Chiral cyclopalladated complex promoted asymmetric synthesis of diester-substituted P,N-ligands via stepwise hydrophosphination and hydroamination reactions

Article abstract of DOI:10.1039/c2dt12379g

A series of enantiomerically pure 1,2-diester substituted P,N-ligands incorporating two chiral carbons in the backbone were generated in high yields and high stereoselectivity from acetylenedicarboxylate via initial hydrophosphination using diphenylphosphine followed by hydroamination with various primary and secondary amines. The reactions were activated and stereochemically controlled by the organopalladium complex containing ortho-palladated (S)-(1-(dimethylamino)ethyl)naphthalene under mild conditions. The absolute stereochemistry and the coordination chemistry of P,N-products were determined by the single crystal X-ray diffraction analysis. All the chiral P,N-ligands could be liberated from the palladium template without loss of optical purity. Subsequent recomplexation to selected chiral palladium centers confirmed the optical purity of the new functionalized chiral P,N-ligands.

Full text of DOI:10.1039/c2dt12379g

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PAPER
Chiral cyclopalladated complex promoted asymmetric synthesis of
diester-substituted P,N-ligands via stepwise hydrophosphination and
hydroamination reactions†
Ke Chen, Sumod A. Pullarkat, Mengtao Ma, Yongxin Li and Pak-Hing Leung*
Received 9th December 2011, Accepted 9th February 2012
DOI: 10.1039/c2dt12379g
A series of enantiomerically pure 1,2-diester substituted P,N-ligands incorporating two chiral carbons in
the backbone were generated in high yields and high stereoselectivity from acetylenedicarboxylate via
initial hydrophosphination using diphenylphosphine followed by hydroamination with various primary
and secondary amines. The reactions were activated and stereochemically controlled by the
organopalladium complex containing ortho-palladated (S)-(1-(dimethylamino)ethyl)naphthalene under
mild conditions. The absolute stereochemistry and the coordination chemistry of P,N-products were
determined by the single crystal X-ray diffraction analysis. All the chiral P,N-ligands could be liberated
from the palladium template without loss of optical purity. Subsequent recomplexation to selected chiral
palladium centers confirmed the optical purity of the new functionalized chiral P,N-ligands.
N derivatives is an area of research that has received much atten-
tion in recent years.
Introduction
It has been well established that bidentate P,N ligands play
important roles in the areas of coordination chemistry and cataly-
sis. For example, heterobidentate P,N-type ligands, by virtue of
the fact that they have soft phosphorus and hard nitrogen donor
atoms, can provide a crucial hybrid environment in a catalytic
process. P,N-type ligands can furthermore stabilize intermediate
oxidation states or geometries during a catalytic cycle in a metal
catalyzed reaction.1 The stereochemistry of such a reaction can
also be controlled by the utilization of a suitable chiral hetero-
bidentate P,N-ligand. Over the past decades, P,N-ligands have
been successfully applied in various catalysis reactions including
allylic alkylations,2,3 hydrogenation,4,5 hydrosilylation,6 and
hydroamination reactions.7,8 Among this class of chiral ligands,
1,2-P,N-bidentates were most commonly employed, perhaps due
to the formation of the corresponding stable 5-membered metal
chelates. When coupled to suitable metal ions, these ligands
have shown significant catalytic activities.2,4,6,7,9–11 Currently,
however, there are only limited chiral 1,2-P,N-bidentates avail-
able and their preparation mainly depend on the resolution from
natural chiral pool sources and subsequent synthetic modifica-
tions.2a,4a,c,9a,b,12–16 Accordingly, the development of the meth-
odologies for the synthesis of structurally designed chiral 1,2-P,
In this article, we report the synthesis of a series of diester
substituted chiral 1,2-P,N ligands from acetylenedicarboxylate
via the stepwise hydrophosphination and hydroamination reac-
tion employing the ortho-palladated (S)-(1-(dimethylamino)
ethyl)naphthalene as chiral auxiliary and reaction promoter. The
initial hydrophosphination reaction produces the palladium coor-
dinated prochiral vinylic phosphine species. The subsequent
hydroamination step, however, generates two stereogenic carbon
centers on the ligand backbone. It is interesting to note that the
simultaneous generation of two stereogenic carbon centers via a
single hydroamination reaction is a stereochemically demanding
novel strategy that has not been reported previously. It is also
noteworthy in this context that phosphine ligands containing
ester functional groups are important reagents for cancer-
chemotherapy.17
Results and discussion
Hydrophosphination and formation of the coordinated prochiral
diphenylphosphino maleate
As illustrated in Scheme 1, hydrophosphination of dimethyl acet-
ylenedicarboxylate with diphenylphosphine promoted by the
chiral metal template (S)-1 gave the neutral complex (S)-2 regio-
selectively. The 31P{1H} NMR spectrum of the crude reaction
mixture in CDCl3 exhibited only one singlet signal at δ 41.7,
indicating that only one phosphine product was formed quantitat-
ively. Therefore the crude monophosphine complex, (S)-2, could
be used directly for the subsequent hydroamination reaction.
However, for storage and characterization purposes, it could be
Division of Chemistry and Biological Chemistry, School of Physical &
Mathematical Sciences, Nanyang Technological University, Singapore
637371, Singapore. E-mail: pakhing@ntu.edu.sg; Fax: +65 63166984;
Tel: +65 63168905
†CCDC 857605–857607. For crystallographic data in CIF format for
complexes (R,S)-8a, (S,R,S)-10g, (R,S)-14f and (R,S)-14′f see DOI:
10.1039/c2dt12379g
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Scheme 1
Scheme 2
Table 1 Asymmetric hydroamination of alkyl aminesa
isolated as a stable complex via silica gel column chromato-
graphy in 75% yield. The regiospecific coordination of the
“soft” phosphine ligand ion in the position trans to the NMe2
moiety of the chiral template is due to the well established elec-
tronic directing effects originating from the σ-donating nitrogen
and the strong π-accepting aromatic carbon of the organopalla-
dium ring.18
Amines
Products
31P{1H} NMR (δ)
dr (%)b
HNMe2
HNEt2
HN(i-Pr)2
(S,R,S)-4a
(S,R,S)-4b
N.R
46.1
45.1
—
99
95
—
a Reactions were performed using (S)-2 (0.15 mmol) and amine
(0.15 mmol) in CH2Cl2 (5 mL) at −40 °C for 12 h. b dr was determined
by 31P NMR.
Stereoselective hydroamination with secondary amines
We have previously reported the palladium complex promoted
hydroamination of alkynyl-phosphines to form the correspond-
ing imino-phosphines.19 Therein it was observed that the hydroa-
mination reaction required both the alkynylphosphine and the
amine to be coordinated simultaneously onto the palladium ion.
In this current work, however, the chloro ligand in the mono-
chloro complex (S)-2 is thermodynamically and kinetically
stable and it cannot be efficiently displaced by most incoming
monodentate ligands, including phosphines and amines.19,20
Therefore, as expected, no reaction was observed between the
chloro complex (S)-2 and various primary and secondary
amines. Accordingly it was indeed necessary to replace the
strong chloro ligand with the very weakly coordinated perchlor-
ato counterpart in order to create a potential vacant site for the
desired asymmetric hydroamination reaction. Complex (S)-3
could be obtained quantitatively via the treatment of (S)-2 with
silver perchlorate. This perchlorato complex can also be isolated
for storage and characterization purposes. We have previously
reported the isolation and the single crystal X-ray structure of a
similar perchlorato species.21 In routine syntheses, however, the
reactive perchlorato species (S)-3 need not be isolated and can be
used directly for subsequent hydroamination reactions
(Scheme 2). The intramolecular hydroamination reaction
between the perchlorato complex (S)-3 and dimethylamine pro-
ceeded smoothly at −40 °C in dichloromethane. After 12 h the
162 MHz 31P NMR spectrum of the crude reaction product in
CDCl3 showed only one singlet at δ 46.1. No other 31P NMR
signal was detected, indicating that the reaction produced stereo-
selectively only one of the four possible diastereomers viz (S,R,
S)-4a was formed. Similarly the pure P,N-complex (S,R,S)-4b
could be obtained efficiently from the reaction between (S)-3 and
diethylamine (Table 1). On the other hand, no hydroamination
reaction was observed when (S)-3 was treated with the diisopro-
pylamine, presumably due to the steric hindrances offered by
this bulky amine to the approach of the chiral reaction promoter.
Single crystals of complexes (S,R,S)-4a,b that are suitable for
X-ray structural analyses could not be obtained. Hence the
5392 | Dalton Trans., 2012, 41, 5391–5400
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Scheme 3
hydroamination products were treated directly with concentrated
hydrochloric acid to remove the chiral naphthylamine auxiliary
chemoselectively (Scheme 3). Interestingly, the structural integ-
rity of the P,N-metal chelate was not affected by this strong acid
treatment. The neutral dichloro complexes (R,S)-8a,b thus
obtained is highly crystalline. The coordination chemistry and
the absolute stereochemistry of complex (R,S)-8a was deter-
mined by X-ray crystallography (Fig. 1). The geometry at palla-
dium center of (R,S)-8a is distorted square planar with angles of
87.3(1)°–92.7(1)° and 174.5(1)°–179.2(1)° (Fig. 1). The absol-
ute stereochemistry at the C(5) and C(6) stereogenic centers are
R and S, respectively. The five membered P,N chelate ring adopts
the conformation with both ester functional groups occupying
the sterically favorable equatorial positions. The difference
between the two Pd–Cl bond distances [2.381(1) and 2.294(1)
Å], with the bond trans- to the phosphorus being noticeably
longer, is consistent with the fact that phosphorus has stronger
trans-electronic influence than the nitrogen. The C(6)–P(1)
[1.849(2) Å] and C(9)–P(1) [1.802(2) Å] distances are typical
for C–P bonds. The C(5)–N(1) [1.518(3) Å] and C(5)–C(6)
[1.531(3) Å] distances are typical for C–N and C–C bonds,
respectively. The C(4)–O(1) [1.201(3)) Å] and C(4)–O(2) [1.328
(3) Å] distances are typical for CvO and C–O bonds, respect-
ively (Table 2).
Fig. 1 Structure of (R,S)-8a.
Table 2 Selected bond lengths (Å) and angles (°) of (R,S)-8a
Pd(1)–Cl(1)
Pd(1)–N(1)
C(1)–N(1)
C(4)–O(2)
C(5)–N(1)
C(6)–P(1)
2.381(1)
2.133(2)
1.486(3)
1.328(3)
1.518(3)
1.849(2)
Pd(1)–Cl(2)
Pd(1)–P(1)
C(2)–N(1)
C(4)–O(1)
C(5)–C(6)
C(9)–P(1)
2.294(1)
2.202(1)
1.494(3)
1.201(3)
1.531(3)
1.802(2)
Stereoselective hydroamination with primary amines
The intramolecular hydroamination reaction between the per-
chlorato complex (S)-3 and primary aryl amines may produce
two carbon and one coordinated nitrogen stereogenic centers.
Thus the reaction may generate up to eight stereomeric com-
plexes (Scheme 4). Compared with their secondary alkyl amine
analogues, primary aryl amines were found to be less reactive
towards the hydromination reaction with the vinylphosphine
complex (S)-3. This is an indication that the addition reactions
adopted an electrophilic mechanism. As shown in Table 3, the
hydroamination reactions with selected primary aryl amines pro-
ceeded smoothly at 60 °C to generate the hydroamination pro-
ducts in high yields (Table 3). The 31P{1H} NMR spectroscopy
was used to monitor the asymmetric addition reactions. In all
reactions, it was observed that only one major pair of diastereo-
mers (arising from the presence of an additional nitrogen stereo-
genic centers) were obtained. These complexes are depicted as
(S,R,S)-10a–h and (S,R,S)-10′a–h in Scheme 4. An X-ray struc-
tural analysis of complex (S,R,S)-10g confirmed the coordination
chemistry and the absolute stereochemistry of the new chiral P,
N-chelate (Fig. 2). Similar to those observed in complex (R,S)-
8a, the absolute stereochemistry at the C(24) and C(27) stereo-
genic centers were R and S, respectively, with both the ester
N(1)–Pd(1)–P(1)
P(1)–Pd(1)–Cl(2)
P(1)–Pd(1)–Cl(1)
N(1)–C(5)–C(6)
C(1)–N(1)–C(2)
C(6)–P(1)–Pd(1)
87.3(1)
87.2(1)
179.2 (1)
110.8(2)
109.7(2)
99.9(1)
N(1)–Pd(1)–Cl(2)
N(1)–Pd(1)–Cl(1)
Cl(2)–Pd(1)–Cl(1)
C(5)–C(6)–P(1)
C(1)–N(1)–Pd(1)
C(5)–N(1)–Pd(1)
174.5(1)
92.8(1)
92.7(1)
105.9(2)
107.1(2)
111.0(1)
functional groups occupying the equatorial positions. It is inter-
esting to note that the inter-chelate N(1)–Pd(1)–N(2) angle [99.9
(1)°] in this square-planar complex (Table 4) is clearly larger
than the C(1)–Pd(1)–P(1) counterpart [94.9 (1)°], despite the
fact that P(1) is bearing two projecting aromatic rings, but only
one on N(2). Evidently, the two ortho-substituted methyl groups
in the N-Ph ring play a significant role in the inter-chelate steric
repulsion. Indeed, due to the severe steric hindrances, no hydroa-
mination reaction was observed when (S)-3 was treated with the
bulky 2,6-diisopropylaniline.
From a stereochemical point of view, the chirality on the
stereogenic nitrogen donors in complexes (S,R,S)-10 is not a key
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Scheme 4
analyzed by X-ray crystallography (Fig. 3 and 4). The stereo-
chemistry of complexes (R,S)-14f and (R,S)-14′f are similar and
they differ only at the coordinated nitrogen stereogenic centers.
The 5-membered P,N-chelates in both diastereomers adopted the
same conformation with the ester functional groups occupying
the sterically favorable equatorial positions. Accordingly N–C*
and the P–C* centers adopt the R and S absolute configurations
respectively. The N-aromatic rings in (R,S)-14f and (R,S)-14′f
occupy the equatorial and axial positions, respectively. Selected
bond distances and angles are given in Tables 5 and 6
respectively.
Table 3 Stereoselectivities and yields of asymmetric hydroamination
of aryl aminesa
31PNMR
(δ)
dr
Yieldd
Ratioc (%)
Amines
Product
b(%)
C6H5NH2
10a &
10′a
10b &
10′b
10c &
10′c
10d &
10′d
10e &
10′e
10f &
10′f
10g &
10′g
10h &
10′h
—
49.6 &
46.6
49.3 &
48.6
50.1 &
46.4
49.7 &
45.9
50.3 &
46.5
49.5 &
45.9
54.9 &
44.3
48.0 &
45.4
—
90
89
90
88
87
85
90
88
—
3.3 : 1 80
1 : 3.1 83
2.9 : 1 85
3.3 : 1 85
3.1 : 1 82
2-MeOC6H4NH2
3-MeOC6H4NH2
4-MeOC6H4NH2
3-MeC6H4NH2
4-MeC6H4NH2
4 : 1
80
Liberation of chiral P,N-bidentates
2,4,6-
(Me)3C6H2NH2
4-NO2C6H4NH2
1 : 3.1 85
Optically pure P,N-bidentates (R,S)-9 and (R,S)-15 could be lib-
erated from the respective dichloro palladium complexes as air-
sensitive oils by the treatment of their respective neutral com-
plexes with aqueous potassium cyanide. The optical purities of
these free ligands were established by the recomplexation of
each of these ligands to the chiral reagent (S)-1 and the equally
accessible (R)-1. The 31P NMR studies of the recomplexation
products confirmed that these liberated ligands are enantiomeri-
cally pure.22
8 : 1
87
2,6-
—
—
(iPr)2C6H3NH2
a Reactions were performed using (S)-2 (0.15 mmol) and amine
(0.15 mmol) in chloroform (3 mL) at 60 °C for 16 h. b dr was
determined by 31P NMR. c Ratio was determined by 31P NMR.
d Isolated yield.
factor. The N-chirality would become insignificant once the P,N-
bidentates are liberated from the palladium reaction promoter.
Therefore, without further separation, N-chiral diastereomers of
(S,R,S)-10a–h and (S,R,S)-10′a–h were treated with concentrated
hydrochloric acid to remove the chiral naphthylamine auxiliary
(Scheme 5).
The acid treatment generated the respective more crystalline
N-chiral dichloro complexes (R,S)-14a–h and (R,S)-14′a–h.
In all cases, the diastereomers co-crystallized together as a
1 : 1 mixture in the same unit cell. A pale yellow crystal contain-
ing the diastereomeric mixture (R,S)-14f and (R,S)-14′f was
Conclusions
In conclusion, we have demonstrated a facile synthesis of diester
functionalized chiral P,N-ligands via the stepwise hydrophosphi-
nation and hydroamination reaction with acetylenedicarboxylate.
Both addition reactions were promoted by the same chiral orga-
nopalladium reagent in high regio- and stereo-selectivities under
mild conditions. Further investigations on the catalytic potential
of transition metal complexes generated from these chiral ligands
and evaluation of their biological activity are currently in
progress.
5394 | Dalton Trans., 2012, 41, 5391–5400
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Fig. 2 Structure of (S,R,S)-10g.
techniques. Solvents were dried and freshly distilled according to
standard procedures and degassed prior to use when necessary.
Table 4 Selected bond lengths (Å) and angles (°) of (S,R,S)-10g
1
The H and 31P{1H} NMR spectra were recorded at 25 °C on
Pd(1)–C(1)
Pd(1)–P(1)
C(1)–C(10)
C(15)–N(2)
C(24)–C(27)
C(25)–O(2)
C(27)–P(1)
2.009(2)
2.233(1)
1.385(3)
1.472(3)
1.532(3)
1.201(3)
1.870(2)
Pd(1)–N(1)
Pd(1)–N(2)
C(11)–N(1)
C(24)–N(2)
C(24)–C(25)
C(25)–O(1)
C(30)–P(1)
2.149(2)
2.264(2)
1.510(3)
1.501(3)
1.538(3)
1.332(4)
1.818(2)
Bruker Avance 300, 400 and 500 spectrometers. Optical
rotations were measured on the specified solution in a 0.1 dm
cell at 20 °C with a Perkin-Elmer 341 polarimeter. Elemental
analysis was performed by the Elemental Analysis Laboratory of
the Division of Chemistry and Biological Chemistry at Nanyang
Technological University. Melting points are uncorrected.
Caution: Perchlorate salts of metal complexes are potentially
explosive compounds and should be handled with care.
C(1)–Pd(1)–N(1)
N(1)–Pd(1)–P(1)
N(1)–Pd(1)–N(2)
C(28)–C(27)–P(1)
C(11)–N(1)–Pd(1)
C(15)–N(2)–Pd(1)
C(36)–P(1)–C(30)
80.9(1)
C(1)–Pd(1)–P(1)
C(1)–Pd(1)–N(2)
P(1)–Pd(1)–N(2)
C(10)–C(1)–Pd(1)
C(24)–C(27)–P(1)
C(24)–N(2)–Pd(1)
C(27)–P(1)–Pd(1)
94.9(1)
178.7(1)
84.3(1)
113.8(2)
109.3(2)
112.8 (2)
102.3(1)
175.7(1)
99.9 (1)
111.5(2)
105.7(1)
119.7(2)
106.5(1)
Preparation of monophosphine palladium (II) complex (S)-2
To a solution of (S)-1 (1300 mg, 1.91 mmol) in dichloromethane
(200 mL) at −78 °C was slowly added diphenylphosphine
(711 mg, 3.82 mmol) in dichloromethane (5 mL), and the
mixture was stirred at −78 °C for 1 h. Then, the dimethyl acety-
lenedicarboxylate (542 mg, 3.82 mmol) was added to the above
Experimental section
Reactions involving air-sensitive compounds were performed
under an inert atmosphere of argon using standard Schlenk
Scheme 5
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Table 5 Selected bond lengths (Å) and angles (°) of (R,S)-14f
Pd(1)–N(1)
Pd(1)–Cl(2)
C(1)–N(1)
C(8)–C(11)
C(9)–O(1)
C(20)–P(1)
2.100(2)
2.297(1)
1.447(3)
1.530(3)
1.208(3)
1.807(3)
Pd(1)–P(1)
Pd(1)–Cl(1)
C(8)–N(1)
C(9)–O(2)
C(11)–P(1)
C(14)–P(1)
2.210(1)
2.369(1)
1.503(3)
1.330(3)
1.854(2)
1.805(3)
N(1)–Pd(1)–P(1)
P(1)–Pd(1)–Cl(2)
P(1)–Pd(1)–Cl(1)
N(1)–C(8)–C(11)
C(11)–P(1)–Pd(1)
86.5(1)
89.4(1)
174.2(1)
109.1(2)
101.3(1)
N(1)–Pd(1)–Cl(2)
N(1)–Pd(1)–Cl(1)
Cl(2)–Pd(1)–Cl(1)
C(8)–N(1)–Pd(1)
C(8)–C(11)–P(1)
175.2(1)
90.9(1)
93.5(1)
111.8(2)
106.8(2)
Table 6 Selected bond lengths (Å) and angles (°) of (R,S)-14′f
Pd(2)–N(2)
Pd(2)–Cl(4)
C(26)–N(2)
C(33)–C(36)
C(34)–O(6)
C(39)–P(2)
2.087(2)
2.284(1)
1.458(3)
1.521(3)
1.324(3)
1.812(2)
Pd(2)–P(2)
Pd(2)–Cl(3)
C(33)–N(2)
C(34)–O(5)
C(36)–P(2)
C(45)–P(2)
2.203(1)
2.371(1)
1.512(3)
1.194(3)
1.876(3)
1.812(2)
N(2)–Pd(2)–P(2)
P(2)–Pd(2)–Cl(4)
P(2)–Pd(2)–Cl(3)
N(2)–C(33)–C(36)
C(36)–P(2)–Pd(2)
87.3(1)
90.4(1)
176.5(1)
112.3(2)
101.9(1)
N(2)–Pd(2)–Cl(4)
N(2)–Pd(2)–Cl(3)
Cl(4)–Pd(2)–Cl(3)
C(33)–N(2)–Pd(2)
C(33)–C(36)–P(2)
177.2(1)
89.3(1)
93.1(1)
112.7(1)
106.5(2)
Fig. 3 Structure of (R,S)-14f.
NMR: (162 MHz, CDCl3): δ 41.7; 1H NMR: (400 MHz,
CDCl3): δ 7.94–7.99 (m, 2H), 7.71–7.76 (m, 3H), 7.63–7.65 (m,
1H), 7.39–7.54 (m, 5H), 7.29–7.36 (m, 3H), 7.02 (d, JPH = 8.6
Hz, 1H), 6.67–6.72 (m, 2H), 4.38 (m, 1H), 3.71 (s, 3H), 3.52 (s,
3H), 2.98 (d, JPH = 3.6Hz, 3H), 2.76 (d, JHH = 1.5 Hz, 3H), 2.06
(d, JHH = 6.4 Hz, 3H); 13C NMR: (100 MHz, CDCl3): δ 165.4
(d, JPC = 7.3 Hz), 164.5 (d, JPC = 17.6 Hz), 149.7, 149.2 (d, JPC
= 1.9 Hz), 142.4 (d, JPC = 33.8 Hz), 136.2 (d, JPC = 10.4 Hz),
135.8 (d, JPC = 12.2 Hz), 135.6, 135.5, 135.3, 135.2, 131.4 (d,
JPC = 2.3 Hz), 131.3 (d, JPC = 2.4 Hz), 131.2, 128.8, 128.68,
128.66, 128.5, 128.3, 128.2, 127.8 (d, JPC = 110.0 Hz), 127.7
(d, JPC = 11.2 Hz), 125.8, 124.8 (d, JPC = 5.9 Hz), 124.2, 123.3,
73.3 (d, JPC = 3.4 Hz), 52.4, 52.3, 51.3 (d, JPC = 3.1 Hz), 48.7
(d, JPC = 2.9 Hz), 23.7.
Synthesis of (S,R,S)-4a,b by asymmetric hydroamination
reaction
A solution of the monochloro complex of (S)-2 (0.15 mmol) in
dichloromethane (3 mL) was treated with silver perchlorate
(0.30 mmol) in water (1 mL) for 30 min. The mixture was then
filtered through Celite, washed with water, and dried over
MgSO4 and the solvent was removed under reduced pressure.
The resulting perchloro complex (S)-3 was dissolved in dichloro-
methane (5 mL) and cooled to −40 °C. Dimethylamine
(0.15 mmol) in THF was added to the solution and the mixture
was stirred for another 12 h at −40 °C. After removal of solvent,
crude hydroamination products were obtained as pale yellow
foaming solid. Without further purification, the crude products
were applied to the next step directly, in which chiral template
auxiliary was removed chemoselectively.
Fig. 4 Structure of (R,S)-14′f.
solution and the triethylamine (387 mg, 3.82 mmol) was added
subsequently. The temperature was increased to room tempera-
ture nature after the mixture was stirred for 4 h at −78 °C and
continued stirred for 10 h at room temperature. The reaction was
monitored by 31P NMR and the mixture was concentrate after
reaction completed. The mixture was purified by column chrom-
atography to give 1915 mg of (S)-2 (75.0% yield). Yellow solid:
mp 120–123 °C; [α]D = +38° (c 0.5, CH2Cl2) at 20 °C. 31P
5396 | Dalton Trans., 2012, 41, 5391–5400
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Table 7 Crystallographic data for complexes (R,S)-8a, (S,R,S)-10g, (R,S)-14f and (R,S)-14′f
(R,S)-8a
(S,R,S)-10g
(R,S)-14f and (R,S)-14′f
Formula
fw
Space group
Cryst syst
a (Å)
b (Å)
c (Å)
C20H24Cl2NO4PPd
550.67
C42H48Cl3N2O8PPd
952.54
P2(1)
Monoclinic
11.2143(4)
17.4999(6)
11.5906(4)
90
C25H26Cl2NO4PPd
612.74
P2(1)
Monoclinic
10.5919(14)
20.528(3)
12.6956(16)
90
P2(1)2(1)2(1)
Orthorhombic
10.8879(2)
12.1286(3)
17.4097(4)
90
α (°)
β (°)
90
90
111.861(2)
90
2111.07(13)
2
109.676(8)
90
2599.2(6)
4
γ (°)
V (Å3)
Z
2299.04(9)
4
T (K)
D
173(2)
1.591
173(2)
1.499
173(2)
1.566
calcd (g cm–3
)
λ (Å)
0.71073
1.134
1112
0.71073
0.722
980
0.71073
1.013
1240
μ (mm–1
F (000)
)
Flack param
−0.049(19)
−0.019(15)
−0.018(12)
R1 (obs data)a
0.0359
0.0415
0.0287
wR2 (obs data)b
0.0534
0.0918
0.0701
2 2
2 2
2
a R1 = ∑||Fo| − |Fc||/∑|Fo|. b wR2 = {∑[w(Fo2 − Fc ) ]/∑[w(Fo ) ]}, w−1 = σ2(Fo ) + (aP)2 + bP.
Palladium complex (S,R,S)-4a. 31P NMR (162 MHz, CDCl3):
δ 46.1.
Palladium complex (S,R,S)-4b. 31P NMR (162 MHz, CDCl3):
4.50 (dd, JHH = 13.2 Hz, JPH = 9.1 Hz, 1H), 4.12–4.18 (m, 1H),
3.81 (s, 3H), 3.39–3.50 (m, 1H), 2.73–2.84 (m, 2H), 1.92 (t, JHH
= 6.9 Hz, 3H), 1.83 (t, JHH = 7.3 Hz, 3H); 13C NMR (125 MHz,
CDCl3): δ 166.3 (d, JPC = 25.0 Hz), 165.9 (d, JPC = 8.4 Hz),
134.9, 134.8, 133.7, 133.6, 133.3 (d, JPC = 2.8 Hz), 132.6 (d,
δ 45.1.
JPC = 2.9 Hz), 129.10, 129.06, 129.01, 128.97, 125.5 (d, JPC
=
60.7 Hz), 124.1 (d, JPC = 56.2 Hz), 68.8 (d, JPC = 10.3 Hz),
56.7, 56.3, 53.3, 52.8, 51.9 (d, JPC = 17.6 Hz), 15.8, 14.3.
Synthesis of (S,R,S)-8a,b
A solution of above crude hydroamination products (S,R,S)-4a,b
in dichloromethane (5 mL) was treated with concentrated hydro-
chloric acid (5 mL) at room temperature for 24 h. The reaction
mixture was then diluted with dichloromethane (20 mL), washed
with water (3 × 5 mL) and dried over anhydrous MgSO4.
Removal of solvent gave the yellow solid, which was readily
grown crystal from dichloromethane and diethyl ether to give the
(R,S)-8a and (R,S)-8b respectively.
Synthesis of (R,S)-9a,b
A
solution of the dichloro complex (R,S)-8a (165 mg,
0.3 mmol) in CH2Cl2 (10 mL) was treated with excess potassium
cyanide (195 mg, 3 mmol) in water (2 mL). The reaction
mixture was stirred vigorously at room temperature for 10 min.
The colorless organic layer was separated, washed with water (3
× 5 mL) and dried over anhydrous MgSO4. Upon the removal of
the solvent under reduced pressure, free ligands (R,S)-9a was
obtained as a pale yellow oil.
(R,S)-8a. Yellow prism crystal: mp 190–191 °C; [α]D = +82°
(c 0.5, CH2Cl2). Anal. Calcd for C20H24Cl2NO4PPd: C, 43.6; H,
4.4; N, 2.5; Found: C, 43.5; H, 4.4; N, 2.6; 31P NMR
(202 MHz, CDCl3): δ 42.3; 1H NMR (500 MHz, CDCl3): δ
7.91–8.01 (m, 4H), 7.62–7.66 (m, 2H), 7.51–7.56 (m, 4H), 4.57
(dd, JHH = 13.2 Hz, JPH = 8.1 Hz, 1H), 4.06 (dd, JHH = 13.2 Hz,
JPH = 7.9 Hz, 1H), 3.79 (s, 3H), 3.39 (s, 3H), 3.36 (s, 3H), 2.94
(s, 3H); 13C NMR (125 MHz, CDCl3): δ 165.6 (d, JPC = 25.5
Hz), 165.2 (d, JPC = 8.7 Hz), 135.2, 135.1, 133.6 (d, JPC = 1.4
Hz), 133.5, 133.4, 132.7 (d, JPC = 3.1 Hz), 129.3, 129.2, 129.0,
128.9, 124.8 (d, JPC = 61.3 Hz), 123.4 (d, JPC = 55.2 Hz),
74.5 (d, JPC = 10.5 Hz), 53.4, 53.3, 52.9, 49.8 (d, JPC = 17.7
Hz), 46.7.
(R,S)-9a. Pale yellow oil: (103 mg, 92%); [α]D = −222° (c
1
0.5, CH2Cl2); 31P NMR (162 MHz, CDCl3): δ −8.1; H NMR
(400 MHz, CDCl3): δ 7.64–7.68 (m, 2H), 7.52–7.55 (m, 2H),
7.31–7.38 (m, 6H), 3.89 (dd, JHH = 12 Hz, JPH = 2.4 Hz, 1H),
3.81 (dd, JHH = 12 Hz, JPH = 4.8 Hz, 1H), 3.69 (s, 3H), 3.06 (s,
3H), 2.12 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 171.4 (d,
JPC = 9.1 Hz), 171.1 (d, JPC = 25 Hz), 136.2 (d, JPC = 15.3 Hz),
135.1 (d, JPC = 18.4 Hz), 134.8, 134.6, 133.7, 133.5, 129.2,
128.6, 128.2, 128.1, 128.0, 127.9, 67.8 (d, JPC = 19.6 Hz), 51.2,
51.1, 46.4 (d, JPC = 22.2 Hz), 41.8.
(R,S)-8b. Yellow prism crystal: mp 170–171 °C; [α]D = +50°
(c 0.5, CH2Cl2); Anal. Calcd for C22H28Cl2NO4PPd: C, 45.7, H,
4.9; N, 2.4, Found: C, 45.5; H, 4.8; N, 2.2.; 31P NMR
(202 MHz, CDCl3): δ 42.5; 1H NMR (500 MHz, CDCl3): δ
8.01–8.05 (m, 2H), 7.84–7.88 (m, 2H), 7.60–7.66 (m, 2H),
7.48–7.56 (m, 4H), 4.82 (dd, JHH = 13.2 Hz, JPH = 9.1 Hz, 1H),
(R,S)-9b. Pale yellow oil (108 mg, 90%) from dichloro
complex (R,S)-8b (174 mg, 0.3 mmol); [α]D = −134° (c 0.5,
CH2Cl2); 31P NMR (162 MHz, CDCl3): δ −8.7; 1H NMR
(400 MHz, CDCl3): δ 7.71–7.75 (m, 2H), 7.39–7.50 (m, 5H),
7.29–7.31 (m, 3H), 4.12 (dd, JHH = 12 Hz, JPH = 5.4 Hz, 1H),
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3.96 (d, JHH = 12 Hz, 1H), 3.69 (s, 3H), 3.02 (s, 3H), 2.49–2.56
(m, 2H), 2.31–2.40 (m, 2H), 0.78 (t, JHH = 7.1 Hz, 6H); 13C
NMR (100 MHz, CDCl3): δ 172.5 (d, JPC = 10.8 Hz), 171.3 (d,
JPC = 1.4 Hz), 136.3 (d, JPC = 15.4 Hz), 135.9 (d, JPC = 19.4
Hz), 134.7, 134.5, 134.1, 133.8, 128.90, 128.88, 128.4, 128.3,
Calcd for C24H24Cl2NO4PPd: C, 48.1; H, 4.0; N, 2.3; Found: C,
48.2; H, 3.2; N, 2.5; 31P NMR (162 MHz, CDCl3): δ1 50.9 and
δ2 44.5 (δ1/δ2 = 0.7/1); 1H NMR (400 MHz, CDCl3): δ
7.16–8.24 (m, 25.5H), 5.38–5.44 (m, 1H), 4.79–4.84 (m, 1.7H),
4.05–4.22 (m, 0.7H), 3.48 (s, 2.1H), 3.45 (s, 3H), 3.41 (s, 2.1H),
3.14 (s, 3H).
127.9, 127.8, 64.4 (d, JPC = 23.5 Hz), 51.2, 50.1, 46.7 (d, JPC
=
21.7 Hz), 44.6, 12.9.
(R,S)-14b and (R,S)-14′b. Yellow solid: mp 211–213 °C
(decomp); 96% yield; [α]D = +102° (c 0.5, CH2Cl2); Anal.
Calcd for C25H26Cl2NO5PPd: C, 47.8; H, 4.2; N, 2.2; Found: C,
46.8; H, 4.8; N, 2.2; 31P NMR (162 MHz, CD2Cl2): δ1 48.1 and
δ2 46.2 (δ1/δ2 = 1/0.8); 1H NMR (400 MHz, CD2Cl2): δ
6.94–8.51 (m, 25.2H), 6.80–6.90 (brs, 1H), 6.50–6.60 (brs,
0.8H), 4.95–5.07 (m, 1.8H), 4.50–4.57 (m, 1H), 4.32–4.42 (m,
1H), 4.02 (s, 3H), 3.59 (s, 2.4H), 3.43 (s, 2.4H), 3.41 (s, 3H),
3.80 (s, 3H), 3.20 (s, 2.4H).
Synthesis of (S,R,S)-10a–h and (S,R,S)-10′a–h by asymmetric
hydroamination reaction
A solution of the monochloro complex of (S)-2 (100 mg,
0.15 mmol) in dichloromethane (3 mL) was treated with silver
perchlorate (68 mg, 0.30 mmol) in water (1 mL) for 30 min. The
mixture was then filtered through Celite, washed with water, and
dried over MgSO4 and the solvent was removed under reduced
pressure. The resulting perchloro complex (S)-3 was dissolved in
chloroform (3 mL). Amine (0.15 mmol) was added to the sol-
ution and the mixture was stirred for another 16 h at 60 °C. After
removal of solvent, crude hydroamination product was obtained
as pale yellow foam. The crude product was separated by
column chromatography give the (S,R,S)-10a–h and (S,R,S)-10′
a–h as a pair N-chiral isomers. Without separation of this pair of
isomers, they were applied to the next step directly, in which
chiral template auxiliary was removed chemoselectively.
(R,S)-14c and (R,S)-14′c. Yellow solid: 191–193 °C
(decomp); 93% yield; [α]D = +100° (c 0.5, CH2Cl2); Anal.
Calcd for C25H26Cl2NO5PPd: C, 47.8; H, 4.2; N, 2.2; Found: C,
46.2; H, 4.7; N, 2.4; 31P NMR (162 MHz, CDCl3): δ1 51.1 and
δ2 44.6 (δ1/δ2 = 0.6/1); 1H NMR (400 MHz, CDCl3): δ
6.71–8.70 (m, 22.4H), 5.45 (m, 1H), 4.85–4.95 (m, 0.6H),
4.75–4.82 (m, 1H), 4.02–4.12 (m, 0.6H), 3.67 (s, 1.8H), 3.56 (s,
1.8H), 3.54 (s, 3H), 3.47 (s, 1.8H), 3.31 (s, 3H), 3.11 (s, 3H).
(R,S)-14d and (R,S)-14′d. Yellow solid 182–184 °C
(decomp); 96% yield; [α]D = +126° (c 0.5, CH2Cl2); Anal.
Calcd for C25H26Cl2NO5PPd: C, 47.8; H, 4.2; N, 2.2; Found: C,
47.6; H, 3.5; N, 3.7; 31PNMR (162 MHz, CDCl3): δ1 51.2 and
δ2 44.3 (δ1/δ2 = 0.7/1); 1H NMR (400 MHz, CDCl3): δ
6.57–8.56 (m, 23.8H), 5.32–5.40 (m, 1H), 4.68–4.74 (m, 1.7H),
3.90–4.01 (m, 0.7H), 3.75 (s, 2.1H), 3.67 (s, 3H), 3.43 (s, 2.1H),
3.40 (s, 3H), 3.33 (s, 2.1H), 3.05 (s, 3H).
(S,R,S)-10g. Pale yellow prism crystal: mp 180–182 °C; 60%
yield; [α]D = +164° (c 0.5, CH2Cl2); Anal. Calcd for
C41H46ClN2O8PPd: C, 56.8; H, 5.3; N, 3.2, Found: C, 54.9; H,
1
5.0; N, 3.4; 31P NMR (162 MHz, CDCl3): δ 42.5; H NMR
(400 MHz, CDCl3): δ 8.05–8.15 (m, 4H), 7.77–7.81 (m, 1H),
7.66–7.70 (m, 2H), 7.58–7.61 (m, 2H), 7.29–7.40 (m, 5H),
7.05–7.07 (m, 1H), 6.89–6.92 (m, 3H), 6.30 (d, JHH = 12.2 Hz),
5.13 (dd, JHH = 12.7 Hz, JPH = 8.8 Hz, 1H), 4.11–4.17 (m, 1H),
3.94–4.03 (m, 1H), 3.53 (s, 3H), 3.47 (s, 3H), 3.19 (s, 3H), 2.56
(R,S)-14e and (R,S)-14′e. Yellow solid: mp 189–191 °C
(decomp); 92% yield; [α]D = +98° (c 0.5, CH2Cl2); Anal. Calcd
for C25H26Cl2NO4PPd: C, 49.0; H, 4.3; N, 2.3; Found: C, 48.8;
H, 5.0; N, 2.3; 31P NMR (162 MHz, CDCl3): δ1 50.9 and δ2
(s, 3H), 2.33 (d, JPH = 3.7 Hz, 3H), 2.27 (s, 6H), 1.91 (d, JHH
=
=
6.4 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ 168.1 (d, JPC
19.2 Hz), 167.3 (d, JPC = 9.0 Hz), 149.3 (d, JPC = 2.7 Hz),
144.1, 137.4, 136.9, 136.7, 136.6, 134.8, 134.7, 133.8 (d, JPC
1
=
44.7 (δ1/δ2 = 0.5/1); H NMR (400 MHz, CDCl3): δ 6.98–8.67
2.6 Hz), 133.3, 133.1, 133.0, 131.5 (d, JPC = 3.8 Hz), 131.4,
131.3, 130.7, 129.9, 129.6, 129.5, 129.0, 128.9, 128.7, 128.5,
126.3, 126.2, 125.94, 125.88, 125.7, 124.8, 123.3, 121.8 (d, JPC
= 42.8 Hz), 74.0 (d, JPC = 2.0 Hz), 63.2 (d, JPC = 9.0 Hz), 52.5,
52.4, 51.2 (d, JPC = 1.9 Hz), 50.3, 50.2, 45.9, 23.8, 21.7, 20.7,
18.5.
(m, 21H), 5.45–5.53 (m, 1H), 4.82–4.90 (m, 0.5H), 4.70–4.81
(m, 1H), 4.05–4.12 (m, 0.5H), 3.52 (s, 1.5H), 3.50 (s, 3H), 3.42
(s, 1.5H), 3.12 (s, 3H), 2.30 (s, 1.5H), 2.06 (s, 3H).
(R,S)-14f and (R,S)-14′f. Yellow solid: 195–197 °C (decomp);
95% yield; [α]D = +146° (c 0.5, CH2Cl2); Anal. Calcd for
C25H26Cl2NO4PPd: C, 49.0; H, 4.3; N, 2.3; Found: C, 48.7; H,
4.9; N, 2.2; 31P NMR (162 MHz, CDCl3): δ1 51.1 and δ2 44.6
Synthesis of (R,S)-14a–h and (R,S)-14′a–h
1
(δ1/δ2 = 0.5/1); H NMR (400 MHz, CDCl3): δ 6.95–8.64 (m,
21H), 5.35–5.42 (m, 1H), 4.75–4.86 (m, 1.5H), 4.04–4.12 (m,
0.5H), 3.51 (s, 1.5H), 3.48 (s, 3H), 3.40 (s, 1.5H), 3.13 (s, 3H),
2.38 (s, 1.5H), 2.26 (s, 3H).
A solution of above crude hydroamination product mixture of (S,
R,S)-10a–h and (S,R,S)-10′a–h in dichloromethane (5 mL) was
treated with concentrated hydrochloric acid (5 mL) at room
temperature for 2 h. The reaction mixture was then diluted with
dichloromethane (20 mL), washed with water (3 × 5 mL) and
dried over anhydrous MgSO4. Removal of solvent gave the
yellow solid, which was readily crystallized from dichloro-
methane and diethyl ether to give the pair (R,S)-14a–h and (R,
S)-14′a–h as a yellow prism co-crystal.
(R,S)-14g. Yellow solid: mp 174–176 °C (decomp); 91%
yield; [α]D
= +70° (c 0.5, CH2Cl2); Anal. Calcd for
C27H30Cl2NO4PPd: C, 50.6; H, 4.7; N, 2.2; Found: C, 48.8; H,
1
4.3; N, 2.8; 31P NMR (202 MHz, CDCl3): δ 46.3; H NMR
(500 MHz, CDCl3): δ 7.94–8.03 (m, 4H), 7.67–7.68 (m, 1H),
7.52–7.68 (m, 5H), 6.87 (s, 1H), 6.76 (s, 1H), 6.04 (brs, 1H),
4.38–4.42 (m, 1H), 4.28–4.30 (m, 1H), 3.47 (s, 3H), 3.42 (s,
3H), 2.88 (s, 3H), 2.36 (s, 3H), 2.21 (s, 3H).
(R,S)-14a and (R,S)-14′a. Yellow solid: mp 202–204 °C
(decomp); 94% yield; [α]D = +144° (c 0.5, CH2Cl2); Anal.
5398 | Dalton Trans., 2012, 41, 5391–5400
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(R,S)-14h and (R,S)-14′h. Yellow solid: mp 171–173 °C
(decomp); 93% yield; [α]D = +96° (c 0.5, CH2Cl2); Anal. Calcd
for C24H23Cl2N2O6PPd: C, 44.8; H, 3.6; N, 4.4; Found: C, 44.2;
H, 4.3; N, 4.3; 31P NMR (162 MHz, CDCl3): δ1 50.7 and δ2
(R,S)-15d. Off white oil; 92% yields; [α]D = −94° (c 0.5,
CH2Cl2); 31P NMR (202 MHz, CDCl3): δ −9.6; 1H NMR
(500 MHz, CDCl3): δ 7.62–7.66 (m, 2H), 7.45–7.48 (m, 2H),
7.39–7.40 (m, 3H), 7.29–7.34 (m, 3H), 6.70 (d, JHH = 8.9 Hz,
1H), 6.46 (d, JHH = 8.9 Hz, 1H), 4.40–4.45 (m, 1H), 3.91 (d, J =
10.1 Hz, 1H, NH), 3.88 (d, J = 8.2 Hz, 1H), 3.73 (s, 3H), 3.68
(s, 3H), 3.28 (s, 3H); 13C NMR (125 MHz, CDCl3): δ 172.7 (d,
JPC = 6.0 Hz), 170.5 (d, JPC = 2.5 Hz), 153.2, 139.9, 135.8 (d,
JPC = 15.5 Hz), 135.1 (d, JPC = 16.9 Hz), 134.1, 133.9, 133.7,
133.5, 129.3, 128.63, 128.58, 128.22, 128.16, 115.9, 114.7, 58.9
(d, JPC = 20.1 Hz), 55.6, 52.4, 51.7, 48.9 (d, JPC = 25.8 Hz).
1
45.9 (δ1/δ2 = 1/1.3); H NMR (400 MHz, CDCl3): δ 7.34–8.68
(m, 32.2H), 5.41–5.46 (m, 1H), 4.49–4.92 (m, 2.3H), 4.22–4.26
(m, 1.3H), 3.52 (s, 3.9H), 3.43 (s, 3.9H), 3.41 (s, 3.0 H), 3.18 (s,
3.0H).
Synthesis of (R,S)-15a–h
(R,S)-15e. Pale yellow oil; 95% yields; [α]D = −82° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −9.5; 1H NMR
(500 MHz, CDCl3): δ 7.64–7.66 (m, 2H), 7.46–7.49 (m, 2H),
7.40–7.42 (m, 3H), 7.29–7.33 (m, 3H), 7.00 (t, JHH = 7.8 Hz,
1H), 6.56 (d, JHH = 7.5 Hz, 1H), 6.25–6.28 (m, 2H), 4.48–4.52
(m, 1H), 4.16 (d, JHH = 9.7 Hz, 1H, NH), 3.91 (dd, JPH = 7.6,
JHH = 0.8 Hz, 1H), 3.71 (s, 3H), 3.30 (s, 3H), 2.21 (s, 3H); 13C
NMR (125 MHz, CDCl3): δ 172.4 (d, J = 2.5 Hz), 170.5 (d, JPC
= 2.8 Hz), 145.7, 139.0, 135.7 (d, JPC = 16.1 Hz), 135.0 (d, JPC
= 17.2 Hz), 134.0, 133.8, 133.7, 129.4, 129.3, 129.1, 128.7,
128.6, 128.24, 128.18, 119.8, 114.5, 111.1, 57.5 (d, JPC = 20.6
Hz), 52.4, 51.7, 48.9 (d, JPC = 26.3 Hz), 21.5.
A CH2Cl2 solution of the dichloro complex (R,S)-14a–h and (R,
S)-14′a–h (0.2 mmol) was treated with excess potassium
cyanide (195 mg, 3 mmol) in water (1 mL). The reaction
mixture was stirred vigorously at room temperature for 10 min.
The yellow organic layer became colorless and then the organic
phase was transferred to the Schlenk tube by syringe under
argon. The solvent was removed by flowing N2 and vacuum to
give the free ligands (R,S)-15a–h.
(R,S)-15a. Pale yellow oil, 94% yield; [α]D = −112° (c 0.5,
CH2Cl2). 31P NMR (162 MHz, CDCl3): δ −9.5; 1H NMR
(400 MHz, CDCl3): δ 7.63–7.68 (m, 2H), 7.45–7.49 (m, 2H),
7.40–7.42 (m, 3H), 7.29–7.33 (m, 3H), 7.10–7.13 (m, 2H), 6.74
(d, JHH = 7.3 Hz, 1H), 6.46 (d, JHH = 7.8 Hz, 1H), 4.49–4.55
(m, 1H), 4.19 (d, JHH = 9.6 Hz, 1H), 3.91 (dd, JPH = 7.3 Hz,
JHH = 0.6 Hz, 1H), 3.70 (s, 3H), 3.29 (s, 3H); 13C NMR
(R,S)-15f. Off white oil; 91% yields; [α]D = −88° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −9.5; 1H NMR
(500 MHz, CDCl3): δ 7.64–7.67 (m, 2H), 7.46–7.49 (m, 2H),
7.29–7.41 (m, 6H), 6.93 (d, JHH = 8.2 Hz, 2H), 6.39 (d, JHH
=
(100 MHz, CDCl3): δ 172.4 (d, JPC = 15.4 Hz), 170.5 (d, JPC
=
8.2 Hz, 2H), 4.46–4.51 (m, 1H), 4.06 (d, JHH = 9.9 Hz, 1H),
3.90 (d, JHH = 7.9 Hz, 1H), 3.69 (s, 3H), 3.29 (s, 3H), 2.22 (s,
3H); 13C NMR (125 MHz, CDCl3): δ 172.6 (d, JPC = 5.8 Hz),
170.5 (d, JPC = 2.5 Hz), 143.5, 135.7 (d, JPC = 15.7 Hz), 135.1
(d, JPC = 17.2 Hz), 134.0, 133.9, 133.8, 133.6, 129.7, 129.4,
129.3, 128.7, 128.6, 128.21, 128.16, 114.1, 58.0 (d, JPC = 20.3
Hz), 52.4, 51.7, 48.9 (d, JPC = 26.1 Hz), 20.4.
2.8 Hz), 145.8, 135.6 (d, JPC = 15.4 Hz), 134.9 (d, JPC = 17.0
Hz), 134.0, 133.82, 133.80, 133.6, 129.44, 129.38, 129.2, 128.7,
128.6, 128.25, 128.17, 118.8, 113.9, 57.5 (d, JPC = 20.4 Hz),
52.4, 51.7, 48.9 (d, JPC = 26.1 Hz).
(R,S)-15b. Colorless oil; 93% yields; [α]D = −102° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −9.1; 1H NMR
(500 MHz, CDCl3): δ 7.64–7.67 (m, 2H), 7.44–7.47 (m, 2H),
7.38–7.40 (m, 3H), 7.30–7.32 (m, 3H), 6.75–6.78 (m, 1H),
6.66–6.72 (m, 2H), 6.44–6.46 (m, 1H), 4.82 (d, JHH = 9.8 Hz,
1H, NH), 4.52–4.57 (m, 1H), 3.97 (d, JPH = 13.3 Hz, 1H), 3.69
(s, 3H), 3.68 (s, 3H), 3.27 (s, 3H); 13C NMR (125 MHz,
CDCl3): δ 172.4 (d, JPC = 6.3 Hz), 170.5 (d, JPC = 2.1 Hz),
147.1, 135.8, 135.6 (d, JPC = 15.5 Hz), 135.0 (d, JPC = 17.3
Hz), 134.1, 134.0, 133.7, 133.5, 129.3, 129.2, 128.6, 128.5,
128.2, 128.1, 121.0, 117.8, 110.7, 109.9, 57.1 (d, JPC = 21.4
Hz), 55.4, 52.4, 51.7, 48.7 (d, JPC = 26.3 Hz).
(R,S)-15g. Off white oil; 93% yields; [α]D = −46° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −11.8; 1H NMR
(500 MHz, CDCl3): δ 7.63–7.65 (m, 2H), 7.43–7.46 (m, 2H),
7.37–7.39 (m, 3H), 7.29–7.33 (m, 3H), 6.72 (s, 2H), 4.28–4.32
(m, 1H), 3.85 (d, JPH = 6.7 Hz, 1H), 3.66 (d, JHH = 12.8 Hz,
1H), 3.57 (s, 3H), 3.28 (s, 3H), 2.18 (s, 3H), 2.11 (s, 6H).
(R,S)-15h. Yellow oil; 96% yields; [α]D = −84° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −9.8; 1H NMR
(500 MHz, CDCl3): δ 8.01 (d, J = 9.1 Hz, 2H), 7.61–7.64 (m,
2H), 7.44–7.47 (m, 5H), 7.30–7.35 (m, 3H), 6.36 (d, JHH = 9.1
Hz, 2H), 4.94 (d, JHH = 7.2 Hz, 1H, NH), 4.58–4.62 (m, 1H),
3.92 (d, JPH = 7.5 Hz, 1H), 3.74 (s, 3H), 3.30 (s, 3H); 13C NMR
(R,S)-15c. Off white oil; 93% yields; [α]D = −92° (c 0.5,
CH2Cl2). 31P NMR (202 MHz, CDCl3): δ −9.3; 1H NMR
(500 MHz, CDCl3): δ 7.64–7.67 (m, 2H), 7.45–7.48 (m, 2H),
7.29–7.41 (m, 6H), 7.01 (t, JHH = 8.0 Hz, 1H), 6.30–6.31 (m,
1H), 6.04–6.06 (m, 2H), 4.48–4.53 (m, 1H), 4.21 (d, JHH = 9.6
Hz, 1H, NH), 3.92 (d, JPH = 7.8 Hz, 1H), 3.70 (s, 3H), 3.70 (s,
3H), 3.28 (s, 3H); 13C NMR (125 MHz, CDCl3): δ 172.4 (d,
JPC = 5.5 Hz), 170.5 (d, JPC = 3.2 Hz), 160.7, 147.2, 135.6 (d,
JPC = 15.9 Hz), 134.9 (d, JPC = 17.2 Hz), 134.0, 133.83, 133.81,
133.6, 130.0, 129.5, 129.4, 128.72, 128.66, 128.25, 128.19,
106.5, 104.4, 99.8, 57.5 (d, JPC = 20.9 Hz), 55.0, 52.5, 51.8,
48.9 (d, JPC = 26.4 Hz).
(125 MHz, CDCl3): δ 171.0 (d, JPC = 5.1 Hz), 170.2 (d, JPC
3.0 Hz), 151.0, 139.3, 134.8 (d, JPC = 15.5 Hz), 133.9 (d, JPC
=
=
7.1 Hz), 133.8, 133.71, 133.66, 129.9, 129.7, 128.94, 128.88,
128.44, 128.38, 126.1, 112.1, 56.4 (d, JPC = 20.3 Hz), 52.9,
52.0, 48.7 (d, JPC = 27.3 Hz).
Acknowledgements
We thank Nanyang Technological University for support of this
research and for Ph.D. scholarships to K. C.
This journal is © The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 5391–5400 | 5399

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8 (a) A. R. Shaffer and J. A. R. Schmidt, Organometallics, 2008, 27, 1259;
(b) S. R. Beeren, S. L. Dabb and B. A. Messerle, J. Organomet. Chem.,
2009, 694, 309; (c) G. Kuchenbeiser, A. R. Shaffer, N. C. Zingales, J.
F. Beck, A. R. Joseph and J. A. R. Schmidt, J. Organomet. Chem., 2010,
695, 179.
References
1 (a) P. Espinet and K. Soulantica, Coord. Chem. Rev., 1999, 193–195,
499; (b) P. J. Guiry and C. P. Saunders, Adv. Synth. Catal., 2004, 346,
497; (c) L. C. Liang, Coord. Chem. Rev., 2006, 250, 1152; (d) I.
D. Kostas, Curr. Org. Synth., 2008, 5, 227; (e) S. Maggini, Coord. Chem.
Rev., 2009, 253, 1793.
2 (a) J. C. Anderson, R. J. Cubbon and J. D. Harling, Tetrahedron: Asym-
metry, 2001, 12, 923; (b) T. Mino, Y. Tanaka, Y. Hattori, T. Yabusaki,
H. Saotome, M. Sakamoto and T. Fujita, J. Org. Chem., 2006, 71, 7346;
(c) R. J. Detz, S. A. Heras, R. de Gelder, P. W. N. M. van Leeuwen,
H. Hiemstra, J. N. H. Reek and J. H. van Maarseveen, Org. Lett., 2006,
8, 3227; (d) S. Fukuzawa, M. Yamamoto, M. Hosaka and S. Kikuchi,
Eur. J. Org. Chem., 2007, 5540; (e) T. Mino, K. Wakui, S. Oishi,
Y. Hattori, M. Sakamoto and T. Fujita, Tetrahedron: Asymmetry, 2008,
19, 2711; (f) F. Leca, F. Fernández, G. Muller, C. Lescop, R. Réau and
M. Gómez, Eur. J. Org. Chem., 2009, 5583.
3 (a) B. M. Trost and M. L. Crawley, Chem. Rev., 2003, 103, 2921; (b) K.
H. Kim, C.-K. Jeong, D.-H. Kim and D.-C. Ha, Tetrahedron: Asymmetry,
2006, 17, 1688; (c) J. D. Huang, X. P. Hu, S. B. Yu, J. Deng, D.
Y. Wang, Z. C. Duan and Z. Zheng, J. Mol. Catal. A: Chem., 2007, 270,
127.
4 (a) R. Guo, A. J. Lough, R. H. Morris and D. Song, Organometallics,
2004, 23, 5524; (b) L. Dahlenburg and R. Götz, Eur. J. Inorg. Chem.,
2004, 888; (c) K. Abdur-Rashid, R. Guo, A. J. Lough, R. H. Morris and
D. Song, Adv. Synth. Catal., 2005, 347, 571; (d) R. Guo, R. H. Morris
and D. Song, J. Am. Chem. Soc., 2005, 127, 516; (e) M. Ito,
A. Sakaguchi, C. Kobayashi and T. Ikariya, J. Am. Chem. Soc., 2007,
129, 290; (f) R. Puchta, L. Dahlenburg and T. Clark, Chem.–Eur. J.,
2008, 14, 8898; (g) L. Dahlenburg and C. Kühnlein, Inorg. Chim. Acta,
2008, 361, 2785; (h) W. Jia, X. Chen, R. Guo, C. Sui-Seng, D. Amoroso,
A. J. Lough and K. Abdur-Rashid, Dalton Trans., 2009, 8301; (i) K.
E. Thiesen, K. Maitra, M. M. Olmstead and S. Attar, Organometallics,
2010, 29, 6334.
9 (a) T. Hayashi, M. Fukushima, M. Konishi and M. Kumada, Tetrahedron
Lett., 1980, 21, 79; (b) T. Hayashi, M. Konishi, M. Fukushima,
K. Kanehira, T. Hioki and M. Kumada, J. Org. Chem., 1983, 48, 2195;
(c) S. Pellet-Rostaing, C. Saluzzo, R. T. Halle, J. Breuzard, L. Vial, F.
L. Guyaderb and M. Lemaire, Tetrahedron: Asymmetry, 2001, 12, 1983.
10 (a) F. Speiser and P. Braunstein, Organometallics, 2004, 23, 2613;
(b) F. Speiser and P. Braunstein, Organometallics, 2004, 23, 2625;
(c) F. Speiser and P. Braunstein, Organometallics, 2004, 23, 2633;
(d) F. Speiser, P. Braunstein and A. Saussine, Acc. Chem. Res., 2005, 38,
784; (e) R. J. Lundgren, M. A. Rankin, R. Robert McDonald and
M. Mark Stradiotto, Organometallics, 2008, 27, 254; (f) P. W. Dyer,
J. Fawcett and M. J. Hanton, Organometallics, 2008, 27, 5082; (g) M.
M. Mogorosi, T. Mahamo, J. R. Moss, S. F. Mapolie, J. C. Slootweg,
K. Lammertsma and G. S. Smith, J. Organomet. Chem., 2011, 696,
3585.
11 (a) J. Andrieu, P. Richard, J.-M. Camus and R. Poli, Inorg. Chem., 2002,
41, 3876; (b) C. Wetzel, P. C. Kunz, I. Thiel and B. Spingler, Inorg.
Chem., 2011, 50, 7863.
12 (a) J. H. Griffin and R. M. Kellogg, J. Org. Chem., 1985, 50, 3261;
(b) B. K. Vriesema and R. M. Kellogg, Tetrahedron Lett., 1986, 27,
2049; (c) G. A. Cross and R. M. Kellogg, J. Chem. Soc., Chem.
Commun., 1987, 1746; (d) G. Cross, B. K. Vriesema, G. Boven and R.
M. Kellogg, J. Organomet. Chem., 1989, 370, 357; (e) J. C. Anderson,
R. J. Cubbon and J. D. Harling, Tetrahedron: Asymmetry, 1999, 10, 2829.
13 F. Liu, S. A. Pullarkat, Y. Li, S. Chen, M. Yuan, Z. Y. Lee and P.
H. Leung, Organometallics, 2009, 28, 3941.
14 (a) P. Rönnholm, M. Södergren and G. Hilmersson, Org. Lett., 2007, 9,
3781; (b) R. Guo, S. Lu, X. Chen, C. W. Tsang, W. Jia, C. Sui-Seng,
D. Amoroso and K. Abdur-Rashid, J. Org. Chem., 2010, 75, 937.
15 A. Kondoh, H. Yorimitsu and K. Oshima, Org. Lett., 2008, 10, 3093.
16 X. Fu, Z. Jiang and C.-H. Tan, Chem. Commun., 2007, 5058.
17 P. H. Leung, S. H. Chan and Y. S. Song, Gold Complexes. PCT Int. Appl,
WO 0177121 A1, 2001.
5 (a) S. Bell, B. Wüstenberg, S. Kaiser, F. Menges, T. Netscher and
A. Pfaltz, Science (Washington, D. C.), 2006, 311, 642; (b) J. Mazuela, P.
O. Norrby, P. G. Andersson, O. Pàmies and M. Dièguez, J. Am. Chem.
Soc., 2011, 133, 13634; (c) A. Franzke and A. Pfaltz, Chem.–Eur. J.,
2011, 17, 4131.
18 P. H. Leung, Acc. Chem. Res., 2004, 37, 169.
19 X. Liu, K. F. Mok and P. H. Leung, Organometallics, 2001, 20, 3918.
20 (a) P. G. Kerr, P. H. Leung and S. B. Wild, J. Am. Chem. Soc., 1987, 109,
4321; (b) V. V. Dunina, E. B. Golovan, N. S. Gulyukina and A.
V. B u y e v i c h , Tetrahedron: Asymmetry, 1995, 6, 2731; (c) D. C. R. Hockless,
P. A. Gugger, P. H. Leung, R. C. Mayadunne, M. Pabel and S. B. Wild,
Tetrahedron, 1997, 53, 4083; (d) G. He, S. K. Loh, J. J. Vittal, K. F. Mok
and P. H. Leung, Organometallics, 1998, 17, 3931.
6 (a) J. W. Faller and K. J. Chase, Organometallics, 1994, 13, 989;
(b) B. Tao and G. C. Fu, Angew. Chem., Int. Ed., 2002, 41, 3892;
(c) M. Stradiotto, J. Cipot and R. McDonald, J. Am. Chem. Soc., 2003,
125, 5618; (d) M. A. Rankin, D. F. MacLean, G. Schatte, R. McDonald
and M. Stradiotto, J. Am. Chem. Soc., 2007, 129, 15855; (e) J. Cipot,
R. McDonald, M. J. Ferguson, G. Schatte and M. Stradiotto, Organome-
tallics, 2007, 26, 594; (f) D. Wechsler, G. Schatte and M. Stradiotto, J.
Organomet. Chem., 2009, 694, 1943; (g) D. Wechsler and M. Stradiotto,
Can. J. Chem., 2009, 87, 72.
21 S. K. Loh, K. F. Mok, P. H. Leung, A. J. P. White and D. J. Williams, Tet-
rahedron: Asymmetry, 1996, 7, 45.
22 S. Y. M. Chooi, P. H. leung, C. C. Lim, K. F. Mok, G. H. Quek, K.
Y. Sim and M. K. Tan, Tetrahedron: Asymmetry, 1992, 3, 529.
7 R.-Y. Lai, K. Surekha, A. Hayashi, F. Ozawa, Y.-H. Liu, S.-M. Peng and
S.-T. Liu, Organometallics, 2007, 26, 1062.
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