Half-sandwich chiral rare-earth metal complexes with linked tridentate amido-indenyl ligand: synthesis, characterization, and catalytic properties for intramolecular hydroamination

Article abstract of DOI:10.1039/c6ra26537e

The enantioselective intramolecular hydroamination of alkenes with free amines has been a touchstone reaction in the development of many new chiral rare-earth (RE) metal complexes. In this article, we describe the synthesis and characterization of four no

Full text of DOI:10.1039/c6ra26537e

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PAPER
Half-Sandwich Chiral Rare-Earth Metal Complexes with Linked
Tridentate Amido-Indenyl Ligand: Synthesis, Characterization,
and Catalytic Properties for Intramolecular Hydroamination
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Zhuo Chai, Jiang Chu, Yunyi Qi, Mujun Tang, Jinsong Hou, Gaosheng Yang*
www.rsc.org/
The enantioselective intramolecular hydroamination of alkenes with free amines has been a touchstone reaction in the
development of many new chiral rare-earth (RE) metal complexes. In this article, we describe the synthesis and
chracterization of four novel rare-earth metal (Y, Sm, Lu, Sc) complexes, featuring a tridentate carbon-linked amido-
indenyl ligand with a shortented linker between the indene ring and the chiral diamine moiety, as compared to our
previously developed structurally similar silicon-linked ligand. Despite the generally lower enantioselectivites obtained in
the current work, the structure-activity analyses of these complexes based on x-ray crystallographic data could be useful
for further development of highly efficient chiral rare-earth metal complexes for asymmetric synthesis.
ligands, chiral vicinal diamine based ligands9 and others,10 with
impressive advances being achieved. On the other hand, the
development of half-sandwich rare-earth metal complexes
Introduction
Rare-earth metal complexes with various organic ligands
belong to a unique class of compounds with both intriguing
structures for coordination chemistry research and special
reactivity for organic synthesis.1 In this field, the design and
synthesis of new chiral ligands and their complexes with
various rare-earth metals has been a research focus as well as
their applications to various organic reactions as chiral
with Cp ligands bearing a short side arm containing additional
chelating functionalities, known as constrained geometry
complexes (CGCs), has received much interest with some
unique structures and reactivities being disclosed.11 However,
the development of chiral CGCs of rare-earth metals, which
could serve as precatalysts for asymmetric synthesis, has been
rarely reported.
(pre)catalysts.
In
particular,
the
enantioselective
In this context, our group have recently demonstrated that
intramolecular hydroamination of unactivated alkenes with
free amines, which represents the earliest and arguably most
studied type of transformation with chiral rare-earth metal
chiral yttrium complex
1 bearing a tridentate silicon-linked
amido-indenyl ligand could catalyse the intramolecular
hydroamination of non-activated olefins with up to 97% ee (Fig.
1).6 However, the poor crystallinity of complexes of this ligand
with other rare-earth metals hampers a thorough structure-
reactivity study with these complexes. Moreover, similar to
many other chiral rare-earth metal complexes examined in this
reaction, the degrees of enantiocontrol achieved with this
complex varied significantly from one substrate to another one,
even in cases with only minor structural changes. It is
presumed that replacing the silicon linker by a smaller carbon
complexes, has become
a touchstone reaction in the
development of many new chiral rare-earth metal complexes.2
The extensive studies in this realm have not only led to the
invention of several highly efficient rare-earth metal catalyst
systems for this particular reaction,3-6 but also provided some
useful mechanistic insight into the structure-reactivity
relationship with important implications for catalyst design in
general asymmetric catalysis.
As epimerization have been identified as a crucial limiting
factor to the chiral inducing power of ansa-lanthanocene
complexes containing cyclopentadienyl group (Cp)-based C1-
symmetric chiral sandwich ligands,3-4 chemists have developed
numerous alternative non-Cp based chiral ligands that can
circumvent this issue, including chiral BINOL7/BINAM8 based
H
Si
structural modification via
C
changing the linker group
H
N
YN(SiMe3)2
N
REN(SiMe3)2
NMe2
more compact chiral environment
due to shor tened bond lengths
NMe2
Reactivity?
Enantioselectivity?
Our pr evious wor k
T his wor k
Key Laboratory of Functionalized Molecular Solids, Ministry of Education, Anhui
Laboratory of Molecule-Based Materials, Institute of Organic Chemistry, College
of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui
241000, China. E-mail: gshyang@mail.ahnu.edu.cn
Fig.
1 Chiral half-sandwich RE metal complexes for intramolecular annulative
hydroamination of unactivated olefins
†Electronic Supplementary Information (ESI) available: Crystallographic data in CIF
files, copies of NMR spectra and HPLC traces. See DOI: 10.1039/x0xx00000x
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O
Table 1 Selected bond lengths (Å) and angles (o) of complexes 4
CO2H
LiAlH4
1) DCC, HOBt, CH2Cl2
HN
HN
THF, 60-70 oC, 48 h
NH2
4a (Y)
2.611(4)
2.630(4)
2.682(4)
2.716(4)
2.679(4)
2.487(3)
2.171(3)
2.238(3)
1.512(6)
1.471(6)
73.52(12)
101.44(12)
113.63(11)
4b (Sm)
2.667(3)
2.715(3)
2.760(3)
2.770(3)
2.729(3)
2.558(2)
2.226(2)
2.301(2)
1.520(5)
1.456(4)
71.84(8)
102.28(9)
113.42(7)
4c (Lu)
2.568(4)
2.576(4)
2.629(5)
2.678(4)
2.660(4)
2.423(3)
2.132(3)
2.193(3)
1.526(6)
1.452(5)
75.39(12)
100.73(12)
113.01(11)
4d (Sc)
2.476(2)
2.467(3)
2.523(3)
2.609(2)
2.588(2)
2.343(2)
2.029(2)
2.087(2)
1.512(5)
1.474(3)
77.93(8)
99.80(8)
114.88(8)
Me2
N
Me2N
2)
2, 83% yield
3, 69% yield
NMe2
C11–RE
C12–RE
C13–RE
C14–RE
C19–RE
N1–RE
1
[(Me3Si)2N]3REIII
(µ-Cl)Li(THF)3
4a (Y), 93 % yield
4b (Sm), 90 % yield
N
REN(SiMe3
NMe2
)
2
toluene, 75 °C
( 90 °C for RE = Sc), 12 h
4c (Lu), 92 % yield
4d (Sc), 94 % yield
Scheme 1 Syntheses of the chiral rare-earth metal complexes 4
N2–RE
N3–RE
C9-C10
one might create a more compact chiral environment around
the metal center, which may have significant influence on the
reactivity and/or chiral induction power of the corresponding
RE metal complexes.12 Herein, we report the results of our
research efforts in this regard.
C9-N2
N1–RE–N2
N1–RE–N3
N2–RE–N3
As shown in Table 1, the M-C bond lengths of
4
(2.467(3)-
2.770(3) Å) between the rare-earth metal atoms and the
indenyl carbon atom correlate well with those of related
complexes previously reported by us and others. The covalent
M-N bond lengths (M-N2 and M-N3) are appreciably shorter
than non-covalent ones (M-N1). Moreover, an apparent
lanthanide contraction effect is observed on both the bond
distances and bond angles: as the radii of the rare-earth metal
atoms decreases, both the M-C and M-N bond lengths
decreases while the bond angles of N-M-N bonds involving the
two nitrogen atoms of the chiral ligand (N1 and N2) increases.
Compared to our previous work with the chiral yttrium (Y)
complex of the silicon-linked amido-indenyl ligand, the bond
lengths of the two yttrium complexes, C9-C10 (1.512(6)) vs Si-C
(1.881(4)) and C9-N2 (1.471(6)) vs Si-N (1.710(3)), would
render the indene ring and the chiral diamine moiety closer as
expected.
Results and discussion
Syntheses and characterization
Our study began with the syntheses of the complexes
(Scheme 1). First, condensation of 2-(1H-inden-3-yl)acetic acid
with the commercially available chiral diamine provided
chiral amide in 83% yield, which was then reduced with
lithium aluminium hydride to furnish the desired methylene-
linked indene-chiral diamine ligand in a yield of 69%.
4
1
2
3
Subsequent treatment of this ligand with [(Me3Si)2N]3Ln(μ-
Cl)Li(THF)3 (Ln = Y, Sm, Lu, Sc) in toluene furnished the
corresponding chiral rare-earth complexes 4a-4d in excellent
yields. The high overall yields for the preparation of this type
of complexes provide an obvious advantage over our previous
developed relevant silicon-linked complexes.6 All of the four
complexes were characterized by NMR and elemental
microanalysis. Moreover, the good crystallinities of these
complexes allows for a more systematic single crystal X-ray
crystallographic analyses, which could provide more useful
insights to the structure-activity relationship (Fig. 2).
Another structural feature of complexes
4 isolated in this
work resides in the planar chirality of the indene ring. In
previous work with the rare-earth metal complexes of the
chiral tridentate amido-indenyl ligand, we observed two
different orientations of the indene ring in the complexes
depending on the rare-earth metal ion (Sp for Y and Rp for Er).
In the current work, only one is observed in all of the four
complexes with the absolute configuration of the indene ring
being Rp irrespective of the metal core. This observation
suggests the carbon-linked chiral ligand might predominate in
determining the coordination orientation of the indene ring in
these complexes.
Description of crystal structures
The X-ray structures of the four complexes are very similar,
differing in only the core rare-earth metal. They all crystallized
as mononuclear structures in the monoclinic space group P21
with four molecules in the unit cell, and the rare-earth metal
atoms are about in a tetrahedral coordination.
Catalysis of reaction
With the chiral rare-earth metal complexes in hand, we then
evaluated their catalytic activities in the intramolecular
annulative hydroamination of aminoalkene 5a (Table 2).
Complex 4d with the smallest ion radii of the core metal (Sc)
demonstrated the poorest activity and enantioselectivity,
while complex 4b with the largest samarium ion is the most
reactive one yet still with a very poor enantioselectivity. The
absolute configuration of the product was assigned based on
comparison of peak orders in HPLC assay on a chiral column
with literature data.6
Fig. 2 ORTEP representation of RE complexes 4 (drawn with 30 % probability ellipsoids).
RE = Y, Sm, Lu or Sc.
2 | J. Name., 2012, 00, 1-3
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Table 2 Evaluation of precatalysts 4a
Table 4 Substrate scope study with precatalyst 4ca
Ph
Ph
NH2
Ph
Ph
Entry
1
Substrate
Product
NH
t (h)
Ee (%)b
87
4 (5 mol %)
Ph
C6D6, T (oC), t (h)
Ph
Ph
Ph
Ph
NH2
NH
Ph
6a
Ph
5a
29.0
Ph
5a
6a
Ee (%)b
67
Entry
4 (Ln)
4a (Y)
T (˚C)
20
t (h)
5.0
Ph
Ph
Ph
Ph
Ph
NH2
NH
1
2
3
4
2
1.5
7.0
68
42
Me
5b
NH2
6b
NH
4b (Sm)
4c (Lu)
4d (Sc)
20
2.0
34
Ph
Ph
20
29.0
50.0
87
3c
Ph
80
30
5c
6c
Br
Br
Ph
Ph
aUnless otherwise noted, the reactions were conducted with 0.27 mmol of
aminoalkene 5a in 0.5 mL of C6D6. All conversions are >95% based on 1H NMR
analysis using ferrocene as the internal standard. bDetermined by chiral HPLC
after acylation of the product 6a to the corresponding amide 7a with 4-
MeOC6H4COCl.
NH
Ph
Ph
NH2
4
1.5
8.0
0.7
65
80
51
6i
NH
5i
Br
Cl
Ph
Ph
NH2
Ph
Br
5d
6c
Ph
5j
6j
Cl
Cl
NH
Ph
Ph
Ph
Ph
Ph
Ph
NH2
NH2
The complex 4c of lutetium (Lu) displayed the highest
enantioselectivity for the reaction, albeit with a moderate
catalytic efficiency (entry 3). These results suggest that a good
match of the sizes of the metal ion and the chiral ligand is
crucial for both reactivity and enantioselectivity.
Cl
Cl
6k
5k
Cl
Me
Ph
Ph
NH
7
3.0
80
67
5l
6l
Ph
NH2
Ph
Ph
Me
NH
For a direct comparison of catalytic power between the
carbon-linked complex and the previously developed silicon-
linked one, we first probed the substrate scope of 4a, in spite
of the moderate enantioselectivity obtained (Table 3). In terms
of enantioselectivity, the carbon-linked yttrium complex 4a is
invariably much inferior to the silicon-linked one, but they
behaved quite similarly in responses to changes in the
substrate structures. Moreover, their differences in
catalytic efficiency varied from substrate to substrate, and in
some cases 4a proved to be much more favoured in this regard
(entries 1, 4 and 8).
8c
17.0
Ph
5m
6m
OMe
Ph
Ph
NH2
Ph
Ph
NH
OMe
9
6.3
8.0
28
61
5n
6n
MeO
NH2
MeO
NH
Ph
Ph
Ph
Ph
10
6o
5o
NH2
Ph
Ph
NH
Ph
Ph
OMe
11
12
6.3
4.9
83
78
6p
5p
OMe
Ph
Ph
Ph
Ph
NH2
NH
Table 3 Substrate scope study with precatalyst 4aa
5q
6q
a,bSee footnotes a and b of table 2 for general reaction conditions. Reactions were
run at 20 oC unless specified otherwise. cRun at 60 oC. dRun at 50 oC.
Entry
1
Substrate
Product
t (h)
Ee (%)c
Ph
Ph
Ph
NH2
NH
Ph
Ph
5.0 (9.6)b
67 (97)b
Ph
5a
6a
Next, we examined the substrate scope with complex 4c
,
Ph
Ph
Ph
Ph
NH2
NH
the optimum precatalyst of the carbon-linked ligand series
(Table 4). This complex provided higher enantioselectivity in
the formation of five-membered pyrrolidines 6a and 6b
(entries 1-2), as compared to the results obtained with the
yttrium complex 4a, while a slightly lower ee value was
obtained in the case of six-membered piperidine 6c (entry 3).
Given the high enantioselectivity obtained with 5a, we then
studied the substituent effect of the benzene ring on the
reaction by examining several substituted styrene-type
aminoalkenes. It is worth mentioning that systematic
examination of this type of internal alkenes in rare-earth
metal-catalysed asymmetric hydroamination reactions is
unprecedented. Both the electronic nature and positions of
the substituents on the benzene ring showed significant
influence on the reaction rate and enantioselectivity. When
the substituent is at the para position, an electron-
withdrawing one, such as a halogen, is clearly favoured over an
electron-withdrawing one in terms of enantioselectivity
(entries 5, 7 vs entries 8, 9). The meta or ortho positions are
not favoured when an electron-withdrawing substituent is
2
3.0 (0.8)
60 (85)
45 (69)
Me
5b
NH2
6b
NH
Ph
Ph
Me
Ph
Ph
3d
16.0 (15.6)
5c
6c
Me
Me
NH2
NH
Me
4
4.0 (13.0)
50.0 (9.0)
68.0 (9.6)
56 (82)
52 (80)
41 (58)
Me
5d
NH2
6d
Me
Me
Me
Me
Me
NH
5d
6d
Me
Ph
Ph
6e
NH
5e
5f
Me
Me
NH2
Me
6f
NH2
NH
Me
7
0.6 (0.6)
65 (75)
43 (72)
5g
NH2
6g
NH
8d
10.0 (62.1)
Me
5h
6h
aSee footnote a of table 2 for general reaction conditions. Reactions were run at
20 oC unless specified otherwise bData in parentheses refer to those obtained
with the silicon-linked yttrium complex, see ref 6. cDetermined by chiral HPLC
after acylation of the products 6 to the corresponding amides 7 with 4-
MeOC6H4COCl. dRun at 60 oC.
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present. Surprisingly, the meta position is mostly favoured in
the case of 5p bearing a strongly electron-donating group
(entries 9-11). The catalytic efficiency of the complex in these
reactions, however, showed no consistent trend.
Mechanistic consideration
In view of the experimental results and previous relevant
studies,2 a tentative reaction mechanism was proposed using
the reaction of aminoalkene 5b as example (Scheme 2). First,
upon the mixing of the chiral rare-earth metal complexes
and aminoalkene 5b, a fast ligand exchange occurred to
provide the intermediate which would undergo
4
I,
intramolecular hydroamination to provide intermediate II. This
intermediate would undergo protonation with the substrate
5b to release the cyclized product 6b while regenerating the
intermediate
might be explained by the transition state model TS, which is
based on the x-ray structures of . In this model, the main
I. The stereochemical results of the reaction
Scheme 2 Proposed reaction mechanism
4
chain of 5b adopts a chair-like conformation with the bulky
diphenyl substituents far away from the chiral diamine
backbone, and the nitrogen atom would attack the Si face of
the alkene as mediated by the rare-earth metal centre to
provide the R-configuration product. We suppose that the
inferior enantiocontrolling power of these complexes, as
compared to the silicon-linked one, might be partly attributed
to the chiral planarity (Sp) of the indene ring. In the current
case, the phenyl group of the indene ring is placed away from
the chiral diamine backbone, which might be detrimental to
the synergy of these two chiral elements of the complex in the
Experimental section
General methods
All reactions with air- or moisture sensitive materials were
performed in oven (120 °C) or flame-dried glassware under an
inert atmosphere of argon, employing standard Schlenk and
glovebox techniques. All solvents were distilled over either
finely divided LiAlH4 or sodium benzophenone ketyl under
argon prior to use unless otherwise noted. CDCl3 was dried
over activated 4 Å molecular sieves. C6D6 was distilled from
13
sodium/benzophenone ketyl. [(Me3Si)2N]3Ln(µ-Cl)Li(THF)3
enantiodifferentiating process. However,
a more exact
was prepared by
a literature method. (1R, 2R)-N,N-
rationale for the highly fluctuating enantioselectivity of this
reaction system requires further in-depth investigation.
dimethylcyclohexane-1,2-diamine is commercially available or
could be prepared by using literature method.14 All the
aminoalkene substrates were synthesized according to
literature protocols.15 Elemental analysis data were obtained
with a Perkin–Elmer 2400 Series II elemental analyzer. 1H NMR
and 13C NMR spectra for analyses of compounds were
Conclusions
In summary, we have synthesised and characterized four novel
chiral half-sandwich rare-earth complexes featuring a carbon-
linked tridentate indene-diamine ligand. When used as
precatalysts for the intramolecular hydroamination of
unactivated alkenes, these complexes demonstrated
significantly varied catalytic activity to provide the chiral
pyrrolidine and piperidine products in moderate to good
enantioselectivities. Although such results are not up to our
expectation for the new carbon-linked ligand featuring a
shortened linker between the indene ring and the chiral
diamine moiety as compared to our previously developed
structurally similar silicon-linked tridentate indene-diamine
ligand, the structure-activity analyses of these complexes
based on x-ray crystallographic data provide some useful
information for further development of highly efficient chiral
rare-earth metal complexes for asymmetric catalysis. Efforts
towards this are currently underway in our laboratories.
recorded with
a Bruker AV 300 NMR or AVANCE-500
spectrometers in C6D6 or CDCl3. High performance liquid
chromatography (HPLC) analyses were performed on a Agilent
1200 chromatograph using chiral Daicel Chiralcel® columns as
noted.
Syntheses
Amide (2). N,N'-Dicyclohexylcarbodiimide (DCC, 2.54 g, 12.3
mmol) was added to a stirred solution of 2-(1H-inden-3-
yl)acetic acid (1.43 g, 8.2 mmol) and 1-hydroxybenzotriazole
(HOBt, 1.99 g, 14.7 mmol) in CH2Cl2 (30 mL) at 0 °C under
argon and the resultant mixture was stirred overnight. The
precipitate was filtered and washed with CH2Cl2 (10 mL × 2).
The filtrate was added to
a solution of (1R, 2R)-N,N-
dimethylcyclohexane-1,2-diamine (1.06 g, 7.4 mmol) in CH2Cl2
(50 mL) at 0 °C under argon. The resultant mixture was stirred
at room temperature for 30 h. Then, saturated aqueous
Na2CO3 (20 mL) was added, followed by stirring for 0.5 h to
quench the reaction. The mixture was extracted with CH2Cl2
(10 mL × 3) and the combined organic extracts were dried over
anhydrous Na2SO4. Concentration in vacuo followed by flash
4 | J. Name., 2012, 00, 1-3
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chromatography on silica gel (dichloromethane–methanol, 50 :
1) afforded
MHz, CDCl3): δ 7.47 (d, J = 7.3 Hz, 1H), 7.39 (d, J = 7.6 Hz, 1H), [(Me3Si)2N]3Sm(μ-Cl) Li(THF)3 (1.43 g, 1.6 mmol) and
(η5:η1:η1-L)Sm[N(SiMe3)2] (4b)
.
This compound was
2
(1.75 g, 83% yield) as a yellow solid. 1H NMR (500 prepared following a procedure similar to that for 4a by using
3
(0.50 g,
7.29 (t, J = 7.5 Hz, 1H), 7.22 (t, J = 7.4 Hz, 1H), 6.44 (s, 1H), 6.39 1.8 mmol) in toluene (10.0 mL) as a yellow solid (0.86 g, 90%
(brs, 1H), 3.56 (d, J = 16.1 Hz, 1H), 3.50 (d, J = 16.1 Hz, 1H), yield). The single crystal suitable for X-ray crystallographic
3.46–3.32 (m, 3H), 2.56–2.48 (m, 1H), 2.16–2.06 (m, 1H), 1.97 analysis was obtained by recrystallization from a mixed solvent
(s, 6H), 1.82–1.68 (m, 2H), 1.67–1.58 (m, 1H), 1.34–1.23 (m, of toluene and THF in volume ratio 20 : 1 at –10 °C. 1H NMR
1H), 1.19–1.05 (m, 2H), 1.04–0.92 (m, 1H). 13C NMR (125 MHz, (500 MHz, C6D6): δ 17.90 (s, 1H), 13.31 (d, J = 8.5 Hz, 1H), 10.75
CDCl3): δ 170.5, 144.4, 144.2, 138.6, 131.9, 126.2, 125.0, 123.7, (s, 1H), 6.77 (d, J = 6.8 Hz, 2H), 6.19 (s, 1H), 5.81 (d, J = 7.9 Hz,
119.4, 66.4, 51.4, 39.6, 38.0, 36.9, 32.5, 25.3, 24.6, 21.3. HRMS 1H), 4.09 (t, J = 7.0 Hz, 1H), 3.69 (d, J = 12.1 Hz, 1H), 3.56 (d, J =
(ESI) calcd for C19H27N2O ([M + H]+) calcd for 299.2123, found 13.1 Hz, 1H), 3.25 (s, 1H), 2.92–2.75 (m, 2H), 2.62 (d, J = 14.2
299.2119.
Hz, 1H), 2.49–2.38 (m, 1H), 1.95 (d, J = 12.7 Hz, 1H), 1.23–1.11
Chiral diamine ligand (3). A solution of
2
(0.60 g, 2.0 mmol) (m, 1H), 0.68 (s, 9H), 0.30 (s, 1H), 0.10 (s, 1H), –0.30 (s, 3H), –
in THF (20 mL) was added dropwise to a suspension of LiAlH4 1.65 (s, 1H), –2.69 (s, 3H), –3.24 (s, 9H). 13C NMR (125 MHz,
(0.76 g, 20 mmol) in THF (30 mL) at 0 °C and the resulting C6D6): δ 131.8, 130.5, 120.7, 117.8, 117.2, 116.9, 112.5, 92.6,
mixture was stirred and heated at reflux for 2 days. After being 86.2, 85.3, 82.5, 43.8, 38.4, 32.1, 27.3, 25.6, 23.6, 23.4, 3.5,
quenched with the addition of Na2SO4·10H2O, the suspension 2.2, 1.0. Anal. Calcd for C25H44N3Si2Sm: C, 50.62; H, 7.48; N,
was passed through a pad of Celite, eluting with ether. The 7.08; Found: C, 50.68; H, 7.45; N, 7.02.
solvent was removed under reduced pressure and the residue
was purified by column chromatography on silica gel following
(dichloromethane–methanol, 100 : 1) to give (0.39 g, 69% [(Me3Si)2N]3Lu(μ-Cl)Li(THF)3 (1.46 g, 1.6 mmol) and
(η5:η1:η1-L)Lu[N(SiMe3)2] (4c). This compound was prepared
procedure similar to that for 4a by using
(0.50 g,
a
3
3
yield) as a yellow oil. [α]D20= –66.8 (c = 0.10, CH2Cl2). H NMR 1.8 mmol) as a white solid (0.91 g, 92% yield). The single
(500 MHz, C6D6): δ 7.35 (d, J = 7.5 Hz, 1H), 7.31 (d, J = 7.3 Hz, crystal suitable for X-ray crystallographic analysis was obtained
1H), 7.24 (t, J = 7.4 Hz, 1H), 7.15 (t, J = 7.5 Hz, 1H), 6.10 (s, 1H), by recrystallization from toluene at –10 °C. 1H NMR (500 MHz,
3.18–3.12 (m, 1H), 3.09 (s, 2H), 2.88–2.69 (m, 4H), 2.32–2.21 C6D6): δ 7.76 (d, J = 7.7, 1H), 7.37 (d, J = 8.4 Hz, 1H), 6.95–6.89
(m, 2H), 2.18–2.11 (m, 1H), 2.01 (s, 6H), 1.66–1.52 (m, 3H), (m, 1H), 6.88–6.76 (m, 2H), 6.24 (d, J = 2.6 Hz, 1H), 4.06 (dd, J =
1.23–1.14 (m, 1H), 1.13–1.00 (m, 2H), 0.99–0.87 (m, 1H). 13C 10.7, 7.6 Hz, 1H), 3.83–3.75 (m, 1H), 3.49 (dd, J = 14.1, 6.1 Hz,
NMR (75.5 MHz, CDCl3): δ 144.3, 143.4, 141.4, 127.6, 125.0, 1H), 3.42–3.33 (m, 1H), 2.74–2.63 (m, 1H), 2.26–2.19 (m, 1H),
123.5, 122.7, 117.9, 65.8, 57.6, 44.8, 38.9, 36.8, 30.9, 27.5, 2.15 (td, J = 10.2, 3.6 Hz, 1H), 1.61–1.43 (m, 4H), 1.31–1.21 (m,
24.4, 23.7, 19.6. HRMS (ESI) calcd for C19H29N2 ([M + H]+) calcd 1H), 1.20–1.14 (m, 1H), 1.12–0.77 (m, 6H), 0.60–0.50 (m, 1H),
1
for 285.2331, found 285.2328.
(η5:η1:η1-L)Y[N(SiMe3)2]
(4a)
0.40 (s, 9H), 0.22 (s, 9H). 13C NMR (125 MHz, C6D6): δ 127.4,
.
To
a
solution of 126.9, 123.5, 122.3, 121.9, 121.4, 119.9, 118.9, 92.6, 67.7,
[(Me3Si)2N]3Y(μ-Cl)Li(THF)3 (1.33 g, 1.6 mmol) in toluene (10.0 66.8, 60.8, 43.8, 34.7, 32.2, 29.5, 26.1, 25.3, 20.7, 6.2, 5.1.
mL) was added a solution of (0.50 g, 1.8 mmol) in toluene Anal. Calcd for C25H44N3Si2Lu: C, 48.60; H, 7.18; N, 6.80; Found:
(10.0 mL) at room temperature. The resulting mixture was C, 48.67; H, 7.13; N, 6.74.
3
stirred and heated at 75 °C for 24 h to give a brown solution.
(η5:η1:η1-L)Sc[N(SiMe3)2] (4d). This compound was prepared
Then, the reaction suspension was filtered to remove the LiCl following
a procedure similar to that for 4a by using
precipitate. The filtrate was evaporated under vacuum to [(Me3Si)2N]3Sc(μ-Cl) Li(THF)3 (1.26 g, 1.6 mmol) and (0.50 g, 1.8
remove all volatiles to leave a residue solid, which was washed mmol), except that the reaction mixture was stirred and
with n-hexane (1 mL × 3) and dried under vacuum to afford 4a heated at 90 °C for 36 h. The product 4d was obtained as a
as a grey solid (0.79 g, 93% yield). The single crystal suitable for purple solid (0.73 g, 94% yield). The single crystal suitable for
X-ray
crystallographic
analysis
was
obtained
by X-ray
crystallographic
analysis
was
obtained
by
recrystallization from a mixed solvent of toluene and THF in recrystallization from a mixed solvent of toluene and THF in
volume ratio 20 : 1 at –10 °C. 1H NMR (500 MHz, C6D6): δ 7.76 volume ratio 20 : 1 at –10 °C. 1H NMR (500 MHz, C6D6): δ 7.76–
(dd, J = 8.4, 0.9 Hz, 1H), 7.38 (dt, J = 8.3, 0.9 Hz), 6.95–6.89 (m, 7.69 (m, 1H), 7.37 (d, J = 8.3 Hz, 1H), 6.94–6.88 (m, 1H), 6.87–
1H), 6.87 (d, J = 3.2 Hz, 1H), 6.85–6.81 (m, 1H), 6.30 (d, J = 3.2 6.80 (m, 2H), 6.29 (d, J = 3.2 Hz, 1H), 3.81–3.68 (m, 2H), 3.50–
Hz, 1H), 3.93 (dd, J = 10.5, 7.7 Hz, 1H), 3.83 (td, J = 11.2, 6.0 Hz, 3.42 (m, 1H), 3.42–3.33 (m, 1H), 3.04–2.96 (m, 1H), 2.07–1.98
1H), 3.56 (dd, J = 14.2, 5.8 Hz, 1H), 3.43 (ddd, J = 14.2, 11.5, 7.9 (m, 2H), 1.62 (s, 3H), 1.54–1.46 (m, 2H), 1.23–1.04 (m, 3H),
Hz, 1H), 2.78–2.69 (m, 1H), 2.30–2.21 (m, 1H), 2.12 (td, J = 0.93–0.86 (m, 1H), 0.75 (s, 3H), 0.58–0.48 (m, 1H), 0.41 (s, 9H),
10.1, 3.4 Hz, 1H), 1.59–1.45 (m, 5H), 1.26–1.18 (m, 1H), 1.12– 0.28 (s, 9H). 13C NMR (126 MHz, C6D6): δ 127.0, 126.4, 123.9,
0.94 (m, 3H), 0.92 (s, 3H), 0.60 (qd, J = 12.1, 3.6 Hz, 1H), 0.39 122.2, 122.1, 121.8, 120.9, 120.2, 94.5, 67.0, 60.7, 44.4, 34.1,
(s, 9H), 0.17 (s, 9H). 13C NMR (125 MHz, C6D6): δ 127.4, 127.2, 31.0, 28.8, 25.5, 24.8, 20.2, 6.2, 6.0. Anal. Calcd for
123.5, 122.1, 121.7, 121.2, 120.7, 119.7, 93.3, 68.1, 67.0, 60.8, C25H44N3Si2Sc: C, 61.56; H, 9.09; N, 8.61; Found: C, 61.62; H,
43.5, 35.0, 32.2, 30.0, 26.1, 25.3, 20.7, 6.1, 4.4. Anal. Calcd for 9.03; N, 8.58.
C25H44N3Si2Y: C, 56.47; H, 8.34; N, 7.90; Found: C, 56.53; H, Crystal structure determination
8.30; N, 7.82.
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4
5
6
7
D. V. Vitanova, F. Hampel and K. C. Hultzsch, J. Organomet.
Chem., 2007, 692, 4690.
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The single crystal X-ray diffraction data for complexes
4 were
collected on a diffractometer with graphite monchromated Mo
Kα radiation (λ = 0.71073 Å) at room temperature. Saint
program and SADABS program carried out the data
integration. The structures were solved by a direct method and
refined on F2 using SHELXTL suite of program. All non-
hydrogen atoms were anisotropically refined by full-matrix
least squares methods. All hydrogen atoms were geometrically
generated and isotropically refined using a riding model.
Crystallographic data in CIF files are provided in the †ESI.
CCDC-1509830 (4a), 1509831 (4b), 1509832 (4c), and 1509833
1637.
Z. Chai, D. Hua, K. Li, J. Chu and G. Yang, Chem. Commun.,
2014, 50, 177.
For examples: (a) D. V. Gribkov, K. C. Hultzsch and F. Hampel,
Chem. Eur. J., 2003, 9, 4796; (b) D. V. Gribkov and K. C.
Hultzsch, Chem. Commun., 2004, 730; (c) D. V. Gribkov, K. C.
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(
4d) contain the supplementary crystallographic data for this
paper.
8
Enantioselective annulative intramolecular hydroamination of
olefins catalysed by complexes 4
Bourdreux, R. Guillot, S. Bezzenine-Lafoll
and J. Hannedouche, ChemCatChem, 2016,
Germain, E. Schulz and J. Hannedouche, ChemCatChem,
2014, , 2065; (d) I. Aillaud, C. Olier, Y. Chapurina, J. Collin, E.
Schulz, R. Guillot, J. Hannedouche and A. Trifonov,
Organometallics, 2011, 30, 3378; (e) Y. Chapurina, H. Ibrahim,
R. Guillot, E. Kolodziej, J. Collin, A. Trifonov, E. Schulz and J.
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é
e, R. Gil, D. Prim
In an argon-filled glovebox, 5 mol % of
internal standard) and aminoalkene
4
, Cp2Fe (6.0 mg,
8, 2455; (c) S.
5
(0.32 mmol) were
weighed into a 5-mm NMR tube equipped with a Teflon valve
(J-Young), and C6D6 (0.6 mL) was added. The hydroamination
1
reaction was then monitored by H NMR analysis for estimate
6
of both conversion and yield using ferrocene as the internal
standard.
K. Anderson and T. Livinghouse, Tetrahedron Lett., 2015, 56
,
3658; (g) H. M. Lovick, D. K. An and T. Livinghouse, Dalton
Trans., 2011, 7697.
9
For examples of chiral vicinal diamine-based complexes: (a)
N. Meyer, A. Zulys and P. W. Roesky, Organometallics, 2006,
25, 4179; (b) P. Benndorf, J. Jenter, L. Zielke and P. W.
Roesky, Chem. Commun., 2011, 2574; (c) Y. Zhang, W. Yao, H.
Li and Y. Mu, Organometallics, 2012, 31, 4670.
Acknowledgements
Financial support of this research from the National Natural
Science Foundation of China (NSFC Nos. 21672005 and
21472001) and the Special and Excellent Research Fund of
Anhui Normal University are gratefully acknowledged.
10 (a) P. N. O’Shaughnessy, P. D. Knight, C. Morton, K. M.
Gillespie and P. Scott, Chem. Commun., 2003, 1770; (b) P. N.
O’Shaughnessy and P. Scott, Tetrahedron Asymmetry, 2003,
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Knight, I. J. Munslow and P. Scott, Dalton Trans., 2004, 2251;
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Notes and references
1
For recent reviews: (a) P.W. Roesky, Molecular Catalysis of
Rare-Earth Elements (Structure and Bonding), Springer,
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6 | J. Name., 2012, 00, 1-3
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Journal Name
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Table of contents
R
R
R
NH2
RE
NH
4 (5 mol %)
C6D6, 20-60 o
R'
C
R
R'
n
n
n = 1 or 2
up to 87% ee
17 examples
4
(RE = Y, Sm, Lu, Sc)
Novel rare-earth metal complexes featuring a tridentate carbon-linked amido-indenyl ligand have been
synthesized and used to catalyze the intramolecular olefin hydroamination.
1