Enantioselective hydrophosphination of enones with diphenylphosphine catalyzed by bis(imidazoline) NCN pincer palladium(II) complexes

Article abstract of DOI:10.1021/om500144b

A series of chiral NCN pincer Pd(II) complexes with 1,3-bis(2′- imidazolinyl)phenyl (Phebim) ligands were synthesized via the C-H activation or oxidative addition method. A dinuclear macrocyclic Pd(II) complex was also prepared by reaction of the Phebim-H

Full text of DOI:10.1021/om500144b

Article
pubs.acs.org/Organometallics
Enantioselective Hydrophosphination of Enones with
Diphenylphosphine Catalyzed by Bis(imidazoline) NCN Pincer
Palladium(II) Complexes
Xin-Qi Hao, Yong-Wei Zhao, Jing-Jing Yang, Jun-Long Niu, Jun-Fang Gong,* and Mao-Ping Song*
College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Zhengzhou
University, Zhengzhou 450001, People’s Republic of China
S
* Supporting Information
ABSTRACT: A series of chiral NCN pincer Pd(II) complexes
with 1,3-bis(2′-imidazolinyl)phenyl (Phebim) ligands were
synthesized via the C−H activation or oxidative addition
method. A dinuclear macrocyclic Pd(II) complex was also
prepared by reaction of the Phebim-H ligand with PdCl2. All of
the new compounds were fully characterized, and X-ray single-
crystal structures were obtained for two of the complexes. The
Pd(II) complexes were successfully applied to enantioselective
hydrophosphination of various enones with diphenylphos-
phine, providing optically active phosphine derivatives in good yields with enantioselectivities of up to 94% ee.
reactions of acrylonitrile with imines, decarboxylative Mannich-
type reactions of cyanoacetic acids with imines, and allylations
of ketimines.6 All of these reactions could provide excellent
stereocontrol (≥90% ee). Furthermore, it was found that
bis(imidazolidine) NCN pincer Pd(II) complexes showed high
levels of enantioselectivities in the reaction of nitroalkenes with
malononitriles (up to 93% ee).7 In 2006, we reported the first
synthesis of the chiral 1,3-bis(2′-imidazolinyl)benzene (Phe-
bim-H) ligands, which are structural analogues of Phebox-H
ligands, as well as the corresponding NCN pincer Pt(II)
complexes via C−H activation of the ligands.8 Then the Pd−,
Ni−, and Rh−Phebim complexes were prepared successively
via a similar C−H activation procedure, and some of them
showed promising stereoselectivities in asymmetric catalysis.9
In particular, a preliminary survey on the catalysis of Pd−
Phebim complexes was carried out. The two complexes A and
B (Chart 1) were examined as the catalysts for enantioselective
hydrophosphination of chalcone with diphenylphosphine (1,4-
conjugate addition of Ph2P to chalcone). Complex A, having a
(4S)-phenyl substituent, could give the expected adduct in 84%
yield with 85% ee.10 Although the catalytic results are fairly
INTRODUCTION
■
Organometallic pincer palladium(II) complexes have found
wide applications in catalytic organic transformations such as
stannylation of allylic or propargylic substrates, allylation of
aldehydes or imines, Michael additions, aldol reactions, and
particularly a variety of cross-coupling reactions.1 Most of the
previous reports have focused on achiral Pd(II) pincers. In
contrast, chiral pincers and their use in asymmetric catalysis
have not been explored extensively. In addition, the reported
enantioselectivities of the catalysis products are often found to
be relatively low.1h For example, the NCN pincer metal
complexes with tridentate bis(oxazolinyl)phenyl (Phebox)
ligands (M = Pd, Pt, Ru, Rh, Ir, etc.) constitute a large family
of chiral pincer complexes.2 The Rh− and Ru−Phebox
complexes exhibited high efficiency and selectivity in many
catalytic reactions such as conjugate reduction, borylation,
hydrogenation, transfer hydrogenation, and several carbon−
carbon bond formation reactions. However, to our knowledge
the Pd−Phebox complexes have only been applied up to now
to asymmetric reactions of 2-cyanocarboxylates with Michael
acceptors, aldol reactions of isocyanides and aldehydes, and
Suzuki−Miyaura couplings. The enantioselectivities obtained
were moderate in all cases (up to 34%, 57% ,and 49% ee,
respectively).3 Encouragingly, some highly stereoselective
reactions catalyzed by pincer Pd complexes have emerged
very recently. Among them, Duan and coauthors developed a
bis(phosphine) PCP pincer Pd(II) catalyst bearing stereogenic
benzylic methylene centers for the asymmetric addition of
R2PH to N-tosylimines4 and some activated alkenes including
enones,5a enals,5b nitroalkenes,5c α,β-unsaturated N-acylpyrro-
les,5d and carboxylic and sulfonic esters.5e−g Nakamura and co-
workers applied bis(imidazoline) NCN pincer Pd(II) com-
plexes to the reaction of benzyl nitriles with imines, aza-MBH
Chart 1
Received: February 7, 2014
Published: March 28, 2014
© 2014 American Chemical Society
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Scheme 1. Synthesis of Chiral Bis(imidazoline) NCN Pincer Pd(II) Chloride Complexes 2a−c via C−H Activation
Scheme 2. Synthesis of Chiral Dinuclear Macrocyclic Pd(II) Complex 3
good, the synthetic yield of this Pd(II) complex via C−H
activation was rather low (<10%), which limited its further
utilization in catalysis. As an extension of the applications of the
chiral pincer Pd(II) catalysts, and also in continuation of our
interests in the pincer metal complexes,11 herein we report our
attempts to improve the yields of the Pd−Phebim complexes as
well as their performance in the enantioselective hydro-
phosphination of enones with diphenylphosphine.
palladated products and improve the efficiency of the expected
C2-palladation. The 5-nitro group was introduced to tune the
electronic effect of the ensuing Pd complex and to optimize the
catalyst. Thus, ligands 1a−c were synthesized starting from
commercially available 5-tert-butyl- or 5-nitroisophthalic acid
according to the procedure previously reported by us (the
synthetic route is given in Scheme S1 in the Supporting
Information).8,9a The following palladation reaction was carried
out by using Pd(OAc)2 as the metal(II) source under the
conditions similar to those used before.9a It was found that
complex 2a with a (4S)-phenyl substituent was obtained in 13%
yield, which was only slightly improved in comparison with
complex A (8% yield) without a tert-butyl group on the central
aryl. Pleasingly, complex 2b with (4S,5S)-diphenyl substituents
was isolated in good yield (75%). However, it was somewhat
confusing that the yield of complex 2c also with (4S,5S)-
diphenyl substituents was rather low (15%), considering that
several related complexes with or without the nitro group could
be produced in 31−54% yields.9a,10 We then tried the reaction
of ligand 1c with PdCl2 in the presence of Et3N in refluxing
toluene; the expected Pd pincer was not obtained, and the
dinuclear macrocyclic Pd(II) complex 3 was isolated instead in
high yield this time (85%, Scheme 2). The result indicated that
Pd(OAc)2 was more effective than PdCl2 in the central aryl C-
palladation of the Phebim-H ligands.
Overall, the yields of the Pd-Phebim complexes via C−H
activation were not very high, which was unfavorable to their
use in catalytic applications. We therefore sought the oxidative
addition method to get these complexes. For this purpose, the
2-bromo-1,3-bis(imidazoline)benzene ligands 4 were required.
The preparation of the ligands can be easily done starting from
2-bromo-m-xylene (the synthetic route is given in Scheme S2 in
the Supporting Information). Oxidation of 2-bromo-m-xylene
by KMnO4 produced 2-bromoisophthalic acid followed by
treatment with SOCl2 to afford 2-bromoisophthalic chloride
according to the published procedure.13 Reaction of the
chloride with various chiral amino alcohols, including L-
phenylglycinol, L-valinol, L-tert-leucinol, and (1R,2S)-2-amino-
1,2-diphenylethanol, gave the known 2-bromo-1,3-bis(amido
RESULTS AND DISCUSSION
■
Among the methods used for the preparation of NCN pincer
Pd(II) complexes, the C(aryl)−H activation of the related
pincer ligand precursors (NCHN) is the most direct and
convenient method, since it does not require prefunctionaliza-
tion of the precursors. However, in some cases this method
often fails. For example, the Pd−Phebox complexes, which are
very closely related to the current Pd−Phebim complexes, were
generally synthesized either by oxidative addition or by a
transmetalation method. The only example of direct C2-
palladation of a Phebox-H ligand gave the Pd pincer in 3%
yield.12 In contrast, in our previous study on the synthesis of
the Pd−Phebim complexes, most of them could be isolated in
reasonable yields (28−54% yields) via C−H activation.9a,10 In
addition, the substituents on the imidazoline ring of the
Phebim-H ligands 1 showed some influence on the yields of the
corresponding pincer Pd(II) complexes (Scheme 1, R = H). It
was found that the N-Ar group was better than the N-alkyl
group (∼34 vs 12% yield)9a and complex B (Chart 1) with
(4S,5S)-diphenyl substituents was produced in a yield higher
than that of complex A with (4S)-phenyl (31 vs 8%).10
Although complex A was obtained in only 8% yield, it displayed
much better stereoselectivity than complex B in the asymmetric
addition of diphenylphosphine to chalcone (85 vs −30% ee)
from the previous study.10 On the basis of the above
observations, we decided to first prepare the new Pd−Phebim
chloride complexes 2a−c via C−H activation (Scheme 1). The
introduction of the bulky 5-tert-butyl group into the central aryl
ring of the ligands 1 was designed to create a steric effect which
might hinder the formation of the undesired C4- or C6-
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alcohols),13 which were converted to the corresponding 2-
bromo-1,3-bis(imidazoline)benzene ligands 4 using a proce-
dure similar to the synthesis of ligands 1a−c.8,9a Then the
oxidative addition method was tried by treatment of the ligands
4 with Pd2(dba)3 in toluene at room temperature for 48 h. We
were pleased to find that the corresponding bis(imidazoline)
pincer Pd(II) bromide complexes 5a−d could be isolated in
reasonable yields in all cases (50−56%) (Scheme 3). All of the
Scheme 3. Synthesis of Chiral Bis(imidazoline) NCN Pincer
Pd(II) Bromide Complexes 5a−d via Oxidative Addition
Figure 2. Molecular structure of pincer palladium bromide complex
5b. Hydrogen atoms are omitted for clarity. Selected bond lengths (Å)
and angles (deg): Pd(1)−C(1) 1.933(6), Pd(1)−N(1) 2.022(4),
Pd(1)−Br(1) 2.5172(8); C(1)−Pd(1)−N(1) 79.37(11), N(1)−
Pd(1)−Br(1) 100.63(11), C(1)−Pd(1)−Br(1) 180.0, N(1)−Pd(1)−
N(1a) 158.7(2).
Previously we found that the PCN pincer Pd(II) complex C
(Chart 2) with an aryl-based aminophosphine-imidazoline
new compounds were fully characterized by spectroscopic
methods and/or elemental analysis. Additionally, the molecular
structures of Pd(II) complexes 3 and 5b were determined by X-
ray single-crystal diffraction. Complex 3 is found to be a
dinuclear macrocyclic complex with each Pd(II) center being
coordinated by two imidazoline-N groups and two trans
chloride ligands (Figure 1). The two coordinated imidazoline-
N groups come from two molecules of the bis(imidazoline)
ligands 1c. For complex 5b, the desired NCN pincer
coordination mode is confirmed (Figure 2).
Chart 2
ligand could catalyze the asymmetric hydrophosphination of β-
aryl enones with diarylphosphines, furnishing the correspond-
ing chiral phosphine derivatives in moderate to excellent
enantioselectivities (13 examples, 40−94% ees).10 Recently, we
also examined the potential of several PCN pincer Pd(II)
complexes with aryl-based phosphinite-imidazoline ligands in
the hydrophosphination of enones, and complex D (Chart 2)
was found to be the most stereoselctive.14 The addition of Ph2P
to chalcone complexes C and D gave 82% and 92% ees,
respectively, under the optimized reaction conditions. How-
ever, the bis(imidazolone) NCN Pd(II) chloride complex A
(Chart 1), containing the same imidazoline donor as complexes
C and D, afforded an 85% ee.10 Consequently, the newly
obtained NCN Pd(II) pincers were first evaluated in the
addition of Ph2P to chalcone with Pd(II) bromide complex 5a
as the catalyst under the optimized conditions10 previously
established. Not unexpectedly, an excellent enantioselectivity of
90% ee was observed (Table 1, entry 1). In contrast, a rather
low ee value of 30% was obtained when complex 5d with
(4S,5S)-diphenyl substituents was used as the catalyst (entry 2).
Then complex 5a was further tested in the hydrophosphination
of other β-aryl enones. In all cases, good to excellent
enantioselectivities could be achieved (13 examples, 79−94%
ee). Both electron-withdrawing substituents such as Br and
NO2 as well as electron-donating substituents including Me and
OMe on the aryl ring of the enone substrates were tolerated. In
particular, when a substituent such as OMe was located on the
ortho position of the β-aryl a good stereocontrol was still
obtained (79% ee, entry 10). The result for this specific
Figure 1. Molecular structure of dinuclear macrocyclic palladium
complex 3. Hydrogen atoms and solvent molecules are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pd(1)−N(1)
2.013(4), Pd(1)−N(9) 2.016(4), Pd(1)−Cl(1) 2.3049(17), Pd(1)−
Cl(2) 2.2978(19), Pd(2)−N(4) 2.015(5), Pd(2)−N(6) 2.021(5),
Pd(2)−Cl(3) 2.3028(19), Pd(2)−Cl(4) 2.3061(19); N(1)−Pd(1)−
Cl(1) 87.65(15), Cl(1)−Pd(1)−N(9) 92.06(14), N(1)−Pd(1)−N(9)
178.2(2), Cl(1)−Pd(1)−Cl(2) 173.19(8), N(4)−Pd(2)−Cl(3)
88.70(17), Cl(3)−Pd(2)−N(6) 92.91(16), N(4)−Pd(2)−N(6)
176.7(2), Cl(3)−Pd(2)−Cl(4) 171.05(7).
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Table 1. Enantioselective Hydrophosphination of β-Aryl Enones with Diphenylphosphine Catalyzed by NCN Pincer Pd(II)
a
Complexes
a
Hydrophosphination reactions were performed with Ph2PH (0.2 mmol) and β-aryl enones (0.3 mmol) in the presence of Pd complex (5 mol %)
b
c
d
and KOAc base (10 mol %) in 2 mL of toluene at 0 °C for 12 h. Isolated yields. Determined by chiral HPLC. The absolute configurations of the
products were assigned to be S by comparison of optical rotations with those in refs 5a and 10 or by analogy.
substrate was much better than those for the related complexes
C and D (51% and 54% ees, respectively).10,14 An enone
bearing an alkyl such as an i-Bu moiety attached to the carbonyl
group could also be employed as a good reaction partner (90%
ee, entry 16). In addition, it was found that the Pd(II) chloride
complex 2a exhibited excellent stereoselectivity in the reaction
of Ph2P with (E)-3-(4-nitrophenyl)-1-phenyl-2-propen-1-one
(94% ee, entry 6). Unfortunately, the yield of complex 2a was
too low when this catalyst was prepared. Overall, complex 5a
gave better or comparable enantioselectivities in comparison
with the related complex C,10 while it was inferior to complex
D in most cases.14
On the other hand, pyridine-functionalized phosphines,
including chiral species, are important bidentate N,P ligands
that have been widely used in organometallic chemistry and
catalysis.15 They have proven to be effective, for example, in
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nickel- or palladium-catalyzed ethylene oligo-/polymerization,16
Ru-catalyzed olefin metathesis and transfer hydrogenation,17
Pd-catalyzed asymmetric allylic alkylation,18 and Rh-catalyzed
enantioselective hydroboration.19 We then tried the hydro-
phosphination of (E)-2-(3-phenylacryloyl)pyridine formed
from 2-acetylpyridine and benzaldehyde to get the correspond-
ing adduct as a potentially useful chiral N,P ligand.
Unfortunately, the reaction did not proceed with complex 5a
as the catalyst under the previous reaction conditions, possibly
because the pyridine N in the substrate was coordinated to the
Pd(II) center, which deactivated the pincer Pd(II) catalyst.
However, the hydrophosphination did occur when the
corresponding pyridine N-oxide was used as the substrate,
giving the product in a 67% yield with 55% ee (Table 2, entry
3). Substrates containing electron-withdrawing or -donating
groups on the aromatic ring such as halide, NO2, MeO, and Me
could react with diphenylphosphine to form the chiral
phosphine oxides in good yields with good to excellent
enantioselectivities (72−90% yields, 63−92% ees, entries 2−9).
Roughly, electron-withdrawing groups were beneficial for better
stereocontrol (entries 2−6) while electron-donating groups
showed some adverse effects (entries 7 and 8). A 1-naphthyl-
containing substrate also gave a good ee value (76% ee, entry
13). Heteroaromatic rings such as 2-furyl and especially 2-
thienyl, which have a strong coordination ability to transition
metals, were tolerated under the current catalytic system (69%
and 78% ees, respectively, entries 10 and 11). In addition to the
aromatic or heteroaromatic ring, an (E)-styryl moiety could
also be used as the reaction partner, furnishing the desired 1,4-
addition product in 59% yield with 64% ee (entry 12). The
utilization of the related pincer Pd(II) chloride complexes 2b,c
as well as the macrocyclic complex 3 in the hydrophosphination
of pyridine N-oxides indicated that all of them were inferior to
complex 5d. Notably, the present NCN pincer Pd(II) complex
provided much better stereoselectivities than the PCN complex
D (Chart 2)14 in the addition of diphenylphosphine to the
pyridine N-oxides, especially in the reactions of o-BrC6H4-, 2-
thienyl-, and 1-naphthyl-containing substrates (85%, 78%, and
76% ees vs 18%, 21%, and 9% ees, respectively).
Table 2. Enantioselective Hydrophosphination of (E)-2-(3-
Phenylacryloyl)pyridine N-Oxide with Diphenylphosphine
a
Catalyzed by Pincer Pd(II) Complexes 5
b
cd
,
entry cat.
base
solvent
temp (°C) yield (%)
ee (%)
1
5a
5a
5a
5a
5a
5a
5a
5a
5b
5c
5d
5d
5d
KOAc
KOAc
KOAc
KOAc
KOAc
Et3N
toluene
THF
0
0
67
58
50
35
32
58
59
57
40
61
47
75
84
55
52
53
55
13
65
38
63
37
37
80
70
80
CONCLUSION
■
2
In summary, seven bis(imidazoline) NCN pincer Pd(II)
complexes and one dinuclear macrocyclic Pd(II) complex
have been synthesized and fully characterized. These complexes
were found to be effective catalysts for the enantioselective
hydrophosphination of enones. In the presence of the optimal
catalysts 5a,d various enones could react with diphenylphos-
phine to provide the optically active phosphine derivatives in
good yields with enantioselectivities of up to 94% ee.
3
CH2Cl2
CHCl3
CH3OH
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
0
4
0
5
0
6
0
7
Cs2CO3
KOAc
KOAc
KOAc
KOAc
Et3N
0
8
−20
0
9
10
11
12
13
0
0
EXPERIMENTAL SECTION
0
■
General Considerations. Solvents were dried with standard
methods and freshly distilled prior to use if needed. The 2-bromo-1,3-
bis(amido alcohols),13 2-acetylpyridine N-oxide,20 2-alkenoyl pyridine
N-oxides,21 and other enone substrates22 used in the asymmetric
catalytic reactions were prepared according to the literature methods.
All other chemicals were used as purchased. NMR spectra were
recorded with CDCl3 as the solvent and TMS as an internal standard
for 1H and 13C NMR and 85% H3PO4 as external standard for 31P{1H}
NMR.
KOAc
25
a
Hydrophosphination reactions were performed with Ph2PH (0.2
mmol) and pyridine N-oxide (0.3 mmol) in the presence of pincer
complex 5 (5 mol %) and base (10 mol %) for 12 h. Isolated yields.
Determined by chiral HPLC. The absolute configuration of the
b
c
d
product was assigned to be S by analogy.
1). Several other solvents in addition to toluene were screened
to optimize the conditions for this reaction. In comparison with
toluene THF, CH2Cl2, and CHCl3 gave reduced yields with
slightly lower or comparable enantioselectivities (entries 2−4).
However, CH3OH was not a suitable solvent for the reaction
(entry 5). Changing the base from KOAc to Et3N or lowering
the temperature from 0 to −20 °C afforded better
enantioselectivities, albeit with decreased yields (∼57% yields
with 64% ees, entries 6−8). Then the other pincer Pd(II)
bromide complexes 5b−d were also evaluated in the reaction
under the same conditions. Gratifyingly, complex 5d could
provide an 80% ee, though the yield was only 47% (entries 9−
11). The yield could be improved to 84% without loss of the
stereoselectivity by elevating the temperature to 25 °C (entries
12 and 13). Thus, for the hydrophosphination of pyridine N-
oxide, the optimized conditions include using complex 5d as
the catalyst in the presence of KOAc base in toluene at 25 °C.
The hydrophosphination of other 2-alkenoylpyridine N-
oxides was investigated under the optimized conditions (Table
Synthesis of Bis(imidazoline) NCN pincer Pd(II) chloride
complexes 2a−c. The complexes 2a−c were synthesized starting
from commercially available 5-tert-butyl- or 5-nitroisophthalic acid
according to the procedure previously reported by us.9a The analytical
data of the new ligands and the complexes are given as follows.
5-tert-Butyl-1,3-bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imida-
zol-2-yl)benzene (1a). Pale yellow solid (301.4 mg, 0.5 mmol, 50%
20
based on the related 1,3-bis(amido alcohol)). Mp: 86−88 °C. [α]D
=
−28° (c 0.190, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.00 (s, 1H,
ArH), 7.38−7.31 (m, 10H, ArH and PhH), 7.24 (t, J = 6.9 Hz, 2H,
PhH), 6.95 (d, J = 8.2 Hz, 4H, NArH), 6.69 (d, J = 8.3 Hz, 4H,
NArH), 5.30 (dd, J = 8.2, 10.7 Hz, 2H, NCH), 4.46 (dd, J = 9.5, 10.6
Hz, 2H, NCH2), 3.78 (app t, J = 8.9 Hz, 2H, NCH2), 2.23 (s, 6H,
CH3), 0.95 (s, 9H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 162.7,
150.2, 144.0, 140.3, 133.7, 130.8, 129.3, 128.6, 127.9, 127.2, 127.0,
126.9, 123.5, 67.7, 61.8, 34.5, 30.7, 20.8. HRMS (positive ESI): [M +
H]+ calcd for C42H43N4 603.3488, found 603.3484.
5-tert-Butyl-1,3-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-
imidazol-2-yl)benzene (1b). White solid (302.0 mg, 0.4 mmol, 40%
based on the related 1,3-bis(amido alcohol)). Mp: 119−121 °C. [α]D
20
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a
Table 3. Hydrophosphination of 2-Alkenoylpyridine N-Oxides with Diphenylphosphine Catalyzed by Pd(II) Complexes
a
Hydrophosphination reactions were performed with Ph2PH (0.2 mmol) and 2-alkenoylpyridine N-oxides (0.3 mmol) in the presence of Pd(II)
b
c
d
complex (5 mol %) and KOAc base (10 mol %) in 2 mL of toluene at 25 °C for 12 h. Isolated yields. Determined by chiral HPLC. The absolute
configurations of the products were assigned to be S by analogy.
1
= +336° (c 0.175, CH2Cl2). H NMR (400 MHz, CDCl3): δ 8.07 (s,
1H, ArH), 7.67 (d, J = 1.6 Hz, 2H, ArH), 7.43−7.25 (m, 20H, PhH),
6.90 (d, J = 8.0 Hz, 4H, NArH), 6.59 (d, J = 8.0 Hz, 4H, NArH), 5.08
(d, J = 7.0 Hz, 2H, NCH), 4.58 (d, J = 7.1 Hz, 2H, NCH), 2.23 (s, 6H,
CH3), 1.06 (s, 9H, C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 163.6,
150.7, 143.7, 143.6, 141.2, 134.9, 130.5, 129.4, 129.0, 128.7, 128.2,
127.8, 127.7, 127.4, 126.8, 126.7, 125.2, 79.1, 78.8, 34.9, 30.8, 21.0.
HRMS (positive ESI): [M + H]+ calcd for C54H51N4 755.4114, found
755.4110.
4-tert-Butyl-2,6-bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imida-
zol-2-yl)phenylpalladium(II) Chloride (2a). Yellow solid (19.3 mg,
20
0.026 mmol, 13%). Mp: > 240 °C. [α]D = +97° (c 0.260, CH2Cl2).
1H NMR (400 MHz, CDCl3): δ 7.51 (d, J = 7.6 Hz, 3H, PhH), 7.33 (t,
J = 7.2 Hz, 4H, PhH), 7.26−7.22 (m, 7H, PhH and NArH), 7.18 (d, J
= 8.4 Hz, 4H, NArH), 6.38 (s, 2H, ArH), 5.38 (dd, J = 4.4, 10.8 Hz,
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2H, NCH), 4.43 (app t, J = 10.0 Hz, 2H, NCH2), 4.05 (dd, J = 4.4, 9.8
Hz, 2H, NCH2), 2.39 (s, 6H, CH3), 0.79 (s, 9H, C(CH3)3). 13C NMR
(100 MHz, CDCl3): δ 170.9, 169.9, 144.9, 142.7, 138.1, 137.1, 132.5,
130.1, 128.5, 127.5, 127.0, 126.7, 124.6, 64.6, 63.2, 34.4, 30.7, 21.1.
Anal. Calcd for C42H41ClN4Pd: C, 67.83; H, 5.56; N, 7.53. Found: C,
67.70; H, 6.38; N, 6.50.
δ 7.51 (d, J = 7.6 Hz, 2H, ArH), 7.44 (d, J = 7.5 Hz, 4H, ArH), 7.39−
7.33 (m, 5H, ArH), 7.28−7.26 (m, 2H, ArH), 6.89 (d, J = 8.3 Hz, 4H,
NArH), 6.59 (d, J = 8.3 Hz, 4H, NArH), 5.34 (app t, J = 10.2 Hz, 2H,
NCH), 4.35 (app t, J = 10.2 Hz, 2H, NCH2), 3.93 (app t, J = 9.3 Hz,
2H, NCH2), 2.23 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ
160.7, 143.6, 138.0, 135.1, 132.7, 131.8, 129.5, 128.5, 127.5, 127.2,
126.9, 122.0, 120.3, 67.6, 59.7, 20.7. HRMS (positive ESI): [M + H]+
calcd for C38H34BrN4 625.1967, found 625.1965.
4-tert-Butyl-2,6-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-
imidazol-2-yl)phenylpalladium(II) Chloride (2b). Yellow solid (134.4
20
mg, 0.15 mmol, 75%). Mp: 220−223 °C. [α]D = +94° (c 0.116,
2-Bromo-1,3-bis((S)-4-isopropyl-1-p-tolyl-4,5-dihydro-1H-imida-
1
CH2Cl2). H NMR (400 MHz, CDCl3): δ 7.41 (d, J = 7.3 Hz, 4H,
zol-2-yl)benzene (4b). Yellow solid (390.2 mg, 70%). Mp: 60−62 °C.
20
1
ArH), 7.35−7.31 (m, 14H, ArH), 7.26−7.22 (m, 3H, ArH), 7.10 (br s,
[α]D = −98° (c 0.326, CH2Cl2). H NMR (400 MHz, CDCl3): δ
7.41 (d, J = 7.5 Hz, 2H, ArH), 7.30 (t, J = 7.6 Hz, 1H, ArH), 6.88 (d, J
= 8.2 Hz, 4H, NArH), 6.55 (d, J = 8.4 Hz, 4H, NArH), 4.08−4.02 (m,
2H, NCH), 3.95 (app t, J = 9.2 Hz, 2H, NCH2), 3.69 (app t, J = 8.6
Hz, 2H, NCH2), 2.23 (s, 6H, CH3), 1.97−1.93 (m, 2H, (CH3)2CH),
1.03 (d, J = 6.8 Hz, 6H, (CH3)2CH), 0.98 (d, J = 6.8 Hz, 6H,
(CH3)2CH). 13C NMR (100 MHz, CDCl3): δ 159.5, 138.4, 135.4,
132.2, 131.6, 129.4, 127.4, 121.9, 120.1, 70.0, 54.0, 32.9, 20.7, 19.0,
18.1. HRMS (positive ESI): [M + H]+ calcd for C32H38BrN4 557.2280,
found 557.2278.
7H, ArH), 6.36 (s, 2H, ArH), 5.29 (d, J = 5.7 Hz, 2H, NCH), 4.88 (d,
J = 5.7 Hz, 2H, NCH), 2.31 (s, 6H, CH3), 0.79 (s, 9H, C(CH3)3). 13
C
NMR (100 MHz, CDCl3): δ 171.3, 169.4, 145.1, 142.7, 140.3, 138.4,
136.2, 132.8, 129.9, 129.1, 128.7, 128.6, 127.6, 127.4, 126.9, 124.7,
79.2, 74.8, 34.5, 30.7, 21.1. Anal. Calcd for C54H49ClN4Pd·
0.75CH2Cl2: C, 68.53; H, 5.30; N, 5.84. Found: C, 68.52; H, 5.39;
N, 5.67.
4-Nitro-2,6-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imida-
zol-2-yl)phenylpalladium(II) Chloride (2c). Yellow solid (26.6 mg,
0.03 mmol, 15%). Mp: 218−219 °C. [α]D20 = +39° (c 0.114, CH2Cl2).
1H NMR (400 MHz, CDCl3): δ 7.39−7.25 (m, 24H, ArH), 7.15 (br s,
6H, ArH), 5.34 (d, J = 6.0 Hz, 2H, NCH), 4.94 (d, J = 6.0 Hz, 2H,
NCH), 2.35 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 183.3,
168.1, 143.4, 142.0, 139.6, 139.2, 135.1, 133.6, 130.5, 129.2, 128.9,
128.8, 128.0, 127.3, 126.9, 122.0, 79.4, 74.9, 21.2. Anal. Calcd for
C50H40ClN5O2Pd: C, 67.88; H, 4.56; N, 7.92. Found: C, 67.56; H,
4.84; N, 7.44.
2-Bromo-1,3-bis((S)-4-tert-butyl-1-p-tolyl-4,5-dihydro-1H-imida-
zol-2-yl)benzene (4c). Pale yellow solid (351.4 mg, 60%). Mp: 87−88
°C. [α]D20 = −74° (c 0.287, CH2Cl2). 1H NMR (400 MHz, CDCl3): δ
7.46−7.41 (m, 2H, ArH), 7.30 (t, J = 7.6 Hz, 1H, ArH), 6.87 (d, J =
8.2 Hz, 4H, NArH), 6.56 (d, J = 8.4 Hz, 4H, NArH), 3.97 (app t, J =
10.7 Hz, 2H, NCH), 3.91 (app t, J = 8.9 Hz, 2H, NCH2), 3.74 (app t, J
= 8.6 Hz, 2H, NCH2), 2.24 (s, 6H, CH3), 0.99 (s, 18H, C(CH3)3). 13
C
NMR (100 MHz, CDCl3): δ 159.5, 138.5, 135.6, 132.0, 131.6, 129.4,
127.4, 120.3, 120.1, 73.9, 52.9, 34.3, 26.1, 20.7. HRMS (positive ESI):
[M + H]+ calcd for C34H42BrN4 585.2593, found 585.2596.
Synthesis of the Dinuclear Palladium Complex 3. A mixture
of 1c (74.4 mg, 0.1 mmol) and PdCl2 (17.7 mg, 0.1 mmol) in toluene
(15 mL) was refluxed in the presence of Et3N (13.9 μL, 0.1 mmol) for
48 h under a nitrogen atmosphere. After the mixture was cooled and
concentrated in vacuo, the residue was purified by preparative TLC on
silica gel plates with CH2Cl2 as eluent to afford complex 3 as a yellow
2-Bromo-1,3-bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imi-
dazol-2-yl)benzene (4d). Pale yellow solid (350.1 mg, 45%). Mp:
115−117 °C. [α]D20 = −35° (c 0.321, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 7.54 (d, J = 6.8 Hz, 2H, ArH), 7.40−7.27 (m, 21H, ArH),
6.77 (d, J = 8.2 Hz, 4H, NArH), 6.63 (d, J = 7.8 Hz, 4H, NArH), 5.21
(d, J = 8.9 Hz, 2H, NCH), 5.00 (d, J = 8.9 Hz, 2H, NCH), 2.12 (s, 6H,
CH3). 13C NMR (100 MHz, CDCl3): δ 161.9, 143.3, 141.9, 137.8,
135.1, 134.2, 132.1, 129.5, 128.9, 128.6, 127.8, 127.4, 127.3, 127.0,
123.6, 79.0, 77.3, 20.8. HRMS (positive ESI): [M + H]+ calcd for
C50H42BrN4 777.2593, found 777.2596.
20
solid (78.3 mg, 85%). Mp: 267−269 °C. [α]D = +494° (c 0.108,
1
CH2Cl2). H NMR (400 MHz, CDCl3): δ 10.47 (t, J = 1.8 Hz, 2H,
ArH), 9.07 (t, J = 1.5 Hz, 2H, ArH), 7.85 (t, J = 1.7 Hz, 2H, ArH),
7.67 (d, J = 7.2 Hz, 4H, PhH), 7.48 (t, J = 7.2 Hz, 4H, PhH), 7.40−
7.30 (m, 28H, PhH), 7.23 (dd, J = 2.0, 7.8 Hz, 4H, PhH), 7.00 (d, J =
8.2 Hz, 4H, NArH), 6.77 (d, J = 8.3 Hz, 4H, NArH), 6.52 (d, J = 8.2
Hz, 4H, NArH), 5.67 (d, J = 8.2 Hz, 4H, NArH), 5.49 (d, J = 7.0 Hz,
2H, NCH), 5.35 (d, J = 8.7 Hz, 2H, NCH), 4.50 (d, J = 7.0 Hz, 2H,
NCH), 4.30 (d, J = 8.8 Hz, 2H, NCH), 2.22 (s, 6H, CH3), 2.08 (s, 6H,
CH3). 13C NMR (100 MHz, CDCl3): δ 164.0, 162.1, 146.9, 141.4,
140.8, 140.7, 140.5, 139.2, 138.8, 137.5, 137.4, 135.5, 130.1, 129.8,
129.7, 129.4, 129.2, 129.1, 128.9, 128.6, 128.5, 128.4, 128.2, 128.1,
128.0, 127.5, 126.2, 125.3, 78.0, 76.6, 21.2, 20.9. Anal. Calcd for
C100H82Cl4N10O4Pd2: C, 65.19; H, 4.49; N, 7.60. Found: C, 65.08; H,
4.62; N, 7.14.
2,6-Bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)-
phenylpalladium(II) Bromide (5a). Yellow solid (123.0 mg, 56%).
Mp: >290 °C. [α]D20 = +70° (c 0.098, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 7.39 (d, J = 7.3 Hz, 4H, PhH), 7.25 (t, J = 7.3 Hz, 4H,
PhH), 7.18−7.13 (m, 6H, PhH and NArH), 7.07 (d, J = 8.2 Hz, 4H,
NArH), 6.54 (t, J = 7.9 Hz, 1H, ArH), 6.36 (d, J = 7.8 Hz, 2H, ArH),
5.36 (dd, J = 3.9, 10.7 Hz, 2H, NCH), 4.34 (app t, J = 10.1 Hz, 2H,
NCH2), 3.93 (dd, J = 4.0, 9.8 Hz, 2H, NCH2), 2.32 (s, 6H, CH3). 13
C
NMR (100 MHz, CDCl3): δ 174.8, 170.0, 142.9, 138.1, 137.0, 133.1,
130.4, 128.6, 127.5, 127.1, 126.9, 126.4, 122.0, 65.0, 63.7, 21.2. Anal.
Calcd for C38H33BrN4Pd·0.5C6H14-n: C, 63.53; H, 5.20; N, 7.23.
Found: C, 63.85; H, 5.25; N, 6.67.
Synthesis of Bis(imidazoline) NCN Pincer Pd(II) Bromide
Complexes 5a−d. The 2-bromo-1,3-bis(amido alcohol) (1.0 mmol)
reacted with thionyl chloride (0.7 mL, 9.6 mmol) at reflux for 12 h.
Excess thionyl chloride was evaporated. The residue was dissolved in
dry CH2Cl2 (2 mL) and this solution added dropwise to a solution of
triethylamine (0.3 mL, 2.2 mmol) and p-toluidine (2 mmol) in
CH2Cl2 (10 mL) at 0 °C. The mixture was then warmed to room
temperature and stirred for 12 h. After that, 10% NaOH (5 mL) was
added and the mixture was stirred for another 12 h. The aqueous
solution was extracted with dichloromethane, and the organic layer
was washed with brine, dried over Na2SO4, and evaporated. The crude
product was purified by preparative TLC on silica gel plates to give 2-
bromo-1,3-bis(imidazoline)benzenes 4a−d. Then a mixture of bis-
(imidazoline)benzene 4 (0.3 mmol) and Pd2(dba)3 (206.0 mg, 0.225
mmol) in toluene (15 mL) was stirred at room temperature for 48 h.
The solvent was evaporated in vacuo, and purification by column
chromatography on silica gel provided the pincer Pd(II) bromide
complexes 5a−d.
2,6-Bis((S)-4-isopropyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)-
phenylpalladium(II) Bromide (5b). Yellow solid (101.6 mg, 51%).
Mp: >290 °C. [α]D20 = +140° (c 0.116, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 7.22 (d, J = 8.1 Hz, 4H, NArH), 7.11 (d, J = 8.2 Hz, 4H,
NArH), 6.54 (t, J = 7.8 Hz, 1H, ArH), 6.34 (d, J = 7.8 Hz, 2H, ArH),
4.40−4.35 (m, 2H, NCH), 4.01 (app t, J = 10.1 Hz, 2H, NCH2), 3.84
(dd, J = 5.0, 9.9 Hz, 2H, NCH2), 2.98−2.90 (m, 2H, (CH3)2CH), 2.40
(s, 6H, CH3), 0.93 (d, J = 7.0 Hz, 6H, (CH3)2CH), 0.88 (d, J = 6.8 Hz,
6H, (CH3)2CH). 13C NMR (100 MHz, CDCl3): δ 173.4, 168.7, 137.7,
137.3, 133.1, 130.2, 126.7, 126.1, 121.9, 66.8, 54.8, 30.3, 21.2, 18.7,
14.3. Anal. Calcd for C32H37BrN4Pd·0.5CH2Cl2: C, 55.25; H, 5.42; N,
7.93. Found: C, 55.53; H, 5.47; N, 7.69.
2,6-Bis((S)-4-tert-butyl-1-p-tolyl-4,5-dihydro-1H-imidazol-2-yl)-
phenylpalladium(II) Bromide (5c). Yellow solid (103.8 mg, 50%).
20
1
Mp: 199−201 °C. [α]D = +361° (c 0.098, CH2Cl2). H NMR (400
MHz, CDCl3): δ 7.21 (d, J = 8.1 Hz, 4H, NArH), 7.13 (d, J = 8.2 Hz,
4H, NArH), 6.54 (t, J = 7.8 Hz, 1H, ArH), 6.35 (d, J = 7.8 Hz, 2H,
ArH), 4.16−4.13 (m, 2H, NCH), 4.07 (app t, J = 9.8 Hz, 2H, NCH2),
2-Bromo-1,3-bis((S)-4-phenyl-1-p-tolyl-4,5-dihydro-1H-imidazol-
2-yl)benzene (4a). Pale yellow solid (319.0 mg, 51%). Mp: 101−103
°C. [α]D20 = −110° (c 0.188, CH2Cl2). 1H NMR (400 MHz, CDCl3):
1807
dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics
Article
3.97−3.94 (m, 2H, NCH2), 2.40 (s, 6H, CH3), 1.12 (s, 18H,
C(CH3)3). 13C NMR (100 MHz, CDCl3): δ 171.4, 169.3, 137.9,
137.0, 133.0, 130.3, 126.3, 126.2, 121.8, 69.4, 58.0, 36.3, 26.8, 21.2.
Anal. Calcd for C34H41BrN4Pd: C, 59.01; H, 5.97; N, 8.10. Found: C,
58.53; H, 6.06; N, 7.65.
39.0. 31P{1H} NMR (162 MHz, CDCl3): δ 34.5. HRMS (positive
ESI): [M + H]+ calcd for C31H26O2P 461.1670, found 461.1671.
(S)-3-(4-Bromophenyl)-3-(diphenylphosphinyl)-1-(4-
methoxyphenyl)propan-1-one (7j). White solid (20.8 mg, 20%). Mp:
245−246 °C. The enantiomeric excess was determined on a Daicel
Chiralcel OD-H column with hexane/2-propanol (90/10) and flow
rate 0.5 mL/min and detected at a UV wavelength of 228 nm.
Retention times: 23.2 min (major), 30.2 min, 88% ee. [α]D20 = −146°
2,6-Bis((S,S)-1-p-tolyl-4,5-diphenyl-4,5-dihydro-1H-imidazol-2-
yl)phenylpalladium(II) Bromide (5d). Yellow solid (135.3 mg, 51%).
20
1
Mp: 211−212 °C. [α]D = +92° (c 0.110, CH2Cl2). H NMR (400
MHz, CDCl3): δ 7.41−7.39 (m, 5H, ArH), 7.36−7.24 (m, 18H, ArH),
7.07 (br s, 5H, ArH), 6.65 (t, J = 7.8 Hz, 1H, ArH), 6.45 (d, J = 7.8 Hz,
2H, ArH), 5.31 (d, J = 5.4 Hz, 2H, NCH), 4.83 (d, J = 5.4 Hz, 2H,
NCH), 2.32 (s, 6H, CH3). 13C NMR (100 MHz, CDCl3): δ 175.1,
169.5, 142.9, 140.3, 138.2, 136.2, 133.3, 130.2, 129.1, 128.7, 128.6,
127.6, 127.2, 126.8, 122.2, 79.5, 75.1, 21.2. Anal. Calcd for
C50H41BrN4Pd·0.5CH2Cl2: C, 65.45; H, 4.57; N, 6.05. Found: C,
65.19; H, 4.60; N, 5.72.
1
(c 0.164, CH2Cl2). H NMR (400 MHz, CDCl3): δ 7.99−7.94 (m,
2H), 7.82 (d, JHH = 8.9 Hz, 2H), 7.53−7.52 (m, 5H), 7.39−7.35 (m,
1H), 7.30−7.26 (m, 6H), 6.84 (d, JHH = 8.9 Hz, 2H), 4.44 (ddd, JHH
=
9.1 and 2.2 Hz, JHP = 6.6 Hz, 1H, PCHCH2), 3.92 (ddd, JHH = 17.9
and 10.6 Hz, JHP = 4.2 Hz, 1H, PCHCHH), 3.81 (s, 3H, OCH3), 3.28
(ddd, JHH = 17.9 and 2.2 Hz, JHP = 10.8 Hz, 1H, PCHCHH). 13C
NMR (100 MHz, CDCl3): δ 194.8 (d, JCP = 13.3 Hz), 163.8, 135.2 (d,
JCP = 5.7 Hz), 131.93 (d, JCP = 51.0 Hz), 131.90 (d, JCP = 51.0 Hz),
131.7 (d, JCP = 28.7 Hz), 131.5 (d, JCP = 5.7 Hz), 131.4 (d, JCP = 1.4
Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.6, 130.5,
129.3, 129.0 (d, JCP = 11.2 Hz), 128.3 (d, JCP = 11.9 Hz), 121.1 (d, JCP
= 3.1 Hz), 113.8, 55.5, 40.6 (d, JCP = 68.9 Hz), 38.4. 31P{1H} NMR
(162 MHz, CDCl3): δ 34.2. HRMS (positive ESI): [M + H]+ calcd for
C28H25BrO3P 519.0725, found 519.0726.
General Procedure for the Enantioselective Hydrophosphi-
nation of Enones with Diphenylphosphine. Under an N2
atmosphere, a Schlenk tube equipped with a magnetic stirring bar
was charged with pincer Pd catalyst (5 mol %), KOAc (2.0 mg, 10 mol
%), and dry toluene (2 mL). The mixture was stirred for 30 min at 0
°C or room temperature (for the hydrophosphination of 2-alkenoyl
pyridine N-oxides). Then diphenylphosphine (37.2 mg, 0.2 mmol)
was added, and stirring was continued for another 30 min. After
addition of enone (0.3 mmol), the resulting mixture was stirred for an
additional 12 h at 0 or 25 °C (for 2-alkenoyl pyridine N-oxides) and
then directly oxidized with H2O2 aqueous solution (30%, 60 μL). After
the mixture was stirred at room temperature for 2 h, saturated
Na2S2O3 aqueous solution was added. The organic layer was separated
and the aqueous phase extracted with CH2Cl2. The combined organic
phases were dried (Na2SO4), and the volatiles were removed under
reduced pressure. Purification by column chromatography on silica gel
provided the chiral phosphine oxide products.
(S)-3-(Diphenylphosphinyl)-3-(3-nitrophenyl)-1-phenylpropan-1-
one (7e). White solid (67.4 mg, 74%). Mp: 248−249 °C. The
enantiomeric excess was determined on a Daicel Chiralpak AD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 15.5
min (major), 27.6 min, 84% ee. [α]D20 = −156° (c 0.116, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.17 (d, JHH = 1.7 Hz, 1H), 8.02−7.95
(m, 3H), 7.86−7.79 (m, 3H), 7.57−7.48 (m, 6H), 7.42−7.28 (m, 6H),
4.58 (ddd, JHH = 10.1 and 2.2 Hz, JHP = 6.9 Hz, 1H, PCHCH2), 4.05
(ddd, JHH = 18.4 and 10.7 Hz, JHP = 4.3 Hz, 1H, PCHCHH), 3.44
(ddd, JHH = 18.4 and 2.3 Hz, JHP = 10.5 Hz, 1H, PCHCHH). 13C
NMR (100 MHz, CDCl3): δ 196.0 (d, JCP = 13.1 Hz), 147.9, 138.4 (d,
(S)-3-(4-Bromophenyl)-3-(diphenylphosphinyl)-1-(4-nitrophenyl)-
propan-1-one (7l). White solid (93.3 mg, 87%). Mp: 246−247 °C.
The enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (85/15) and flow rate 0.5 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 37.8
min (major), 52.4 min, 85% ee. [α]D20 = −126° (c 0.118, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.22 (d, JHH = 8.9 Hz, 2H), 7.99−7.94
(m, 4H), 7.56−7.48 (m, 5H), 7.41−7.37 (m, 1H), 7.32−7.25 (m, 6H),
4.40 (ddd, JHH = 10.0 and 2.4 Hz, JHP = 7.6 Hz, 1H, PCHCH2), 3.95
(ddd, JHH = 18.4 and 10.0 Hz, JHP = 4.4 Hz, 1H, PCHCHH), 3.43
(ddd, JHH = 18.4 and 2.4 Hz, JHP = 11.2 Hz, 1H, PCHCHH). 13C
NMR (100 MHz, CDCl3): δ 195.3 (d, JCP = 13.0 Hz), 150.5, 140.5,
134.8 (d, JCP = 5.6 Hz), 132.10 (d, JCP = 49.2 Hz), 132.08 (d, JCP
=
49.4 Hz), 131.6 (d, JCP = 1.7 Hz), 131.5 (d, JCP = 15.5 Hz), 131.3 (d,
JCP = 5.5 Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.4
(d, JCP = 5.2 Hz), 129.14, 129.11 (d, JCP = 11.5 Hz), 128.4 (d, JCP
=
11.9 Hz), 123.8, 121.5 (d, JCP = 2.9 Hz), 40.7 (d, JCP = 68.3 Hz), 39.6.
31P{1H} NMR (162 MHz, CDCl3): δ 33.3. HRMS (positive ESI): [M
+ H]+ calcd for C27H22BrNO4P 534.0470, found 534.0472.
(S)-1,3-Bis(4-bromophenyl)-3-(diphenylphosphinyl)propan-1-one
(7m). White solid (102.2 mg, 90%). Mp: 261−262 °C. The
enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (85/15) and flow rate 0.7 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 10.7
min (major), 13.1 min, 89% ee. [α]D20 = −145° (c 0.252, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 7.98−7.93 (m, 2H), 7.68 (d, JHH = 8.6
Hz, 2H), 7.54−7.47 (m, 7H), 7.39−7.35 (m, 1H), 7.31−7.24 (m, 6H),
4.40 (ddd, JHH = 10.0 and 2.5 Hz, JHP = 6.8 Hz, 1H, PCHCH2), 3.89
(ddd, JHH = 18.1 and 10.4 Hz, JHP = 4.6 Hz, 1H, PCHCHH), 3.33
(ddd, JHH = 18.1 and 2.5 Hz, JHP = 10.7 Hz, 1H, PCHCHH). 13C
JCP = 5.7 Hz), 135.9, 135.5 (d, JCP = 5.0 Hz), 133.7, 133.22 (d, JCP
=
50.5 Hz), 133.20 (d, JCP = 50.5 Hz), 131.18 (d, JCP = 8.6 Hz), 131.17
(d, JCP = 35.4 Hz), 130.7 (d, JCP = 9.0 Hz), 130.2 (d, JCP = 31.1 Hz),
129.198, 129.197 (d, JCP = 11.4 Hz), 128.7, 128.5 (d, JCP = 11.9 Hz),
128.1, 125.0 (d, JCP = 5.8 Hz), 122.1, 41.1 (d, JCP = 67.5 Hz), 38.7.
31P{1H} NMR (162 MHz, CDCl3): δ 33.5. HRMS (positive ESI): [M
+ H]+ calcd for C27H23NO4P 456.1365, found 456.1365.
NMR (100 MHz, CDCl3): δ 195.5 (d, JCP = 13.2 Hz), 135.0 (d, JCP
=
(S)-3-(Diphenylphosphinyl)-3-(naphthalen-1-yl)-1-phenylpro-
pan-1-one (7g). White solid (80.1 mg, 87%). Mp: 225−226 °C. The
enantiomeric excess was determined on a Daicel Chiralpak AD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 19.2
min (major), 23.1 min, 89% ee. [α]D20 = −166° (c 0.142, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.40 (s, 1H), 8.05−8.00 (m, 2H), 7.91−
7.87 (m, 2H), 7.81−7.77 (m, 2H), 7.58−7.42 (m, 9H), 7.36−7.32 (m,
1H), 7.27−7.23 (m, 2H), 7.17−7.07 (m, 3H), 4.53 (ddd, JHH = 9.8
and 2.3 Hz, JHP = 6.7 Hz, 1H, PCHCH2), 4.19 (ddd, JHH = 17.9 and
10.4 Hz, JHP = 4.4 Hz, 1H, PCHCHH), 3.52 (ddd, JHH = 17.9 and 2.4
Hz, JHP = 11.1 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ
196.5 (d, JCP = 13.3 Hz), 136.0 (d, JCP = 5.7 Hz), 135.6, 133.7, 132.4,
132.0 (d, JCP = 25.2 Hz), 131.8 (d, JCP = 63.2 Hz), 131.7 (d, JCP = 63.4
Hz), 131.3 (d, JCP = 8.4 Hz), 131.2, 131.0 (d, JCP = 8.9 Hz), 130.2,
129.9 (d, JCP = 5.7 Hz), 129.6, 129.0 (d, JCP = 11.2 Hz), 128.7, 128.36
(d, JCP = 2.2 Hz), 128.34 (d, JCP = 1.9 Hz), 128.1 (d, JCP = 11.8 Hz),
127.7, 127.1 (d, JCP = 2.2 Hz), 126.8, 123.6, 41.2 (d, JCP = 69.1 Hz),
5.5 Hz), 134.9, 131.99 (d, JCP = 50.7 Hz), 131.96 (d, JCP = 50.6 Hz),
131.94, 131.6 (d, JCP = 15.7 Hz), 131.5 (d, JCP = 1.5 Hz), 131.4 (d, JCP
= 5.7 Hz), 131.2 (d, JCP = 8.6 Hz), 130.9 (d, JCP = 8.9 Hz), 130.6 (d,
JCP = 8.8 Hz), 129.6, 129.1 (d, JCP = 11.4 Hz), 128.8, 128.3 (d, JCP
=
11.8 Hz), 121.3 (d, JCP = 3.0 Hz), 40.6 (d, JCP = 68.7 Hz), 38.9.
31P{1H} NMR (162 MHz, CDCl3): δ 33.6. HRMS (positive ESI): [M
+ Na]+ calcd for C27H21Br2NaO2P 588.9544, found 588.9546.
(S)-2-(3-(Diphenylphosphinyl)-3-phenylpropionyl)pyridine N-
Oxide (7o). White solid (71.8 mg, 84%). Mp: 169−170 °C. The
enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 17.1
min (major), 22.8 min, 80% ee. [α]D20 = −110° (c 0.386, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H), 8.01−7.96
(m, 2H), 7.55−7.51 (m, 3H), 7.47−7.43 (m, 2H), 7.37−7.33 (m, 1H),
7.27−7.22 (m, 3H), 7.15−7.05 (m, 7H), 4.44 (ddd, JHH = 12.8 and 4.0
Hz, JHP = 8.9 Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz,
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JHP = 8.0 Hz, 1H, PCHCHH), 3.73 (ddd, JHH = 18.0 and 4.0 Hz, JHP
=
mL/min and detected at a UV wavelength of 228 nm. Retention times:
29.3 min (major), 61.4 min, 87% ee. [α]D = −170° (c 0.854,
20
8.6 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.5 (d,
JCP = 15.1 Hz), 146.7, 140.1, 135.3 (d, JCP = 5.7 Hz), 131.78 (d, JCP
58.5 Hz), 131.75 (d, JCP = 58.6 Hz), 131.6 (d, JCP = 8.8 Hz), 131.2 (d,
JCP = 8.8 Hz), 130.8, 130.6, 129.8 (d, JCP = 5.2 Hz), 128.8 (d, JCP
=
CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.13 (d, JHH = 6.4 Hz, 1H),
8.01−7.97 (m, 4H), 7.58−7.50 (m, 5H), 7.45−7.38 (m, 3H), 7.32−
7.28 (m, 4H), 7.17 (t, JHH = 7.4 Hz, 1H), 4.59 (ddd, JHH = 11.2 and
3.4 Hz, JHP = 8.6 Hz, 1H, PCHCH2), 4.20 (ddd, JHH = 18.2 and 10.8
Hz, JHP = 6.7 Hz, 1H, PCHCHH), 3.79 (ddd, JHH = 18.4 and 3.4 Hz,
JHP = 9.1 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.2
(d, JCP = 14.6 Hz), 146.8 (d, JCP = 2.7 Hz), 145.9, 143.7 (d, JCP = 5.7
Hz), 140.5, 132.22 (d, JCP = 45.9 Hz), 132.20 (d, JCP = 45.9 Hz), 131.4
(d, JCP = 8.7 Hz), 130.9 (d, JCP = 8.8 Hz), 130.7 (d, JCP = 5.1 Hz),
130.3, 129.8, 129.1 (d, JCP = 11.6 Hz), 128.5 (d, JCP = 12.0 Hz), 128.4
(d, JCP = 2.1 Hz), 127.0, 125.4, 123.2 (d, JCP = 1.4 Hz), 43.1, 41.9 (d,
JCP = 65.0 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.9. HRMS
(positive ESI): [M + H]+ calcd for C26H22N2O5P 473.1266, found
473.1269.
=
11.2 Hz), 128.2 (d, JCP = 1.9 Hz), 128.1 (d, JCP = 11.7 Hz), 127.8,
127.1 (d, JCP = 2.6 Hz), 126.6, 125.4, 43.0, 41.8 (d, JCP = 66.9 Hz).
31P{1H} NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive ESI): [M
+ H]+ calcd for C26H23NO3P 428.1416, found 428.1413.
(S)-2-(3-(4-Bromophenyl)-3-(diphenylphosphinyl)propionyl)-
pyridine N-Oxide (7p). Pale yellow solid (86.5 mg, 85%). Mp: 208−
209 °C. The enantiomeric excess was determined on a Daicel Chiralcel
OD-H column with hexane/2-propanol (70/30) and flow rate 1.0
mL/min and detected at a UV wavelength of 228 nm. Retention times:
20
18.3 min (major), 28.9 min, 87% ee. [α]D = −121° (c 0.462,
CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.4 Hz, 1H),
7.99−7.94 (m, 2H), 7.55−7.47 (m, 5H), 7.40−7.36 (m, 1H), 7.31−
7.21 (m, 5H), 7.19−7.06 (m, 4H), 4.42 (ddd, JHH = 12.2 and 3.7 Hz,
(S)-2-(3-(Diphenylphosphinyl)-3-(3-nitrophenyl)propionyl)-
pyridine N-Oxide (7t). Pale yellow solid (76.5 mg, 81%). Mp: 214−
215 °C. The enantiomeric excess was determined on a Daicel Chiralcel
OD-H column with hexane/2-propanol (60/40) and flow rate 0.8
mL/min and detected at a UV wavelength of 228 nm. Retention times:
JHP = 8.8 Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz, JHP
7.3 Hz, 1H, PCHCHH), 3.71 (ddd, JHH = 18.0 and 3.7 Hz, JHP = 8.8
Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.9 (d, JCP
14.9 Hz), 146.3, 140.3, 134.6 (d, JCP = 5.8 Hz), 131.93 (d, JCP = 48.9
Hz), 131.91 (d, JCP = 46.2 Hz), 131.48 (d, JCP = 9.0 Hz), 131.47 (d,
JCP = 4.9 Hz), 131.3 (d, JCP = 1.6 Hz), 131.1 (d, JCP = 8.8 Hz), 130.7,
130.3, 128.9 (d, JCP = 11.4 Hz), 128.3 (d, JCP = 11.7 Hz), 128.1, 126.8,
125.3, 121.2 (d, JCP = 3.4 Hz), 43.0, 41.2 (d, JCP = 66.7 Hz). 31P{1H}
NMR (162 MHz, CDCl3): δ 32.1. HRMS (positive ESI): [M + H]+
calcd for C26H22BrNO3P 506.0521, found 506.0519.
=
=
20
18.9 min (major), 30.5 min, 92% ee. [α]D = −128° (c 0.730,
CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.13 (d, JHH = 6.4 Hz, 1H),
8.02−7.96 (m, 3H), 7.90 (d, JHH = 1.9 Hz, 1H), 7.76 (d, JHH = 7.0 Hz,
1H), 7.58−7.50 (m, 5H), 7.40−7.27 (m, 6H), 7.17−7.13 (m, 1H),
4.59 (ddd, JHH = 12.0 and 3.6 Hz, JHP = 8.7 Hz, 1H, PCHCH2), 4.16
(ddd, JHH = 18.2 and 10.7 Hz, JHP = 6.9 Hz, 1H, PCHCHH), 3.80
(ddd, JHH = 18.4 and 3.6 Hz, JHP = 9.1 Hz, 1H, PCHCHH). 13C NMR
(100 MHz, CDCl3): δ 194.3 (d, JCP = 14.5 Hz), 147.7, 146.0, 140.5,
137.9 (d, JCP = 5.7 Hz), 135.7 (d, JCP = 4.4 Hz), 132.19 (d, JCP = 44.9
(S)-2-(3-(2-Bromophenyl)-3-(diphenylphosphinyl)propionyl)-
pyridine N-Oxide (7q). Pale yellow oil (81.0 mg, 80%). The
enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 13.3
min (major), 22.3 min, 85% ee. [α]D20 = −96° (c 0.358, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.06−8.02 (m, 3H), 7.73−7.70 (m, 1H),
7.53−7.52 (m, 3H), 7.31−7.16 (m, 5H), 7.13−7.07 (m, 3H), 7.02−
6.98 (m, 2H), 6.90−6.85 (m, 1H), 5.01 (ddd, JHH = 12.0 and 4.2 Hz,
Hz), 132.16 (d, JCP = 45.1 Hz), 131.5 (d, JCP = 8.8 Hz), 130.9 (d, JCP
=
8.8 Hz), 130.3, 129.8, 129.2 (d, JCP = 2.0 Hz), 129.0 (d, JCP = 11.6
Hz), 128.4 (d, JCP = 11.9 Hz), 128.3, 126.9, 125.3, 124.9 (d, JCP = 5.7
Hz), 122.1 (d, JCP = 2.1 Hz), 43.0, 41.6 (d, JCP = 65.6 Hz). 31P{1H}
NMR (162 MHz, CDCl3): δ 32.1. HRMS (positive ESI): [M + H]+
calcd for C26H22N2O5P 473.1266, found 473.1270.
(S)-2-(3-(Diphenylphosphinyl)-3-(4-methylphenyl)propionyl)-
pyridine N-Oxide (7u). Pale yellow solid (69.8 mg, 79%). Mp: 185−
187 °C. The enantiomeric excess was determined on a Daicel Chiralcel
OD-H column with hexane/2-propanol (70/30) and flow rate 1.0
mL/min and detected at a UV wavelength of 228 nm. Retention times:
14.3 min (major), 21.4 min, 63% ee. [α]D20 = −89° (c 0.736, CH2Cl2).
1H NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.5 Hz, 1H), 7.99−7.94
(m, 2H), 7.54−7.46 (m, 5H), 7.38−7.34 (m, 1H), 7.28−7.24 (m, 3H),
7.08 (d, JHH = 4.6 Hz, 2H), 7.03−7.01 (m, 2H), 6.89 (d, JHH = 7.9 Hz,
2H), 4.41 (ddd, JHH = 13.1 and 4.0 Hz, JHP = 10.7 Hz, 1H, PCHCH2),
4.03 (ddd, JHH = 18.0 and 10.7 Hz, JHP = 8.0 Hz, 1H, PCHCHH), 3.71
(ddd, JHH = 17.7 and 3.9 Hz, JHP = 8.6 Hz, 1H, PCHCHH), 2.20 (s,
3H, CH3). 13C NMR (100 MHz, CDCl3): δ 195.5 (d, JCP = 15.2 Hz),
146.6, 140.1, 136.7 (d, JCP = 2.7 Hz), 132.0 (d, JCP = 6.1 Hz), 131.72
(d, JCP = 53.6 Hz), 131.70 (d, JCP = 53.6 Hz), 131.6 (d, JCP = 8.7 Hz),
131.3 (d, JCP = 8.7 Hz), 130.9, 130.8, 129.6 (d, JCP = 5.2 Hz), 128.9 (d,
JCP = 1.9 Hz), 128.8 (d, JCP = 11.2 Hz), 128.1 (d, JCP = 11.6 Hz),
127.8, 126.7, 125.3, 43.0, 41.4 (d, JCP = 67.3 Hz), 21.0. 31P{1H} NMR
(162 MHz, CDCl3): δ 32.6. HRMS (positive ESI): [M + H]+ calcd for
C27H25NO3P 442.1572, found 442.1570.
JHP = 8.0 Hz, 1H, PCHCH2), 3.91 (ddd, JHH = 19.4 and 11.0 Hz, JHP
8.3 Hz, 1H, PCHCHH), 3.76 (ddd, JHH = 16.9 and 4.2 Hz, JHP = 7.4
Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 194.9 (d, JCP
=
=
15.7 Hz), 146.4, 140.3, 135.0 (d, JCP = 5.2 Hz), 132.3 (d, JCP = 2.3
Hz), 131.8 (d, JCP = 8.7 Hz), 131.30 (d, JCP = 56.0 Hz), 131.26 (d, JCP
= 57.4 Hz), 131.2, 131.1, 130.8, 129.9, 128.9 (d, JCP = 11.4 Hz), 128.6
(d, JCP = 2.3 Hz), 128.0, 127.8 (d, JCP = 11.8 Hz), 127.7 (d, JCP = 2.2
Hz), 126.8, 126.4 (d, JCP = 7.3 Hz), 125.2, 43.4, 39.7 (d, JCP = 65.6
Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive
ESI): [M + H]+ calcd for C26H22BrNO3P 506.0521, found 506.0523.
(S)-2-(3-(4-Chlorophenyl)-3-(diphenylphosphinyl)propionyl)-
pyridine N-Oxide (7r). White solid (72.0 mg, 78%). Mp: 210−212 °C.
The enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 16.7
min (major), 25.1 min, 89% ee. [α]D20 = −134° (c 0.800, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H), 7.99−7.94
(m, 2H), 7.56−7.46 (m, 5H), 7.40−7.36 (m, 1H), 7.31−7.27 (m, 3H),
7.19−7.06 (m, 6H), 4.43 (ddd, JHH = 12.4 and 3.8 Hz, JHP = 8.7 Hz,
1H, PCHCH2), 4.05 (ddd, JHH = 18.0 and 10.8 Hz, JHP = 7.4 Hz, 1H,
PCHCHH), 3.71 (ddd, JHH = 18.0 and 3.8 Hz, JHP = 8.7 Hz, 1H,
PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.0 (d, JCP = 14.8
Hz), 146.4, 140.3, 134.0 (d, JCP = 5.7 Hz), 133.0 (d, JCP = 3.2 Hz),
(S)-2-(3-(Diphenylphosphinyl)-3-(4-methoxyphenyl)propionyl)-
pyridine N-Oxide (7v). Pale yellow solid (65.5 mg, 72%). Mp: 196−
198 °C. The enantiomeric excess was determined on a Daicel Chiralcel
OD-H column with hexane/2-propanol (70/30) and flow rate 1.0
mL/min and detected at a UV wavelength of 228 nm. Retention times:
131.93 (d, JCP = 50.3 Hz), 131.90 (d, JCP = 50.5 Hz), 131.5 (d, JCP
=
20
8.7 Hz), 131.10 (d, JCP = 5.8 Hz), 131.08 (d, JCP = 8.4 Hz), 130.7,
130.3, 128.9 (d, JCP = 11.4 Hz), 128.33 (d, JCP = 2.2 Hz), 128.25 (d,
JCP = 11.9 Hz), 128.0, 126.8, 125.3, 43.1, 41.2 (d, JCP = 66.7 Hz).
31P{1H} NMR (162 MHz, CDCl3): δ 32.4. HRMS (positive ESI): [M
21.9 min (major), 30.9 min, 77% ee. [α]D = −143° (c 0.116,
CH2Cl2). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, JHH = 6.5 Hz, 1H),
7.99−7.94 (m, 2H), 7.55−7.44 (m, 5H), 7.38−7.34 (m, 1H), 7.28−
7.24 (m, 3H), 7.10−7.04 (m, 4H), 6.63 (d, JHH = 8.6 Hz, 2H), 4.39
(ddd, JHH = 12.7 and 3.9 Hz, JHP = 9.0 Hz, 1H, PCHCH2), 4.01 (ddd,
JHH = 17.8 and 11.0 Hz, JHP = 7.8 Hz, 1H, PCHCHH), 3.73−3.65 (m,
4H, PCHCHH and OCH3).13C NMR (100 MHz, CDCl3): δ 195.6 (d,
+ H]+ calcd for C26H22ClNO3P 462.1026, found 462.1028.
(S)-2-(3-(Diphenylphosphinyl)-3-(4-nitrophenyl)propionyl)-
pyridine N-Oxide (7s). Pale yellow solid (85.1 mg, 90%). Mp: 197−
198 °C. The enantiomeric excess was determined on a Daicel Chiralcel
OD-H column with hexane/2-propanol (70/30) and flow rate 1.0
JCP = 15.4 Hz), 158.6 (d, JCP = 2.3 Hz), 146.7, 140.1, 131.72 (d, JCP
=
55.4 Hz), 131.69 (d, JCP = 55.4 Hz), 131.5 (d, JCP = 8.7 Hz), 131.2 (d,
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JCP = 8.8 Hz), 131.0, 130.8 (d, JCP = 5.4 Hz), 130.7, 128.8 (d, JCP
=
propanol (60/40) and flow rate 1.0 mL/min and detected at a UV
11.2), 128.1 (d, JCP = 11.6), 127.8, 127.0 (d, JCP = 5.9 Hz), 126.7,
125.3, 113.6 (d, JCP = 1.9 Hz), 55.1, 43.0, 40.9 (d, JCP = 67.8 Hz).
31P{1H} NMR (162 MHz, CDCl3): δ 32.6. HRMS (positive ESI): [M
wavelength of 228 nm. Retention times: 12.0 min (major), 17.1 min,
20
64% ee. [α]D = −57° (c 0.327, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 8.14 (d, JHH = 6.3 Hz, 1H), 7.94−7.89 (m, 2H), 7.79−7.74
(m, 2H), 7.53−7.41 (m, 7H), 7.33−7.29 (m, 1H), 7.24−7.13 (m, 6H),
6.30 (dd, J = 4.3, 15.9 Hz, 1H), 6.08 (ddd, JHH = 14.9 and 9.1 Hz, JHP
= 5.7 Hz, 1H), 4.20−4.12 (m, 1H, PCHCH2), 3.76 (ddd, JHH = 17.7
and 10.0 Hz, JHP = 8.0 Hz, 1H, PCHCHH), 3.61 (ddd, JHH = 17.5 and
4.0 Hz, JHP = 9.8 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3):
δ 195.2 (d, JCP = 14.3 Hz), 146.7, 140.3, 136.5 (d, JCP = 2.9 Hz), 135.1
(d, JCP = 11.2 Hz), 132.02 (d, JCP = 21.1 Hz), 131.99 (d, JCP = 21.1
Hz), 131.6 (d, JCP = 8.8 Hz), 131.5 (d, JCP = 8.7 Hz), 130.7, 130.4,
128.8 (d, JCP = 11.3 Hz), 128.5 (d, JCP = 3.1 Hz), 128.45 (d, JCP = 11.5
Hz), 128.0, 127.7, 127.1, 126.3, 125.5, 123.4 (d, JCP = 7.4 Hz), 41.4,
40.0 (d, JCP = 68.5 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 33.1.
HRMS (positive ESI): [M + H]+ calcd for C28H25NO3P 454.1572,
found 454.1573.
+ H]+ calcd for C27H25NO4P 458.1521, found 458.1525.
(S)-2-(3-(Diphenylphosphinyl)-3-(3-methoxyphenyl)propionyl)-
pyridine N-Oxide (7w). Pale yellow oil (75.2 mg, 82%). The
enantiomeric excess was determined on a Daicel Chiralcel OD-H
column with hexane/2-propanol (70/30) and flow rate 1.0 mL/min
and detected at a UV wavelength of 228 nm. Retention times: 17.0
min (major), 24.3 min, 78% ee. [α]D20 = −95° (c 0.383, CH2Cl2). 1H
NMR (400 MHz, CDCl3): δ 8.10 (d, JHH = 6.5 Hz, 1H), 8.00−7.95
(m, 2H), 7.54−7.45 (m, 5H), 7.38−7.33 (m, 1H), 7.28−7.23 (m, 3H),
7.11−7.08 (m, 2H), 6.99 (t, JHH = 7.9 Hz, 1H), 6.72 (d, JHH= 7.4 Hz,
1H), 6.67−6.62 (m, 2H), 4.43 (ddd, JHH = 13.2 and 4.1 Hz, JHP = 10.7
Hz, 1H, PCHCH2), 4.06 (ddd, JHH = 18.0 and 10.8 Hz, JHP = 8.2 Hz,
1H, PCHCHH), 3.72 (ddd, JHH = 17.8 and 4.1 Hz, JHP = 8.6 Hz, 1H,
PCHCHH), 3.60 (s, 3H, OCH3). 13C NMR (100 MHz, CDCl3): δ
195.4 (d, JCP = 14.8 Hz), 159.2 (d, JCP = 2.1 Hz), 146.6, 140.1, 136.7
(d, JCP = 5.5 Hz), 131.8 (d, JCP = 48.2 Hz), 131.78 (d, JCP = 54.3 Hz),
131.5 (d, JCP = 8.6 Hz), 131.2 (d, JCP = 8.8 Hz), 130.8, 130.6, 129.1 (d,
JCP = 1.7 Hz), 128.8 (d, JCP = 11.5 Hz), 128.1 (d, JCP = 11.7 Hz),
127.8, 126.7, 125.4, 122.2 (d, JCP = 5.2 Hz), 114.7 (d, JCP = 5.2 Hz),
113.5 (d, JCP = 2.3 Hz), 55.1, 42.8, 41.9 (d, JCP = 66.6 Hz). 31P{1H}
NMR (162 MHz, CDCl3): δ 32.8. HRMS (positive ESI): [M + H]+
calcd for C27H25NO4P 458.1521, found 458.1518.
(S)-2-(3-(Diphenylphosphinyl)-3-(1-naphthyl)propionyl)pyridine
N-Oxide (7aa). Pale yellow oil (66.8 mg, 70%). The enantiomeric
excess was determined on a Daicel Chiralcel OD-H column with
hexane/2-propanol (60/40) and flow rate 1.0 mL/min and detected at
a UV wavelength of 228 nm. Retention times: 9.7 min (major), 15.2
min, 76% ee. [α]D20 = −64° (c 0.100, CH2Cl2). H NMR (400 MHz,
1
CDCl3): δ 8.15−8.10 (m, 2H), 8.01 (d, JHH = 6.4 Hz, 1H), 7.86−7.83
(m, 1H), 7.74 (d, JHH = 8.5 Hz, 1H), 7.62−7.59 (m, 5H), 7.39 (t, JHH
= 7.6 Hz, 1H), 7.28−7.15 (m, 4H), 7.08−6.92 (m, 4H), 6.73 (t, JHH
=
7.6 Hz, 1H), 6.65−6.62 (m, 1H), 5.48 (ddd, JHH = 13.6 and 4.6 Hz,
JHP = 10.4 Hz, 1H, PCHCH2), 4.10 (ddd, JHH = 14.2 and 7.1 Hz, JHP
3.3 Hz, 1H, PCHCHH), 3.95 (ddd, JHH = 17.2 and 4.6 Hz, JHP = 7.0
Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3): δ 195.7 (d, JCP
(S)-2-(3-(Diphenylphosphinyl)-3-(2-furanyl)propionyl)pyridine N-
Oxide (7x). Pale yellow oil (52.5 mg, 63%). The enantiomeric excess
was determined on a Daicel Chiralcel OD-H column with hexane/2-
propanol (60/40) and flow rate 1.0 mL/min and detected at a UV
wavelength of 228 nm. Retention times: 11.8 min (major), 17.0 min,
=
=
15.5 Hz), 146.6, 139.9, 133.2, 132.1, 132.0 (d, JCP = 33.2 Hz), 131.99
(d, JCP = 39.3 Hz), 131.9, 131.8 (d, JCP = 8.6 Hz), 131.3 (d, JCP = 2.7
Hz), 130.9, 130.8 (d, JCP = 9.1 Hz), 130.4, 128.9 (d, JCP = 11.2 Hz),
128.5, 127.7, 127.6 (d, JCP = 11.2 Hz), 126.4, 125.8, 125.4 (d, JCP = 2.5
Hz), 125.2, 125.1, 122.2, 44.2, 34.5 (d, JCP = 66.8 Hz). 31P{1H} NMR
(162 MHz, CDCl3): δ 32.6.
20
69% ee. [α]D = −42° (c 0.270, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 8.14 (d, JHH = 6.4 Hz, 1H), 7.90−7.85 (m, 2H), 7.55−7.43
(m, 6H), 7.40−7.30 (m, 4H), 7.23−7.19 (m, 1H), 7.11 (s, 1H), 6.17
(dd, JHH = 1.9, 3.2 Hz, 1H), 6.05 (t, JHH = 3.2 Hz, 1H), 4.75 (ddd, JHH
= 14.8 and 4.6 Hz, JHP = 10.3 Hz, 1H, PCHCH2), 3.96 (ddd, JHH
=
X-ray Diffraction Studies. Crystals of 3 and 5b (CCDC file
numbers 980716 and 980605) were obtained by recrystallization from
CH2Cl2/n-hexane at ambient temperature. The data were collected on
an Oxford Diffraction Gemini E diffractometer with graphite-
monochromated Cu Kα radiation (λ = 1.5418 Å for complex 3) or
Mo Kα radiation (λ = 0.7107 Å) at ambient temperature. The
structures were solved by direct methods using the SHELXS-97
program, and all non-hydrogen atoms were refined anisotropically on
F2 by the full-matrix least-squares technique, which used the SHELXL-
97 crystallographic software package.23 The hydrogen atoms were
included but not refined. Details of the crystal structure determination
are summarized in Table S1 in the Supporting Information.
18.2 and 10.1 Hz, JHP = 8.6 Hz, 1H, PCHCHH), 3.78 (ddd, JHH = 18.1
and 4.6 Hz, JHP = 8.6 Hz, 1H, PCHCHH). 13C NMR (100 MHz,
CDCl3): δ 194.9 (d, JCP = 13.1 Hz), 149.0 (d, JCP = 6.2 Hz), 146.4,
141.7 (d, JCP = 2.9 Hz), 140.3, 132.04 (d, JCP = 29.4 Hz), 132.01 (d,
JCP = 29.6 Hz), 131.6 (d, JCP = 5.8 Hz), 131.5 (d, JCP = 5.8 Hz), 130.7
(d, JCP = 40.9 Hz), 129.9, 128.7 (d, JCP = 11.7 Hz), 128.2 (d, JCP = 11.7
Hz), 128.0, 127.0, 125.5, 110.8 (d, JCP = 2.8 Hz), 109.0 (d, JCP = 5.9
Hz), 41.1, 36.4 (d, JCP = 68.7 Hz). 31P{1H} NMR (162 MHz, CDCl3):
δ 31.9. HRMS (positive ESI): [M + H]+ calcd for C24H21NO4P
418.1208, found 418.1209.
(S)-2-(3-(Diphenylphosphinyl)-3-(2-thienyl)propionyl)pyridine N-
Oxide (7y). Pale yellow solid (62.4 mg, 72%). Mp: 167−168 °C. The
enantiomeric excess was determined on a Daicel Chiralpak AD column
with hexane/2-propanol (60/40) and flow rate 1.0 mL/min and
detected at a UV wavelength of 228 nm. Retention times: 32.8 min
ASSOCIATED CONTENT
■
S
* Supporting Information
20
1
(major), 55.4 min, 78% ee. [α]D = −91° (c 0.366, CH2Cl2). H
NMR (400 MHz, CDCl3): δ 8.12 (d, JHH = 6.4 Hz, 1H), 7.98−7.93
(m, 2H), 7.57−7.52 (m, 5H), 7.43−7.39 (m, 1H), 7.34−7.28 (m, 3H),
7.23−7.20 (m, 1H), 7.16−7.12 (m, 1H), 7.01−6.99 (m, 1H), 6.85 (t,
A table giving crystallographic details for the Pd(II) complexes
3 and 5b, figures giving synthetic routes for the ligands 1a−c
and 4a−d, text giving characterization data of the known
catalysis products, figures giving NMR spectra of the new
compounds 1−5 and NMR spectra of the catalysis products as
well as their chiral HPLC spectra, and CIF files giving
crystallographic data for complexes 3 and 5b. This material is
available free of charge via the Internet at http://pubs.acs.org.
JHH = 2.6 Hz, 1H), 6.77 (dd, JHH = 3.6, 5.0 Hz, 1H), 4.81 (ddd, JHH
=
13.8 and 3.9 Hz, JHP = 10.6 Hz, 1H, PCHCH2), 4.00 (ddd, JHH = 17.9
and 10.8 Hz, JHP = 7.4 Hz, 1H, PCHCHH), 3.72 (ddd, JHH = 17.7 and
4.0 Hz, JHP = 8.0 Hz, 1H, PCHCHH). 13C NMR (100 MHz, CDCl3):
δ 195.0 (d, JCP = 14.5 Hz), 146.5, 140.2, 137.1 (d, JCP = 6.5 Hz),
132.00 (d, JCP = 46.2 Hz), 131.92 (d, JCP = 46.0 Hz), 131.8 (d, JCP
8.8 Hz), 131.3 (d, JCP = 8.8 Hz), 131.1, 130.3, 130.2, 128.9 (d, JCP
=
=
AUTHOR INFORMATION
■
11.5 Hz), 128.2 (d, JCP = 11.7 Hz), 128.0, 127.5 (d, JCP = 6.0 Hz),
126.8 (d, JCP = 2.8 Hz), 125.5, 124.9 (d, JCP = 2.9 Hz), 44.1, 37.3 (d,
JCP = 68.8 Hz). 31P{1H} NMR (162 MHz, CDCl3): δ 31.8. HRMS
(positive ESI): [M + H]+ calcd for C24H21NO3PS 434.0980, found
434.0981.
(S,E)-2-(3-(Diphenylphosphinyl)-5-phenyl-4-pentenoyl)pyridine
N-Oxide (7z). Pale yellow oil (53.8 mg, 59%). The enantiomeric excess
was determined on a Daicel Chiralcel OD-H column with hexane/2-
Corresponding Authors
*J.-F.G.: e-mail, gongjf@zzu.edu.cn.
*M.-P.S.: tel/fax, (+86)-371-6778-3012; e-mail, mpsong@zzu.
edu.cn.
Notes
The authors declare no competing financial interest.
1810
dx.doi.org/10.1021/om500144b | Organometallics 2014, 33, 1801−1811

Organometallics
Article
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ACKNOWLEDGMENTS
■
We are grateful to the National Natural Science Foundation of
China (21272217), the Program for Science & Technology
Innovation Talents in Universities of Henan Province
(2012HASTIT003), and the Key Technologies R & D Program
of Henan Province (102101210200) for financial support of
this work.
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