Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth-Metal Complexes Supported with Phenoxy-Functionalized TsDPEN Ligands

Article abstract of DOI:10.1021/acs.organomet.1c00272

Six novel chiral rare-earth-metal complexes bearing the phenoxy-functionalized TsDPEN ligand H3L1 (H3L1 = N-((1R,2R)-2-((3,5-di-Tert-butyl-2-hydroxybenzyl)amino)-1,2-diphenylethyl)-4-methylbenzenesulfonamide) were synthesized successfully and well characterized. The solid-state structures of four tetranuclear rare-earth-metal complexes [RE2L13]2 (RE = Nd (1), Sm (2), Eu (3), Gd (4)) and the dual-core yttrium complex Y2L13 (5) were determined by X-ray diffraction, respectively. The structure of lanthanum complex 6 was speculated by the 1H DOSY spectroscopy in THF-d8 together with DFT calculations. Complexes 1-5 were employed to catalyze the enantioselective hydroboration of ketones and α,β-unsaturated ketones using pinacolborane (HBpin) as a reductant, and complex 1 gave better outcomes in comparison to the others. The corresponding secondary alcohols were obtained in excellent yields and moderate ee values. The same results were also achieved using the combined catalyst system of the neodymium amide Nd[N(SiMe3)2]3 with the phenoxy-functionalized TsDPEN ligand H3L1 in a 1:1.5 molar ratio.

Full text of DOI:10.1021/acs.organomet.1c00272

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Article
Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth-
Metal Complexes Supported with Phenoxy-Functionalized TsDPEN
Ligands
Qishun Yu, Chengrong Lu,* and Bei Zhao*
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ABSTRACT: Six novel chiral rare-earth-metal complexes bearing the
phenoxy-functionalized TsDPEN ligand H3L1 (H3L1 = N-((1R,2R)-2-
((3,5-di-tert-butyl-2-hydroxybenzyl)amino)-1,2-diphenylethyl)-4-methylben-
zenesulfonamide) were synthesized successfully and well characterized. The
solid-state structures of four tetranuclear rare-earth-metal complexes
[RE2L1 ] (RE = Nd (1), Sm (2), Eu (3), Gd (4)) and the dual-core
3 2
yttrium complex Y2L1 (5) were determined by X-ray diffraction,
3
respectively. The structure of lanthanum complex 6 was speculated by the
1H DOSY spectroscopy in THF-d8 together with DFT calculations.
Complexes 1−5 were employed to catalyze the enantioselective hydro-
boration of ketones and α,β-unsaturated ketones using pinacolborane
(HBpin) as a reductant, and complex 1 gave better outcomes in comparison
to the others. The corresponding secondary alcohols were obtained in
excellent yields and moderate ee values. The same results were also achieved using the combined catalyst system of the neodymium
amide Nd[N(SiMe3)2]3 with the phenoxy-functionalized TsDPEN ligand H3L1 in a 1:1.5 molar ratio.
In order to enhance the enantioselectivities of the catalysts,
one efficient strategyphenoxy-functionalized chiral ligands
was introduced in the design of ligands. In the past decade,
phenoxy-functionalized prolinolates were developed to im-
prove the chiral induction of prolinols in a variety of the
asymmetric reactions by our group. Many systems of rare-
earth-metal complexes bearing chiral phenoxy-functionalized
prolinolates were synthesized and well characterized and were
employed in asymmetric Michael additions,6 epoxidations,7
hydroborations,8 and hydrophosphonylations,9 respectively. It
is noted that only one case of chiral phenoxy-functionalized
TsDPEN ligands (Figure 1b) was employed in the preparation
of chiral silicon Lewis acid catalysts, which were used in
asymmetric Diels−Alder cycloadditions.10 If the prolinolates
we used are replaced by the above TsDPEN subunit, what kind
of rare-earth-metal complexes will we get and will the
enantioselectivities of the desired complexes be improved in
the asymmetric catalytic reactions? In order to find the answer,
the modification of phenoxy-functionalized TsDPEN ligands,
INTRODUCTION
■
Metal-catalyzed enantioselective reactions are some of the
important practical strategies for the synthesis of chiral
compounds. The enantioselectivities mainly depend on the
chiral ligands; thus, the design of chiral ligands is of great
importance. N-(p-Tosyl)-1,2-diphenylethylene-1,2-diamine,
simplified as TsDPEN (Figure 1a), and its derivatives have
Figure 1. TsDPEN and phenoxy-functionalized TsDPEN.
proved to be excellent ligands and were used in asymmetric
transfer hydrogenations catalyzed by Ru or Rh complexes,1
Michael addition reactions catalyzed by Ru or Co complexes,2
and Mannich reactions catalyzed by Ni complexes.3 Epox-
idation4 and alkynylation5 were catalyzed by FeCl3·6H2O or
VOSO4 and CuI combined with TsDPEN in an in situ catalysis
manner, respectively. In the above cases, the catalyst loading
was relatively low, from 0.1 to 10 mol %, the yields of the
target molecules were good to excellent (33−100%), and the
enantioselectivities were good to excellent (42−99%).
Received: May 4, 2021
Published: July 9, 2021
https://doi.org/10.1021/acs.organomet.1c00272
© 2021 American Chemical Society
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followed by the preparation of the corresponding rare-earth-
metal complexes, and tests of their effectiveness in
enantioselective transformation were carried out.
Scheme 2. Synthesis of Complexes 1−5
Enantioselective hydroboration is a common, efficient, and
safe method to produce optically enantiopure secondary
alcohols from ketones. Metal-based catalytic enantioselective
hydroborations of ketones were developed using Co complexes
bearing iminopyridine oxazoline ligands,11 Mn complexes
bearing bis(oxazolinylmethylidene)-isoindoline pincer li-
gands,12 Ni complexes bearing oxazoline ligands,13 or Mg14
and Al15 complexes bearing BINOLs as the catalytic system;
meanwhile RE-based complexes combined with N,N′-dioxide
ligands,16 phenoxy-functionalized prolinolates,8 or Trost
ligands17 were also employed in the transformation. Though
enantioselective hydroboration is a reaction that has attracted
much attention, highly efficient systems are still rare and need
to be constantly developed, because the target enantiopure
secondary alcohols are key organic synthesis intermediates.18
Thus, some rare-earth-metal complexes supported with
phenoxy-functionalized TsDPEN ligands were prepared and
their catalytic behavior for enantioselective hydroboration of
ketones was investigated. Herein we report these results.
metal complexes [RE2L1 ] (RE = Nd (1), Sm (2), Eu (3), Gd
3 2
(4)) were characterized and determined. Since complexes 1−4
are isostructural, only the representative molecular structure of
complex 1 is depicted in Figure 3. Details of the crystallo-
graphic data of crystals 1−4 are summarized in Table S1, and
the corresponding selected bond lengths and angles are
provided in Tables S2−S5.
RESULTS AND DISCUSSION
■
With the commercially available chiral TsDPEN in hand, the
phenoxy-functionalized TsDPEN ligand H3L1 (N-((1R,2R)-2-
((3,5-di-tert-butyl-2-hydroxybenzyl)amino)-1,2-diphenyleth-
yl)-4-methylbenzenesulfonamide) was prepared according to a
previous work.19 The reaction is shown in Scheme 1.
Scheme 1. Synthesis of H3L1
Figure 3. Molecular structure of complex 1. Aromatic substituents are
shown in the form of wireframes, whereas the other atoms are shown
by thermal ellipsoids drawn at the 50% probability level. Hydrogen
atoms, except those on the N4−N6 and N10−N12 atoms, are
omitted for clarity.
Occasionally, the crystal structure was characterized by X-ray
diffraction, shown in Figure 2. The chiralities of the two chiral
centers C8 and C15 are both the R configuration, indicating
that the ligand did not racemize during the phenoxy
functionalization.
Reactions of the rare-earth-metal amides RE[N(SiMe3)2]3
(RE = Nd (1), Sm (2), Eu (3), Gd (4), Y (5)) with H3L1 in a
1:1.5 molar ratio in THF gave the final products in high yields
(Scheme 2). Crystals of complexes 1−4 suitable for X-ray
diffraction were obtained from a hexane/toluene mixed solvent
at room temperature, and four chiral tetranuclear rare-earth-
Complexes 1−4 are complicated monoclinic systems and
have tetranuclear structures bearing six ligands. As shown in
Figure 3, the solid-state structure of 1 is a dimer, linked by the
oxygen atoms from sulfonyl groups. The geometric config-
urations around Nd1 and Nd3 are the same, as are those of
Nd2 and Nd4. Only the coordination environments of Nd1
and Nd2 are discussed in detail. The central metal Nd1 has a
7-coordinated structure and a twisted-decahedral configura-
tion, where O4 and O10 atoms occupy the two vertices with a
O4−Nd1−O10 bond angle of 174.0°, slightly deviating from
the ideal 180°; meanwhile N1, N2, O3, O7, and O2 atoms
form the equatorial plane, since the sum of the bond angles
361.9° (N(1)−Nd(1)−N(2) 62.9(2)°, N(2)−Nd(1)−O(3)
74.2(2)°, O(3)−Nd(1)−O(7) 87.3(2)°, O(7)−Nd(1)−O(2)
83.4(2)°, O(2)−Nd(1)−N1 54.1(2)°) are close to the ideal
360°. The Nd1−N1 and Nd1−N2 bond lengths are 2.462(7)
and 2.660(7) Å, respectively. The Nd1−μ-O2 (sulfonyl
oxygen) bond length is 2.681(6) Å, much longer than
2.190(6) Å for Nd1−O3 (aryloxo), a type of σ bond. Other
Nd1−μ-O bond lengths, such as the distances from Nd1 to
Figure 2. ORTEP diagram of the structure of the chiral ligand H3L1.
Thermal ellipsoids are drawn at the 50% probability level. Hydrogen
atoms, except those on C22 and O3 atoms, are omitted for clarity.
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bridging oxygen atoms O4, O7, and O10, are 2.404(6),
2.415(6), and 2.421(5) Å, respectively. This indicates that the
interactions between Nd1 and the three oxygen atoms from
three sulfonyl groups are similar.
plane is comprised by the two aryl oxygen atoms O6 and O9
and the two sulfonyl oxygen atoms O5 and O8, since the sum
of the bond angles around Y2 is 365.8° (O(6)−Y(2)−O(9)
91.7(3)°, O(9)−Y(2)−O(5) 90.9(2)°, O(5)−Y(2)−O(8)
85.8(2)°, O(8)−Y(2)−O(6) 97.4(3)°). The two vertices are
N4 and N6 atoms, with a bond angle of 169.0(3)°, deviating
from the ideal 180°. The Y2−N3, Y2−N4, Y2−N5, and Y2−
N6 bond lengths are 2.479(8), 2.500(8), 2.418(9), and
2.580(8) Å, respectively. The average Y2−O (aryloxo) bond
length is 2.158 Å, while the average Y2−μ-O (sulfonyl oxygen)
bond length is 2.587 Å.
When the differences in ionic radii between Nd(III) and
Y(III) are taken into account, the different aggregation
structures of complexes 1 and 5 are reasonable and acceptable.
The more open environment around neodymium may be more
conducive to the coordination and dissociation process of the
substrate and is beneficial for the reactivities.
The central metal Nd2 has an 8-coordinated structure and a
twisted-octahedral configuration. The approximate equatorial
plane is comprised by the two aryl oxygen atoms O6 and O9
and the two sulfonyl oxygen atoms O5 and O8, since the sum
of the bond angles around Nd2 is 362.8° (O(6)−Nd(2)−
O(9) 91.3(3)°, O(9)−Nd(2)−O(5) 92.3(3)°, O(5)−Nd(2)−
O(8) 83.6(2)°, O(8)−Nd(2)−O(6) 95.6(2)°), close to the
ideal 360°. The two vertex N4 and N6 atoms are located on
the both sides of the equatorial plane, with a bond angle of
176.9(2)°, close to the ideal 180°. The Nd2−N3, Nd2−N4,
Nd2−N5, and Nd2−N6 bond lengths are 2.494(8), 2.615(7),
2.466(7), and 2.679(7) Å, respectively. The average Nd2−O
(aryloxo) bond length is 2.207 Å, while the average Nd2−μ-O
(sulfonyl oxygen) bond length is 2.720 Å.
In order to gain a deeper insight into the aggregation in
solution, the structure of complex 5 in THF was confirmed by
The bond parameters in complexes 2−4 are similar to the
corresponding values in complex 1, when the differences in
ionic radii are taken into account.
The solid-state structure of complex 5 is shown in Figure 4,
and it was proved to be a dual-core structure bearing three
1
1
a H DOSY NMR analysis. The H DOSY spectrum (Figure
S14; diffusion coefficient Dt determined as 4.50 × 10−10 m2/s)
shows that the hydrodynamic radius (rh) of complex 5 in THF-
d8 is 10.4
0.5 Å (calculated by the Stocks−Einstein
equation), which is comparable to the corresponding value rav
of 9.9 0.5 Å calculated from crystal 5 according to a known
method.20 It reveals that complex 5 has the same dual-core
structure whether it is in THF or in the solid state.
Using the same metathesis reaction, complex 6 was prepared
by the treatment of La[N(SiMe3)2]3 with H3L1 in a 1:1.5 molar
ratio in THF. However, crystals suitable for an X-ray
diffraction analysis were not available. To clarify the possible
structure of complex 6, a diffusion coefficient Dt determination
of powder 6 in THF-d8 was conducted. The 1H DOSY
spectrum (Figure S15; diffusion coefficient Dt determined as
4.26 × 10−10 m2/s) shows that the hydrodynamic radius (r′h)
of complex 6 in THF-d8 is 11.0 0.6 Å (calculated by the
Stocks−Einstein equation). When we replaced the Y atom of
the dual-core structure 5 by an La atom, the structure could be
optimized using Gaussian16 at the B3PW91/6-31G** level
(MWB46 for La)21 and the corresponding value (rav) was
Figure 4. Molecular structure of complex 5. Aromatic substituents are
in the form of wireframes, whereas the other atoms are shown by
thermal ellipsoids drawn at the 50% probability level. Hydrogen
atoms, except those on the N4−N6 atoms, and the coordinated
solvents toluene and DCM are omitted for clarity.
calculated as 9.9
tetranuclear structure 2 was replaced by an La atom, the
corresponding value (r′av) of 14.4 0.7 Å was obtained.
0.5 Å, while when the Sm atom of
ligands: that is, Y2L1 is the simplified formula. Details of the
According to the above calculations, the hydrodynamic radius
of complex 6 (11.0 Å) is relatively closer to the average radius
(9.9 Å) when 6 is assumed to be a dinuclear molecule; thus,
complex 6 in THF is speculated to exist as a dual-core
complex.
3
crystallographic data of crystal 5 are summarized in Table S1,
and selected bond lengths and angles are provided in Table S6.
The coordination environments of Y1 and Y2 atoms are similar
to those of the corresponding Nd1 and Nd2 atoms in complex
1. The central metal Y1 has a 6-coordinated structure and a
pentagonal configuration, where an O4 atom occupies the
vertex and N1, N2, O3, O7, and O2 atoms form the equatorial
plane, since the sum of the bond angles 362.8° is close to the
ideal 360° (N(1)−Y(1)−N(2) 66.9(3)°, N(2)−Y(1)−O(3)
76.4(3)°, O(3)−Y(1)−O(7) 89.4(3)°, O(7)−Y(1)−O(2)
72.5(3)°, O(2)−Y(1)−N1 57.6(3)°). The Y1−N1 and Y1−
N2 bond lengths are 2.350(9) and 2.527(9) Å, respectively.
The Y1−μ-O2 (sulfonyl oxygen) bond length is 2.516(8) Å,
much longer than 2.135(7) Å for Y1−O3 (aryloxo). Other
Y1−μ-O bond lengths, such as the distances from Y1 to
bridging oxygen atoms O4 and O7, are 2.289(7) and 2.281(7)
Å, respectively.
To investigate the catalytic behavior of the chiral complexes
1−5, enantioselective hydroboration of acetophenone 6a was
carried out as a model reaction. Fortunately, using HBpin as a
reducing agent, we could get the chiral 1-phenyl-1-ethanol 7a
quantifably in THF with ee values varying from 18 to 57% for
12 h at room temperature (Table 1, entries 2−6). Obviously,
the enantioselectivities of 7a decreased when the central rare-
earth-metal atom radii of complexes 1−5 decreased, and the
catalyst Nd-1 performed well. No better enantioselectivities of
7a were obtained after screening of additives (Table S7) and
solvents (Table S10). A deliberate addition of 30 mol % of
HN(SiMe3)2 in the catalytic system of Nd-based complex 1
was carried out, which was a test to simulate the in situ catalyst
system. A comparable moderate ee value (60%) was observed,
and meanwhile the excellent yield of 7a was maintained (Table
The central metal Y2 has an 8-coordinated structure and a
twisted-octahedral configuration. The approximate equatorial
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Table 1. Enantioselective Hydroboration of Acetophenone
Catalyzed by Complexes 1−5
Table 2. Screening of the Ligands and Temperature of
a
Enantioselective Hydroboration of Acetophenone Catalyzed
a
by Nd[N(SiMe3)2]3
b
c
entry
cat.
additive
yield (%) ee (%)
1
2
3
4
5
trace
>99
>99
>99
>99
>99
>99
>99
>99
nd
57
43
40
37
18
60
60
35
Nd-1
Sm-2
Eu-3
Gd-4
Y-5
b
c
entry
ligand
H3L1
T (°C)
yield (%)
ee (%)
d
6
1
2
3
4
5
6
7
8
0
−10
−20
−10
−10
−10
−10
−10
−10
−10
−10
−10
−10
−10
−10
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
62
73
71
69
55
37
39
42
47
e
7
Nd-1
HN(SiMe3)2
H3L1
H3L1
H3L2
H3L3
H3L4
H3L5
H3L6
H3L7
H3L8
H3L9
H3L10
H3L11
H3L12
TsDPEN
f
8
f
Nd[N(SiMe3)2]3/H3L1
La[N(SiMe3)2]3/H3L1
9
a
Reaction conditions unless specified otherwise: 6a (0.3 mmol), THF
(2 mL). HPLC yield. Determined by chiral HPLC. The amount of
b
c
d
e
Y-5 was 5 mol %. The amount of HN(SiMe3)2 was 30 mol %.
f
Ln[N(SiMe3)2]3 10 mol %, H3L1 15 mol %.
9
1, entries 7 and 8). This indicates that complex 1 is likely to be
the real catalytic species in the reaction and the existence of
HN(SiMe3)2 has no negative effect on the transformation.
Therefore, the following investigation was carried out in an in
situ catalysis manner. The enantioselective hydroboration in
the presence of an in situ La-based system was then checked;
however, a disappointing outcome was obtained (Table 1,
entry 9). Thus, the Nd-based catalytic combination is the
optimal choice for the model reaction.
10
11
12
13
14
15
−35
−60
−54
38
45
15
a
b
Reaction conditions: 6a (0.3 mmol), THF (2 mL), 12 h. HPLC
c
yield. Determined by chiral HPLC.
In general, variation of the temperature has an obvious effect
on the enantioselectivities. After screening, the ee value of 7a
increased to 73% at −10 °C. However, further cooling to −20
°C was deleterious to the enantioselectivities (Table 2, entries
1−3). In view of the important role of chiral ligands in the
enantioselectivities, a series of phenoxy-functionalized
TsDPEN ligands H3L2−H3L12 were prepared and tested
subsequently.20 Disappointingly, the aforementioned proligand
H3L1 remains the best choice in the current transformation
(Table 2, entries 4−14). To make sure of the effectiveness of
the phenoxy-functionalized strategy, a study of chiral TsDPEN
was carried out as well and the ee value was as low as 15%
(Table 2, entry 15). The chiral ligand H3L13 with the more
rigid bridge (R,R)-cyclohexanediamino was synthesized and
employed in the transformation. The ee value of 7a decreased
to 38% (Scheme S3), while on replacement with ligand H3L1,
the ee value was 73% under the same conditions (Table 2,
entry 2). Hence, the enantioselective hydroboration of
acetophenone occurred smoothly for 12 h at −10 °C in the
presence of 10 mol % of the precatalyst Nd[N(SiMe3)2]3 with
15 mol % of the phenoxy-functionalized TsDPEN ligand H3L1.
A variety of substituted kenones were investigated under the
optimal conditions. The results are summarized in Table 3.
Substrates with both electron-donating and electron-with-
drawing groups on the phenyl rings gave the corresponding
alcohol in high yields, varying from 95% to 99%. The location
of the substituents has a slight effect on the enantioselectivies
of the target alcohols. The substrates bearing ortho-position
substituents gave comparably good ee values, while the ee
values of the para-substituted substrates decreased, such as 7b
versus 7d and 7e versus 7g. Meanwhile, substrates with
electron-donating substituents gave slightly better ee values.
When the substrate was not a methyl ketone, such as
Table 3. Enantioselective Hydroboration of Ketones
Catalyzed by Nd[N(SiMe3)2]3 Combined with H3L1
a c
−
a
Reaction conditions: 6 (0.3 mmol), Nd[N(SiMe3)2]3 (0.03 mmol),
b
c
H3L1 (0.045 mmol), THF (2 mL). Isolated yield. Determined by
chiral HPLC.
propiophenone 6i, the enantioselective hydroboration also
occurred quantitatively with a comparable ee value of 71%.
In comparison with that of simple ketones, enantioselective
hydroboration of α,β-unsaturated ketones is more challenging,
which is generally complicated by competitive 1,2- and 1,4-
reduction processes. Enantioselective reduction of substituted
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α,β-unsaturated ketones was investigated with the reductant
HBpin in the current system, and Table 4 recorded the results.
According to the 1H DOSY experiments of complexes 5 and
6, the complexes are likely to be dinuclear in THF. In
combination with the DFT calculations, it is seen that the
relatively open space around RE1 is conducive to the
coordination of the substrate. Thus, it is possible that RE1
plays a catalytic role, while RE2 and the surrounding ligands
stabilize the entire complex. Thus, catalysts are simplified as
[RE1L], while the second half containing RE2 is omitted for
clarity.
Table 4. Enantioselective Hydroboration of α,β-
Unsaturated Ketones Catalyzed by Nd[N(SiMe3)2]3
a c
−
Combined with H3L1
On the basis of a proposed mechanism,17 a similar
mechanism was suggested and is depicted in Scheme 4.
Scheme 4. Possible Mechanism of Enantioselective
Hydroboration of Ketones Catalyzed by [RE1L]
a
Reaction conditions: 8 (0.3 mmol), Nd[N(SiMe3)2]3 (0.03 mmol),
b
c
H3L1 (0.045 mmol), THF (2 mL). Isolated yield. Determined by
chiral HPLC.
A good tolerance of the various substituents was observed.
Excellent yields for the allylic alcohols 9a−l were obtained,
while the ee values varied significantly (48−80%). When R3
was a strongly electron withdrawing group, such as a
trifluoromethyl or nitro group, the ee values of the
corresponding allylic alcohols were improved (Table 4, 9e−
g). However, when R4 was either an electron-donating group,
such as a methoxyl group, or an electron-withdrawing group,
such as fluorine, the ee values were worse (Table 4, 9k, l). In
comparison with previous works, the outcomes for enantiose-
lective reduction of substituted α,β-unsaturated ketones using
current chiral rare-earth-metal catalysts are much better than
those of rare-earth-metal-based catalyst bearing Trost ligands
(1 example; the ee value was 30%)17 but slightly inferior to
those of functionalized prolinolates (12 examples; ee values
varied from 77% to 89%).8 Furthermore, as shown in Scheme
3, the hydroboration of α,β-unsaturated ketones on a gram
scale proceeded smoothly with a satisfactory yield and high
enantioselectivity.
Initially, the substrate ketone 6a coordinates to the rare-earth
metal to give the complex AR, followed by the coordination of
the reducing agent HBpin with the alkoxy oxygen via a boron
atom to generate the complex BR. Hydride migration to a
carbonyl carbon takes place to produce IntR through TS1R, and
then σ-bond metathesis of O−B and O-RE1 occurs to yield
complex CR via the tetracyclic TS2R. Finally, the dissociation of
the desired borate PR occurs in concert with the regeneration
of catalyst 1.
CONCLUSION
■
In conclusion, four chiral tetranuclear rare-earth-metal
complexes [RE2L1 ] (RE = Nd (1), Sm (2), Eu (3), Gd
3 2
(4)) and a dual-core yttrium complex Y2L13 (5) were prepared
and were well characterized by X-ray diffraction. The La-based
complex 6 was also synthesized in the same way, and the
structure was speculated by 1H DOSY spectroscopy in THF-d8
and DFT calculations. The catalytic reactivities of complexes
1−5 in the enantioselective hydroboration of ketones were
investigated using HBpin as the reductant. Finally, the catalytic
system has optimal conditions for the enantioselective
reduction of simple ketones of 10 mol % of Nd[N(SiMe3)2]3
combined with 15 mol % of H3L1 in THF for 12 h at −10 °C.
The desired chiral alcohols with excellent yields (95−99%)
and moderate ee values (65−82%) were obtained. Further-
Subsequently, the absolute configurations of the secondary
alcohol series 7 and 9 were determined by HPLC spectra and
optical rotation on comparison with our previous work.8,17
Scheme 3. Amplification Reaction of the Preparation of
Compound 9g
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1558.4, 1488.5, 1441.5, 1396.6, 1360.5, 1196.3, 1112.9, 1056.4, 936.6,
809.1, 698.9, 668.8. Anal. Calcd for C108H126Y2N6O9S3·Tol·2DCM:
C, 64.22; H, 6.36; N, 3.84. Found: C, 63.94; H, 6.46; N, 4.14.
Characteristic data of complex 6: colorless crystal, 0.75 g, yield
74%; 1H NMR (400 MHz, THF-d8) δ 7.16 (d, J = 2.5 Hz, 3H), 6.97
(d, J = 6.7 Hz, 9H), 6.88−6.79 (m, 6H), 6.67 (d, J = 6.5 Hz, 3H),
6.62−6.47 (m, 24H), 6.38 (d, J = 2.5 Hz, 3H), 4.48 (d, J = 10.6 Hz,
3H), 4.03−3.88 (m, 6H), 3.11 (d, J = 10.7 Hz, 3H), 2.61 (s, 3H),
2.09 (s, 9H), 1.52 (s, 27H), 1.12 (s, 27H); IR (cm−1) ν 2955.7,
2361.9, 1473.1, 1445.9, 1411.2, 1293.8, 1264.3, 1144.1, 1116.6,
1066.8, 931.3, 805.3, 696.9, 671.5. Anal. Calcd for
C108H126La2N6O9S3: C, 64.02; H, 6.27; N, 4.15. Found: C, 63.97;
H, 6.35; N, 4.12.
General Procedure for the Hydroboration Reaction of
Ketones. RE[N(SiMe3)2]3 (0.03 mmol) was added to a solution of
H3L1 (0.045 mmol) in THF (1 mL). The reaction mixture was stirred
at room temperature for 15 min. HBpin (0.6 mmol) was added in one
portion, and the mixture was stirred at −10 °C for an additional 15
min before the corresponding ketone (0.3 mmol) in 1 mL of THF
was added. After it was stirred for 12 h at −10 °C, the reaction
mixture was quenched with SiO2 (1 g) and the solvent was
evaporated. The residue was purified by flash column chromatography
on silica gel to afford the pure chiral alcohol. The enantiomeric excess
of the alcohol was determined by an HPLC analysis on a chiral
stationary phase.
more, the more challenging enantioselective hydroboration of
α,β-unsaturated ketones was carried out with the current
catalytic system, which gave us the corresponding chiral allylic
alcohols with excellent yields (92−99%) and moderate ee
values (48−80%) as well.
EXPERIMENTAL SECTION
■
General Procedures. All reagents were commercially available
(reagent grade) and were used as received unless otherwise noted.
Experiments involving air- and moisture-sensitive components were
performed in a glovebox or using the standard Schlenk techniques
with freshly distilled solvents. Solvents, such as tetrahydrofuran,
toluene, and hexane, were degassed and distilled from sodium
benzophenone ketyl before use. Various readily available ketones were
distilled after treatment with calcium hydride. Flash chromatography
was performed using 200/300 mesh silica gel with freshly distilled
solvents with a SepaBean machine. Different types of commercial
silica flash columns were used and equilibrated with the appropriate
solvent system prior to use. Carbon, hydrogen, and nitrogen analyses
were performed by direct combustion with a Thermo Scientific Flash
Smart Elemental Analyzer instrument. IR spectra were recorded with
a VERTEX 70+ HYPERION 2000 instrument. Nuclear magnetic
resonance spectra were obtained on a Bruker 400/500 MHz
spectrometer (CDCl3, C6D6, and THF-d8 were used as solvents).
Chemical shifts for NMR spectra are reported in units of parts per
million (ppm) downfield from SiMe4 (0.0) and are relative to the
signal of the deuterated solvent. Multiplicities are given as s (singlet),
d (doublet), t (triplet), q (quartet), dd (doublets of doublets), or m
(multiplets). High-resolution mass spectra were obtained using a
Bruker ESI-TOF instrument. HPLC analysis was performed with a
SHIMADZU LC-20AD instrument equipped with a quaternary
pump, employing a Daicel Chiralcel column at 35 °C. Optical
rotation was measured using a SGW-2 Polarimeter equipped with a
sodium vapor lamp at 589 nm.
Characteristic Data of Secondary Alcohols 7. (R)-1-Phenylethan-
1-ol (7a):17 colorless oil, 36.3 mg, yield 99%; [α]20 = +33.60 (c =
D
0.21 in CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.45−7.30 (m, 1H),
7.28−7.13 (m, 4H), 4.82 (d, J = 6.4 Hz, 1H), 1.82 (s, 1H), 1.42 (d, J
= 6.5 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 144.8, 127.5, 126.5,
124.4, 69.4, 24.1; 73% ee, HPLC Daicel column OD-H, 98% hexanes,
2% iPrOH, 1.0 mL/min, 10.4 min (major), 11.5 min (minor); HRMS
(ESI-MS) m/z [M + Na]+ calcd for C8H10ONa 145.0624, found
145.0632.
(R)-1-(2-Methoxyphenyl)ethan-1-ol (7b):17 colorless oil, 45.0 mg,
1
yield 99%; [α]20 = +23.54 (c = 0.23 in CHCl3); H NMR (400
D
General Procedure for the Preparation of Complexes 1−6.
To a THF (10 mL) solution of the proligand H3L1 (0.8764 g, 1.5
mmol) was slowly added a THF solution of RE[N(SiMe3)2]3 (1
mmol). The mixture was stirred at room temperature for 12 h. After
THF was removed under vacuum, the solid residue was washed with
hexane to remove HN(SiMe3)2. Crystals were obtained at room
temperature from a mixed solvent of hexane and THF.
MHz, CDCl3) δ 7.34 (dd, J = 7.5, 0.9 Hz, 1H), 7.28−7.20 (m, 1H),
6.96 (t, J = 7.5 Hz, 1H), 6.88 (d, J = 8.2 Hz, 1H), 5.09 (q, J = 6.5 Hz,
1H), 3.86 (s, 3H), 2.66 (s, 1H), 1.51 (d, J = 6.5 Hz, 3H); 13C NMR
(101 MHz, CDCl3) δ 156.6, 133.4, 128.3, 126.1, 120.8, 110.5, 66.6,
55.3, 22.9; 82% ee, HPLC Daicel column OD-H, 98% hexanes, 2%
iPrOH, 1.0 mL/min, 8.4 min (minor), 10.1 min (major); HRMS
(ESI-MS) m/z [M + Na]+ calcd for C9H12O2Na 175.0730, found
175.0728.
Characteristic data of complex [Nd2L1 ] (1): light blue crystal,
3 2
0.86 g, yield 85%; IR (cm−1) ν 2949.5, 2360.4, 1472.7, 1440.2, 1413.2,
1359.9, 1182.7, 1110.1, 931.0, 909.6, 806.5, 742.7, 697.6, 666.7. Anal.
Calcd for C216H252Nd4N12O18S6: C, 63.68; H, 6.24; N, 4.13. Found:
C, 63.24; H, 6.23; N, 3.93.
(R)-1-(3-Methoxyphenyl)ethan-1-ol (7c):17 colorless oil, 44.8 mg,
1
yield 98%; [α]20 = +34.28 (c = 0.24 in CHCl3); H NMR (400
D
MHz, CDCl3) δ 7.26 (t, J = 8.1 Hz, 1H), 6.94 (d, J = 5.6 Hz, 2H),
6.84−6.78 (m, 1H), 4.86 (d, J = 6.4 Hz, 1H), 3.81 (s, 3H), 1.99 (d, J
= 11.2 Hz, 1H), 1.48 (d, J = 6.5 Hz, 3H); 13C NMR (101 MHz,
CDCl3) δ 159.8, 147.6, 129.6, 117.7, 112.9, 110.9, 70.4, 55.2, 25.1;
Characteristic data of complex [Sm2L1 ] (2): colorless crystal,
3 2
0.84 g, yield 82%; IR (cm−1) ν 2950.9, 2342.1, 1599.8, 1473.3, 1440.5,
1359.7, 1189.8, 1110.4, 1048.3, 934.2, 910.7, 806.9, 698.2, 666.3.
Anal. Calcd for C216H252Sm4N12O18S6: C, 63.30; H, 6.20; N, 4.10.
Found: C, 62.82; H, 6.33; N, 3.96.
i
81% ee, HPLC Daicel column OD-H, 98% hexanes, 2% PrOH, 1.0
mL/min, 12.1 min (major), 13.4 min (minor); HRMS (ESI-MS) m/z
[M + Na]+ calcd for C9H12O2Na 175.0730, found 175.0730.
Characteristic data of complex [Eu2L1 ] (3): maroon crystal, 0.80
3 2
(R)-1-(4-Methoxyphenyl)ethan-1-ol (7d):17 colorless oil, 45.0 mg,
g, yield 78%; IR (cm−1) ν 2950.1, 2361.8, 1598.5, 1441.0, 1360.0,
1189.3, 1110.5, 1049.6, 1016.0, 933.2, 873.5, 807.5, 698.5, 666.5.
Anal. Calcd for C216H252Eu4N12O18S6·4Tol: C, 65.52; H, 6.40; N,
3.76. Found: C, 65.22; H, 6.64; N, 4.15.
1
yield 99%; [α]20 = +52.42 (c = 0.18 in CHCl3); H NMR (400
D
MHz, CDCl3) δ 7.32−7.22 (m, 2H), 6.91−6.82 (m, 2H), 4.77 (d, J =
6.4 Hz, 1H), 3.77 (s, 3H), 3.29 (s, 1H), 1.44 (d, J = 6.5 Hz, 3H); 13C
NMR (101 MHz, CDCl3) δ 158.8, 138.3, 126.7, 113.8, 69.6, 55.2,
25.1; 74% ee, HPLC Daicel column OD-H, 98% hexanes, 2% iPrOH,
1.0 mL/min, 11.1 min (major), 13.4 min (minor); HRMS (ESI-MS)
m/z [M + Na]+ calcd for C9H12O2Na 175.0730, found 175.0729.
Characteristic data of complex [Gd2L1 ] (4): colorless crystal,
3 2
0.90 g, yield 87%; IR (cm−1) ν 2949.4, 2364.7, 1599.7, 1472.0, 1440.0,
1359.5, 1161.6, 1110.3, 1047.3, 1016.1, 931.1, 806.5, 697.3, 666.4.
Anal. Calcd for C216H252Gd4N12O18S6·Tol: C, 63.50; H, 6.21; N, 3.98.
Found: C, 63.15; H, 6.75; N, 3.98.
(R)-1-(2-Chlorophenyl)ethan-1-ol (7e):17 colorless oil, 44.3 mg,
1
yield 96%; [α]20 = +32.55 (c = 0.19 in CHCl3); H NMR (400
Characteristic data of complex Y2L13 (5): colorless crystal, 0.69 g,
D
1
MHz, CDCl3) δ 7.58 (d, J = 7.7 Hz, 1H), 7.29 (d, J = 14.0 Hz, 2H),
7.20 (d, J = 5.9 Hz, 1H), 5.27 (s, 1H), 2.19 (s, 1H), 1.48 (d, J = 6.4
Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 143.1, 131.6, 129.4, 128.4,
127.2, 126.4, 67.0, 23.5; 81% ee, HPLC Daicel column IE, 98%
hexanes, 2% iPrOH, 1.0 mL/min, 9.8 min (major), 13.1 min (minor);
HRMS (ESI-MS) m/z [M + Na]+ calcd for C8H9ClONa 179.0234,
found 179.0233, isotopic peak C8H937ClONa found 181.0245.
yield 72%; H NMR (400 MHz, THF-d8) δ 7.41 (s, 2H), 7.23 (s,
3H), 7.07 (s, 2H), 6.96 (s, 15H), 6.86 (s, 2H), 6.75 (d, J = 25.9 Hz,
11H), 6.60 (s, 7H), 6.50 (s, 1H), 6.45 (s, 5H), 6.35 (s, 3H), 5.14 (s,
1H), 5.02 (s, 1H), 4.69 (s, 1H), 4.21 (s, 1H), 4.00 (s, 2H), 3.31 (s,
2H), 3.00 (s, 2H), 2.92−2.72 (m, 2H), 2.62 (s, 1H), 2.22 (s, 3H),
1.63 (s, 12H), 1.34 (d, J = 15.6 Hz, 4H), 1.30 (s, 8H), 1.25 (s, 2H),
1.19 (s, 5H), 1.04 (d, J = 19.8 Hz, 30H); IR (cm−1) ν 2950.5, 2360.7,
2534
https://doi.org/10.1021/acs.organomet.1c00272
Organometallics 2021, 40, 2529−2537

Organometallics
pubs.acs.org/Organometallics
Article
(R)-1-(3-Chlorophenyl)ethan-1-ol (7f):17 colorless oil, 44.8 mg,
(R,E)-3-(4-Bromophenyl)-1-phenylprop-2-en-1-ol (9d): colorless
oil, 81.2 mg, yield 95%; [α]20D = +9.84 (c = 0.32 in CHCl3); 1H NMR
(400 MHz, CDCl3) δ 7.44−7.26 (m, 7H), 7.22 (t, J = 7.0 Hz, 2H),
6.59 (d, J = 15.9 Hz, 1H), 6.34 (dd, J = 15.8, 6.3 Hz, 1H), 5.33 (d, J =
6.1 Hz, 1H), 2.26 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 142.6,
135.5, 132.3, 131.7, 129.2, 128.7, 128.1, 126.4, 121.6, 75.0; 61% ee,
HPLC Daicel column IB, 95% hexanes, 5% iPrOH, 1.0 mL/min, 12.4
min (major), 15.3 min (minor); HRMS (ESI-MS) m/z [M + Na]+
calcd for C15H13BrONa 311.0042, found 311.0041, isotopic peak
C15H1381BrONa found 312.9976.
1
yield 97%; [α]20 = +47.45 (c = 0.22 in CHCl3); H NMR (400
D
MHz, CDCl3) δ 7.37 (s, 1H), 7.25 (d, J = 5.5 Hz, 3H), 4.87 (q, J =
6.4 Hz, 1H), 1.89 (s, 1H), 1.48 (d, J = 6.5 Hz, 3H); 13C NMR (101
MHz, CDCl3) δ 147.9, 134.4, 129.8, 127.5, 125.6, 123.5, 69.8, 25.3;
i
70% ee, HPLC Daicel column IE, 99% hexanes, 1% PrOH, 1.0 mL/
min, 17.3 min (minor), 21.1 min (major); HRMS (ESI-MS) m/z [M
+ Na]+ calcd for C8H9ClONa 179.0234, found 179.0230, isotopic
peak C8H937ClONa found 181.0256.
(R)-1-(4-Chlorophenyl)ethan-1-ol (7g):17 colorless oil, 43.9 mg,
(R,E)-3-(4-Fluorophenyl)-1-phenylprop-2-en-1-ol (9e):8 colorless
1
yield 95%; [α]20 = +40.28 (c = 0.24 in CHCl3); H NMR (400
D
1
oil, 65.0 mg, yield 96%; [α]20 = +10.29 (c = 0.28 in CHCl3); H
MHz, CDCl3) δ 7.31 (s, 4H), 4.88 (q, J = 6.5 Hz, 1H), 1.76 (s, 1H),
1.47 (d, J = 6.5 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 144.3,
130.9, 127.8, 126.8, 69.8, 25.3; 68% ee, HPLC Daicel column IE, 99%
D
NMR (400 MHz, CDCl3) δ 7.46−7.26 (m, 7H), 6.98 (t, J = 8.6 Hz,
2H), 6.63 (d, J = 15.9 Hz, 1H), 6.29 (dd, J = 15.8, 6.5 Hz, 1H), 5.35
(d, J = 6.1 Hz, 1H), 2.14 (s, 1H); 13C NMR (101 MHz, CDCl3) δ
162.4 (d, J = 247.0 Hz), 142.8, 132.7 (d, J = 3.4 Hz), 131.3, 131.3,
129.4, 128.7, 128.2 (d, J = 8.0 Hz), 127.9, 126.4, 115.5 (d, J = 21.6
Hz), 75.1; 19F NMR (377 MHz, CDCl3) δ −114.12; 72% ee, HPLC
i
hexanes, 1% PrOH, 1.0 mL/min, 15.7 min (minor), 18.3 min
(major); HRMS (ESI-MS) m/z [M + Na]+ calcd for C8H9ClONa
179.0234, found 179.0234, isotopic peak C8H937ClONa found
181.0245.
i
(R)-1-(4-(Trifluoromethyl)phenyl)ethan-1-ol (7h):11 colorless oil,
Daicel column IB, 95% hexanes, 5% PrOH, 1.0 mL/min, 11.3 min
(major), 13.3 min (minor); HRMS (ESI-MS) m/z [M + Na]+ calcd
for C15H13FONa 251.0843, found 251.0836.
1
55.9 mg, yield 98%; [α]20 = +31.84 (c = 0.18 in CHCl3); H NMR
D
(400 MHz, CDCl3) δ 7.60 (d, J = 8.1 Hz, 2H), 7.48 (d, J = 8.1 Hz,
2H), 4.95 (q, J = 6.5 Hz, 1H), 2.03 (s, 1H), 1.50 (d, J = 6.5 Hz, 3H);
13C NMR (101 MHz, CDCl3) δ 149.7, 129.5 (q, J = 32.4 Hz), 125.6,
125.4 (q, J = 3.6 Hz), 124.2 (q, J = 271.9 Hz), 69.7, 25.2; 19F NMR
(377 MHz, CDCl3) δ −62.47; 65% ee, HPLC Daicel column OD-H,
(R,E)-1-Phenyl-3-(4-(trifluoromethyl)phenyl)prop-2-en-1-ol (9f):
colorless oil, 75.9 mg, yield 92%; [α]20 = +11.32 (c = 0.39 in
D
1
CHCl3); H NMR (400 MHz, CDCl3) δ 7.54 (d, J = 8.3 Hz, 2H),
7.49−7.35 (m, 6H), 7.34−7.28 (m, 1H), 6.72 (d, J = 15.9 Hz,
1H),6.47 (dd, J = 15.9, 6.1 Hz, 1H), 5.39 (d, J = 5.8 Hz, 1H), 2.22 (s,
1H); 13C NMR (101 MHz, CDCl3) δ 142.4, 140.1, 134.1, 129.6 (d, J
= 32.5 Hz), 128.9, 128.8, 128.1, 126.8, 126.4, 125.5 (d, J = 3.7 Hz),
74.9; 19F NMR (377 MHz, CDCl3) δ −62.50; 80% ee, HPLC Daicel
column IB, 90% hexanes, 10% iPrOH, 1.0 mL/min, 6.9 min (major),
7.4 min (minor); HRMS (ESI-MS) m/z [M + Na]+ calcd for
C16H13F3ONa 301.0811, found 301.0809.
i
99% hexanes, 1% PrOH, 1.0 mL/min, 16.0 min (minor), 17.4 min
(major); HRMS (ESI-MS) m/z [M + Na]+ calcd for C9H9F3ONa
213.0498, found 213.0503.
(R)-1-Phenylpropan-1-ol (7i):22 colorless oil, 40.4 mg, yield 99%;
[α]20D = +32.4 (c = 0.20 in CHCl3); 1H NMR (400 MHz, CDCl3) δ
7.40−7.35 (m, 4H), 7.34−7.29 (m, 1H), 4.62 (t, J = 6.6 Hz, 1H),
1.97 (s, 1H), 1.90−1.72 (m, 2H), 0.94 (t, J = 7.4 Hz, 3H); 13C NMR
(101 MHz, CDCl3) δ 144.6, 128.4, 127.5, 126.0, 76.1, 31.9, 10.2; 71%
(R,E)-3-(4-Nitrophenyl)-1-phenylprop-2-en-1-ol (9g):8 colorless
1
oil, 72.0 mg, yield 95%; [α]20 = +32.44 (c = 0.35 in CHCl3); H
D
i
ee, HPLC Daicel column OD-H, 98% hexanes, 2% PrOH, 1.0 mL/
NMR (400 MHz, CDCl3) δ 8.08 (d, J = 8.6 Hz, 2H), 7.42 (d, J = 8.7
Hz, 2H), 7.33 (q, J = 8.1 Hz, 4H), 7.26 (d, J = 6.7 Hz, 1H), 6.70 (d, J
= 15.9 Hz, 1H), 6.48 (dd, J = 15.9, 5.8 Hz, 1H), 5.35 (d, J = 5.7 Hz,
1H), 2.18 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 143.2, 142.1,
136.3, 128.9, 128.3, 127.9, 127.1, 126.4, 124.0, 74.7; 75% ee, HPLC
min, 13.5 min (major), 14.6 min (minor); HRMS (ESI-MS) m/z [M
+ Na]+ calcd for C9H12ONa 159.0780, found 159.0773.
Characteristic Data of Allylic Alcohols 9. (R,E)-1,3-Diphenylprop-
2-en-1-ol (9a):8 colorless oil, 62.4 mg, yield 99%; [α]20D = +17.84 (c
= 0.38 in CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.42 (d, J = 7.2 Hz,
2H), 7.36 (t, J = 7.9 Hz, 4H), 7.33−7.25 (m, 3H), 7.25−7.19 (m,
1H), 6.67 (d, J = 15.8 Hz, 1H), 6.37 (dd, J = 15.8, 6.5 Hz, 1H), 5.36
(d, J = 6.3 Hz, 1H), 2.18 (s, 1H); 13C NMR (101 MHz, CDCl3) δ
142.8, 136.6, 131.6, 130.6, 128.6, 127.8, 126.7, 126.4, 75.2; 70% ee,
HPLC Daicel column OD-H, 90% hexanes, 10% iPrOH, 1.0 mL/min,
13.9 min (minor), 17.4 min (major); HRMS (ESI-MS) m/z [M +
Na]+ calcd for C15H14ONa 233.0937, found 233.0937.
i
Daicel column OD-H, 90% hexanes, 10% PrOH, 1.0 mL/min, 21.8
min (major), 23.4 min (minor); HRMS (ESI-MS) m/z [M + Na]+
calcd for C15H13NO3Na 278.0788, found 278.0784.
(R,E)-1-Phenyl-3-(p-tolyl)prop-2-en-1-ol (9h):8 colorless oil, 64.6
mg, yield 97%; [α]20D = +18.85 (c = 0.42 in CHCl3); 1H NMR (400
MHz, CDCl3) δ 7.48 (d, J = 7.3 Hz, 2H), 7.42 (t, J = 7.4 Hz, 2H),
7.34 (t, J = 8.0 Hz, 3H), 7.17 (d, J = 7.9 Hz, 2H), 6.69 (d, J = 15.8 Hz,
1H), 6.38 (dd, J = 15.8, 6.6 Hz, 1H), 5.40 (d, J = 6.6 Hz, 1H), 2.39 (s,
3H), 2.26 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 143.0, 137.7,
133.8, 130.6, 129.3, 128.6, 127.8, 126.5, 75.2, 21.3; 67% ee, HPLC
(R,E)-3-(3-Bromophenyl)-1-phenylprop-2-en-1-ol (9b): colorless
1
oil, 83.0 mg, yield 97%; [α]20 = +10.25 (c = 0.26 in CHCl3); H
D
i
NMR (400 MHz, CDCl3) δ 7.56 (s, 1H), 7.49−7.28 (m, 7H), 7.19 (t,
J = 7.8 Hz, 1H), 6.65 (d, J = 15.8 Hz, 1H), 6.41 (dd, J = 15.8, 6.2 Hz,
1H), 5.40 (d, J = 6.0 Hz, 1H), 2.22 (s, 1H); 13C NMR (101 MHz,
CDCl3) δ 142.5, 138.8, 133.1, 130.61, 130.1, 129.5, 128.8, 128.0,
126.4, 125.3, 122.8, 74.9; 50% ee, HPLC Daicel column IB, 95%
Daicel column IB, 95% hexanes, 5% PrOH, 1.0 mL/min, 12.0 min
(major), 15.2 min (minor); HRMS (ESI-MS) m/z [M + Na]+ calcd
for C16H16ONa 247.1093, found 247.1094.
(R,E)-3-(4-(tert-Butyl)phenyl)-1-phenylprop-2-en-1-ol (9i):8 color-
less oil, 79.1 mg, yield 99%; [α]20D = +15.74 (c = 0.42 in CHCl3); 1H
NMR (400 MHz, CDCl3) δ 7.42−7.23 (m, 9H), 6.63 (d, J = 15.8 Hz,
1H), 6.31 (dd, J = 15.8, 6.6 Hz, 1H), 5.31 (d, J = 4.4 Hz, 1H), 2.34
(d, J = 3.1 Hz, 1H), 1.29 (s, 9H); 13C NMR (101 MHz, CDCl3) δ
156.0, 143.0, 133.8, 130.9, 130.4, 128.6, 127.8, 126.4, 125.6, 75.2,
34.7, 31.4; 50% ee, HPLC Daicel column IB, 98% hexanes, 2% iPrOH,
1.0 mL/min, 17.4 min (major), 18.4 min (minor); HRMS (ESI-MS)
m/z [M + Na]+ calcd for C19H22ONa 289.1563, found 289.1564.
i
hexanes, 5% PrOH, 1.0 mL/min, 14.1 min (minor), 20.5 min
(major); HRMS (ESI-MS) m/z [M + Na]+ calcd for C15H13BrONa
311.0042, found 311.0044, isotopic peak C15H1381BrONa found
312.9964.
(R,E)-3-(3-Methoxyphenyl)-1-phenylprop-2-en-1-ol (9c): colorless
1
oil, 71.3 mg, yield 99%; [α]20 = +12.37 (c = 0.30 in CHCl3); H
D
NMR (400 MHz, CDCl3) δ 7.41 (d, J = 7.2 Hz, 2H), 7.35 (t, J = 7.4
Hz, 2H), 7.29 (d, J = 7.1 Hz, 1H), 7.20 (t, J = 8.1 Hz, 1H), 6.96 (d, J
= 7.7 Hz, 1H), 6.90 (s, 1H), 6.78 (dd, J = 8.1, 2.2 Hz, 1H), 6.63 (d, J
= 15.8 Hz, 1H), 6.35 (dd, J = 15.8, 6.5 Hz, 1H), 5.34 (d, J = 6.4 Hz,
1H), 3.77 (s, 3H), 2.32 (s, 1H); 13C NMR (101 MHz, CDCl3) δ
159.8, 142.8, 138.0, 131.9, 130.4, 129.6, 128.7, 127.8, 126.4, 119.4,
113.6, 111.9, 75.1, 55.3; 68% ee, HPLC Daicel column IB, 90%
(R,E)-3-(Naphthalen-2-yl)-1-phenylprop-2-en-1-ol (9j): colorless
1
oil, 76.4 mg, yield 98%; [α]20 = +23.52 (c = 0.45 in CHCl3); H
D
NMR (400 MHz, CDCl3) δ 7.79−7.68 (m, 4H), 7.59−7.52 (m, 1H),
7.48−7.39 (m, 4H), 7.37 (t, J = 7.7 Hz, 2H), 7.29 (t, J = 7.2 Hz, 1H),
6.80 (d, J = 15.8 Hz, 1H), 6.48 (dd, J = 15.8, 6.5 Hz, 1H), 5.39 (d, J =
6.4 Hz, 1H), 2.28 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 142.7,
134.1, 133.6, 133.1, 132.0, 130.7, 128.7, 128.3, 127.9, 126.8, 126.4,
126.0, 123.7, 75.2; 62% ee, HPLC Daicel column IB, 90% hexanes,
i
hexanes, 10% PrOH, 1.0 mL/min, 13.4 min (minor), 23.8 min
(major); HRMS (ESI-MS) m/z [M + Na]+ calcd for C16H16O2Na
i
263.1043, found 263.1041.
10% PrOH, 1.0 mL/min, 11.0 min (major), 12.2 min (minor);
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Article
HRMS (ESI-MS) m/z [M + Na]+ calcd for C19H16ONa 283.1093,
found 283.1100.
ACKNOWLEDGMENTS
■
We gratefully acknowledge financial support from the National
Natural Science Foundation of China (Grant No. 21572151),
the Natural Science Foundation of the Jiangsu Higher
Education Institutions of China (Grant No. 19KJA320007),
the project of scientific and technologic infrastructure of
Suzhou (SZS201708), and the PAPD.
(R,E)-1-(4-Fluorophenyl)-3-phenylprop-2-en-1-ol (9k): colorless
1
oil, 67.1 mg, yield 98%; [α]20 = +8.84 (c = 0.48 in CHCl3); H
D
NMR (400 MHz, CDCl3) δ 7.38 (dd, J = 8.1, 6.2 Hz, 4H), 7.30 (t, J =
7.5 Hz, 2H), 7.24 (d, J = 7.0 Hz, 1H), 7.03 (t, J = 8.6 Hz, 2H), 6.65
(d, J = 15.9 Hz, 1H), 6.33 (dd, J = 15.8, 6.5 Hz, 1H), 5.34 (d, J = 6.5
Hz, 1H), 2.21 (s, 1H); 13C NMR (101 MHz, CDCl3) δ 162.4 (d, J =
245.8 Hz), 138.5 (d, J = 3.1 Hz), 136.4, 131.3, 130.8, 128.7, 128.1 (d,
J = 8.1 Hz), 128.0, 126.7, 115.5 (d, J = 21.6 Hz), 74.5. 19F NMR (377
MHz, CDCl3) δ −114.7; 48% ee, HPLC Daicel column IB, 90%
hexanes, 10% iPrOH, 1.0 mL/min, 6.9 min (minor), 7.4 min (major);
HRMS (ESI-MS) m/z [M + Na]+ calcd for C15H13FONa 251.0843,
found 251.0838.
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.1c00272.
■
sı
Experimental procedures, characterization data, HPLC
chromatograms, and X-ray data for complexes 1−5
(PDF)
Accession Codes
CCDC 2050142, 2050145, 2050150, 2051400, 2054260,
2055968, and 2081007 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Authors
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Chengrong Lu − College of Chemistry, Chemical Engineering
and Materials Science, Key Laboratory of Organic Synthesis
of Jiangsu Province, Dushu Lake Campus, Soochow
University, Suzhou 215123, People’s Republic of China;
Email: luchengrong@suda.edu.cn
Bei Zhao − College of Chemistry, Chemical Engineering and
Materials Science, Key Laboratory of Organic Synthesis of
Jiangsu Province, Dushu Lake Campus, Soochow University,
Suzhou 215123, People’s Republic of China; orcid.org/
0000-0001-8687-2632; Email: zhaobei@suda.edu.cn
Author
Qishun Yu − College of Chemistry, Chemical Engineering and
Materials Science, Key Laboratory of Organic Synthesis of
Jiangsu Province, Dushu Lake Campus, Soochow University,
Suzhou 215123, People’s Republic of China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.1c00272
Notes
The authors declare no competing financial interest.
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