Synthesis of new calix[4]arene based chiral ligands bearing β-amino alcohol groups and their application in asymmetric transfer hydrogenation

Article abstract of DOI:10.1016/j.tetasy.2007.07.018

A new series of chiral calix[4]arenes bearing β-amino alcohol groups have been synthesised. The crucial steps consist of the binding of glycidyl groups on the lower rim of the calix[4]arenas, followed by their regioselective opening with amines. These lig

Full text of DOI:10.1016/j.tetasy.2007.07.018

Tetrahedron: Asymmetry 18 (2007) 1926–1933
Synthesis of new calix[4]arene based chiral ligands bearing
b-amino alcohol groups and their application in asymmetric
transfer hydrogenation
*
*
´
Adrien Quintard, Ulrich Darbost, Francis Vocanson, Stephane Pellet-Rostaing
and Marc Lemaire
ICBMS, Institut de Chimie et Biochimie Mole´culaire et Supramole´culaire, UMR-CNRS 5246, Universite´ de Lyon,
Universite´ Claude Bernard Lyon 1, CPE Lyon, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
Received 6 July 2007; accepted 20 July 2007
Available online 4 September 2007
Abstract—A new series of chiral calix[4]arenes bearing b-amino alcohol groups have been synthesised. The crucial steps consist of the
binding of glycidyl groups on the lower rim of the calix[4]arenas, followed by their regioselective opening with amines. These ligands
were successfully tested in an asymmetric transfer hydrogenation. The best results (conversion max = 97% and ee max = 87%) were
obtained using calix[4]arene mono-functionalised ligands. These results are the best ones obtained using calixarene based ligands in
asymmetric catalysis.
ꢀ 2007 Elsevier Ltd. All rights reserved.
1. Introduction
(ee = 88%) and conversions (97%) on the reduction of
acetophenone,5 and better than the Pericas et al. ether ami-
no alcohol type ligand.6
Obtaining enantiomerically pure species is one of the great-
est challenges in fine and medicinal chemistry. In this
respect, enantioselective catalysis, a method of choice often
used in the industry, fulfils this purpose.
Calixarenes are pre-organised molecules useful in ion and
metal complexation because of their orientation power
depending on their conformation and their relatively easy
functionalisation.7 These metal complexation and orienta-
tion properties have been translated to metal-catalysis by
many groups, in particular Matt et al. with surprisingly
good results in hydroformylation8 and C–C bond forming
reactions.9
Among the numerous asymmetric reactions developed by
chemists, the asymmetric transfer hydrogenation of prochi-
ral ketones has received a lot of interest over the last decade
since it occurs under mild and environmentally friendly
conditions, essential in modern synthesis.1 Research efforts
over the last decade have led to the discovery of several
efficient systems in terms of either activity or selectivity.
Among the Ir, Rh or Ru complexes, the latter are the
most common ones. The best results are obtained when
Ru(II) is associated with monotosylated diamines2 or
b-amino alcohol ligands.3 Noyori showed that the amino
alcohols cause a significant acceleration effect on the reduc-
tion.4 Among these amino alcohols, our group has
described the use of amino alcohol trityl-ether ligands,
which gave good results in terms of enantioselectivities
Although these are good results, the use of calix[4]arenes as
a platform for chiral ligands in asymmetric catalysis has
been less studied and only a few applications have been
described without giving significant results. In the first,
Matt made use of chiral diphosphine calix[4]arenes in allylic
alkylation with 67% ee and hydrogenation with 48% ee.
Despite these poor transfers of chirality, he obtained excel-
lent results in terms of conversion (100%).10 More recently,
Neri reported the synthesis of amino-acid calix[4]arene-like
ligands applied to an aldol reaction with limited enantio-
selectivities (ee max = 28%),11 while Tomaselli et al. used
a salen calixarene ligand in an asymmetric epoxidation
obtaining up to 72% ee.12
*
Corresponding authors. Tel.: +33 04 72 43 14 07; fax: +33 04 72 43 14
08; e-mail: pellet@univ-lyon1.fr
0957-4166/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2007.07.018

A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
1927
Herein, we report the synthesis of new chiral calix[4]arene
ligands bearing b-amino alcohol groups and their use in
the metal-catalyzed transfer hydrogenation of ketones,
which was compared to the reference b-amino alcohol
ligand 7 already published by our group.5 The role of a
number of amino-alcohols and the symmetry of the ligand
have been well established.
groups. This indicated that the stereochemistry of the start-
ing material was recovered in the calix[4]arenes. The same
result was postulated on the calix[4]arene bearing only one
glycidyl function.
The conformations of all compounds were established by
1H and 13C NMR spectra and compared to the literature.14
1
In the H NMR spectrum of 3a the presence of two dou-
blets (3.03 and 4.08 ppm, J = 12 Hz) and a singlet around
3.5 ppm for ArCH2Ar groups indicated a partial cone
conformation. Furthermore, the three ArCH2Ar signals
observed at 30.9, 37.6 and 37.9 ppm in the 13C NMR spec-
trum confirmed this assignment. The partial cone confor-
mation of 3a with the glycidyl group was firmly
established by NOESY experiment.
2. Results and discussion
2.1. Ligands synthesis
As the starting point of our work, we decided to protect a
determined number of phenolic groups, in order to not let
them disturb the metal coordination during the catalysis.
When using an n-propyl as the protecting group with a
tert-butyl group at the upper rim, the system was seen to
rigidify. However with H at the upper rim, it was seen to
induce flexibility. The di-functionalisation of the lower
rim was supposed to give C2 symmetric ligands, which
are famous for their strong activity in catalysis.
In the 13C NMR spectrum of compounds 3b and 3c the
presence of two ArCH2Ar signals around 38 ppm indicates
an 1,3 alternate structure. Corroborating these observa-
1
tions, the H NMR spectrum displayed a singlet for two
ArCH2Ar and an AB system for the two others. The sim-
plified NMR spectrum of those two compounds agrees
with a C2 symmetrical structure.
The methodology used for the second step was previously
described by Neri and Takata during the tetra-functional-
isation of calix[4]arenes with glycidyl groups.13 Reactions of
(R)-glycidyl tosylate in the presence of Cs2CO3 in DMF
easily gave the products 3a–c in good yields (48–83%)
(Scheme 1). Attempts to add glycidyl groups in the pres-
ence of K2CO3 or NaH with the use of (R)-epichlorhydrin
or (R)-glycidyl tosylate failed. As previously described,13
the regioselective attack on the tosylate-bearing carbon
was confirmed by the absence of diastereoisomeric peaks
in 1H NMR for the compounds bearing two glycidyl
The regioselective opening of glycidyl by amines has
already been described in the literature using numerous
methodologies.15 Surprisingly, the reactivity of the com-
pounds was weak and the opening by benzylamine failed,
using classical methods such as reaction in DMF or CHCl3
in the presence of CaCl2 as Lewis acid. These results
prompted us to realise the reaction using pure benzylamine
as solvent in the presence of CaCl2. This methodology gave
compound 4a after 11 h; this compound was easily purified
by simple precipitation in MeOH in 81% yield.
O
But
t
But
Bu
OnPr
OnPr
OnPr
HO
O
TsO
O
nPrI, DMF
O
nPr
O
O
Cs2CO3, DMF
83%
BaO
nPr
nPr
Ba(OH)2 8H2O
But
But
But
But
OH
But
HO
OH
66%
HO
3a
2a
O
O
R
OnPr
OnPr
HO
R
R
R
O
R
R
OH
nPrI
TsO
1a: R = t-Bu
1b: R = H
O
O
O
K2CO3
CH3CN
Cs2CO3, DMF
O
Prn
nPr
R
R
R
R
R
R
2b: R = t-Bu (63%)
2c: R= H ( 53%)
3b : R = t-Bu (76%)
3c : R = H (48%)
Scheme 1.

1928
A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
PhH2C
CH2Ph
PhH2C
NH
HN
NH
OH
But
OH
HO
But
But
R
R
O
Method A: Benzylamine
CaCl2
O
3a-c
O
O
Method B: Benzylamine
Micro-wave
O
O
nPr
O
O
nPr
nPr
Prn
nPr
But
R
R
Method B:
4b : R = t-Bu (76%)
4c : R = H (28%)
Method A: yield = 83%
Method B: yield = 62%
4a
Scheme 2.
Attempts to apply this methodology to the synthesis of
compounds 4b and 4c failed since the reaction gave a mix-
ture of inseparable products. Fortunately, the use of an
alternative microwave procedure on those compounds gave
a notable acceleration of the reaction without a Lewis acid
as previously described by Zhao.16 Moreover, the number
of side products was diminished which allowed an easy
purification by simple precipitation or recrystallisation.
Compounds 4a–c were obtained using this method in 28–
76% yield in 1.5 h at 200 W and 150 ꢁC (Scheme 2). The
specific opening at the least hindered position of the epox-
ide was firmly proven by the presence in all the 13C spectra
of the CH(OH) signal around 67 ppm and the two
simple purification by recrystalisation or precipitation. As
with compound 4a, compound 5 was in a partial cone
conformation.
2.2. Application of ligands to asymmetric transfer
hydrogenation
The catalytic activity of the new ligands was studied under
standard conditions on the transfer hydrogenation of ace-
tophenone (Scheme 4). A ruthenium(II) complex was pre-
pared in situ by heating the [Ru(p-cymene)Cl2]2 precursor
at 80 ꢁC with the ligand in 2-propanol for 30 min. Initial
studies were performed using an S/C = 100 ratio at room
temperature. The results are summarised in Table 1.
1
CH2NH2 signals around 54 and 51 ppm. The H and 13C
NMR indicated that the conformation of the final com-
pounds was unchanged. Indeed, the ArCH2Ar signals
retained the same characteristics after the reaction.
The reduction of acetophenone is not quantitative using
the different ligands. The loss of enantiomeric excess after
prolonged reaction times is due to the formation of the
thermodynamic products. The best results in terms of con-
version (97%) were obtained using ligand 4a. The good
conversion (97%) and enantioselectivity (87%) (entry 1)
can be compared to those obtained using reference ligand
In order to study the influence of the amino group on the
catalysis, compounds 5 and 6 were synthesised using the
same microwave methodology (Scheme 3). Good yields
(77% and 78%) were obtained after 1 h of reaction and
CyCH2
NH
But
OH
But
But
H2N
O
3a
Micro-wave
77%
O
O
nPr
O
nPr
5
nPr
But
H2N
CH2Cy
NH
Micro-wave
O
6
Ph3C
O
78%
Ph3C
O
OH
Scheme 3.

A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
1929
O
OH
Ph3C
O
OH
L*
[Ru(p-cymene)Cl2]2
iPrOH; tBuOK
NH
CH2Ph
7
Scheme 4.
Table 1. Asymmetric transfer hydrogenation of acetophenone
Entrya
Ligand
L*/Ru
S/C
Time (h)
Conversionb (%)
ee (%) enantiomer (S)b
1
2
3
4
5
6
7
8
9
4a
4a
4b
4c
4c
5
2
1
1
1
1
2
2
2
2
100
100
100
100
100
100
100
100
100
1(3)
1(3)
1(3)
1(3)
22(6 days)
1(24)
48
1(24)
1(15)
75(97)
47(67)
12(18)
14(16)
55(71)
39(60)
71
87(86)
87(87)
84(83)
87(78)
74(69)
90(88)
88
5
6
75
42(47)
71(95)
89(87)
88(87)
a Reaction conditions: acetophenone (0.5 mmol); [Ru(p-cymene)Cl2]2 (0.005 mmol); and t-BuOK (0.6 mmol) in 6 ml 2-propanol at room temperature.
b Conversion and ee were determined by chiral GC analysis.
7 (entry 9). Using an L*/Ru ratio of 1 (entry 2) caused a
small decrease in conversion. This was surprising since
the [Ru(p-cymene)Cl2]2 is known to bind to two amino-
alcohols. A hypothesis to explain this result can be that
the active species is an RuLꢀ2 complex while the remaining
Ru is deactivated by another species such as the excess
base.
tivities (ee max = 90%) and very good conversions (conver-
sion max = 97%) using mono-branched ligands 4a and 5.
Results were rather disappointing with ligands 4b and 4c
containing C2 symmetry.
The results obtained are actually the best obtained by using
calixarene based ligands in asymmetric catalysis. This
shows that those supramolecules can be efficiently used in
asymmetric synthesis. To increase the activity of our
ligands, works are currently under study in our laboratory
by diversifying the amine at the last step and modifying the
alkyl groups on the calixarenes.
The disappointing low conversions (18%) while keeping
good ee values (around 85%) obtained using C2 symmetry
ligands 4b and 4c (entries 3 and 4) might be due to a strong
steric hindrance of the complex. This results in a difficulty
of the acetophenone to gain access to the metal. The better
conversion obtained after prolonged reaction time with
ligand 4c (entry 5) corroborates this hypothesis since the
absence of tert-butyl group in this ligand results in a
decrease of the steric hindrance.
4. Experimental
All the organic and organometallic reagents used were pure
commercial products. Acetonitrile was distilled over CaH2
1
under nitrogen. H and 13C NMR spectra were recorded
As expected, ligands 5 and 6 (entries 6 and 8) caused a
small increase in the enantiomeric excess (ee max = 90%).
Unfortunately, this gain in enantiomeric excess goes with
a loss in terms of conversion. The activity after a prolonged
reaction time of the calixarene ligand 5 (entry 7) versus
trityl ether ligand 6 can be due the better resistance of
the associated Ru–5 complex to deactivation.
with a Bruker-ALS-300 (300 MHz for 1H and 75 MHz
for 13C) in CDCl3 or DMSO as solvent. The following sym-
bols are used to describe the spectrums: s: singlet, d: dou-
blet, t: triplet, q: quadruplet, m: multiplet, J: coupling
constant in hertz. Trimethylsilane was used as the internal
standard in CDCl3: 7.26 ppm in 1H NMR, 77.0 ppm in 13
NMR. DMSO: 2.50 ppm in H NMR. Mass spectra were
recorded in electrospray mode on a thermo LCQ avantage
C
1
´
´
at the centre commun de spectrometrie de masse (Univer-
sity Claude Bernard Lyon1). Polarimetric measurements
were performed on a Perkin–Elmer 241 apparatus at ambi-
ent temperature. Melting points were performed on electro-
thermal 9100 apparatus. IR spectra were performed on a
Perkin–Elmer spectrum-one FT-IR spectrometer.
3. Conclusion
To conclude, we have developed an efficient and easy syn-
thesis of new calix[4]arene b-amino alcohol ligands. This
synthesis was conducted through the binding of glycidyl
groups followed by the regioselective opening by two differ-
ent amines. The yields obtained were acceptable to good,
depending on the type of the calix[4]arenes.
4.1. Compound 2a
These ligands were studied on the asymmetric transfer
hydrogenation of acetophenone to give good enantioselec-
p-tert-Butyl-calix[4]arene
(10.5 mmol) of BaO and 1.7 g (5.39 mmol) of Ba(OH)2Æ
(1.0 g,
1.5 mmol),
1.6 g

1930
A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
1
8H2O were dissolved under nitrogen in 20 ml of DMF for
30 min. Then 4.5 ml (46 mmol) of n-PrI was added and the
mixture was stirred under nitrogen for 1 h. Then 60 ml of
H2O was added and the mixture was stirred for ten more
minutes. The aqueous layer was extracted by 3 · 30 ml
CH2Cl2. The organic layer was then washed by 30 ml of
brine and by 2 · 20 ml H2O (pH 9), dried over Na2SO4,
filtrated and evaporated. The obtained solid was dissolved
in 20 ml of ethyl acetate and filtrated. The filtrate was evap-
orated to give crude product that was purified by re-crys-
tallisation in CH2Cl2/MeOH to give 0.76 g (0.98 mmol)
of 2a14b as white crystals. Yield = 66%. TLC: eluant:
CH2Cl2/n-heptane: 1/1. Visualisation: UV + iodine.
Rf = 0.48. H NMR (300 MHz, CDCl3, 298 K): d 8.32 (s,
2H, OH); 7.05 (d, 4H, J = 7.5 Hz, H–Ar); 6.,92 (d, 4H,
J = 7.7 Hz, H–Ar); 6.75 (t, 2H, J = 7.5 Hz, H–Ar); 6.64
(t, 2H, J = 7.5 Hz, H–Ar); 4.32 (d, 4H, J = 12.8 Hz, Ar–
CH2–Ar); 3.98 (t, 4H, J = 6.2 Hz, 2O–CH2–CH2–CH3);
3.38 (d, 4H, J = 12.8 Hz, Ar–CH2–Ar); 2.04–2.11 (m, 4H,
2O–CH2–CH2–CH3); 1.32 (t, 6H, J = 7.3 Hz, 2O–CH2–
CH2–CH3).
4.4. Compound (R)-3a
Compound 2a (0.40 g, 0.5 mmol) and 0.843 g (2.60 mmol)
of Cs2CO3 were dissolved under nitrogen in 7 ml of
DMF for 30 min. Then 0.18 g (0.77 mmol) of (R)-gly-
cidyl-tosylate was added and the mixture stirred at 80 ꢁC
under nitrogen for 8 h and then stopped. Twenty millilitres
of H2O was added and the aqueous layer extracted by
3 · 20 ml CH2Cl2. The resulting organic layer was then
washed by 4 · 30 ml of H2O, dried over Na2SO4, filtrated
and evaporated. The pure product 3a (0.353 g, 0.425 mmol)
was obtained as a white powder by re-crystallisation
(CH2Cl2/MeOH). Yield = 83%. TLC: eluant: CH2Cl2/n-
heptane: 1/1. Visualisation: UV. Rf = 0.72. 1H NMR
(300 MHz, CDCl3, 298 K): d 7.20 (d, 2H, J = 6 Hz, H–
Ar); 7.09 (s, 2H, H–Ar); 7.01 (d, 1H, J = 2.4 Hz, H–Ar);
6.90 (d, 1H, J = 2.7 Hz, H–Ar); 6.58 (s, 2H, H–Ar); 4.08
(d, 2H, J = 12.0 Hz, Ar–CH2–Ar); 3.99 (dd, 1H, J = 11.5,
3.0 Hz, O–CH2–CHO); 3.37–3.78 (m, 11H, 3O–CH2–
CH2–CH3; 1O–CH2–CHO and 2Ar–CH2–Ar); 3.20 (m,
1H, O–CH2–CHO–CH2); 3.03 (d, 2H, J = 12.6 Hz, Ar–
CH2–Ar); 2.85 (t, 1H, J = 4.8 Hz, CH2–CHO–CH2–O);
2.52 (dd, 1H, J = 5.1, 2.7 Hz, CH2–CHO–CH2–O); 1.88–
1.80 (m, 4H, 2O–CH2–CH2–CH3); 1.48–1.56 (m, 2H, O–
CH2–CH2–CH3); 1.39 (s, 9H, t-Bu); 1.34 (s, 9H, t-Bu);
1.04 (s, 18H, t-Bu); 1.00 (t, 6H, J = 7.5 Hz, 2O–CH2–
CH2–CH3); 0.70 (t, 3H, J = 7.3 Hz, O–CH2–CH2–CH3).
13C NMR (75 MHz, CDCl3, 298 K): 153.8 (ArC–O–
CH2); 153.6 (ArC–O–CH2); 144.9 (ArC–t-Bu); 143.5
(ArC–t-Bu); 135.9 (ArC–CH2); 133.2 (ArC–CH2); 132.4
(ArC–CH2); 131.8 (ArC–CH2); 127.8 (ArCH); 125.6
(ArCH); 125.3 (ArCH); 76.2 (ArOCH2–CH2); 75.4 (Ar-
OCH2–CH2); 73.6 (O–CH2–CHO); 50.77 (O–CH2–CHO–
CH2); 45.1 (CH2–CHO–CH2–O); 37.9 (Ar–CH2–Ar); 37.6
(Ar–CH2–Ar); 34.1 (Ar–C(CH3)3); 33.68 (Ar–C(CH3)3);
31.7 (CH3); 30.9 (Ar–CH2–Ar); 23.7 (O–CH2–CH2–CH3);
21.6 (O–CH2–CH2–CH3); 10.7 (O–CH2–CH2–CH3); 9.4
(O–CH2–CH2–CH3). ES-MS m/z = 831.3 [M+H]+. IR
1
Rf = 0.65. H NMR (300 MHz, CDCl3, 298 K): d 7.13 (s,
2H, H–Ar); 7.04 (s, 2H, H–Ar); 6.51 (s, 4H, H–Ar); 5.58
(s, 1H, OH); 4.35 (t, 4H, J = 12.8 Hz, Ar–CH2–Ar); 3.84
(t, 2H, J = 8.4 Hz, O–CH2–CH2–CH3); 3.75 (t, 4H,
J = 6.7 Hz, 2O–CH2–CH2–CH3); 3.21 (d, 2H, J =
13.1 Hz, Ar–CH2–Ar); 3.15 (d, 2H, J = 12.6 Hz, Ar–
CH2–Ar); 2.30–2.38 (m, 2H, O–CH2–CH2–CH3); 1.84–
2.02 (m, 4H, 2O–CH2–CH2–CH3); 1.10 (t, 6H,
J = 7.3 Hz, 2O–CH2–CH2–CH3); 1.33 (s, 18H, t-Bu); 0.95
(t, 3H, J = 7.5 Hz, O–CH2–CH2–CH3); 0.82 (s, 18H, t-Bu).
4.2. Compound 2b
p-tert-Butyl-calix[4]arene (1.0 g, 1.5 mmol) and 1.3 g
(9.4 mmol) of K2CO3 were stirred under nitrogen in
50 ml of anhydrous CH3CN for 30 min. 1-Iodopropan
(0.6 ml, 6.1 mmol) was added to the obtained suspension.
The mixture was then refluxed under nitrogen for 24 h
and then stopped. The solvent was evaporated, and the
residue dissolved in 60 ml of CH2Cl2 and 40 ml of H2O.
After separation, the organic layer was washed by a
20 ml solution of HCl (1 M), then by 3 · 30 ml H2O. The
organic layer was then dried over Na2SO4, filtrated and
evaporated. The crude product was purified by re-crystal-
lisation (CH2Cl2/MeOH) to give 0.69 g (0.95 mmol) of 2b14b
as white crystals. Yield = 63%. TLC: eluant: CH2Cl2/n-
heptane: 1/1. Visualisation: UV + iodine. Rf = 0.52. 1H
NMR (300 MHz, CDCl3, 298 K): d 7.89 (s, 2H, OH);
7.03 (s, 4H, H–Ar); 6.85 (s, 4H, H–Ar); 4.30 (d, 4H,
J = 12.8 Hz, Ar–CH2–Ar); 3.94 (t, 4H, J = 6.4 Hz, 2O–
CH2–CH2–CH3); 3.30 (d, 4H, J = 12.8 Hz, Ar–CH2–Ar);
2.00–2.06 (m, 4H, 2O–CH2–CH2–CH3); 1.28 (s + t, 24H,
2O–CH2–CH2–CH3 + t-Bu); 1.01 (s, 18H, t-Bu).
4.3. Compound 2c
(solid): m = 2958, 2873, 1474, 1196, 1120, 1044, 1012, 869.
½aꢁD ¼ ꢂ2:2 (c 1.135, CHCl3), mp = 279–283 ꢁC.
20
Calix[4]arene (1 g, 2.3 mmol) and 1.3 g (9.4 mmol) of
K2CO3 were stirred under nitrogen in 50 ml of anhydrous
CH3CN for 30 min. 1-Iodopropane (0.9 ml, 9.4 mmol)
was added to the obtained suspension. The mixture was
then refluxed under nitrogen for 18 h and then stopped.
The solvent was evaporated, and the residue dissolved in
45 ml of CH2Cl2. The aqueous layer was then extracted
by 2 · 40 ml CH2Cl2. The resulting organic extract was
washed by 2 · 45 ml H2O, dried over Na2SO4, filtrated
and then evaporated. The crude product was purified
by re-crystallisation (CH2Cl2/MeOH) to give 0.620 g
(1.2 mmol) of 2c17 as white crystals. Yield = 52%. TLC:
eluant: CH2Cl2/n-heptane: 1/1. Visualisation: UV + iodine.
4.5. Compound (R,R)-3b
Compound 2b (0.497 g, 0.68 mmol) and 1.78 g (5.43 mmol)
of Cs2CO3 were dissolved under nitrogen in 8 ml of DMF
for 30 min. Then 0.464 g (2.04 mmol) of (R)-glycidyl-tosyl-
ate was added and the mixture stirred at 80 ꢁC under nitro-
gen for 13.5 h and then stopped. Then 20 ml of H2O was
added and the aqueous layer extracted by 3 · 25 ml
CH2Cl2. The resulting organic layer was then washed by
2 · 30 ml of H2O, dried over Na2SO4, filtrated and evapo-
rated. The pure product 3b (0.436 g, 0.515 mmol) was
obtained as a white powder by re-crystallisation (CH2Cl2/

A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
1931
MeOH). Yield = 76%. TLC: eluant: CH2Cl2/n-heptane: 8/
2. Visualisation: UV, Rf = 0.54, 1H NMR (300 MHz,
CDCl3, 298 K): d 7.11 (d, 2H, J = 2.4 Hz, H–Ar); 7.01
(d, 2H, J = 2.7 Hz, H–Ar); 6.98 (s, 4H, H–Ar); 3.87–3.71
(s + AB, 8H, 4Ar–CH2–Ar); 3.54 (dd, 2H, J = 11.2,
3.3 Hz, O–CH2–CHO); 3.38 (t, 4H, J = 7.5 Hz, 2O–CH2–
CH2–CH3); 3.23 (dd, 2H, J = 11.3, 5.2 Hz, O–CH2–
CHO); 2.79 (m, 2H, 2O–CH2–CHO–CH2); 2.57 (t, 2H,
J = 5.1 Hz, CH2–CHO–CH2–O); 2.30 (dd, 2H, J = 5.4,
2.7 Hz, CH2–CHO–CH2–O); 1.38–1.15 (m, 43H, 2O–
CH2–CH2–CH3, 4t-Bu and 1O–CH2–CH2–CH3); 0.73 (t,
3H, J = 7.8 Hz, O–CH2–CH2–CH3). 13C NMR (75 MHz,
CDCl3, 298 K): 154.7 (ArC–O–CH2); 154.0 (ArC–O–
CH2); 143.9 (ArC–t-Bu); 143.8 (ArC–t-Bu); 133.3 (ArC–
CH2); 133.0 (ArC–CH2); 126.4 (ArCH); 72.3 (O–CH2–
CH2–CH3); 71.4 (O–CH2–CHO); 50.7 (O–CH2–CHO–
CH2); 44.6 (CH2–CHO–CH2); 38.8 (Ar–CH2–Ar); 38.6
(Ar–CH2–Ar); 33.9 (Ar–C(CH3)3); 31.4 (CH3); 22.4
(O–CH2–CH2–CH3); 10.0 (O–CH2–CH2–CH3). ES-MS
ing organic mixture was then washed twice with 10 ml
H2O, dried over Na2SO4, filtrated and evaporated. The
pure product 4a (0.204 g, 0.217 mmol) was obtained as a
white powder by precipitation in the residual benzylamine.
Yield = 81%. TLC: eluant: n-heptane/ethyl acetate: 8/2.
1
Visualisation: UV, Rf = 0.3, H NMR (300 MHz, CDCl3,
298 K): d 7.30–7.35 (m, 5H, H–Ar); 7.21 (s, 2H, H–Ar);
7.08 (s, 2H, H–Ar); 6.92 (d, 1H, J = 3.0 Hz, H–Ar); 6.87
(d, 1H, J = 3.0 Hz, H–Ar); 6.63 (dd, 2H, J = 6.7, 1.0 Hz,
H–Ar); 4.14–4.21 (m, 1H, O–CH2–CH(OH)–CH2); 4.10
(d, 2H, J = 12.3 Hz, Ar–CH2–Ar); 3.84–3.91 (AB, 2H,
J = 13.2 Hz, O–CH2–CH(OH)); 3.43–3.76 (m, 12H, 3O–
CH2–CH2–CH3, 2Ar–CH2–Ar and NH–CH2–Ar); 3.04
(d, 2H, J = 12.6 Hz, Ar–CH2–Ar); 2.75 (dd, 1H, J = 8.2,
3.9 Hz CH2NHCH2Ar); 2.66 (dd, 1H, J = 9.6, 6.9 Hz
CH2NHCH2Ar); 1.81–1.85 (m, 4H, 2O–CH2–CH2–CH3);
1.51–1.59 (m, 2H, O–CH2–CH2–CH3); 1.39 (s, 9H, t-Bu);
1.33 (s, 9H, t-Bu); 0.95–1.08 (m, 24H, 2t-Bu and 2O–
CH2–CH2–CH3); 0.71 (t, 3H, J = 7.5 Hz, O–CH2–CH2–
CH3). 13C NMR (75 MHz, CDCl3, 298 K): 154.7 (ArC–
O–CH2); 153.8 (ArC–O–CH2); 145.0 (ArC–t-Bu); 143.8
(ArC–t-Bu); 135.7 (ArC–CH2); 132.6 (ArC–CH2); 132.4
(ArC–CH2); 128.5 (ArCH); 127.2 (ArCH); 76.2
(ArOCH2–CH2); 75.4 (ArOCH2–CH2); 74.7 (O–CH2–
CH(OH)); 69.1 (O–CH2–CH(OH)–CH2); 53.5 (NH–CH2–
Ar); 50.9 (CH2–CH(OH)–CH2–O); 37.8 (Ar–CH2–Ar);
37.6 (Ar–CH2–Ar); 34.0 (Ar–C(CH3)3); 31.4 (CH3); 30.8
(Ar–CH2–Ar); 23.6 (O–CH2–CH2–CH3); 21.7 (O–CH2–
CH2–CH3); 10.6 (O–CH2–CH2–CH3); 9.4 (O–CH2–CH2–
CH3). ES-MS m/z = 938.7 [M+H]+, IR (solid) m = 2958,
m/z = 845.3 [M+H]+, IR (solid): m = 2961, 2870, 1473,
20
1454, 1361, 1197, 1117, 1029, 1012, 909, 869. ½aꢁD ¼ ꢂ6:2
(c 0.975, CHCl3), decomposition if T >305 ꢁC.
4.6. Compound (R,R)-3c
Compound 2c (0.40 g, 0.80 mmol) and 2.10 g (6.4 mmol) of
Cs2CO3 were dissolved under nitrogen in 8 ml of DMF for
30 min. (R)-Glycidyl-tosylate (0.500 g, 2.18 mmol) was
then added and the mixture stirred at 80 ꢁC under nitrogen
for 11 h and then stopped. Twenty milliliters of H2O were
added and the aqueous layer extracted by 3 · 20 ml
CH2Cl2. The resulting organic layer was then washed by
3 · 30 ml of H2O (pH 6), dried over Na2SO4, filtrated
and evaporated. The pure product 3c (0.238 g, 0.383 mmol)
was obtained as a yellowish-white powder by re-crystallisa-
tion (CH2Cl2/MeOH). Yield = 48%. TLC: eluant: CH2Cl2/
n-heptane: 8/2. Visualisation: UV, Rf = 0.12, 1H NMR
(300 MHz, CDCl3, 298 K): d 7.10 (t, 4H, J = 5.6 Hz, H–
Ar); 7.02 (d, 4H, J = 7.3 Hz, H–Ar); 6.73 (t, 4H,
J = 5.6 Hz, H–Ar); 3.82 (dd, 2H, J = 6.7, 2.4 Hz, O–
CH2–CHO); 3.46–3.65 (m, 14H, 3O–CH2 and 4Ar–CH2–
Ar); 3.12 (m, 2H, O–CH2–CHO–CH2); 2.79 (t, 2H,
J = 4.1 Hz, CH2–CHO–CH2–O); 2.55 (dd, 2H, J = 2.8,
2.6 Hz, CH2–CHO–CH2–O); 1.68–1.56 (m, 4H, O–CH2–
CH2–CH3); 0.90 (t, 6H, J = 7.4 Hz, O–CH2–CH2–CH3).
13C NMR (75 MHz, CDCl3, 298 K): 156.7 (ArC–O–
CH2); 156.6 (ArC–O–CH2); 133.9 (ArC–CH2); 130.1
(ArCH); 121.8 (ArCH); 121.7 (ArCH); 73.4 (O–CH2–
CH2–CH3); 71.7 (O–CH2–CHO); 50.9 (O–CH2–CHO–
CH2); 44.7 (CH2–CHO–CH3); 38.7 (Ar–CH2–Ar); 38.5
(Ar–CH2–Ar); 22.5 (O–CH2–CH2–CH3); 10.1 (O–CH2–
2873, 1474, 1197, 1119, 1045, 1011, 868, 733, 697.
20
½aꢁD ¼ ꢂ2:5 (c 0.91, CHCl3), mp = 238–239 ꢁC.
4.8. Compound (R,R)-4b
Compound 3b (0.102 g, 0.120 mmol) was dissolved in 1 ml
(9.2 mmol) of benzylamine in a micro-wave vial. The
mixture was heated in the microwave for 1.5 h at 150 ꢁC;
200 W. Benzylamine was then reduced to third and the
pure product 4b (0.036 g, 0.033 mmol) was obtained as
white crystals through crystallisation by adding MeOH.
Yield = 28%. 1H NMR (300 MHz, CDCl3, 298 K): d
7.21–7.30 (m, 10H, H–Ar); 7.03 (d, 2H, J = 2.1 Hz, H–
Ar); 6.97 (m, 6H, H–Ar); 3.78–3.92 (m, 8H, 4Ar–CH2–
Ar); 3.70 (s, 4H, 2NH–CH2–Ar); 3.57 (t, 2H, J = 8.7 Hz,
1O–CH2–CH(OH)); 3.44 (m, 2H, 2O–CH2–CH(OH)–
CH2); 3.37 (dd, 2H, J = 5.4, 2.4 Hz, O–CH2–CH(OH));
3.25 (t, 4H, J = 7.8 Hz, 2O–CH2–CH2–CH3); 2.42 (AB,
4H, J = 3.9 Hz, 2CH2NHCH2Ar); 1.37 (s, 2H, t-Bu);
1.26–1.27 (2s, 34H, t-Bu); 0.83 (m, 4H, 2O–CH2–CH2–
CH3); 0.58 (t, 6H, J = 7.8 Hz, 2O–CH2–CH2–CH3), 13C
NMR (300 MHz, CDCl3, 298 K): 154.7 (ArC–O–CH2);
154.4 (ArC–O–CH2); 149.8 (ArC–t-Bu); 132.7 (ArC–
CH2); 132.2 (ArC–CH2); 128.8 (ArCH); 12.9 (ArCH);
125.87 (ArCH); 73.4 (O–CH2–CH2–CH3); 71.9 (O–CH2–
CH(OH)); 68.2 (O–CH2–CH(OH)–CH2); 53.3 (NH–CH2–
Ar); 51.0 (CH(OH)–CH2–NH); 39.2 (Ar–CH2–Ar); 39.0
(Ar–CH2–Ar); 33.9 (Ar–C(CH3)3); 31.5 (CH3); 21.9 (O–
CH2–CH2–CH3); 9.8 (O–CH2–CH2–CH3), ES-MS m/z =
1059.6 [M+H]+, IR solid m = 3513, 2959, 2901, 2870,
1760, 1481, 1361, 1208, 1122, 1015, 867, 744, 697.
CH2–CH3). ES-MS m/z = 621.2 [M+H]+, IR (solid):
20
m = 2933, 1449, 1245, 1188, 1008, 759. ½aꢁD ¼ ꢂ8:5 (c
1.015, CHCl3), mp = 217–221 ꢁC.
4.7. Compound (R)-4a
Compound 3a (0.196 g, 0.267 mmol) and 0.123 g
(1.06 mmol) of CaCl2 were stirred at 80 ꢁC in 2 ml
(18.4 mmol) of benzylamine. The reaction was stopped
after 11 h by adding 10 ml of a solution of aqueous NH4Cl,
followed by extraction by 3 · 20 ml of CH2Cl2, The result-

1932
20
A. Quintard et al. / Tetrahedron: Asymmetry 18 (2007) 1926–1933
½aꢁD ¼ þ3:4 (c 0.75, CHCl3), mp decomposition if T
(Ar–C(CH3)3); 31.5 (CH3); 31.3 (Ar–CH2–Ar); 31.2 (CH–
2(CH2)); 26.6 (CH–2(CH2)) 25.9 (CH2–2(CH2)); 23.6
(O–CH2–CH2–CH3); 21.7 (O–CH2–CH2–CH3); 10.7 (O–
CH2–CH2–CH3); 9.4 (O–CH2–CH2–CH3). ES-MS m/z =
>224 ꢁC.
4.9. Compound (R,R)-4c
944.8 [M+H]+, IR (solid) m = 3548, 2952, 2926, 2864,
20
Compound 3c (0.105 g, 0.169 mmol) was dissolved in 1 ml
(9.2 mmol) of benzylamine in a micro-wave vial. The mix-
ture was heated in the microwave for 2 h at 150 ꢁC; 200 W.
Benzylamine was then reduced to third, 40 ml of CH2Cl2
added and the organic layer was washed by a 30 ml solu-
tion of HCl (1 M), then by 40 ml of H2O, dried over
Na2SO4, filtrated and evaporated. The product 4c
(0.103 g, 0.123 mmol) was precipitated from the obtained
oil by adding ether to give a yellow powder. Yield = 73%.
1H NMR (300 MHz, CDCl3, 298 K): d 7.54–7.66 (m, 5H,
H–Ar); 7.37–7.41 (m, 5H, H–Ar); 6.78–7.03 (m, 12H, H–
Ar); 4.27 (s, 4H, 2Ar–CH2–Ar); 3.67–3.93 (m, 10H, 2O–
CH2–CH(OH)–CH2; 2Ar–CH2–Ar and 2NH–CH2–Ar);
3.28 (t, 4H, J = 8.1 Hz, O–CH2–CH2–CH3); 3.19 (t, 4H,
1474, 1197, 1120, 1044, 1011, 871. ½aꢁD ¼ þ1:4 (c 0.93,
CHCl3), mp = 226–227 ꢁC.
4.11. Compound (R)-6
(R)-Glycidyl tritylether (0.198 g, 0.62 mmol) was dissolved
in 1 ml (7.7 mmol) of cyclohexanemethylamine in a micro-
wave vial. The mixture was heated in the microwave for 1 h
at 150 ꢁC; 200 W. 40 ml of CH2Cl2 was added and the
organic layer washed by a 20 ml solution of HCl 1 N, then
by 2 · 20 ml H2O, dried over Na2SO4, filtrated and evapo-
rated. The pure product 6 (0.205 g, 0.477 mmol) was
obtained as a white powder by recrystallisation (CH2Cl2/
1
ethyl acetate). Yield = 77%. H NMR (300 MHz, DMSO,
J = 7.5 Hz,
O–CH2–CH(OH));
2.42
(m,
4H,
298 K): d 8.66 (s, 1H, NH); 7.54–7.66 (m, 5H, H–Ar);
7.27–7.41 (m, 15H, H–Ar); 5.70 (s, 1H, –OH); 4.10 (m,
1H, O–CH2–CH(OH)–CH2); 3.02–3.11 (m, 2H, O–CH2–
CH(OH)); 3.78–2.89 (m, 4H, 2NH–CH2); 1.61–1.81 (m,
6H, CH2 of cyclohexane); 1.10–1.27 (m, 3H, CH2 and
CH of cyclohexane); 0.87–0.98 (m, 2H, CH2 of cyclohex-
ane). 13C NMR (75 MHz, CDCl3, 298 K): 146.8 (ArC);
129.6 (ArCH); 128.6 (ArCH); 127.9 (ArCH); 127.2
(ArCH); 82.0 (Ph3–C–O); 67.4 (O–CH2–CH(OH)–CH2);
64.1 (O–CH2–CH(OH)); 54.6 (NH–CH2–Ar); 51.3 (CH2–
CH(OH)–CH2–O); 34.4 (CH2–CH–2(CH2)); 30.6 (CH–
2(CH2)); 25.8 (CH–2(CH2)); 25.3 (CH2–2(CH2)). ES-MS
CH2NHCH2Ar); 0.94 (m, 4H, O–CH2–CH2–CH3); 0.60
(t, 6H, J = 7.2 Hz, 2O–CH2–CH2–CH3), 13C NMR
(300 MHz, CDCl3, 298 K): 157.2 (ArC–O–CH2); 155.7
(ArC–O–CH2); 134.2 (ArC–CH2); 133.9 (ArC–CH2);
130.8 (ArCH); 130.2 (ArCH); 129.6 (ArCH); 128.6
(ArCH); 124.0 (ArCH); 123.4 (ArCH); 72.4 (O–CH2–
CH2–CH3); 71.5 (O–CH2–CH(OH)); 65.8 (O–CH2–
CH(OH)–CH2); 51.4 (NH–CH2–Ar); 48.3 (CH(OH)–
CH2–NH); 38.5 (Ar–CH2–Ar); 38.3 (Ar–CH2–Ar); 22.4
(O–CH2–CH2–CH3); 10.2 (O–CH2–CH2–CH3), ES-MS
m/z = 835.3 [M+H]+, IR (solid) m = 3291, 3022, 2956,
20
m/z = 430.0 [M+H]+, IR (solid) m = 3301, 2919, 2847,
2926, 2873, 1455, 1205, 1092, 1012, 751, 697. ½aꢁD
¼
20
ꢂ36:3 (c 0.885, CHCl3), mp decomposition if T >217 ꢁC.
4.10. Compound (R)-5
2760, 1492, 1445, 1096, 1072, 754, 699. ½aꢁD ¼ þ10:6 (c 1,
CHCl3), mp = 196–197 ꢁC.
4.12. General procedure for reduction of acetophenone
Compound 3a (0.122 g, 0.146 mmol) was dissolved in 1 ml
(7.7 mmol) of cyclohexanemethylamine in a micro-wave
vial. The mixture was heated in the microwave for 1 h at
150 ꢁC; 200 W. The pure product 5 (0.108 g, 0.114 mmol)
was obtained as white crystals through precipitation by
adding MeOH. Yield = 78%. TLC: eluant: n-heptane/ethyl
acetate: 8/2. Visualisation: UV, Rf = 0.16, 1H NMR
(300 MHz, CDCl3, 298 K): d 7.21 (s, 2H, H–Ar); 7.09 (s,
2H, H–Ar); 6.96 (s, 1H, H–Ar); 6.86 (s, 1H, H–Ar); 6.62
(d, 2H, J = 5.8, 2.1 Hz, H–Ar); 4.10 (d, 2H, J = 12.1 Hz,
Ar–CH2–Ar + covered O–CH2–CH(OH)–CH2); 3.43–3.74
(m, 12H, O–CH2–CH(OH), 3O–CH2–CH2–CH3 and
2Ar–CH2–Ar); 3.04 (d, 2H, J = 12.3 Hz, Ar–CH2–Ar);
2.45–2.68 (m, 4H, CH2NHCH2Ar and NH–CH2–Ar);
1.20–1.86 (m, 35H, 3O–CH2–CH2–CH3, 2t-Bu and cyclo-
hexane protons); 1.04 (s, 18H, 2t-Bu); 1.00 (t, 6H,
J = 6 Hz, 2O–CH2–CH2–CH3); 0.71 (t, 3H, J = 7.2 Hz,
O–CH2–CH2–CH3). 13C NMR (75 MHz, CDCl3, 298 K):
154.7 (ArC–O–CH2); 153.8 (ArC–O–CH2); 145.0 (ArC–t-
Bu); 143.8 (ArC–t-Bu); 135.7 (ArC–CH2); 132.6 (ArC–
CH2); 132.1 (ArC–CH2); 128.0 (ArCH); 125.9 (ArCH);
125.7 (ArCH); 125.3 (ArCH); 76.2 (ArOCH2–CH2);
75.4 (ArOCH2–CH2); 74.9 (O–CH2–CH(OH)); 68.8
(O–CH2–CH(OH)–CH2); 56.3 (NH–CH2–Ar); 51.7 (CH2–
CH(OH)–CH2–O); 37.8 (CH2–CH–2(CH2)); 37.7 (Ar–
CH2–Ar); 37.6 (Ar–CH2–Ar); 34.0 (Ar–C(CH3)3); 33.7
`
[Ru(p-cymene)Cl2]2 (3.1 mg, 0.005 mmol) and an appropri-
ate amount of chiral ligand were dissolved in 2 ml of 2-pro-
panol and stirred at 80 ꢁC under argon for 30 min. The
solution turned to red. The mixture is cooled down to room
temperature and t-BuOK (0.60 mg, 0.600 mmol) in 3 ml of
2-propanol added followed by acetophenone (60 mg,
0.500 mmol) in 1 ml of 2-propanol. The solution was stir-
red under argon for the time indicated. The reaction is
monitored by chiral GC.
GC: Shimadzu GC-14A. Column: J&W Scientific Inc, Cly-
codex B, Integrator: Shimadzu C-R6A Chromatopac,
Program: initial temperature: 50 ꢁC, initial time: 5 min,
program rate: 1 ꢁC/min, final temperature: 200 ꢁC, final
time: 1 min, retention time: 21.9 min for acetophenone,
30.0 min for (R)-phenylethanol and 31.0 min for (S)-
phenylethanol.
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