Lanthanide complexes coordinated by N-substituted (R)-1,1′- binaphthyl-2,2′-diamido ligands in the catalysis of enantioselective intramolecular hydroamination

Article abstract of DOI:10.1002/chem.200401203

A new family of lanthanide ionic complexes derived from chiral, substituted (R)-binaphthylamine ligands, [Li(thf)₄][Ln{(R)-C₂₀H ₁₂(NR)₂}₂] (Ln = Yb, Sm, Nd, or Lu), has been synthesized and characterized by X-ray crystal structure analyses. All complexes have been tested as new catalysts for the hydroamination/cyclization of 1-(aminomethyl)-1-allylcyclohexane. Ytterbium complexes proved to be both the most active and the most enantioselective, and the use of the complex [Li(thf)₄][Yb{(R)-C₂₀H₁₂(NC₃H ₇)₂}₂], bearing isopropyl radicals on the nitrogen atoms, allowed the formation of the corresponding spiropyrrolidine in high yield with up to 70% ee.

Full text of DOI:10.1002/chem.200401203

FULL PAPER
Lanthanide Complexes Coordinated by N-Substituted (R)-1,1’-Binaphthyl-
2,2’-diamido Ligands in the Catalysis of Enantioselective Intramolecular
Hydroamination
Jacqueline Collin,[a] Jean-Claude Daran,[c] Olivier Jacquet,[a] Emmanuelle Schulz,*[a] and
Alexander Trifonov*[b]
Abstract: A new family of lanthanide
ionic complexes derived from chiral,
substituted (R)-binaphthylamine li-
gands, [Li(thf)4][Ln{(R)-C20H12(NR)2}2]
(Ln=Yb, Sm, Nd, or Lu), has been
synthesized and characterized by X-ray
crystal structure analyses. All com-
plexes have been tested as new cata-
lysts for the hydroamination/cyclization
of 1-(aminomethyl)-1-allylcyclohexane.
Ytterbium complexes proved to be
both the most active and the most
enantioselective, and the use of the
complex
[Li(thf)4][Yb{(R)-C20H12-
(NC3H7)2}2], bearing isopropyl radicals
on the nitrogen atoms, allowed the for-
mation of the corresponding spiropyr-
rolidine in high yield with up to
70% ee.
Keywords: amido ligands · enantio-
selectivity · homogeneous catalysis ·
hydroamination · lanthanides
Introduction
formation of any by-product or salts.[4] Pioneering work on
the lanthanide-catalyzed intramolecular hydroamination re-
action has been performed by Marks and co-workers and
was recently reviewed.[5] Cyclopentadienyl-based alkyl or
amido lanthanides were found to be active catalysts to per-
form efficiently the hydroamination/cyclization of aminoal-
kenes,[6] aminoalkynes,[7] aminodienes,[8] and aminoallenes.[9]
The first examples of the enantioselective intramolecular hy-
droamination of aminoalkenes were also reported by Marks
and co-workers, by the use of C1-symmetric chiral organo-
lanthanide complexes. In the first generation, ansa lanthano-
cenes were modified by introduction of a menthyl-type sub-
stituent,[10] and in subsequent studies a more stereodemand-
ing octahydrofluorenyl replaced the achiral cyclopentadienyl
group.[11] To the best of our knowledge, no other lanthanide
catalysts for intramolecular hydroamination of alkenes were
reported until the work of Kim et al., who showed that such
efficient (nonchiral) reactions could be performed with lan-
thanide trisamides.[12] As a real breakthrough in this re-
search field, these results opened the way to the develop-
ment and use of new cyclopentadienyl-free lanthanide com-
plexes as more easily accessible catalysts.[13] Scott and co-
workers recently published the enantioselective hydroami-
nation/cyclization of 2,2’-dimethylaminopent-4-ene (up to
50% ee) with in situ prepared catalysts obtained from chiral
nonracemic N-aryl-substituted biphenyl diamines and yttri-
um silyl amides.[14] The same group synthesized and charac-
terized several further chiral lanthanide bisaryloxide com-
Efficient synthetic and environmentally friendly methods for
the preparation of enantiomerically enriched nitrogen-con-
taining heterocycles are frequently required nowadays be-
cause of the potential biological activity of such com-
pounds.[1] Intramolecular hydroamination of unsaturated
amino derivatives appears to be a good example of an
atom-economical reaction, which illustrates the concept de-
veloped simultaneously by Trost[2] and Sheldon[3] in the
1990s. Indeed, the hydroamination reaction proceeds
ꢀ
through a formal addition of the N H unit onto a carbon–
carbon unsaturated bond, with all atoms of the reactants
being transferred into the reaction product and without the
[a] Dr. J. Collin, O. Jacquet, Dr. E. Schulz
Laboratoire de Catalyse Molꢀculaire, ICMMO
Universitꢀ Paris-Sud, 91405 Orsay (France)
Fax : (+33)169-154-680
E-mail: emmaschulz@icmo.u-psud.fr
[b] Dr. A. Trifonov
G. A. Razuvaev Institute of Organometallic Chemistry
of the Russian Academy of Sciences
Tropinia 49, 603600 Nizhny Novgorod GSP-445 (Russia)
Fax : (+7)8312-127-497
E-mail: trif@imoc.sinn.ru
[c] Dr. J.-C. Daran
Laboratoire de Chimie de Coordination
205 route de Narbonne, 31077 Toulouse (France)
Chem. Eur. J. 2005, 11, 3455 – 3462
DOI: 10.1002/chem.200401203
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3455

plexes arising from the reduction of salicylaldimine ligands
and subsequent N-methylation. The lanthanum complex al-
lowed the cyclization of 2,2’-dimethylaminopent-4-ene with
60% ee.[15] By preparing a new chiral zirconium alkyl cation
coordinated with a similar aminobiphenoxide ligand, Scott
and co-workers obtained a highly active and enantioselec-
tive catalyst for the hydroamination/cyclization of secondary
amines (up to 82% ee).[16] At the same time as this work,
Hultzsch and co-workers prepared new yttrium and lantha-
num amides, coordinated by ancillary chiral biphenolate or
binaphtholate ligands, that led to the cyclization of amino-
pentenes with up to 57% ee.[17] An improvement in terms of
activity and selectivity was reported by this team in prepar-
ing more sterically hindered yttrium complexes in order to
favor a monomeric structure.[18] The 3,3’-bis(tris(aryl)silyl)-
substituted binaphtholate ligands allow the isolation of an
yttrium aryl complex that is active at room temperature and
leads to an enantiomeric excess of 83% for the hydroamina-
tion of aminopent-4-ene, the best enantiomeric excess ob-
tained to date. At the same time, Marks and co-workers
have employed C2-symmetric bis(oxazolinato) ligands for in
situ preparation of lanthanide catalysts that are also active
at room temperature, with enantiomeric excesses up to 67%
for the lanthanum complex.[19] Enantioselective hydroamina-
tion of other substrates has been less frequently described
but some results are reported concerning aminodienes with
an ansa fluorenyl samarium complex[20] and aminoallenes
with chiral titanium aminoalcohol complexes.[21]
counterion.[26] The ytterbium complex containing (R)-1,1’-bi-
naphthyl-2,2’-bis(neopentylamine) (1a) is an efficient cata-
lyst for the hydroamination of 1-(aminomethyl)-1-allylcyclo-
hexane at room temperature and afforded the correspond-
ing spiropyrrolidine in 41% ee.
In order to gain insight into the effect of the nature of the
central metal atom and the bulkiness of the chiral ligands
on the efficiency and enantioselectivity of the above reac-
tion, we have now extended this study to the synthesis and
characterization of new complexes containing various lan-
thanides and radicals on nitrogen atoms.
Results and Discussion
Preparation of new complexes of type [Li(thf)4][Ln{(R)-
C20H12(NR)2}2]: The new family of ionic lanthanide amides
that we have described arose at first from the (R)-1,1’-bi-
naphthyl-2,2’-bis(neopentylamine) ligand.[27] The ytterbium
and samarium complexes [Li(thf)4][Ln{(R)-C20H12N2-
(C10H22)}2] (Ln=Yb (1a), Sm (1b)) have been recently syn-
thesized by metathetic reactions of anhydrous LnCl3 (Ln=
Sm, Yb) with two equivalents of Li2[(R)-C20H12N2-
(C10H22)][27] in tetrahydrofuran at ambient temperature. By
following the same procedure, we have prepared further re-
lated derivatives with neodymium and lutetium, [Li(thf)4]-
[Ln{(R)-C20H12N2(C10H22)}2] (Ln=Nd (1c), Lu (1d);
Scheme 1). Complexes 1c and 1d were purified by extrac-
tion of the solid residue with toluene, after evaporation of
We aimed at preparing asymmetric lanthanide catalysts
coordinated by chiral amine li-
gands for intramolecular hydro-
amination. In contrast to bi-
naphthol, which has been large-
ly employed as a ligand in lan-
thanide catalysis,[22–24] no bi-
naphthylamine complex has
been reported yet, as far as we
know. Different families of Scheme 1. Preparation of [Li(thf)4][Ln{(R)-C20H12N2(C10H22)}2]: Ln=Yb (1a), Sm (1b), Nd (1c), or Lu (1d).
complexes, with mono- or bi-
coordinated binaphthol, have
been described, and Shibasaki and co-workers focused on
lanthanide heterobimetallic complexes of general formula
[M3Ln(binol)3] (M=alkali metal, Ln=lanthanide, binol=bi-
naphthol) as highly active and enantioselective catalysts for
a wide range of reactions.[22,25] Many complexes have been
prepared, and X-ray crystal structures indicated that the
three binaphthol ligands were coordinated to both the lan-
thanide and alkali metals with a L or D configuration. The
influence of the nature of the alkali metal on the activity
and selectivity of these catalysts has been demonstrated.
We have previously reported the preparation of a new
family of lanthanide ate complexes derived from chiral, sub-
stituted (R)-binaphthylamine ligands, [Li(thf)4][Ln{(R)-
C20H12N2(C10H22)}2] (Ln=Yb (1a), Sm (1b); see Scheme 1).
In compounds 1a and 1b, coordination of two (R)-binaph-
thylamine ligands to the lanthanide atom resulted in the for-
mation of a complex anion with a discrete [Li(thf)4]+ as
THF, and subsequent recrystallization from THF/hexane
mixtures. Complexes 1c and 1d were isolated as air- and
moisture-sensitive brownish-orange and yellow crystals in
reasonable yields (74 and 61%, respectively). Both com-
pounds are soluble in THF and aromatic solvents but insolu-
ble in hexane.
1
Complex 1d is diamagnetic; its H NMR spectrum has no
particular features and presents the expected set of signals.
Complex 1c is paramagnetic with the value of the magnetic
moment being 3.3 mB (293 K), a value that is characteristic
for derivatives of trivalent neodymium.[28]
To modify the steric environment of the lanthanide atom
and to tune the complex properties for the catalytic reaction
requirements, we have prepared the chiral, substituted (R)-
binaphthylamine ligands bearing various hydrocarbon radi-
cals on the nitrogen atoms, that is, (R)-C20H12(NHR)2 (R=
iBu (2a), benzyl (Bn; 2b), iPr (2c)).[29] The ytterbium deriv-
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Chem. Eur. J. 2005, 11, 3455 – 3462

Catalytic Lanthanide Complexes
FULL PAPER
atives were chosen as a model system because they have
demonstrated the highest activity and enantioselectivity (see
ref. [26] and the results detailed below), and the series of
novel complexes [Li(thf)4][Yb{(R)-C20H12(NR)2}2] (R=iBu
(3a), Bn (3b), iPr (3c)) have been synthesized. The reac-
tions of anhydrous YbCl3 with two equivalents of Li2[(R)-
C20H12(NR)2] were carried out in THF at ambient tempera-
ture (Scheme 2). The lithium derivatives Li2[(R)-
C20H12(NR)2] were prepared by following the general
method described by Lappert and co-workers.[27]
Evaporation of THF, extraction of the solid residue with
toluene, and subsequent recrystallization from THF/hexane
mixtures resulted in the isolation of complexes 3a–c in 54,
52, and 68% yields, respectively. Complexes 3a and 3c are
red crystalline solids and 3b is a brownish-green crystalline
solid. Complexes 3a–c are paramagnetic, with magnetic mo-
ments corresponding to the trivalent state of ytterbium.[28]
All the compounds are readily soluble in THF and toluene
but insoluble in hexane.
Figure 1. Molecular structure of complex 1c. The hydrogen atoms are
omitted for the sake of clarity. Selected bond lengths [ꢂ] and angles [8]:
ꢀ
ꢀ
ꢀ
ꢀ
Nd N1 2.366(3), Nd N2 2.350(3), Nd N3 2.391(3), Nd N4 2.397(3),
ꢀ
ꢀ
ꢀ
ꢀ
Nd C111 2.819(3), Nd C211 2.813(3), Nd C311 2.770(4), Nd C312
ꢀ
2.830(3), Nd C411 2.842(3), N1-Nd-N2 115.98(9), N1-Nd-N3 100.73(9),
N2-Nd-N3 106.54(10), N1-Nd-N4 115.01(10), N2-Nd-N4 101.88(9), N3-
Nd-N4 117.05(10).
to those in the related ionic de-
rivative of tetracoordinated ne-
odymium [Li(thf)][Nd(N-iPr2)4]
(2.283(17), 2.291(16), 2.393(15),
2.406(16) ꢂ),[31] but they are
substantially shorter than the
Scheme 2. Preparation of [Li(thf)4][Yb{(R)-C20H12(NR)2}2]: R=CH2-iPr (a), CH2Ph (b), or iPr (c).
analogous lengths in the meso-
octaethylporphyrinogen com-
plex
[{[(h5:h1:h5:h1-Et8N4)Nd-
X-ray crystal structure analyses of complexes 1c,d and 3a,c:
Single-crystal samples of complexes 1c,d and 3a,c suitable
for X-ray diffraction study were obtained by slow condensa-
tion of hexane in the THF/complex solutions at room tem-
perature. Complex 3a was isolated as a THF solvate [Li-
(thf)4][Yb{(R)-C20H12(NCH2CHMe2)2}2]·0.5THF. The molec-
ular structures of complexes 1c,d and 3a,c are shown in Fig-
ures 1–4, respectively. Details of the crystal data collections
and the structure refinements are listed in Table 3 in the Ex-
perimental Section. The X-ray crystal structure analysis re-
vealed that compounds 1c,d and 3a,c are isostructural ionic
complexes containing a discrete [Li(thf)4]+ ion and a dis-
crete [Ln{(R)-C20H12(NR)2}2]ꢀ complex anion resulting from
coordination of two diamido ligands to the trivalent lantha-
nide atom. The structures are very similar to those formerly
reported for complexes 1a,b.
(dme)]-h3-Na}(dioxane)1.5]
(dme=1,2-dimethoxyethane;
2.461(4), 2.527(4) ꢂ) in which the coordination sphere of ne-
The coordination environment of the central metal atom
in complexes 1a,b, made up of four nitrogen atoms of
two chelating diamido ligands, may be classified as a distort-
ed tetrahedron. Vicinal bulky hydrocarbyl radicals on the ni-
Figure 2. Molecular structure of complex 1d. The hydrogen atoms are
omitted for the sake of clarity. Selected bond lengths [ꢂ] and angles [8]:
ꢀ
trogen atoms adopt a trans orientation. The average Ln N
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Lu N1 2.257(3), Lu N2 2.275(3), Lu N3 2.218(3), Lu N4 2.250(3), Lu
bond lengths in 1c (2.376(3) ꢂ) and 1d (2.250(3) ꢂ) are
ꢀ
ꢀ
ꢀ
C111 2.719(4), Lu C211 2.666(4), Lu C212 2.711(4), Lu C311 2.733(4),
very similar despite the difference in the ionic radii of triva-
ꢀ
Lu C411 2.710(4), N1-Lu-N2 122.26(12), N1-Lu-N3 99.50(12), N2-Lu-N3
lent neodymium and lutetium.[30] The Nd N bond lengths in
ꢀ
103.79(12), N1-Lu-N4 111.61(12), N2-Lu-N4 100.71(11), N3-Lu-N4
120.12(11).
1c (2.350(3), 2.366(3), 2.391(3), 2.397(3) ꢂ) are comparable
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E. Schulz, A. Trifonov et al.
(AlCl4)3]
(2.799(1)–2.902(1) ꢂ)[35]
and
[{2,6-
(C6H5)2C6H3O}3Lu] (2.787(8)–3.087(12) ꢂ),[36] probably re-
flects a h1,h2 interaction of the LnIII atoms with the aromatic
ꢀ
rings of the binaphthyl ligands. The average Yb N distances
in complexes 3a and 3c are 2.246(4) and 2.252(4) ꢂ, respec-
tively, and do not differ drastically from those observed in
1a; evidently, the lanthanide–nitrogen bond lengths in this
class of compounds are not dramatically influenced by the
steric bulk of the hydrocarbyl radicals bound to the nitrogen
atoms.
Catalytic tests: These new ionic lanthanide amides have
been evaluated as catalysts for the hydroamination/cycliza-
tion of 1-(aminomethyl)-1-allylcyclohexane (4, Scheme 3).
Figure 3. Molecular structure of complex 3a. The hydrogen atoms are
omitted for the sake of clarity. Selected bond lengths (ꢂ) and angles (8):
ꢀ
ꢀ
ꢀ
ꢀ
Yb N1 2.243(5), Yb N2 2.260(4), Yb N3 2.255(4), Yb N4 2.252(5),
ꢀ
ꢀ
ꢀ
ꢀ
Yb C111 2.695(6), Yb C112 2.804(5), Yb C211 2.682(6), Yb C212
ꢀ
ꢀ
ꢀ
ꢀ
2.739(5), Yb C311 2.690(5), Yb C312 2.776(6), Yb C411 2.675(6), Yb
C412 2.748(5), N1-Yb-N2 121.43(17), N1-Yb-N3 101.83(17), N2-Yb-N3
103.79(16), N1-Yb-N4 106.01(17), N2-Yb-N4 102.96(18), N3-Yb-N4
122.31(16).
Scheme 3. Hydroamination/cyclization of 1-(aminomethyl)-1-allylcyclo-
hexane (4). Cat* =1a–d and 3a–c.
All the reactions were performed in C6D6 at room tempera-
ture. The complexes obtained by metathetic reactions of an-
hydrous LnCl3 with two equivalents of Li2[(R)-C20H12N2-
(C10H22)] were first tested and compared in terms of activity
and enantioselectivity for the formation of the correspond-
ing spiropyrrolidine 5. The results obtained by varying the
lanthanide atom are reported in Table 1.
Table 1. The effect of the metal center on the activity and enantioselec-
tivity of the catalyst in the intramolecular hydroamination reaction.
Entry Catalyst Ln
Catalyst ratio Reaction Conversion ee
[%]
time [h]
[%]
[%]
Figure 4. Molecular structure of complex 3c. The hydrogen atoms are
omitted for the sake of clarity. Selected bond lengths [ꢂ] and angles [8]:
1
2
3
4
1a
1b
1c
1d
Yb
Sm
Nd
Lu
3.5
5
7
1.5
2
3
87
78
84
91
41
24
1
ꢀ
ꢀ
ꢀ
ꢀ
Yb N1 2.263(4), Yb N2 2.249(4), Yb N3 2.239(4), Yb N4 2.236(4),
ꢀ
ꢀ
ꢀ
ꢀ
Yb C311 2.718(5), Yb C312 2.857(5), Yb C411 2.774(5), Yb C412
2.893(6), N1-Yb-N2 120.08(16), N1-Yb-N3 101.24(16), N2-Yb-N3
108.34(19), N1-Yb-N4 109.03(18), N2-Yb-N4 99.67(17), N3-Yb-N4
119.66(17).
17
3
16
odymium also contains four nitrogen atoms.[32] In the luteti-
Catalysts prepared from neodynium and lutetium allowed
ꢀ
um analogue (1d) the values of the Lu N bond lengths
the transformation of the unsaturated amine with high con-
version in a reaction time of 3 h by using higher catalyst
ratios than with the corresponding ytterbium derivative (see
entries 3,4 relative to entry 1). Neodymium afforded race-
mic spiropyrrolidine, whereas the lutetium amide complex
led to the expected product with 16% ee (entry 4).
As using ytterbium led to the best results, further varia-
tions were performed on the complexꢃs amide ligands by in-
troducing different substituents on the nitrogen atom. Li-
gands with sterically more and less hindered radicals relative
to neopentyl were synthesized, and the corresponding yt-
terbium catalysts were tested in the same intramolecular hy-
droamination reaction. The results are reported in Table 2.
(2.218(3), 2.257(3), 2.275(3), 2.250(4) ꢂ) are close to those
reported for octaethylporphyrinato [{(Et2C4NCH2)4}LuCH-
(SiMe3)2] (2.356(7), 2.263(6), 2.296(7), 2.256(6) ꢂ)[33] and
pyrazolato
[{(Me3C)2C3N2}3Lu(NC5CMe3)]
(2.294(4),
2.299(4), 2.300(4), 2.371(4) ꢂ) complexes.[34] The lanthanide
atom in both 1c and 1d has a formal coordination number
of four, which is very low for these elements. The presence
in complexes 1c,d of the short contacts between the metal
atoms and the carbon atoms in the ipso and ortho positions
to the amido groups (1c: 2.770(4)–2.842(3) ꢂ; 1d: 2.666(4)–
ꢀ
2.733(4) ꢂ), which are comparable to the Ln C distances
reported for the lanthanide p complexes [Nd(h6-C6H5CH3)-
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Catalytic Lanthanide Complexes
FULL PAPER
Table 2. The effect of the N-substituent on the ligand on activity and
enantioselectivity of the intramolecular hydroamination reaction.
ing for enantioselective intramolecular hydroamination. We
are continuing our efforts to optimize the asymmetric induc-
tions and to widen the scope of substrates for hydroamina-
tion reactions.
Entry Catalyst Substituent Catalyst
ratio [%]
Reaction Conversion ee
time [h] [%] [%]
1
2
3
4
5
6
1a[a]
3a[a]
3b[a]
3c[a]
3c[b]
3c[b,c]
CH2-tBu
CH2-iPr
CH2-Ph
iPr
iPr
iPr
3.5
3
7
5
5
1.5
1.5
0.5
18
48
144
87
98
100
14
67
100
41
9
12
49
70
66
Experimental Section
5
General remarks: All procedures were performed under vacuum by
using standard Schlenk and glove-box techniques. After drying over
KOH, THF was distilled from sodium benzophenone ketyl prior to use.
Hexane and toluene were purified by distillation from sodium/triglyme
benzophenone ketyl or CaH2. Deuterated benzene was dried with
sodium benzophenone ketyl and vacuum-transferred. Anhydrous LnCl3
was purchased from Aldrich. All other commercially available chemicals
were used after the appropriate purification. Bruker AM 250 and Bruker
DRX 400 NMR spectrometers (operating at 250 and 400 MHz, respec-
tively) were used for recording the NMR spectra. Chemical shifts for 1H
and 13C spectra were referenced internally according to the residual sol-
vent resonances and are reported relative to tetramethylsilane. IR spectra
were recorded on a Specord M80 instrument as Nujol mulls. Lanthanide
metal analyses were carried out by complexometric titration. Elemental
analyses were performed by the Microanalytical Laboratory of the Insti-
tute of Organometallic Chemistry of the Russian Academy of Sciences.
Optical rotations were measured with a Perkin–Elmer 341 polarimeter.
[a] Recrystallized complex. [b] Complex used without any purification.
[c] Reaction performed on a preparative scale (see the Experimental Sec-
tion).
Sterically less hindered substituents such as the iBu or Bn
functionalities led to very active but less enantioselective
catalysts than 1a (see entries 2,3 relative to entry 1). The
best results in terms of enantioselectivity were obtained
with the introduction of iPr groups on the nitrogen atoms,
as an ee value of 49% was measured for the spiropyrrolidine
5, although this catalyst gave a poor conversion (14%) after
18 h reaction time (entry 4). These first experiments (en-
tries 1–4) were run with catalysts in pure form, that is, after
recrystallization. As complex 3c led to nonreproducible re-
sults in terms of activity in the catalytic reaction after a few
days storage, it was also used directly in catalytic tests with-
out any purification. To our delight, under similar conditions
(5 mol% nonisolated catalyst, estimated on the basis of
NMR signal integration), spiropyrrolidine 5 was obtained
with 70% ee (entry 5). Total conversion was obtained after a
reaction time of 6 days (entry 6); in this case, the product
Synthesis of [Li(thf)4][Nd{(R)-C20H12N2(C10H22)}2] (1c): NdCl3 (0.044 g,
0.175 mmol) was slowly added to a solution of Li2[(R)-C20H12N2(C10H22)]
(0.153 g, 0.350 mmol) in THF (5 mL) at 208C under vigorous stirring.
The reaction mixture was stirred for 3 h, THF was evaporated in vacuo,
and the resulting solid was extracted with toluene (15 mL). The extracts
were filtered, toluene was evaporated, and the solid residue was dissolved
in THF (1 mL). Slow condensation of hexane in the THF/complex so-
lution at 208C resulted in brownish-orange crystals of 1c (0.166 g, 74%).
IR (KBr, Nujol): n˜ =3030 (w), 1610 (s), 1600 (s), 1500 (s), 1340 (s), 1315
(s), 1280 (s), 1250 (m), 1200 (m), 1150 (m), 1025 (w), 810 (s), 745 (s),
725 cmꢀ1 (s); elemental analysis calcd (%) for C76H100LiN4NdO4 (1284.8):
C 71.04, H 7.78, Nd 11.22; found: C 70.62, H 8.32, Nd 11.64.
was isolated and its enantiopurity was measured by GC
[37]
analysis of amides prepared with Mosherꢃs chloride
and
Synthesis of [Li(thf)4][Lu{(R)-C20H12N2(C10H22)}2] (1d): LuCl3 (0.097 g,
0.344 mmol) was slowly added to a solution of Li2[(R)-C20H12N2(C10H22)]
(0.300 g, 0.688 mmol) in THF (5 mL) at 208C under vigorous stirring.
The reaction mixture was stirred for 3 h, THF was evaporated in vacuo,
and the resulting solid was extracted with toluene (20 mL). The extracts
were filtered, toluene was evaporated, and the solid residue was dissolved
in THF (2 mL). Slow condensation of hexane in the THF/complex so-
lution at 208C resulted in yellow crystals of 1d (0.276 g, 61%). 1H NMR
(200 MHz, CD2Cl2): d=7.70 (d, J=9.1 Hz, 4H), 7.53 (d, J=7.8 Hz, 4H),
7.32 (d, J=9.2 Hz, 4H), 6.89 (dd, J=7.5 Hz, 4H), 6.73 (brs, 4H), 6.42 (d,
J=7.7 Hz, 4H), 3.58 (brs, 24H; THF and CH2), 1.91 (s, 16H; THF),
0.43 ppm (s, 36H); IR (KBr, Nujol): n˜ =3030 (w), 1610 (s), 1600 (s), 1545
(m), 1500 (s), 1440 (s), 1340 (s), 1325 (s), 1275 (s), 1250 (m), 1215 (m),
1160 (m), 1040 (m), 930 (w), 880 (w), 815 (s), 745 cmꢀ1 (s); elemental
analysis calcd (%) for C76H100LiLuN4O4 (1315.6): C 69.38, H 7.60, Lu
13.29; found: C 69.77, H 8.00, Lu 12.99.
by optical rotation. Comparison of entries 5 and 6 showed
that there was no measurable variation of enantiomeric
excess during the reaction course.
Conclusion
A new family of ionic lanthanide amides based on (R)-1,1’-
binaphthyl-2,2’-bis(alkylamine) ligands with various lantha-
nide and N-alkyl substituents has been synthesized and char-
acterized. All the complexes have similar structures contain-
ing a complex anion with a discrete [Li(thf)4]+ as counter-
ion. Although X-ray crystal structure studies indicated that
the cation is not coordinated to the ligand, we will further
study the possible influence of its nature on the activity and
enantioselectivity of the corresponding catalyst, as its behav-
ior in solution could be different. These lanthanide amides
are coordinated by 1,1’-binaphthyl-2,2’-bis(alkylamine), a
family of asymmetric ligands that are easily prepared and
that allow the bulkiness and electronic properties to be
tuned. The present studies have allowed the enantiomeric
excess for the cyclization of 1-(aminomethyl)-1-allylcyclo-
hexane (4) into spiropyrrolidine 5 to be increased up to
70%, a result showing that these catalysts are highly promis-
Synthesis of [Li(thf)4][Yb{(R)-C20H12N2(C8H18)}2]·0.5THF (3a): YbCl3
(0.048 g, 0.171 mmol) was slowly added to a solution of Li2[(R)-C20H12N2-
(C8H18)] (0.140 g, 0.342 mmol) in THF (5 mL) at 208C under vigorous
stirring. The reaction mixture was stirred for 3 h, THF was evaporated in
vacuo, and the resulting solid was extracted with toluene (15 mL). The
extracts were filtered, toluene was evaporated, and the solid residue was
dissolved in THF (2 mL). Slow condensation of hexane in the THF/com-
plex solution at 208C resulted in red crystals of 3a (0.119 g, 54%). IR
(KBr, Nujol): n˜ =3030 (w), 1625 (s), 1605 (s), 1575 (s), 1435 (s), 1375 (s),
1345 (s), 1315 (s), 1300 (s), 1250 (s), 1225 (m), 1160 (m), 1100 (w), 1025
(m), 925 (w), 750 cmꢀ1 (s); elemental analysis calcd (%) for
C74H96LiN4O4.5Yb (1293.6): C 68.71, H 7.42, Yb 13.37; found: C 68.50, H
6.99, Yb 13.59.
Chem. Eur. J. 2005, 11, 3455 – 3462
www.chemeurj.org
ꢁ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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E. Schulz, A. Trifonov et al.
Synthesis of [Li(thf)4][Yb{(R)-C20H12N2(C14H14)}2] (3b): YbCl3 (0.072 g,
0.257 mmol) was slowly added to a solution of Li2[(R)-C20H12N2(C14H14)]
(0.245 g, 0.515 mmol) in THF (5 mL) at 208C under vigorous stirring.
The reaction mixture was stirred for 12 h, THF was evaporated in vacuo,
and the resulting solid was extracted with toluene (20 mL). The extracts
were filtered, toluene was evaporated, and the solid residue was dissolved
in THF (5 mL). Slow condensation of hexane in the THF/complex so-
lution at 208C resulted in a brownish-green microcrystalline solid 3b
(0.187 g, 52%). IR (KBr, Nujol): n˜ =3030 (w), 1625 (s), 1605 (s), 1580
(s), 1505 (m), 1425 (s), 1345 (s), 1300 (w), 1150 (m), 1305 (s), 1025 (m),
815 (s), 710 (s), 700 cmꢀ1 (m); elemental analysis calcd (%) for
C84H84LiN4O4Yb (1392.92): C 72.43, H 6.03, Yb 12.41; found: C 72.01, H
6.47, Yb 12.91.
lecular sieves) was added to the complex (see Tables 1 and 2 for catalytic
ratios) charged in an NMR tube equipped with a teflon stopcock. After
disappearance of the olefinic protons as monitored by NMR spectrosco-
py, CH2Cl2 was added and amine 5 was transformed into the correspond-
ing amide by reaction with Mosherꢃs chloride. The reaction mixture was
diluted with CH2Cl2 (2 mL) and treated with Et3N (100 mL), 4-dimethyla-
minopyridine (20 mg), and (R)-(ꢀ)-a-methoxy-a-(trifluoromethyl)pheny-
lacetyl chloride (Mosherꢃs chloride, 30 mL). After being stirred for 2 h at
room temperature, the mixture was washed with saturated NH4Cl so-
lution and extracted with CH2Cl2. After drying, the crude product dis-
solved in diethyl ether was injected onto a GC DB-1 capillary column
(808C, rise of 108Cminꢀ1, 2008C for 10 min, rise of 108Cminꢀ1, 2508C
for 10 min; injector temperature 2508C, detector temperature 2508C).
The retention times of diastereoisomeric amides formed from the cy-
clized amine 3-methyl-2-aza-spiro[4,5]decane (5) and of the amide
formed from the nonreacted 1-(aminomethyl)-1-allyl-cyclohexane (4) are
21.6, 22.4, and 23.15 min, respectively. Enantiomeric excesses of 3-
methyl-2-aza-spiro[4,5]decane (5) and GC yields of the cyclized product
were determined by integration of these three peaks.
Synthesis of [Li(thf)4][Yb{(R)-C20H12N2(C6H14)}2] (3c): YbCl3 (0.064 g,
0.228 mmol) was slowly added to a solution of Li2[(R)-C20H12N2(C6H14)]
(0.174 g, 0.457 mmol) in THF (5 mL) at 208C under vigorous stirring.
The reaction mixture was stirred for 3 h, THF was evaporated in vacuo,
and the resulting solid was extracted with toluene (15 mL). The extracts
were filtered, toluene was evaporated, and the solid residue was dissolved
in THF (2 mL). Slow condensation of hexane in the THF/complex so-
lution at 208C resulted in red crystals of 3c (0.187 g, 68%). IR (KBr,
Nujol): n˜ =3030 (w), 1615 (s), 1600 (s), 1500 (s), 1425 (s), 1375 (s), 1350
(s), 1325 (s), 1305 (s), 1280 (s), 1250 (m), 1215 (m), 1175 (m), 1070 (w),
1040 (m), 925 (w), 880 (w), 815 (s), 745 cmꢀ1 (s); elemental analysis calcd
(%) for C68H84LiN4O4Yb (1201.4): C 67.98, H 6.99, Yb 14.39; found: C
67.42, H 6.94, Yb 14.77.
In situ preparation of catalyst 3c: YbCl3 (0.034 g, 0.12 mmol) was slowly
added to a solution of Li2[(R)-C20H12N2(C6H14)] (0.091 g, 0.24 mmol) in
THF (5 mL) at 208C under vigorous stirring. The reaction mixture was
stirred for 3 h and THF was evaporated in vacuo to yield a greenish-
brown solid (3c) that was used without further purification.
Preparative enantioselective hydroamination/cyclization of 1-(amino-
methyl)-1-allylcyclohexane (4, see Table 2, entry 6): Inside a glove box, a
solution of 1-(aminomethyl)-1-allyl-cyclohexane (4, 0.122 g, 0.8 mmol) in
C6D6 (2 mL, dried over molecular sieves) was added to the complex 3c
(0.048 g, 0.04 mmol). After the reaction mixture was stirred for 6 days at
room temperature, the solvent was evaporated and the residue was distil-
lated in a Kugelrohr apparatus (b.p. 1758C, 0.1 mbar) to afford the spiro-
pyrrolidine 5 (33% yield). 1H NMR (CDCl3): d=3.08 (m, 1H), 2.71 (d,
J=11 Hz, 1H), 2.52 (d, J=11 Hz, 1H), 2.14 (brs, 1H), 1.69 (dd, J=11,
Catalytic test procedures
NMR-spectroscopy-scale intramolecular hydroaminations of 1-(amino-
methyl)-1-allylcyclohexane (4) and determination of enantiomeric excess
values were performed with catalysts 1c, 1d (entries 3 and 4, Table 1),
and 3a–c as isolated crystals (entries 2–4, Table 2).
Typical procedure: Inside a glove box, a solution of 1-(aminomethyl)-1-
allyl-cyclohexane (4, 0.02 g, 0.131 mmol) in C6D6 (0.5 mL, dried over mo-
Table 3. Crystallographic data and structure refinement details for 1c,d and 3a,c.
1c
1d
3a
3c
formula
Mr
C76H100LiN4NdO4
1284.84
C76H100LiLuN4O4
1315.57
C74H96LiN4O4.50Yb
1293.58
C68H84LiN4O4Yb
1201.42
T [K]
180
180
180
180
crystal system
space group
a [ꢂ]
b [ꢂ]
c [ꢂ]
orthorhombic
P212121
11.114(5)
25.073(5)
25.236(5)
908
orthorhombic
P212121
25.200(5)
11.074(5)
24.954(5)
908
orthorhombic
P212121
10.480(5)
17.846(5)
37.228(5)
908
orthorhombic
P212121
10.529(5)
17.796(5)
35.282(5)
908
a [8]
b [8]
908
908
908
908
g [8]
908
7032(4)
4
1.213
0.788
2716
0.60ꢄ0.50ꢄ0.25
1.807–24.186
ꢀ12ꢁhꢁ12,
ꢀ28ꢁkꢁ28,
ꢀ28ꢁlꢁ29
57599
908
6964(4)
4
1.255
1.467
2760
0.52ꢄ0.48ꢄ0.26
2.449–26.202
ꢀ31ꢁhꢁ30,
ꢀ13ꢁkꢁ13,
ꢀ30ꢁlꢁ30
69315
908
6963(4)
4
1.234
1.392
2708
0.45ꢄ0.15ꢄ0.10
1.999–24.144
ꢀ12ꢁhꢁ12,
ꢀ20ꢁkꢁ20,
ꢀ42ꢁlꢁ42
38353
908
6611(4)
4
1.207
1.461
2500
0.60ꢄ0.55ꢄ0.34
2.076–26.078
ꢀ12ꢁhꢁ12,
ꢀ20ꢁkꢁ21,
ꢀ43ꢁlꢁ43
54819
V [ꢂ3]
Z
1calcd [mgmꢀ3
]
m [mmꢀ1
F(000)
]
crystal size [mm3]
q range [8]
index ranges
reflections collected
independent reflections
max/min transmission
data/restraints/parameters
goodness-of-fit on F
11176 (Rint =0.04)
0.821/0.616
10015/0/672
1.0539
13687 (Rint =0.05)
0.683/0.478
11920/0/672
1.0723
10980 (Rint =0.06)
0.869/0.747
8294/5/656
1.1229
12544 (Rint =0.06)
0.609/0.428
9737/2/600
1.0610
final R indices (I>3s(I))
R indices (all data)
R1 =0.0317, Rw =0.0369
R1 =0.0349, Rw =0.0370
0.014(9)
1.37/ꢀ0.87
R1 =0.0317, Rw =0.0368
R1 =0.0380, Rw =0.0377
0.016(6)
1.50/ꢀ1.65
R1 =0.0342, Rw =0.0365
R1 =0.0459, Rw =0.0387
0.013(9)
1.34/ꢀ0.70
R1 =0.0443, Rw =0.0451
R1 =0.0548, Rw =0.0452
0.017(9)
2.04/ꢀ3.34
Flack parameters
largest diff. peak/hole [eꢂꢀ3
]
3460
ꢁ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 3455 – 3462

Catalytic Lanthanide Complexes
FULL PAPER
J=7 Hz, 1H), 1.32 (m, 10H), 1.07 (d, J=7 Hz, 3H), 0.93 ppm (dd, J=10,
J=9 Hz, 1H); 13C NMR (CDCl3, 208C): d=59.30, 54.42, 47.84, 44.37,
39.00, 37.62, 26.46, 24.24, 24.06, 21.71 ppm; IR (NaCl, CCl4): n˜ =3854
(w), 3747 (w), 3672 (w), 3650 (w), 3630 (w), 2928 (s), 2856 (m), 1450 (w),
Arredondo, C. L. Stern, T. J. Marks, Organometallics 1999, 18, 2568–
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Chem. 2001, 66, 4344–4347; i) J. S. Ryu, T. J. Marks, F. E. McDonald,
Org. Lett. 2001, 3, 3091–3094.
1376 cmꢀ1 (w); MS (electrospray): m/z (%): 154.2 (100) [M+H]+; [a]2D0
+28 (c=1, CHCl3); 66% enantiomeric excess.
=
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were mounted under inert perfluoropolyether at the tip of a glass fiber
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The structures were solved by direct methods (SIR92)[38] and refined by
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P
refinement cycles was w=w’[1ꢀ{DF/6s(Fo)}2]2, in which w’=1/ nArTr(x)
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fraction contribution of the inverted enantiomer to vary,[41] with the
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Crystal data and refinement parameters are shown in Table 3. The views
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This work has been supported by the CNRS and the Russian Academy
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Received: November 24, 2004
Published online: March 22, 2005
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