to the reaction mixture at −78
HH 3 HH
13
1
3
2
2
3
3
161.67 (d, J = 9.60 Hz), 155.40 (d, J = 10.32 Hz), 136.28,
CP
CP
3
°C. The reaction mixture was allowed to warm to room temperature
133.28−132.83 (m), 131.86, 128.53−128.23 (m), 120.77 (d, J
=
CP
26.5 Hz), 118.61, 116.90, 40.50, 26.59. 31P{ H} NMR (161 MHz,
1
and stirred for 20 h at room temperature. A white precipitate was
formed. The precipitate was dissolved in DCM (100 mL) and washed
with degassed water (2 × 50 mL). The organic layer was dried over
CD Cl , 297 K): δ (ppm) −22.85. Mp: 121 °C. Mass (FD MS+) m/z
2
2
+
+
calcd for [C H O P + H] 739.2737 [M + H] , observed 739.2728
46
44
5 2
+
−1
MgSO , and the solvent was removed under high vacuum. The
remaining sticky solid was purified by crystallization from DCM and
hexane (1.913 g, 67%). H NMR (400 MHz, CD Cl , 297 K): δ
(
[M + H] . FT-IR (ATR mode, solid, selected peaks): ν (cm ) 3071
(CH), 3039 (CH), 2968 (CH), 2931 (CH), 2874 (CH), 1758 (C
O), 1592, 1560, 1480, 1435, 1382, 1370, 1356, 1253, 1214, 1165,
1094, 1084, 1053, 1023 771, 741, 731, 720, 694. Anal. Calcd for
C H O P : C, 74.78; H, 6.00. Found: C, 74.64; H, 5.93.
4
1
2
2
3
ppm) 7.36−7.7.18 (m, 22H), 6.59 (d, 2H; J = 8.2 Hz), 6.17 (dd,
HH
3 3 13 1
2
H; J = 8.2 Hz, J = 2.8 Hz), 3.45 (s, 6H, CH ). C{ H} NMR
HH HP 3
46 44
5 2
(
100 MHz, CD Cl , 297 K): δ (ppm) 163.66, 162.10 (d, J = 15.3
(S,S)-Bis(2-diphenylphosphino(3-(2-(4-isobutylphenyl)-
propionyl))phenyl)ether 17c. A solution of 16 (3.06 g, 5.37 mmol),
(S)-(+)-ibuprofen ((S)-(+)-2-(4-isobutylphenyl)propionic acid, 2.21
2
2
CP
Hz), 137.84 (d, JCP = 12.3 Hz), 133.15 (d, JCP = 20.7 Hz), 132.51,
28.14 (d, JCP = 6.7 Hz), 127.82, 115.59 (d, JCP = 24.5 Hz), 112,12
1
H
DOI: 10.1021/om5008055
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
−
1
31
1
g, 10.74 mmol), and DMAP (0.13 g, 1.09 mmol) in DCM (50 mL)
was added to a solution of EDC·HCl (2.95 g, 15.39 mmol) and N,N-
diisopropylethylamine (2.66 mL, 15.39 mmol) in DCM (150 mL) at 0
(KBr): νCO 2004, 1945 cm . L = DPEPhos: P{ H} NMR (161
−1
MHz, CD Cl , 297 K): δ (ppm) 25.9 IR (KBr): ν 1999, 1940 cm .
Synthesis of PtCl L. In a typical experiment, ligand (1 equiv) and
2
2
CO
2
°C. The reaction was allowed to warm to room temperature and
cis-PtCl (MeCN) (1 equiv) were placed in a Schlenk flask and flushed
2
2
stirred for 20 h. The reaction mixture was worked up as for 17a and
purified by crystallization from acetone and water (yield: 3.234 g,
with argon. CH Cl (∼0.05 M) and an equal amount of acetonitrile
2
2
were added, and the reaction mixture was stirred overnight at room
temperature. The solvent was removed in vacuo, and the resulting
yellow powder was washed three times with diethyl ether and dried in
1
6
2%). H NMR (400 MHz, CD Cl , 297 K): δ (ppm) 7.28−7.07 (br
2
2
3
3
m, 30H), 6.59 (br d, 2H, J = 8.2 Hz), 6.15 (br d, 2H; J = 8.3
Hz), 3.63 (q, 2H; J = 7.1 Hz), 2.45 (d, 4H; J = 7.2 Hz), 1.84
m, 2H), 1.30 (d, 6H; J = 7.12 Hz), 0.89 (d, 12H; J = 6.56 Hz).
C{ H} NMR (100 MHz, CD Cl , 297 K): δ (ppm) 173.12, 161.50
HH
HH
3
3
31
1
vacuo. The precipitate was analyzed by P{ H} NMR spectroscopy.
HH
HH
3
3
(
L = 15: The product precipitated directly from the MeCN/CH Cl
HH
HH
2
2
1
3
1
mixture to give a sparingly soluble white solid (starting from 0.171
2
2
3
3
1
(
(
2
d, J = 9.6 Hz), 155.10 (d, J = 10.3 Hz), 141.11, 137.11−127.69
mmol of ligand, 110 mg, 74%, cis/trans 2:1). cis-Compound. H NMR
CP
CP
3
m), 120.75 (d, J = 26.3 Hz), 118.36, 116.87, 45.31, 44.75, 30.60,
(500 MHz, CDCl
3
, 297 K): δ 7.96−7.81 (br m, 2H), 7.72−7.55 (br m,
CP
2.50, 18.41. 31P{ H} NMR (161 MHz, CD Cl , 297 K): δ (ppm)
1
3
6H), 7.37−7.16 (m, 14H), 6.31 (dd, 4H, JHH = 8.0, 2.8 Hz), 2.92 (s,
2 2
31
1
−
22.60. Mp 103 °C. Mass (FD MS+) m/z calcd for [C H O P +
6H). P{ H} NMR (202 MHz, CDCl
3
, 297 K): δ (ppm) −3.26
62
60
5 2
+
+
+
1
1
H] 947.3989 [M + H] , observed 947.3974 [M + H] . FT-IR (ATR
( JP−Pt = 3858 Hz, cis), −9.85 ( JP−Pt = 2283 Hz, trans). Mass (ESI MS
−1
+
+
mode, solid, selected peaks): ν (cm ) 3052 (CH), 2952 (CH), 2928
+) m/z calcd for [C38H32ClO P Pt] 828.1157 [M − Cl] , observed
3 2
+
(
CH), 2866 (CH), 1754 (CO), 1589, 1561, 1434, 1212, 1130, 117,
828.1149 [M − Cl] . Anal. Calcd for C38
H32Cl
2
O
P
5
2
Pt: C, 52.79; H,
1
7
087, 1067, 1020, 999, 741, 692. Anal. Calcd for C H O P : C,
3.73. Found: C, 52.88; H, 3.63.
62
60
5 2
8.63; H, 6.39. Found: C, 78.61; H, 6.28.
S,S)-Bis(2-diphenylphosphino(3-(2-(6-methoxy-2-
naphthyl)propionyl))phenyl)ether 17d. A solution of 16 (1.43 g,
.5 mmol), (S)-naproxen ((S)-(+)-2-(6-methoxy-2-naphthyl)-
L = 17a: Recrystallization from CH
off-white crystalline solid (starting from 0.073 mmol, 15 mg, 22%). H
2
Cl
2
layered with Et O gave an
2
1
(
NMR (400 MHz, CDCl , 297 K): δ 7.80−7.60 (m, 8H), 7.40−7.27
3
3
2
(m, 14H), 6.69−6.55 (m, 4H), 1.34 (q, 4H, J = 7.5 Hz), 0.74 (t,
6H, J = 7.5 Hz). P{ H} NMR (162 MHz, CDCl , 297 K): δ
HH
3
31
1
propionic acid, 1.21 g, 5.25 mmol), and DMAP (7.48 mg, 0.061
mmol) in DCM (30 mL) was added to a solution of EDC·HCl (1.34
g, 7 mmol) and N,N-diisopropylethylamine (1.20 mL, 7 mmol) in
DCM (70 mL) at 0 °C. The reaction was allowed to warm to room
temperature and stirred for 20 h. The reaction mixture was worked up
as described above and purified by quick filtration over silica gel under
HH
3
1
(ppm) −3.49 ( J
= 3863 Hz). Mass (ESI MS+) m/z calcd for
P−Pt
+
+
[C H ClO P Pt] 912.1369 [M − Cl] , observed 912.1358 [M −
4
2
36
5 2
+
Cl] . Anal. Calcd for C H Cl O P Pt: C, 53.18; H, 3.83. Found: C,
4
2
36
2
5 2
52.92; H, 3.65.
L = 17b: Recrystallization from CH Cl layered with Et O gave a
2
2
2
1
an argon atmosphere and with dichloromethane as eluent (yield:
white solid (starting from 0.12 mmol, 75 mg, 62%). H NMR (400
1
5
0%). H NMR (400 MHz, CD Cl , 297 K): δ (ppm) 7.69−7.66 (br
MHz, CDCl , 297 K): δ 7.82−7.62 (m, 8H), 7.41−7.21 (m, 14H),
2
2
3
3
3
3
m, 4H), 7.55 (s, 2H), 7.30−7.25 (m, 30 H, 6.57 (br d, 2H; J = 8.2
Hz), 6.13 (br d, 2H; J = 8.3 Hz), 3.88 (s, 6H), 3.33 (q, 2H; J
.0 Hz), 1.38 (d, 6H; J = 7.0 Hz) ppm. C{ H} NMR (100 MHz,
C Cl , 297 K): δ (ppm) 173.02, 161.53 (d, J = 9.6 Hz), 158.14,
55.11 (d, J = 10.3 Hz), 136.98−126.60 (m), 120.75 (d, J = 27.2
Hz), 119.31, 118.35, 116.86, 105.91, 55.65, 45.95, 18.27. P{ H}
6.65 (br d, 2H; J = 6.7 Hz), 6.59 (br d, 2H; J = 6.7 Hz), 1.36−
HH
HH
HH
3
3
=
1.24 (m, 2H), 1.23−1.10 (m, 2H), 1.09−0.99 (m, 2H), 0.77−0.67 (m,
HH
HH
3
13
1
31 1
7
12H). P{ H} NMR (162 MHz, CDCl , 297 K): δ (ppm) −3.63
1
HH
3
3
2
2
CP
( J
= 3862 Hz). Mass (ESI MS+) m/z calcd for
P−Pt
3
3
+
+
1
[C H ClO P Pt] 968.1995 [M − Cl] , observed 968.1976 [M −
CP
CP
46 44
5 2
31
1
+
Cl] . Anal. Calcd for C H Cl O P Pt: C, 54.99; H, 4.41. Found: C,
46 44 2 5 2
NMR (161 MHz, CD Cl , 297 K): δ (ppm) −22.69. Mass (FD MS+)
54.87; H, 4.48.
L = 17c: Precipitation from CH Cl using hexane and Et O gave a
white solid (starting from 0.054 mmol, 25 mg, 38%). H NMR (400
2
2
+
+
m/z calcd for [C H O P + H] 995.3261 [M + H] , observed
6
4
52
7
2
2
2
2
+
1
9
(
95.3265 [M + H] FT-IR (ATR mode, solid, selected peaks): ν
.
−
1
cm ) 3052 (CH), 2952 (CH), 2928 (CH), 2866 (CH), 1754 (C
O), 1699, 1668, 1589, 1561, 1511, 1480, 1434, 1375, 1330, 1251,
212, 1130, 117, 1087, 1067, 1020, 999, 741, 692. Anal. Calcd for
C H O P : C, 77.25; H, 5.27. Found: C, 77.14; H, 5.39.
MHz, CD Cl , 297 K): δ (ppm) 8.00−6.77 (br m, 30H), 6.75−6.44
2
2
3
(m, 2H), 6.38−6.06 (m, 2H), 2.48 (d, 4H; J = 7.0 Hz), 2.21 (q,
HH
3
3
1
2H; J = 6.9 Hz), 1.97−1.79 (m, 2H), 1.01 (d, 6H; J = 5.9 Hz),
HH
HH
3
31
1
64
52
5
2
0.93 (d, 12H; J 6.6 Hz). P{ H} NMR (162 MHz, CDCl , 297 K):
HH
3
1
Synthesis of Phosphine Selenide of L. In a typical experiment,
δ (ppm) −3.12 ( J
= 3877 Hz). Mass (ESI MS+) m/z calcd for
P−Pt
+
+
the appropriate ligand (0.05 mmol) and an excess of selenium were
suspended in toluene and stirred overnight at 60 °C. After being
cooled to room temperature, the solution was filtered, the solvent was
removed in vacuo, and the 31P{ H} NMR spectrum of the crude solid
[C H ClO P Pt] 1176.3247 [M − Cl] , observed 1176.3229 [M −
6
2
60
5 2
+
Cl] . Attempts to recrystallize the material for elemental analysis failed
to give a stable complex.
1
3
Synthesis of [Pd( η-allyl)L]X. In a typical small-scale experiment,
ligand (0.05 mmol), [Pd( η-allyl)Cl] (0.025 mmol), and NH PF
3
1
1
3
(
obtained in near-quantitative yields) was recorded. L = 15: P{ H}
2
4
6
1
NMR (161 MHz, CD Cl , 297 K): δ (ppm) 23.4 ( J = 740 Hz). L
(0.05−0.15 mmol) were placed in a Schlenk flask, flushed with argon,
and dissolved in DCM (5 mL). The reaction mixture was stirred
overnight at room temperature before water was added (5 mL).
Extraction with CH Cl (3 × 5 mL) was followed by drying the
2
2
P−Se
1
=
17a: 31P{ H} NMR (161 MHz, CD Cl , 297 K): δ (ppm) 23.6
2 2
31
1
(
1J
= 749 Hz). L = 17b: P{ H} NMR (161 MHz, CD Cl , 297
P−Se 2 2
1
31
1
K): δ (ppm) 23.90, 23.67 ( J
(
= 750 Hz). L = 17c: P{ H} NMR
P−Se
2
2
1
161 MHz, CD Cl , 297 K): δ (ppm) 24.61, 23.48 ( J
= 749 Hz).
organic layer over MgSO and removal of volatiles in vacuo. The crude
2
2
P−Se
4
31
1
31
1
1
L = DPEPhos: P{ H} NMR (161 MHz, CD Cl , 297 K): δ (ppm)
precipitate was analyzed by P{ H} NMR and H NMR spectroscopy
(see Table 4).
2
2
1
2
9.4 ( J
= 734 Hz).
P−Se
Synthesis of Ni(CO) L. In a typical experiment, an equimolar
In the case of ligand 15, 299.33 mg (0.5 mmol) of ligand and 87.0
mg of Pd dimer (0.23 mmol) were reacted together with 224.94 mg
(1.38 mmol) of NH PF . An analytical sample was obtained via
2
amount of Ni(CO) (PPh ) and ligand (0.10 mmol) was placed in a
2
3 2
Schlenk tube, flushed with argon, and dissolved in 1 mL of deuterated
THF. The reaction mixture was stirred for 48−72 h at room
temperature. Addition of pentane resulted in precipitation of a green
solid. After removal of the mother liquor, the solid was analyzed by
4
6
recrystallization of the precipitate from CH Cl layered with hexane to
2
2
1
give a crystalline orange solid. H NMR (500 MHz, CD Cl , 297 K): δ
2
2
3
(ppm) 7.49−7.32 (m, 14H), 7.32−7.21 (m, 8H), 6.61 (d, 2H, J
=
HH
3
1
1
31
1
3
3
P{ H} NMR and IR spectroscopy. L = 15: P{ H} NMR (161
8.4 Hz), 6.53 (br d, 2H, J = 8.0 Hz), 5.59 (tt, 1H, J = 13.7, 7.3
HH HH
−1
31
1
MHz, CD Cl , 297 K): δ (ppm) 16.4. IR (KBr): ν 1986, 1920 cm .
Hz), 3.70−3.63 (m, 2H), 3.11 (s, 6H), 3.10−3.02 (m, 2H). P{ H}
13 1
2
2
CO
L = 17a: 3 P{ H} NMR (161 MHz, CD Cl , 297 K): δ (ppm) 17.6. IR
1
1
NMR (202 MHz, CD Cl , 297 K): δ (ppm) 5.6 (s). C{ H} NMR
2 2
2
2
−1
31
1
(
KBr): νCO 1992, 1932 cm . L = 17b: P{ H} NMR (161 MHz,
(100 MHz, CDCl , 297 K): 162.1, 161.0, 134.2, 132.5, 131.6, 130.3,
3
−
1
CD Cl , 297 K): δ (ppm) 17.6. IR (KBr): ν 1999, 1936 cm . L =
1
128.6, 122.1, 111.1, 108.7, 55.4. Mass (ESI MS+) m/z calcd for
2
2
CO
3
1
1
+
+
+
7c: P{ H} NMR (161 MHz, CD Cl , 297 K): δ (ppm) 17.3. IR
[C H O P Pd] 747.1409 [M] , observed 747.1239 [M] . Anal.
2
2
41 37 3 2
I
DOI: 10.1021/om5008055
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Calcd for C H F O P Pd: C, 55.26; H, 4.19. Found: C, 55.10; H,
bound to boron had the position of the lead hydrogen atom
determined from the difference Fourier map, after which the positions
of the other two were generated using a riding model. They were
refined isotropically subject to distance restraints, with thermal
parameters free to refine.
41
37
6
3 3
4
.28.
The Pd allyl complexes of 17a−d were prepared in situ as described
above.
1
L = 14: H NMR (400 MHz, CDCl , 297 K): δ (ppm) 7.59, 7.36−
3
6
(
.98, 6.46−6.12, 5.70 (1H), 3.85, 3.60 (1H), 3.48 (1H), 3.41, 3.26
Details for Compound 13. C H FB O P , Fw = 874.43, 0.15 ×
5
6
70
2
3 2
31
1
3
1H), 3.06 (1H), 2.28, 2.10, 1.53−1.43, 1.25−0.87, 0.78. P{ H}
0.05 × 0.02 mm , triclinic, P1 (no. 1), a = 9.115(3) Å, b = 9.309(4) Å,
c = 17.363(8) Å, α = 83.17(5)°, β = 76.35(4)°, γ = 70.69(4)°, V =
1349.9(10) Å , Z = 1, D = 1.076 g/cm , μ = 0.12 mm , T = 93 K.
2
NMR (161 MHz, CDCl , 297 K): δ (ppm) 5.7 and 4.1 (AB J = 38
3
PP
3
3
−1
Hz).
x
1
L = 17a: H NMR (400 MHz, CDCl , 297 K): δ (ppm) 7.48−7.26
R1/wR2 [I > 2σ(I)]: 0.0816/0.1751. Residual electron density
3
3
(
(
22H), 6.80 (2H), 6.55 (2H), 5.75 (1H), 3.52 (2H), 3.18 (2H), 1.43,
between −0.304 and 0.399 e/Å .
4H), 0.77 (6H). 31P{ H} NMR (161 MHz, CDCl , 297 K): δ (ppm)
1
Details for Complex 21. C40
H
32NiO
P
1
, Fw = 713.34, 0.03 × 0.03
/n (no. 14), a = 12.371(4)
Å, b = 20.311(7) Å, c = 13.564(5) Å, β = 92.283(10)°, V = 3406(2)
3
5
2
3
7
.5 (s).
× 0.03 mm , green prism, monoclinic, P2
1
L = 17b: H NMR (400 MHz, CDCl , 297 K): δ (ppm) 7.49−7.36
3
3
3
−1
(
(
22H), 6.83 (2H), 6.62 (2H), 5.63 (1H), 3.58 (2H), 3.08 (4H), 1.35
2H), 1.25 (2H), 0.78 (6H), 0.75 (6H). P{ H} NMR (161 MHz,
Å , Z = 4, D = 1.391 g/cm , μ = 0.709 mm , T = 93 K. R1/wR2 [I >
x
31
1
2σ(I)]: 0.07777/0.0997. Residual electron density between −0.42 and
2
3
CDCl , 297 K): δ (ppm) 7.08 and 7.02 (AB, J = 30 Hz).
0.41 e/Å .
3
PP
1
L = 17c: H NMR (400 MHz, CDCl , 297 K): δ (ppm) 7.70−7.30,
.20, 7.03, 6.85, 6.53, 6.48, 5.78 (1H), 3.64 (1H), 3.55 (1H), 3.48
Details for Complex 22. C41
H
37
F
6
O
3
P
3
Pd, Fw = 891.05, 0.15 ×
0.10 × 0.03 mm , orange platelet, monoclinic, P1 /1 (no. 7), a =
14.976(7) Å, b = 14.669(6) Å, c = 18.633(8) Å, β = 108.245(8)°, V =
3
3
7
n
3
1
1
(
2H), 3.28 (1H), 3.14 (1H), 2.40, 2.20 (2H), 1.81, 1,18, 1.06. P{ H}
2
3
3
−1
NMR (161 MHz, CDCl , 297 K): δ (ppm) 7.8 and 7.0 (AB, J = 37
3888(3) Å , Z = 4, D = 1.553 g/cm , μ = 0.668 mm , T = 93 K. R1/
x
3
PP
Hz).
wR2 [I > 2σ(I)]: 0.0638/0.1652. Residual electron density between
1
3
L = 17d: H NMR (400 MHz, CDCl , 297 K): δ (ppm) 7.58, 7.60−
−1.33 and 1.67 e/Å .
3
7
3
.20, 7.18−6.98, 6.48−6.32, 5.70 (1H), 4.02−3.84 (8H), 3.59 (1H),
CCDC-1059267, CCDC-1059268, and CCDC-1059269 contain
the supplementary crystallographic data for this paper of 13, 21, and
22, respectively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.
uk/data_request/cif.
31
1
.47 (1H), 3.25 (1H), 3.05 (1H), 1.51 (6H). P{ H} NMR (161
2
MHz, CDCl , 297 K): δ (ppm) 7.4 and 7.1 (AB, J = 38 Hz).
3
PP
General Catalytic Procedure for Asymmetric Allylic Alkyla-
3
tion Reactions. In a Schlenk tube, [Pd(η -C H )Cl] (0.005 mmol)
3
5
2
and the respective ligand (0.01 mmol) were dissolved in 1 mL of
CH Cl2 and degassed. (E)-1,3-Diphenylprop-2-ene-1-yl acetate or
2
ASSOCIATED CONTENT
■
cyclohex-2-ene-1-yl acetate (1 mmol) was added as the substrate, and
after 20 min of stirring at room temperature, dimethyl malonate (3
mmol), BSA (N,O-bis(trimethylsilyl)acetamide, 3 mmol), and a
catalytic amount of KOAc (0.024 mmol) were added consecutively.
The reaction mixture was degassed again and stirred at the given
temperature.
*
S
Supporting Information
NMR spectra of compounds, cif files for 13, 21, and 22. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Analytical Methods. (E)-1,3-Diphenylprop-2-ene-1-yl acetate.
Conversion by GC (column = Rtx-1 (fused silica), Restek, 30 m ×
.25 mm × 0.1 μm; carrier gas = helium; GC settings = 90 kPa, inlet
injector = 220 °C, oven (50 °C; 20 °C/min; 300 °C; 10 min), FID
detector 220 °C). Retention times: (R/S)-(E)-dimethyl 2-(1,3-
diphenylallyl)malonate = 12.2 min; (E)-1,3-diphenylallyl acetate =
0.7 min; dodecane 5.5 min. Enantioselectivity by HPLC (column =
Chiralcel OD-H; HPLC settings: hexane, 99%; isopropyl alcohol, 1%;
.5 mL flow). Retention times: (R)-(E)-dimethyl 2-(1,3-diphenylallyl)-
malonate = 21.73 min; (S)-(E)-dimethyl 2-(1,3-diphenylallyl)malonate
AUTHOR INFORMATION
■
0
Corresponding Author
E-mail: pcjk@st-andrews.ac.uk.
*
Notes
1
The authors declare no competing financial interest.
0
ACKNOWLEDGMENTS
■
This work was supported by an EASTCHEM fellowship (to
C.F.C.) and by the European Union, through a Marie Curie
Excellence Grant MEXT-2004-014320. A.G.J. thanks the UK
Catalysis Hub for resources and support provided via our
membership of the UK Catalysis Hub Consortium and funded
by EPSRC (portfolio Grants EP/K014706/1, EP/K014668/1,
EP/K014854/1, and EP/K014714/1) and the EPSRC for
EPSRC Critical mass grant ‘Clean catalysis for sustainable
development’ (EP/J018139/1). J.I.v.d.V. thanks the ERC for a
Starting Grant 2790097. F.J.L.H. thanks the European Union
=
23.60 min.
Cyclohex-2-ene-1-yl acetate. Conversion by GC (column = Rtx-1
fused silica), Restek, 30 m × 0.25 mm × 0.1 μm; carrier gas = helium;
(
GC settings = 90 kPa, inlet injector = 220 °C, oven (50 °C; 20 °C/
min; 300 °C; 10 min), FID detector 220 °C). Retention times:
dimethyl 2-(cyclohex-2-en-1-yl)malonate = 12.5 min; cyclohex-2-en-1-
yl acetate = 4.3 min; dodecane 5.5 min. Enantioselectivity (column =
Varian Chirasil DEX-CB, 25 m × 0.25 mm × 0.25 μm; carrier gas =
helium; GC settings = 120 kPa, inlet injector = 200 °C, oven (120 °C;
3
0 min, 5 °C/min; 180 °C; 0 min), FID detector = 200 °C). Retention
times: dimethyl 2-(cyclohex-2-en-1-yl)malonate (S) = 23.95 min;
dimethyl 2-(cyclohex-2-en-1-yl)malonate (R) = 24.55 min; cyclohex-2-
en-1-yl acetate = 5.21 min.
(
Marie Curie ITN SusPhos, Grant Agreement No. 317404) for
financial support. We thank Stephen Boyer (London
Metropolitan University) for elemental analysis, and the
EPSRC UK National Mass Spectrometry Facility (NMSF),
Swansea, for MS analysis. We are grateful to members of COST
action CM0802 (PhoSciNet) for scientific discussions.
X-ray Crystal Structure Determinations. X-ray crystal data were
collected at 93 K by using a Rigaku MM007 high brilliance RA
generator/confocal optics with a Mercury CCD diffractometer system.
Intensity data were collected using both ω- and φ-steps, accumulating
area detector images spanning at least a hemisphere of reciprocal
space. All the data were corrected for Lorentz polarization effects. A
3
3
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■
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DOI: 10.1021/om5008055
Organometallics XXXX, XXX, XXX−XXX

Organometallics
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DOI: 10.1021/om5008055
Organometallics XXXX, XXX, XXX−XXX