Ruthenium-catalyzed asymmetric epoxidation of olefins using H 2O2, part I: Synthesis of new chiral N,N,N,-tridentate pybox and pyboxazine ligands and their ruthenium complexes

Article abstract of DOI:10.1002/chem.200501261

The synthesis of chiral tridentate N,N,N-pyridine-2.6-bisoxazolines 3 (pyhox ligands) and N,N,N-pyridine-2.6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful tool-box for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure α- or β-amino al cohols with dimethyl pyridine-2,6-dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully char acterized by spectroscopic means. Four of these ruthenium complexes have been characterized by X-ray crystallography. For the first time the molecular structure of a pyboxazine complex (2,6-bis-[(4S)-4-phenyl-5,6- dihydro-4H-[1,3]oxazinyl]pyridine)(pyridine-2,6-dicarboxylate)ruthenium (S)-2aa, is presented.

Full text of DOI:10.1002/chem.200501261

FULL PAPER
Chem. Eur. J. 2006, 12, 1855 – 1874
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1855

DOI: 10.1002/chem.200501261
Ruthenium-Catalyzed Asymmetric Epoxidation of Olefins Using H2O2,
Part I: Synthesis of New Chiral N,N,N-Tridentate Pybox and
Pyboxazine Ligands and Their Ruthenium Complexes
Man Kin Tse,[a] Santosh Bhor,[a] Markus Klawonn,[a] Gopinathan Anilkumar,[a]
Haijun Jiao,[a] Christian Dçbler,[a] Anke Spannenberg,[a] Wolfgang Mägerlein,[b]
Herbert Hugl,[b] and Matthias Beller*[a]
Abstract: The synthesis of chiral tri-
dentate N,N,N-pyridine-2,6-bisoxazo-
lines 3 (pybox ligands) and N,N,N-pyri-
dine-2,6-bisoxazines 4 (pyboxazine li-
gands) is described in detail. These
novel ligands constitute a useful tool-
box for the applicationinasymmetric
catalysis. Compounds 3 and 4 are con-
veniently prepared by cyclization of
enantiomerically pure a- or b-amino al-
cohols with dimethyl pyridine-2,6-dicar-
boximidate. The corresponding ruthe-
nium complexes are efficient asymmet-
ric epoxidationcatalysts and have been
prepared ingood yield and fully char-
acterized by spectroscopic means. Four
of these ruthenium complexes have
beencharacterized by X-ray crystallog-
raphy. For the first time the molecular
structure of a pyboxazine complex {2,6-
bis-[(4S)-4-phenyl-5,6-dihydro-4H-
[1,3]oxazinyl]pyridine}(pyridine-2,6-di-
carboxylate)ruthenium (S)-2aa, is pre-
sented.
Keywords:
epoxidation
·
homogeneous catalysis · N ligands ·
olefins · ruthenium
Introduction
substrate needs its own optimized catalyst and ligand
system. Hence, it is a significant advantage of a given ligand
class if it allows for easy steric and electronic tuning of the
structure.
Transition-metal-catalyzed asymmetric reactions provide us
with efficient and direct methods for the synthesis of enan-
tiomerically pure compounds.[1] For the development of new
asymmetric reactions as well as the optimization of known
processes the design and synthesis of a suitable chiral con-
Some time ago we started a project onthe development
of efficient oxidation methods for olefins,[10] especially the
[12]
use of ruthenium catalysts[11,15e] for olefinepoxidation.
In
troller ligand is the crucial step.[2] Inthe last two decades
this regard, we became interested in pyridine-2,6-bisoxazo-
lines (so-called pybox ligands).[13] The versatile coordination
ability of the pybox structure, from early to late transition
metals as well as lanthanides, and its rigidity as coplanar
N,N,N-tridentate ligands makes them excellent chiral con-
troller ligands for a variety of asymmetric reactions.[22a] Ac-
cordingly transition-metal complexes of pybox ligands show
a wide range of reactivity pattern including reduction,[14] oxi-
dation,[15] aldol-type reactions,[16] Diels–Alder reactions,[17]
cyclopropanation,[18] aziridation,[19] cross-coupling reac-
tions,[20] polymerization,[21] and others.[18c,22]
At the start of our investigations we were especially at-
tracted by Nishiyamaꢁs catalyst [Ru-(pyridinebisoxazoline)-
(pyridine-dicarboxylate)] (1) for asymmetric epoxidation
(Scheme 1).[15e] Unfortunately, this system had several draw-
backs such as low reactivity (96 h were needed for full con-
version) and the limited scope of the catalyst (epoxidation
was only demonstrated for trans-stilbene).
[3]
certaintypes of ligadns
for asymmetric catalysis have
evolved such as binaphthol derivatives,[4] salens,[5] bisoxazo-
lines,[6] phosphinooxazolines,[7] tartrate derivatives,[8] and cin-
chona alkaloids,[9] which allow for a more general use in var-
ious asymmetric reactions. Unfortunately, small structural
variations within substrate molecules may dramatically
change the outcome of the catalytic reaction. Basically, each
[a] Dr. M. K. Tse, Dr. S. Bhor, Dr. M. Klawonn, Dr. G. Anilkumar,
Dr. H. Jiao, Dr. C. Dçbler, Dr. A. Spannenberg, Prof. Dr. M. Beller
Leibniz-Institut für Organische Katalyse
ander Universität Rostock e.V.
Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
Fax : (+49)381-1281-5000
E-mail: matthias.beller@ifok-rostock.de
[b] Dr. W. Mägerlein, Prof. Dr. H. Hugl
Lanxess Deutschland GmbH
BU Fine Chemicals, 51369 Leverkusen (Germany)
1856
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Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
for asymmetric epoxidation. Therefore as a starting point
for our synthetic work, we analyzed the possibility of modi-
fications of catalyst 1 with respect to the availability of start-
ing materials, literature knowledge, and the ease of synthesis
(Scheme 3).
Scheme 1. Nishiyamaꢁs epoxidationof trans-stilbene.
By carefully studying the reaction we discovered that ad-
ditionof a defined amount of water to the reactionmixture
leads to a faster and more general epoxidation proce-
dure.[12e] More recently, we developed enantioselective epox-
idationprotocols with these catalysts applying alkyl perox-
ides[12d] and hydrogen peroxide (Scheme 2).[12a–b] Animpor-
tant factor for the success was the use of a systematic varied
toolbox of pybox ligands, which also led to the development
of a novel class of ligands, the so-called pyboxazines.
Scheme 3. Possible positions for modification of 1.
It is clear that from the abundant naturally occurring
amino acids, the corresponding 2-aminoethan-1-ol deriva-
tives are in general obtained without much problem. Hence,
the synthesis of the five-membered oxazoline becomes
straightforward. Evenif the substituted a-amino acid is not
available for the synthesis of
the corresponding chiral amino
alcohol, asymmetric aminohy-
[24]
droxylationof olefins
or en-
zymatic resolutionof the race-
mic amino acids[25] provide
practical alternative pathways.
Incotnrast to five-membered
oxazolines, six-membered oxa-
zines have been only sporadi-
cally studied due to the more
difficult access of the corre-
sponding 3-aminopropan-1-ol
Scheme 2. Epoxidation of olefins catalyzed by [Ru(pyboxazine)(pydic)] (R)-2ca.[12b]
derivatives.[26]
resolutionby co-crystallization
Nevertheless,
Inthis paper we report a full account of the strategy of
the synthesis of these novel pybox and pyboxazine ligand li-
brary and their full characterization. In addition, their ruthe-
nium complexes have also been synthesized and fully char-
acterized. The comparisonof the structures of pybox and
pyboxazine are discussed in detail with the aid of their
ruthenium complexes.[23]
of b-amino acid esters with enantiomerically pure organic
acids,[26c,27] enzymatic resolution of b-amino acids[28] or direct
asymmetric Mannich reaction[29] make chiral nonracemic 3-
substituted 3-aminopropan-1-ols accessible. Some of the b-
amino acids are even commercially available.[30] Inaddition
to variations of the oxazoline moiety, we were also interest-
ed inthe electronic effects to the catalyst. Therefore, we de-
cided to synthesize para-substituted pybox[14b,31] and 2,6-pyri-
dinedicarboxylic acid (H2pydic)[32] derivatives as well.
Results and Discussion
The pybox ligands 3 used inthis study are shownhere.
They cover a broad range of substitution patterns, including
4-, 5-, cis-4,5-di-, trans-4,5-di- and 4,5,5-tri-substitution on
the oxazoline ring, para-substitution on the pyridine ring,
ortho- or meta-substitutiononthe phenyl ring at the 4-posi-
tion of the oxazoline, and a wide range of functional groups,
such as halogen, alcohol, amine, silyl ether, ester, aryl- and
alkyl-groups. Except for 3a, 3n and 3p, which are commer-
In order to apply (pybox)(pyridinedicarboxylate)ruthenium
complexes in a more general sense and to find the optimal
catalyst for a respective transformation, we were interested
in systematic variations of steric and electronic parameters
of the corresponding ligands. The obtained results should
contribute to a more rational design of improved catalysts
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1857

M. Beller et al.
cially available,[33] all other pybox ligands were prepared in
a straightforward manner.
hydroxyamide 6b with diethylaminosulfur trifluoride
(DAST) indichloromethane at ꢀ208C gave the 4-chloropy-
box 3b in 50% yield (Scheme 4). The corresponding 4-(di-
methylamino)pybox 3c was easily obtained in 73% yield by
the substitutionreactionof 3b with aqueous dimethylamine
(40 wt%) inTHF at 40 8C. Inaddition, we were able to per-
form the synthesis of 4-phenyl- and 4-naphthyl-substituted
ligands 3d,e by palladium-catalyzed Suzuki reactions.[32b] Ini-
tial efforts of the direct synthesis from 4-chloropybox 3b
were unsuccessful. This can be explained by palladium deac-
tivation due to its strong coordination with pybox. Therefore
we changed our strategy to first perform the Suzuki reaction
followed by cyclization. To our delight treatment of the
bishydroxyamide 6b with phenyl boronic acid or naphthyl
The synthesis of the new ligands 3b–e started from com-
mercially available chelidamic acid 5b, which was converted
into the bis(hydroxyamide)pyridine 6b in90% yield intwo
steps with thionylchloride and (S)-phenylglycinol. For ring
closure we initially followed the conventional method,
which was developed mainly by Nishiyama and others,[22a] to
convert the hydroxyl group to the chloride followed by in-
tramolecular nucleophilic substitution. However, cyclization
of the bis(chloroamide)pyridine 7 with NaH inTHF did not
yield the desired pybox 3b.
Therefore, we turned our interest to a recently developed
method of direct cyclizationof 6b.[42] Treatment of the bis-
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Homogeneous Catalysis
FULL PAPER
Ingeenral, there are four
commonsytnhetic routes for
the preparationof pybox li-
gands 3 (Scheme 6). After the
preparationof this toolbox of
ligands, we found that the imi-
date method (route D) is the
most convenient one. The
short synthetic route, easy han-
dling of reagents, mild reaction
conditions and no heavy metal
waste makes route D most ad-
vantageous. However, route C,
which uses DAST as the key
reagent for the cyclization, is
preferable for the preparation
of 4-substituted pyridine deriv-
atives.
Next, we turned our interest
to the synthesis of the pyboxa-
zine ligands 4. Due to above
mentioned advantages all py-
boxazine ligands were pre-
pared according to route D.
The availability of the enantio-
pure 3-aminopropan-1-ols is an
important pre-requisite for the
synthesis of novel pyboxazine
ligands 4. We successfully ap-
Scheme 4. a) SOCl2, DMF, reflux, 2 d; b) (S)-phenyl glycinol, CHCl3, NEt3, 08C to RT, 18 h, 90% in2 steps;
c) SOCl2, reflux, 9 h; d) NaH, THF, RT; e) 3 equiv DAST, CH2Cl2, ꢀ208C, 30 min, 3b 50%, 3d 55%, 3e 40%;
f) 40 wt% aqueous dimethylamine, THF, 408C, 24 h, 73%; g) aryl boronic acid, 5 mol% Pd(OAc)2, 10 mol%
P(o-Tolyl)3, 3.5 equiv CsF inDME at 100 8C for 18 h, 6d 64%, 6e 75%.
plied resolutionof
b-amino
acid derivatives by co-crystalli-
boronic acid using 5 mol% Pd(OAc)2, 10 mol% P(o-Tolyl)3,
3.5 equivalents CsF in DME (DME = 1,2-dimethoxyethane)
at 1008C for 18 h gave the corresponding 4-substituted bis-
hydroxyamide 6d and 6e in61 and 75% yield, respectively.
4-Phenyl- and 4-naphthyl-substituted pybox ligands 3d and
3e were finally obtained by cyclization of 6d and 6e, respec-
tively, with diethylaminosulfur
zation[26c] and enzymatic resolution[28a] as well as commercial
available starting materials[45] to synthesize eight enantio-
merically pure pyboxazines 4. These ligands include aryl
groups with different electronic and steric properties as well
as an alkyl group. In two cases both enantiomers of the li-
gands (4a and 4b) were synthesized.
trifluoride (DAST) indichloro-
methane at ꢀ208C.
Pybox 3h, which has two
phenyl groups on the 5-posi-
tion of the oxazoline rings and
unsubstituted 4-positions, has
been mentioned in the litera-
ture, but no experimental de-
[36]
tails have beenreported.
Starting from (R)-2-amino-1-
phenylethanol (8), compound
3h was obtained in 35% yield
after refluxing 8 with imidate 9
inahnydrous CH 2Cl2 for 2–
4 days.[18a] Likewise, ligands 3k
and 3l were synthesized from
amino alcohol 10[43] and 11[44]
in81% and 25%, respectively
(Scheme 5).
Scheme 5. a) CH2Cl2, reflux, 2–4 d, 3h 35%, 3k 81%, 3l 25%.
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M. Beller et al.
zationof the filtrate with d-
tartaric acid yielded (R)-14a in
42% yield (>98% ee; (Scheme
8).[26c,27,47] However, rac-14b
and rac-14c could not be
resolved by this method.
Therefore, we applied enzy-
matic resolutionprotocols for
these substrates.[28a] Thus, rac-
14b was hydrolyzed to (S)-12b
with Amano Lipase PS at
room temperature at pH 8.2 in
45% yield (>99% ee) with
(R)-14b remained in 43–48%
yield (>98% ee). Applying the
same reaction conditions rac-
14c was not hydrolyzed in the
presence of Amano Lipase PS.
However, prolonged reaction
time (4 days) at 368C gave (S)-
12c in45% yield (44% ee)
with 35% (R)-14c (95% ee)
Scheme 6. Synthetic routes for pybox ligands 3. Typical reaction conditions: Route A: i) SOCl2, ii) amino alco-
hol, iii) SOCl2, iv) NaOH; Route B: i) ZnCl2, PhCl, reflux; Route C: i) amino alcohol, ii) DAST; Route D:
i) amino alcohol, CH2Cl2, reflux.[21a]
Racemic 3-aryl b-amino acids and their derivatives were
synthesized according to literature methods in good yields
(Scheme 7).[26c,46] Co-crystallizationof rac-14a with l-tartaric
acid gave (S)-14a in43% yield ( >98% ee) and co-crystalli-
unreacted. As 95% ee of (R)-14c is still not yet suitable for
ligand preparation, we used only enantiopure 14a and 14b
Scheme 8. Resolutionof b-amino acids and derivatives. a) l-Tartaric acid
crystallized with (S)-14a and the filtrate crystallized with d-tartaric acid
for (R)-14a, MeOH, ꢀ208C; b) NaHCO3, ethyl acetate, (S)-14a 43%
(>98% ee), (R)-14a 42% (>98% ee); c) Amano Lipase PS, pH 8.2
(phosphate buffer), RT, 24 h, (S)-12b 43–45% (>99% ee), (R)-14b 45%
(>98% ee); Amano Lipase PS, pH 8.2 (phosphate buffer), 368C, 96 h,
(S)-12c 45% (44% ee), (R)-14c 35% (95% ee).
Scheme 7. Synthesis of racemic substituted b-amino acids and derivatives.
a) EtOH, reflux, 6 h, 12a 38–65%, 12b 38%, 12c 30–65%; b) HCl,
MeOH, 13a 74–96%, 13b 68–86%, 13c 81–88%; c) NaHCO3, ethyl ace-
tate, 14a 78–96%, 14b 92%, 14c 87%.
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Homogeneous Catalysis
FULL PAPER
and commercially available
12c–f to the following ligand
syntheses.
Next, the enantiopure 3-
amino-propan-1-ols
15a–f
were obtained by reduction of
the corresponding b-amino
acid ester with NaBH4 inTHF
or the b-amino acids directly
with LiAlH4 (Scheme 9). Sub-
sequently, cyclization with imi-
date 9 inahnydrous CH 2Cl2
yielded pyboxazine ligands
4a–f. Compounds 4a–f canbe
used for complexationdirectly
or purified by flash chromatog-
Scheme 10. a) SOCl2, DMF, reflux, 2 d; b) H2O; c) P2O5, Bu4NBr, toluene; d) MeOH, NaOMe, reflux, 2 h;
e) K2CO3, MeOH/H2O, RT, 18 h; f) MeOH; g) phenyl boronic acid, 5 mol% Pd(OAc)2, 10 mol% P(o-Tolyl)3,
3.5 equiv CsF inDME at 100 8C for 18 h.
raphy
through
alumina
(CH2Cl2/Et3N 100:1). The new
pyboxazine ligands are stable
inair as white solids, but slowly hydrolyze inthe presence
of water.
tion with phenyl boronic acid to yield dimethyl 4-phenyl-
2,6-pyridinedicarboxylate 19.[32b] Hydrolysis of 19 yielded 4-
phenyl-2,6-pyridinedicarboxylic
acid (5 f). Inaddition, prepara-
tionof 4-bromo-2,6-pyridinedi-
carboxylic acid (5d) was per-
formed according to literature
from chelidamic acid.[32a]
The different pybox 3a–u,
pyboxazine 4a–f, and pydic
5a–f ligands were then subject-
ed to complex formationwith
Scheme 9. Synthesis of pyboxazines 4a–f. a) NaBH4, THF, (R)-15a 78%, (S)-15a 72%, (R)-15b 55%, (S)-15b
45%, (R)-15c 97%; b) LiAlH4, THF, (R)-15d 80%, (R)-15e 85%, (R)-15 f 83%; c) CH2Cl2, reflux, 2–4 days,
(R)-4a 52%, (S)-4a 51%, (R)-4b 59%, (S)-4b 68%, (R)-4c 81%, (S)-4d 79%, (S)-4e 26%, (R)-4 f 61%.
[{Ru(p-cymene)Cl2}2] (Scheme
11).[15e] It is also possible to
synthesize these complexes
with RuCl3·xH2O, but drastic
reaction conditions are needed
To rationalize the electronic effects on the 2,6-pyridinedi-
carboxylate side of the catalysts, para-substituted 2,6-pyri-
dinedicarboxylic acids were also synthesized according to lit-
erature procedures (Scheme 10).[32] All co-ligands were pre-
pared starting from chelidamic acid (5b), which was first
chlorinated with thionyl chloride under refluxing conditions
to give 16.[32d] Compound 16 was treated with water to give
the 4-chloro-2,6-pyridinedicarboxylic acid (5c) and substitu-
tionof the chlorine of 16 to a
(refluxing in nBuOH under Ar for 12 h)[12a] and only low
yields are obtained.[48] [Ru(pybox)(pydic)] complexes (1)
were obtained in moderate to excellent yields (47–98%) as
crystalline solids, except 1oa and 1ua, since 3o and 3u are
unstable under the reaction conditions (Table 1).
It is worth noting that pyboxazines 4 canbe used for the
preparation of the corresponding [Ru(pyboxazine)(pydic)]
complexes (2) without any purification, though the yields
methoxy group was achieved
by using sodium methoxide in
methanol to afford dimethyl 4-
methoxy-2,6-pyridinedicarbox-
ylate 17. Compound 17 was
hydrolyzed to 4-methoxy-2,6-
pyridinedicarboxylic acid (5e)
by using potassium carbonate
in a mixture of methanol and
water. Compound 18 was also
transformed by palladium-cat-
alyzed Suzuki coupling reac-
Scheme 11. Synthesis of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2.
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M. Beller et al.
Table 1. Synthesis of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)]
2 complexes.
tallographic data of the complexes are giveninTable 2 and
selected distances and angles are shown in Table 3.
Entry Pybox 3 or
pyboxazine 4
H2Pydic 5 [Ru(pybox)(pydic)] 1 or
[Ru(pyboxazine)(pydic)] 2
Yield (%)
As shown in Figure 1 the central ruthenium atom is coor-
dinated by the pybox(azine) unit as well as the pydic unit in
a distorted octahedral geometry. The pybox(azine) coordi-
nates to Ru on one plane as a N,N,N-tridentate ligand and
the pydic acts as a dianionic O,N,O-tridentate ligand on an-
other plane, in which they are nearly perpendicular to each
other (86.9–93.08). The bond lengths between Ru and all the
core nitrogenand oxygenatoms inall the complexes inthis
study are comparable. This implies that the ligands mainly
affect the steric environment of the metal center rather than
disturb the electronic properties. The bond lengths of Ru1
to N2 and N4 (1.940(3)–1.976(3) Š) are shorter than those
to N1 and N3 (2.053(3)–2.087(3) Š); this difference arises
from the steric limitations of the pybox(azine) ligands. This
is also reflected by the small bond angle a (108.0(3)–
109.5(3)8 in 1ia, 1ja, an d1na and 110.8(2)–111.0(3)8 in( S)-
2aa). The angle between the planes defined by N1, N2, N3,
Ru1 and O1, N4, O2, Ru1 are close to 908 (86.9–-93.08) an d
the mean deviations from the best plane through the atoms
N1, N2, N3, N4 and Ru1 are very small (0.0074–0.0375 Š).
When all the nitrogen atoms are considered to coordinate
all four equatorial positions of Ru with two trans axial
oxygenatoms, this geometric feature resembles the well-es-
tablished ruthenium–porphyrin structures.[49] Unlike the
planar five-membered oxazoline rings, the six-membered ox-
azine rings adopt to a twist chair conformation. It is worth
noting that (S)-2aa shows a defined geometry in the oxazine
rings, whereas in some other cases it is quite flexible.[26] This
may be due to the effect of the tridentate pydic ligand.
It should also beenpointed out that the orientationof the
substituent at the chiral center adjacent to the nitrogen
donor atoms may change when the oxazoline is replaced by
oxazine. Indeed this chiral center is 3.147/3.192 Š away
from Ru in( S)-2aa, which is less thanthat of 1 (3.311–
3.369 Š; Table 3).
1
3a
5a
5b
5c
5d
5e
5 f
5a
5a
5a
5a
5a
5a
5a
5a
5a
5a
5a
5a
5a
5a
1p
5a
5a
5a
5a
5a
5a
5c
5a
5a
5a
5a
5a
5a
5a
1aa
1ab
1ac
1ad
1ae
1af
1ba
1ca
1da
1ea
1 fa
1ga
1ha
1ia
1ja
1ka
1la
1ma
1na
1oa
79
86
75
86
53
98
53
64
47
62
86
64
71
74
75
54
70
79
82
23
79
85
59
63
71
18
40
38
29
49
48
2
3a
3
3a
4
3a
5
3a
6
3a
7
3b
8
3c
9
3d
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
3e
3 f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p5aa
3q
3r
3 s
3t
3u
1qa
1ra
1 sa
1ta
1ua
(R)-4a[a]
(R)-4a[a]
(S)-4a[a]
(R)-4b[a]
(S)-4b[a]
(R)-4c[a]
(S)-4d
(S)-4e
(R)-4 f
(R)-2aa
(R)-2ac
(S)-2aa
(R)-2ba
(S)-2ba
(R)-2ca
(S)-2da
(S)-2ea
(R)-2 fa
60 (89[b]
)
54
53
28
[a] The ligand was used directly without purification. [b] Pure ligand was
used.
are somewhat lower (Table 1, entries 27–35). All complexes
are highly stable at room temperature and can be easily
handled in air. In spite of the interesting catalytic perfor-
mance of complexes 1 and 2,
The structures of the ligands 3i and 3j are controver-
sial.[16d,35,50] Though the crystal structure of a La complex of
so far no X-ray crystal struc-
Table 2. Crystallographic data.
tures of these complexes have
1ia
1ja
1na
(S)-2aa
[12b]
beenreported.
We were in-
crystal system
space group
a [Š]
b [Š]
c [Š]
monoclinic
C2
orthorhombic
P212121
10.061(2)
15.844(3)
24.035(5)
orthorhombic
P212121
10.505(2)
12.812(3)
21.145(4)
monoclinic
P21
terested inthe detailed struc-
tural information in order to
rationalize the catalytic activity
to structural features. Crystals
suitable for X-ray crystallogra-
phy were obtained by slow dif-
fusionof hexane to a solution
of the complex (1ja, 1na and
(S)-2aa) indichloromethane or
chloroform at room tempera-
ture and single crystals of 1ia
were obtained by slow evapo-
21.590(4)
11.377(2)
15.903(3)
101.40(3)
3829.2(12)
4
1.468
0.535
200
12280
7222
9.072(2)
10.456(2)
14.714(3)
90.23(3)
1395.7(5)
2
1.579
0.616
200
7532
4186
3874
388
0.0228
0.0533
b [8]
V [Š3]
Z
3831.3(13)
4
1.560
0.609
200
20627
6103
5459
2845.9(10)
4
1.603
0.879
200
15252
4521
4284
1calcd [gcmꢀ3
]
m(MoKa) [mmꢀ1
T [K]
]
reflns (measd)
reflns (indep)
reflns (obsd)
parameters
R1 [I>2s(I)]
wR2 (all data)
5317
494
0.0381
0.0625
522
0.0350
0.0814
352
0.0262
0.0709
rationof a solutionof
1ia in
hexane/CH2Cl2/MeOH. Crys-
1862
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Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
Table 3. Selected bond lengths [Š] and angles [8] incomplexes 1na, 1ia, 1ja and (S)-2aa.
1ia
1ja
1na
(S)-2aa
ꢀ
Ru1 N1/N3
2.053(3)/2.080(3)
1.970(4)
1.975(4)
2.111(3)/2.072(3)
78.05(15)
175.3(2)
2.064(3)/2.087(3)
1.975(3)
1.976(3)
2.077(3)/2.114(3)
77.92(12)
178.45(15)
156.39(11)
2.081(3)/2.087(3)
1.965(3)
1.976(3)
2.118(2)/2.090(2)
78.08(12)
177.24(12)
156.47(9)
2.065(3)/2.087(3)
1.940(3)
1.976(3)
2.107(2)/2.083(2)
78.68(11)
176.01(11)
157.04(8)
ꢀ
Ru1 N2
ꢀ
Ru1 N4
ꢀ
Ru1 O1/O2
N1-Ru1-N2
N2-Ru1-N4
O1-Ru1-O2
157.26(13)
108.7(4)/109.4(4)
108.1(3)/108.9(4)
108.0(3)/109.5(3)
110.8(2)/111.0(3)
112.4(4)/111.7(4)
3.311/3.306
112.6(3)/112.6(3)
3.369/3.327
112.3(3)/113.2(3)
3.345/3.349
112.5(3)/112.5(3)
3.147/3.192
g[b]
86.9
0.0375
88.5
0.0074
88.9
0.0128
93.0
0.0315
[c]
meandeviation
[a] The distance between Ru and the carbon atom a to the imine. [b] The angle between mean plane N1, N2, N3, Ru1 and mean plane O1, N4, O2, Ru1.
[c] Mean deviation from the best plane defined by N1, N2, N3, N4 and Ru1.
1
3j was reported, to the best of our knowledge, there is no
direct comparisonof the crystal structures of both the cis-
and trans-isomers known. From the crystal structures of 1ia
and 1ja (Figure 1), the structures reported by Desimoni are
confirmed.[16d,35] There is no significant difference in the
core structure of 1ia and 1ja observed. Therefore, one could
expect that any reactivity and selectivity difference between
1ia and 1ja is probably due to steric reasons.
The signal pattern in both H an d13C NMR spectra con-
firmed a C2-chiral monomeric complex also in solution.
Comparing to the pybox(azine) ligands, the signal of the
proton at the chiral center adjacent to the nitrogen donor
atom inthe ruthenium complexes moves about 0.5 ppm up-
field inpybox and about 1 ppm inpyboxazine (Table 4).
This also suggests that inthe solutionstructure the chiral
center adjacent to the nitrogen donor atom is closer to the
1
Table 4. Selected H an d13C chemical shifts [ppm] and UV/Vis absorption maxima [nm].
1aa
1ab
1ac
1ad
1ae
1af
1ba
1ca
1da
1ea
1H d[a]
5.18
167.4
375
5.39
5.39
169.4
383
5.19
167.3
384
5.11
167.7
366
5.17
167.3
394
5.18 (5.70)[b]
166.8 (163.1)
371
5.11 (5.38)
166.6 (163.6)
388
5.18 (5.47)
167.5 (163.7)
345
5.18 (5.48)
167.5 (162.7)
364
13C d[c]
166.7
359[e]
472[e]
UV/Vis lmax(1)[d]
UV/Vis lmax(2)[d]
484
484
484
483
488
493
505
495
492
(R)-2aa
(R)-2ac
(R)-2ba
(R)-2ca
(S)-2da
(S)-2ea
(R)-2 fa
1H d[a]
3.75 (4.80)
160.3 (155.1)
384
3.72
160.4
393
4.50 (5.62)
161.0 (155.8)
383
3.89 (5.00)
160.5 (155.1)
384
3.72 (4.79)
160.6 (155.3)
386
3.68 (4.75)
160.1 (155.0)
387
2.51 (2.95)
159.2 (153.5)
395
13C d[c]
UV/Vis lmax(1)[d]
UV/Vis lmax(2)[d]
482
485
481
484
483
482
481
[a] Chemical shift of the proton at the chiral center adjacent to the nitrogen donor in ppm (shown above). [b] The corresponding chemical shift of the
ligand is in the parentheses. [c] Chemical shift of the imine carbon in ppm (shown above). [d] lmax of the UV/Vis absorptionspectrum of the complex in
CH2Cl2. [e] The UV/Vis absorptionspectrum of the complex inMeOH.
Chem. Eur. J. 2006, 12, 1855 – 1874
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1863

M. Beller et al.
energy. Here, the parent or unsubstituted complexes 1’ and
2’ (Scheme 12) were compared. The optimized structural pa-
rameters are giveninTable 5.
Scheme 12. Parent complexes for structure optimization and excitation
energy calculation.
Table 5. Selected bond lengths [Š], angles [8] and absorption maxima in
calculated 1’ and 2’.[a,b]
1’
2’
ꢀ
Ru N1
2.103
1.988
2.017
2.123
2.116
1.967
2.018
2.127
ꢀ
Ru N2
ꢀ
Ru N4
ꢀ
Ru O1
N1-Ru-N2
N1-Ru-N3
N1-Ru-N4
O1-Ru-N1
O1-Ru-N2
O1-Ru-N3
O1-Ru-N4
O1-Ru-O2
lmax (1)[c,d]
lmax (2)[c,d]
77.6
155.2
102.4
92.6
102.0
92.6
78.0
156.0
78.2
156.3
101.8
93.0
102.1
91.9
77.9
155.9
347 (0.11)
440 (0.29)
359 (0.07)
441 (0.26)
[a] At B3LYP/LANL2DZ(d). [b] Using the same numbering systems in
X-ray crystal structure. [c] At TD-B3P86/LANL2DZ(d)//B3LYP/
LANL2DZ(d). [d] The oscillator strength in parenthesis.
Figure 1. [Ru(pybox)(pydic)] and [Ru(pyboxazine)(pydic)] complexes
1ia, 1ja, 1na, an d S()-2aa. Hydrogenatoms are omitted for clarity and
the thermal ellipsoids correspond to 30% probability.
All the structures have C2 symmetry and they are found
to be energy minima on the potential-energy surface. The
close agreement between the computed bond parameters
and that determined by X-ray crystallography in Table 3
demonstrates the quality of the computational method.
Inadditionto the structural parameters, the excitationen-
ergies for the comparisonwith the observed UV-visible
spectra were computed. In the calculations we found two ex-
cited states with very strong oscillator strengths. Detailed
analysis shows that the lmax(1) corresponds to the allowed
excitation(347 ( 1’) and 359 nm (2’)) from the Ru d orbitals
to the p* orbital of the pydic ligand (Ru(d)!pydic(p*)),
and the lmax(2) corresponds mainly to the allowed excitation
(440 (1’) and 441 nm (2’)) from the Ru d orbitals to the p*
orbitals of the pybox or pyboxazine ligands (Ru(d)!pybox-
(azine)(p*)). Inaddition, there is a set of excited states with
very low oscillator strengths. As given in Table 5, both
lmax(1) and lmax(2) agree reasonably with the experimental
data for the phenyl-substituted systems.
metal in[Ru(pyboxazine)(pydic)] 2 thanthat in[Ru(pybox)-
(pydic)] 1 as showninthe crystal structures. The imien
carbon of both the pybox and pyboxazine rings deshields (3
to 5 ppm) indicating loss of electron density due to coordi-
nation to the metal center.
The UV-visible absorptionspectra of the ruthenium com-
plexes gave us some insights in the electronic structure of
the complexes and the effects of the substituents as well. As
showninTable 4, there are two absorptionpeaks for both
complexes 1 and 2. The absorptionmaximum at aroudn
480 nm (e~20000mꢀ1 cmꢀ1) is about six times stronger than
that at around 380 nm (e~3000mꢀ1 cmꢀ1). To assignthese
observed UV-visible adsorptionspectra, we carried out
time-dependent density functional theory computations
(TD-DFT). Direct comparisonbetweencomputed and ob-
served adsorptionmaxima should provide a more detailed
insight into the electronic interaction. Computations were
done in two steps by geometry optimization and excitation
Electron-deficient or aromatic para-substituents on the
pyridine ring lead to significant red shifts on the 380 nm
peak, while the electron-donating methoxy group gives a
1864
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Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
(100.6 MHz, CDCl3): d=55.9, 66.0, 116.3, 125.6, 126.8, 128.0, 128.9, 138.5,
150.0, 162.8 ppm; MS (EI, 70 eV): m/z (%): 408 (100), 390 (70), 288 (93),
258 (17), 91 (47); FAB-MS: m/z: 440 [M+]; HRMS (ESI+): m/z calcd
for C23H23ClN3O4: 440.13770; found: 440.13771.
blue shift (Table 4, 1aa–1af, 1ab could not be accounted,
since the UV-visible spectrum was taken in MeOH rather
thanCH Cl2 due to solubility problems). Evidently an elec-
2
tron-deficient or aromatic group substituted on the pydic
side stabilizes the pydic(p*) orbital, which results ina red
shift for 1aa and 1ac–1af for the transition of Ru(d) to
pydic(p*). Stabilizationof the pydic( p*) orbital by introduc-
ing an electron-withdrawing chloro group also leads to a red
shift of the near UV absorption of 2ac (384 nm) relative to
2aa (393 nm). Electron-withdrawing or aromatic groups at
the para-positionof pybox stabilizes the Ru(d) orbital. Ac-
cordingly, blue shifts are observed for 1aa, 1ba, 1da, an d
1ea. The red shift for 1ca can be explained by protona-
tion.[51] On the other hand the strong visible absorption at
~480 nm is influenced more by the electronic nature of the
pybox ligands. As a para-substitution of the pyridine ring of
the pybox ligand affects its p* orbital more thanthe Ru(d)
orbital, the energy difference between Ru(d) and pybox(p*)
orbitals decreases with anelectro-nwithdrawign group.
Therefore red shifts were observed inthe visible absorption
at ~480 nm (Table 4, 1aa–1ea, except for 1ca infra supra).
This effect diminishes when the substituents are far away
from the metal center (Table 4, 2aa–2ea). It should be
noted that the electronic environment of the metal com-
plexes can be fine tuned easily by the para-substitution
strategy onboth ligands.
In conclusion, we have synthesized 29 neutral N,N,N-tri-
dentate pybox and pyboxazine ligands. In combination of
these ligands with 2,6-pyridinedicarboxylic acid and deriva-
tives, 35 new ruthenium(ii) complexes have beensynthesized
and fully characterized. In addition, four new ruthenium(ii)
complexes have beencharacterized by X-ray crystallogra-
phy; this allows for detailed comparisonof structure rela-
tionships. Structural investigations also revealed that pybox-
azine ligands not only resemble the well-known pybox li-
gands, but also change the orientation of the a-carbonatom
at the chiral center adjacent to the nitrogen donor atoms. In
general, these novel ligands and catalysts constitute an inter-
esting toolbox for a variety of catalytic asymmetric reac-
tions. In the following paper their use in asymmetric epoxi-
dationis described indetail.
Synthesis of 2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-chloropyri-
dine (3b): Diethylaminosulfur trifluoride (DAST) (313.44 ml, 385.5 mg,
2.4 mmol) was slowly added to
a solutionof bishydroxyamide 6b
(350 mg, 0.8 mmol) inCH 2Cl2 (5 mL) at ꢀ208C under argon. After 8 h
stirring at ꢀ208C, ammonium hydroxide solution (1 mL) was added
slowly. Subsequently the cooling bath was removed and water (20 mL)
was added. Whenthe reactionmixture had reached room temperature,
two layers were separated and the aqueous layers were extracted with
CH2Cl2 (20 mL”2). The combined organic layer was dried over MgSO4
and concentrated under reduced pressure. The crude product was puri-
fied by columnchromatography to give 3b as a white solid (60 mg,
0.4 mmol, 50%). Rf =0.35 (hexane/EA 1:1); m.p. 169–1708C; [a]D =
1
ꢀ108.68 (c=0.5 inCHCl ); H NMR (400.1 MHz, CDCl3): d=4.67 (unre-
3
solved dd, 2H), 5.17 (unresolved dd, 2H), 5.70 (unresolved dd, 2H),
7.54–7.63 (m, 10H), 8.59 ppm (s, 2H); 13C NMR (100.6 MHz, CDCl3):
d=70.8, 76.1, 126.9, 127.2, 128.4, 129.3, 141.8, 146.1, 148.4, 163.1 ppm;
MS (EI, 70 eV): m/z (%): 403 (76) [M]+, 253 (24), 118 (27), 104 (100),
91(51); HRMS (ESI+): m/z calcd for C23H18ClN3O2: 403.10876; found:
403.10474.
Synthesis of 2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-(N,N-dime-
thylamino)pyridine (3c): Anaqueous solutionof dimethylamien (40
wt%, 25 mL) was added to a solutionof 3b (250 mg, 0.62 mmol) inTHF
(8 mL). The mixture was stirred for one day at 408C. The mixture was
thenextracted with CH 2Cl2 (25 mL), dried over MgSO4, and concentrat-
ed under reduced pressure. The crude product was crystallized in ethyl
acetate to give 3c as white solid (185 mg, 0.45 mmol, 73%). Rf =0.52
(CH2Cl2/methanol 9:1); m.p. 154–1568C; [a]D =ꢀ9.58 (c=0.26 in
CHCl3); 1H NMR (400.1 MHz, CD2Cl2): d=3.06 (s, 6H), 4.31 (t, J=
8.5 Hz, 2H), 4.84 (dd, J=10.3, 8.5 Hz, 2H), 5.38 (dd, J=10.3, 8.5 Hz,
2H), 7.28–7.39 (m, 10H), 7.45 ppm (s, 1H); 13C NMR (100.6 MHz,
CD2Cl2): d=38.5, 69.4, 74.5, 107.6, 126.9, 127.9, 141.5, 146.0, 154.3,
163.6 ppm; MS (EI, 70 eV): m/z (%): 412 ([M]+, 100), 147 (70), 91(30);
elemental analysis calcd (%) for C25H24N4O2·H2O: C 69.74, H 6.09, N
13.01; found: C 70.01, H 6.03, N 13.31.
4-Phenyl-2,6-bis[hydroxyamide]pyridine (6d): Bishydroxyamide 6b
(500 mg, 1.13 mmol), phenyl boronic acid (165.5 mg, 1.35 mmol) and P(o-
Tolyl)3 (5 mol%) were dissolved inDME (8 mL). CsF (2.5 equiv) was
added and the mixture was purged with argon. Pd(OAc)2 (5 mol%) was
added and the mixture was refluxed for 18 h. After cooling to room tem-
perature, water was added and the mixture was extracted with ethyl ace-
tate (50 mL”2). The organic layer was dried over MgSO4 and concen-
trated. The residue was purified by silca gel columnchromatography to
give 6d as a white solid (350 mg, 0.72 mmol, 64%). Rf =0.26 (hexane/EA
7:3); m.p. 84–858C; [a]D =ꢀ15.78 (c=0.20, CHCl3); 1H NMR
(400.1 MHz, CD2Cl2): d=3.21 (brs, 2H), 3.95 (brs, 4H), 5.20 (ddd, J=
7.5, 4.9, 2.4 Hz, 2H), 7.24–7.44 (m, 13H), 7.65–7.68 (m, 2H), 8.43 (s, 2H),
8.75 ppm (d, J=7.5 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=55.5,
65.6, 121.9, 126.3, 126.7, 128.3, 128.8, 129.5, 136.0, 138.8, 149.0, 151.1,
163.3 ppm; MS (EI, 70 eV): m/z (%): 450 (100), 450 (16), 330 (72), 197
(36), 91 (13); FAB-MS: m/z: 482 [M]+.
Experimental Section
Synthesis of 2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-phenylpyri-
dine (3d): Diethylaminosulfur trifluoride (DAST) (204.3 ml, 251.3 mg,
4-Chloro-2,6-bis[hydroxyamide]pyridine (6b): Chelidamic acid (5b; 1 g,
5.46 mmol) was treated with SOCl2 (27 mL) at refluxing temperature for
2 d. Excess SOCl2 was thenremoved under reduced pressure to give the
acid chloride as a white solid. A solutionof the acid chloride (1.3 g,
1.6 mmol) was slowly added to
a solutionof bishydroxyamide 6d
(250 mg, 0.52 mmol) inCH 2Cl2 (5 mL), at ꢀ208C under argon. After 8 h
stirring at ꢀ208C, ammonium hydroxide solution (1 mL) was added
slowly. Subsequently the cooling bath was removed and water (20 mL)
was added. Whenthe reactionmixture had reached room temperature,
the two layers were separated and the aqueous layer was extracted with
CH2Cl2 (2”20 mL). The combined organic layers were dried over
MgSO4, and concentrated under reduced pressure. The crude product
was purified by columnchromatography to give 3d as a white solid
5.46 mmol) inCHCl (25 mL) was slowly to a solutionof ( S)-phenyl gly-
3
cinol (1.64 g, 12 mmol) and triethylamine (5.0 mL, 36 mmol) in CHCl3
(25 mL), added at 08C. The mixture was stirred for 18 h at room temper-
ature and water was added. The mixture was extracted with CH2Cl2
(50 mL”2), dried over MgSO4, and concentrated. The residue was puri-
fied by silica gel columnchromatography with 1:2 ethyl acetate (EA) and
hexane to give 6b as a white solid (2.16 g, 4.9 mmol, 90%). Rf =0.14
(hexane/EA 1:1); m.p. 75–788C; [a]D =ꢀ89.18 (c=1.0 inCHCl 3);
1H NMR (400.1 MHz, CDCl3): d=4.03 (m, 4H), 5.18 (unresolved dd,
2H), 7.09–7.37 (m, 10H), 8.22 (s, 2H), 8.77 ppm (d, 2H); 13C NMR
(130 mg, 0.29 mmol, 55%). Rf =0.46 (hexane/EA 7:3); m.p. 178–1818C;
1
[a]D =+10.18 (c=0.12 inCHCl ); H NMR (400.1 MHz, CDCl3): d=4.43
3
(t, J=8.5 Hz, 2H), 4.44 (dd, J=10.3, 8.5 Hz, 2H), 5.47 (dd, J=10.3,
Chem. Eur. J. 2006, 12, 1855 – 1874
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1865

M. Beller et al.
8.5 Hz, 2H), 7.30–7.35 (m, 10H), 7.44–7.46 (m, 3H), 7.73 (m. 2H),
8.58 ppm (s, 2H); 13C NMR (100.6 MHz, CDCl3): d=70.4, 75.6, 126.2,
127.8, 127.8, 128.8, 128.8, 128.9, 129.2, 129.8, 141.7, 147.3, 150.2,
163.7 ppm; MS (EI, 70 eV): m/z (%): 445 (78) [M]+, 104 (100), 91(49);
HRMS (ESI+): m/z calcd for C29H23N3O2: 445.17902; found: 445.17412.
10.3 Hz, 2H), 5.74 (dd, J=10.3, 8.1 Hz, 2H), 7.32–7.42 (m, 10H), 7.92 (t,
J=7.7 Hz, 1H), 8.20 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.6 MHz,
CD2Cl2): d=63.0, 82.0, 125.8, 126.1, 128.5, 128.8, 137.4, 140.7, 146.9,
162.6 ppm; MS (EI, 70 eV): m/z (%): 370 (27) [M+1]+, 369 (96) [M]+,
105 (23), 104 (100), 91 (35); HRMS: m/z calcd for C23H19N3O2:
369.14774; found: 369.14386; elemental analysis calcd (%) for
C23H19N3O2: C 74.78, H 5.18, N 11.37; found: C 74.61, H 5.12, N 11.46.
4-(1-Naphthyl)-2,6-bis[hydroxyamide]pyridine (6e): Bishydroxyamide 6b
(500 mg, 1.13 mmol), 1-naphthyl boronic acid (165.5 mg, 1.35 mmol) and
P(o-Tolyl)3 (5 mol%) were dissolved inDME (8 mL). CsF (2.5 equiv)
was added and mixture was purged with argon. Pd(OAc)2 (5 mol%) was
added and the mixture was refluxed for 18 h. After cooling to room tem-
perature, water was added (25 mL) and the resulting mixture was extract-
ed with ethyl acetate (50 mL”2). The organic layer was dried over
MgSO4 and concentrated. The residue was purified by silca gel column
chromatography to give 6e as a white solid (450 mg, 0.85 mmol, 75%).
Rf =0.26 (CH2Cl2/methanol 100:6); m.p. 109–1118C; [a]D =+148 (c=0.15
inCH 2Cl2); 1H NMR (400.1 MHz, CD2Cl2): d=3.39 (unresolved d, 4H),
5.22 (unresolved ddd, J=7.5, 5.1 Hz, 2H), 7.27 (tt, J=7.1, 2.4 Hz, 2H),
7.32–7.43 (m, 10H), 7.47 (m, 2H), 7.70 (unresolved dd, J=8.3 Hz, 2H),
7.90 (unresolved dd, J=7.9 Hz, 2H), 8.35 (s, 2H), 8.80 ppm (d, J=
7.5 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=55.9, 66.2, 124.6, 125.3,
126.1, 126.3, 126.8, 127.4, 127.8, 128.8, 128.6, 128.8, 129.6, 130.4, 133.8,
136.0, 139.4, 149.1, 152.2, 163.7 ppm; MS (EI, 70 eV): m/z (%): 500 (100),
482 (38), 380 (36), 247 (31), 203 (17), 91 (14); FAB-MS: m/z: 532 [M]+;
HRMS (ESI+): m/z calcd for C33H30N3O4: 532.22363; found: 532.22401.
(S)-2-Chlorophenyl glycinol (10): (S)-2-Chlorophenylglycine (2.5 gm,
13.4 mmol) was added to
a
stirred solutionof NaBH
(1.26 gm,
4
33.5 mmol) inTHF (15 mL). The mixture was immersed inanice bath
and solution of conc. H2SO4 (1 mL) inEt O was added dropwise, stirring
2
was continued at room temperature for overnight. Methanol (15 mL) and
NaOH (5n 70 mL) were successively added. After removal of organic
solvents, the aqueous solution was refluxed for two hours and extracted
with CH2Cl2 (20 mL”3) after cooling. The residue was purified by crys-
tallization in ethyl acetate and hexane to give 34 (850 mg, 40%). M.p.
63–648C; [a]D =+40.18 (c=0.5 inEtOH); 1H NMR (400.1 MHz, CDCl3):
d=3.54 (dd, J=10.7, 7.9 Hz, 1H), 3.81 (dd, J=10.7, 3.8 Hz, 1H), 4.48
(dd, J=10.7, 3.8 Hz, 1H), 7.15 (ddd, J=8.9, 7.7, 1.5 Hz, 1H), 7.24 (ddd,
J=8.9, 7.8, 1.3 Hz, 1H), 7.30 (dd, J=7.8, 1.5 Hz, 1H), 7.45 ppm (dd, J=
7.7, 1.3 Hz, 1H); 13C NMR (100.6 MHz, CDCl3): d=54.6, 65.6, 127.1,
127.4, 128.5, 129.7, 132.9, 139.3 ppm; MS (EI, 70 eV): m/z (%): 140 (100),
77 (38); HRMS (ESI+): m/z calcd for C8H10ClNO: 172.05292; found:
172.05243.
Synthesis of 2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-(1-naph-
thyl)pyridine (3e): Diethylaminosulfur trifluoride (DAST) (296.3 ml,
364.1 mg, 2.2 mmol) was slowly added to a solutionof bishydroxyamide
6e (400 mg, 0.75 mmol) inCH 2Cl2 (8 mL) at ꢀ208C under argon. After
8 h stirring at ꢀ208C, ammonium hydroxide solution (1 mL) was added
slowly. Subsequently the cooling bath was removed and water (25 mL)
was added. Whenthe reactionmixture had reached room temperature,
the two layers were separated and the aqueous layer was extracted with
CH2Cl2 (25 mL”2). The combined organic layers were dried over MgSO4
and concentrated under reduced pressure. The crude product was puri-
fied by columnchromatography to give 3e as a white solid (130 mg,
Synthesis of 2,6-bis-[(4S)-4-(2-chlorophenyl)-4,5-dihydrooxazol-2-yl]pyri-
dine (3k): By general procedure A from compounds 10 and 9 (281 mg,
1.45 mmol), 3k was obtained as a white solid (520 mg, 1.18 mmol, 81%).
Rf =0.34 (CHCl3/methanol 100:5); m.p. 199–2008C; [a]D =+ 89.18 (c=
0.5 inCHCl 3); 1H NMR (400.1 MHz, CD2Cl2): d=4.19 (t, J=8.7 Hz,
2H), 4.99 (dd, J=10.4, 8.7 Hz, 2H), 5.73 (dd, J=10.4, 8.7 Hz, 2H), 7.13–
7.21 (m, 4H), 7.30–7.37 (m, 4H), 7.90 (t, J=7.7 Hz, 1H), 8.31 (d, J=
7.7 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=67.8, 75.4, 126.8, 127.6,
128.2, 129.2, 129.7, 132.7, 138.1, 140.4, 147.1, 164.6 ppm; MS (EI, 70 eV):
m/z (%): 437 (52) [M]+, 253 (31), 138 (72), 89 (100); HRMS (ESI+): m/
z calcd for C23H17Cl2N3O2: 437.06979; found: 437.06540.
0.26 mmol, 40%). Rf =0.45 (CH2Cl2/methanol 100:6); m.p. 198–2008C;
(S)-1-Amino-1-phenyl-2-methylpropan-2-ol (11):[43] Ina 100 mL roudn
bottomed flask with reflux condenser and CaCl2 drying tube, MeI
(2.6 mL, 42 mmol) was added dropwise to the magnesium (1 g, 42 mmol)
inanhydrous diethyl ether ( ~20 mL). The Grignard reagent was decanted
under an argon atmosphere. (S)-Phenylglycine methyl ester hydrochlo-
ride (700 mg, 3.47 mmol) was added with care to this solution. The reac-
tionmixture was stirred at room temperature for 20 h. The reactionmix-
ture was then quenched with acetone. Ammonia solution (25%, 10 mL)
and NH4Cl solution(20 mL) were added and the reactionmixture was
extracted with Et2O (30 mL”2). The ether extract was further extracted
with 5% HCl (30 mL”2). NaOH (4 g) was added to this solutionand it
was extracted with Et2O (30 mL”2). The organic layer was dried over
K2CO3. After removal of solvent, an oil was obtained that crystallized on
standing. The crude product was then subjected to chromatography on
silica gel with EtOAc/MeOH/Et3N (50:50:2) as the eluent. Compound 11
was obtained in 43% yield. M.p. 47–50 8C; [a]D =+258 (c=1.21 in
CHCl3); 1H NMR (400.1 MHz, CDCl3): d=1.03 (s, 3H), 1.18 (s, 3H),
2.98–3.21 (brs, 3H), 3.82–3.95 (s, 1H), 7.20–7.34 ppm (m, 5H); 13C NMR
(100.6 MHz, CDCl3): d=24.3, 27.7, 65.8, 72.2, 127.6, 127.9, 128.2,
140.6 ppm; MS (EI, 70 eV): m/z (%): 133 (3), 107 (27), 106 (100).
1
[a]D =+3.88 (c=0.35 inCH Cl2); H NMR (400.1 MHz, CD2Cl2): d=4.21
2
(dd, J=8.5, 8.5 Hz, 2H), 4.94 (dd, J=10.3, 8.5 Hz, 2H), 5.48 (dd, J=10.3,
8.5 Hz, 2H), 7.28–7.39 (m, 10H), 7.49–7.59 (m, 4H), 7.83–7.85 (m, 1H),
7.94–7.97 (m, 2H), 8.43 ppm (s, 1H); 13C NMR (100.6 MHz, CD2Cl2): d=
69.6, 74.7, 124.0, 124.6, 125.5, 126.0, 126.2, 126.5, 126.6, 126.9, 127.8,
127.9, 128.6, 129.8, 133.0, 135.28, 141.3, 146.2, 149.7, 162.7 ppm; MS (EI,
70 eV): m/z (%): 495 (100) [M]+, 203 (69),104 (27), 91(50); HRMS
(ESI+): m/z calcd for C33H25N3O2: 495.19467; found: 495.19453.
Dimethyl pyridine-2,6-dicarboximidate 9:[26c] Pyridine-2,6-carbodinitrile
(5.35 g, 41.5 mmol) was dissolved in anhydrous MeOH (100 mL) under
Ar. Na (120 mg, 5.2 mmol) was thenadded. After stirring for 40 h at
room temperature, HOAc (300 mL, 5.25 mmol) was added, and the sol-
vent was removed under reduced pressure. Compound 9 was obtained as
a yellow powder (8.5 g, 100%) and was used directly.
General procedure A for pybox(azine) ligand synthesis: Compound 9
(1.044 g, 5.4 mmol), amino alcohol (10.8 mmol), and anhydrous dichloro-
methane (20 mL) were stirred at 40–508C ina pressure tube under Ar
for 48 h. The reactionmixture was thenwashed with water and the or-
ganic layer was separated, dried over MgSO4, and evaporated under re-
duced pressure to dryness. The product was then subjected to chromatog-
raphy onsilica gel with CH 2Cl2/MeOH (98:2) as the eluent or recrystal-
lized from EtOAc.
Synthesis of 2,6-bis-[(4S)-5,5-dimethyl-4-phenyl-4,5-dihydrooxazol-2-yl]-
pyridine (3l): By general procedure A from compounds 11 and 9, 3l was
obtained as a white solid in 25% yield. Rf =0.7 (EtOAc); m.p. 137–
1388C; 1H NMR (400.1 MHz, CDCl3): d=0.94 (s, 6H), 1.64 (s, 6H), 5.03
(s, 2H), 7.18–7.30 (m, 10H), 7.88 (m, 1H), 8.24 ppm (m, 2H); 13C NMR
(100.6 MHz, CDCl3). d=23.9, 29.2, 78.2, 89.2, 126.2, 127.2, 127.7, 128.3,
137.4, 138.0, 147.2, 162.8 ppm; MS (EI, 70 eV): m/z (%): 425 (23) [M]+,
367 (36), 132 (100), 131 (54); HRMS (ESI+): m/z calcd for
C27H27N3O2 +H+: 426.21814; found: 426.21861.
For the pyboxazine ligands, the solvent of the reaction mixture was first
removed under reduced pressure. The crude mixture was subjected to
chromatography under Ar over alumina by using CH2Cl2/Et3N (100:1) as
the eluent (alumina was dried at 2008C under high vacuum; CH2Cl2 was
dried over K2CO3).
Synthesis of 2,6-bis-[(5S)-5-phenyl-4,5-dihydrooxazol-2-yl]pyridine (3h):
By general procedure A from compounds 8 and 9, 3h was obtained in
35% after recrystallizationfrom EtOAc. Rf =0.1–0.2 (EtOAc); m.p.
179.5–180.58C; [a]D =+2528 (c=0.61 inCH 2Cl2); 1H NMR (400.1 MHz,
CD2Cl2): d=4.01–4.11 (dd, J=15.5, 8.1 Hz, 2H), 4.52 (dd, J=15.5,
Synthesis of 2,6-bis-[(4S)-4-methyl-4,5-dihydrooxazol-2-yl]pyridine (3m):
By the general procedure A, from (S)-(+)-2-amino-1-propanol and com-
pound 9, 3m was obtained as a white solid in 53% yield. Rf =0.1–0.2
(CH2Cl2/Et3N 99:1); m.p. 163.0–165.58C; [a]D =ꢀ131.88 (c=0.72 in
1866
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
CH2Cl2); 1H NMR (400.1 MHz, CD2Cl2): d=1.36 (d, J=6.5 Hz, 6H);
4.06 (dd, J=8,1 Hz, 2H), 4.38–4.47 (m, 2H), 4.60 (dd, J=9.5, 8,1 Hz,
2H), 7.85 (t, J=7.7 Hz, 1H), 8.16 ppm (d, J=7.7 Hz, 2H); 13C NMR
(100.6 MHz, CDCl3): d=21.8, 62.7, 75.1, 126.0, 137.7, 147.3, 162.7 ppm;
MS (EI, 70 eV): m/z (%): 245 (77) [M]+, 230 (100), 202 (42), 131 (33),
104 (89), 102 (56); elemental analysis calcd (%) for C13H15N3O2·0.25H2O:
C 62.51, H 6.25, N 16.82; found: C 62.74, H 6.21, N 17.09.
(R)-3-Amino-3-(1-naphthyl)propan-1-ol ((R)-15b): M.p. 42–458C; HPLC
(Crownpak CR(ꢀ), HClO4 (pH 2)/MeOH 90:10, flow rate 1.0 mLminꢀ1
)
1
100% ee; [a]D =+50.88 (c=1 in CH2Cl2); H NMR (400.1 MHz, CD2Cl2):
d=1.90–1.99 (m, 1H), 2.02–2.09 (m, 1H), 2.73 (brs, 3H), 3.79 (ddd, J=
10.9, 5.8, 3.8 Hz, 1H), 3.89 (ddd, J=10.9, 8.1, 3.2 Hz, 1H), 4.99 (dd, J=
9.0, 3.3 Hz, 1H), 7.48–7.57 (m, 3H), 7.60 (d, J=7.1 Hz, 1H), 7.78 (d, J=
8.3 Hz, 1H), 7.90 (d, J=7.9 Hz, 1H), 8.09 ppm (d, J=8.3 Hz, 1H);
13C NMR (100.6 MHz, CD2Cl2): d=39.2, 52.0, 62.3, 121.9, 122.7, 125.6,
126.2, 127.4, 129.0, 130.4, 134.0, 142.2 ppm.
General procedure for 3-amino-propan-1-ol synthesis and resolution: b-
Amino acids 12,[26c,45] b-amino acid methyl ester 14[27] were synthesized
according to literature procedures. Compound 14a was resolved by co-
crystallizationwith d- or l-tartaric acids.[26c] Compounds 14b and 14c
were enzymatically resolved by Amano Lipase PS (Aldrich).[28a] 3-
(S)-3-Amino-3-(1-naphthyl)propan-1-ol ((S)-15b): HPLC (Crownpak
CR(+), HClO4 (pH 2)/MeOH 95:5, flow rate 1.0 mLminꢀ1) >99% ee.
Resolution of methyl rac-3-amino-3-(2-naphthyl)propanoate 14c: Anap-
propriate quantity of freshly prepared sodium hydroxide solution (2n,
~47 mL) was added to a solutionof potassium dihydrogenphosphate
(KH2PO4; 0.5m, 200 mL), until the pH value was adjusted to 8.2. rac-14c
(4 g) and Amano Lipase PS (2 g) were stirred in this phosphate buffer
(120 mL) at 368C for 96 h. The product was thenfiltered and washed
with H2O and dried over KOH under high vacuum. The powdery product
was thenstirred with EtOAc (50 mL) and filtered. After removal of sol-
vent, (R)-14c was obtained in 35% (1.4 g). The residue was dissolved in
NaOH solution(2 n) and filtered. The filtrate was acidified to pH 6 and
the product precipitated. After filtration, washed with H2O and dried
over KOH under high vacuum, (S)-12c was obtained in 45% (1.7 g).
Amino-propan-1-ols 15 were obtained by reduction of the methyl ester
[26c]
14 with NaBH4
or the acid 12 directly with LiAlH4.[53]
Methyl (R)-3-amino-3-phenylpropanoate ((R)-14a): HPLC (Chiralcel
OD-H, hexane/EtOH 98:2, flow rate 1.0 mLminꢀ1
>99% ee; [a]D =
)
+21.38 (c=1 inCHCl 3); 1H NMR (400.1 MHz, CD2Cl2): d=1.69 (brs,
2H), 2.63 (d, J=8.2 Hz, 1H), 2.63 (d, J=5.6 Hz, 1H), 3.65 (s, 3H), 4.38
(dd, J=8.2, 5.6 Hz 1H), 7.23–7.27 (m, 1H), 7.31–7.38 ppm (m, 4H);
13C NMR (100.6 MHz, CD2Cl2): d=44.1, 51.5, 52.7, 126.2, 127.2, 128.5,
145.2, 172.3 ppm.
(R)-3-Amino-3-phenylpropan-1-ol ((R)-15a): HPLC (Crownpak CR(+),
HClO4 (pH 2), 108C, flow rate 0.5 mLminꢀ1) 98% ee; [a]D =+24.28 (c=
0.5 inCH 2Cl2); 1H NMR (400.1 MHz, CD2Cl2): d=1.82–1.87 (m, 2H),
2.49 (brs, 3H), 3.69–3.80 (m, 2H), 4.09 (dd, J=8.0, 5.1 Hz, 1H), 7.22–
7.26 (m, 1H), 7.28–7.37 ppm (m, 4H); 13C NMR (100.6 MHz, CD2Cl2):
d=39.9, 56.5, 62.1, 125.8, 127.0, 128.6, 146.8 ppm.
Methyl (R)-3-amino-3-(2-naphthyl)propanoate ((R)-14c): HPLC (Chiral-
cel OD-H, hexane/EtOH 99:1, flow rate 1.0 mLminꢀ1) 95% ee.
(S)-3-Amino-3-(2-naphthyl)propanoic acid ((S)-12c): M.p. 227–2298C;
HPLC (Crownpak CR(+), HClO4 (pH 2)/MeOH 90:10, 408C, flow rate
1.0 mLminꢀ1) 44% ee.
Methyl (S)-3-amino-3-phenylpropanoate ((S)-14a): HPLC (Chiralcel
OD-H, hexane/EtOH 98:2, flow rate 1.0 mLminꢀ1
) 100% ee; [a]D =
Methyl (R)-3-amino-3-(2-naphthyl)propanoate ((R)-14c): Gaseous HCl
was purged for 2 h into the suspension of (R)-12c (5 g, 23 mmol, Pep-
Tech) inanhydrous MeOH (120 mL) at 0 8C. The product was dissolved
in MeOH. After removal of solvent and dried over KOH under high
vacuum, (R)-13c was obtained in 97% (6 g). It was further neutralized
with Na2CO3 inEtOAc to give ( R)-14c in94% (4.85 g). M.p. 77–79 8C;
[a]D =ꢀ5.88 (c=1 inMeOH); 1H NMR (400.1 MHz, CD2Cl2): d=1.75
(brs, 2H), 2.69 (dd, J=15.9, 8.7 Hz, 1H), 2.75 (dd, J=15.9, 5.3 Hz, 1H),
3.66 (s, 3H), 4.57 (unresolved dd, 1H), 7.44–7.52 (m, 3H), 7.82–7.84 ppm
(m, 4H); 13C NMR (100.6 MHz, CD2Cl2): d=44.1, 51.5, 52.8, 124.7, 124.8,
125.8, 126.1, 127.6, 127.8, 128.2, 132.9, 133.5, 135.8, 172.3 ppm; elemental
analysis calcd (%) for C14H16NO2: C 73.34, H 6.59, N 6.11; found: C
73.26, H 6.74, N 6.00.
ꢀ21.78 (c=1 inCHCl 3); 1H NMR (400.1 MHz, CD2Cl2): d=1.70 (brs,
2H), 2.63 (d, J=8.2 Hz, 1H), 2.63 (d, J=5.6 Hz, 1H), 3.65 (s, 3H), 4.38
(dd, J=8.2, 5.6 Hz 1H), 7.23–7.27 (m, 1H), 7.31–7.38 ppm (m, 4H);
13C NMR (100.6 MHz, CD2Cl2): d=44.1, 51.5, 52.7, 126.2, 127.2, 128.5,
145.2, 172.3 ppm.
(S)-3-Amino-3-phenylpropan-1-ol ((S)-15a): HPLC (Crownpak CR(+),
HClO4 (pH 2), 108C, flow rate 0.5 mLminꢀ1) 100% ee; [a]D =ꢀ22.58 (c=
0.5 inCH 2Cl2);1H NMR (400.1 MHz, CD2Cl2): d=1.81–1.88 (m, 2H),
2.53 (brs, 3H), 3.69–3.80 (m, 2H), 4.10 (dd, J=8.0, 5.1 Hz, 1H), 7.22–
7.27 (m, 1H), 7.28–7.37 ppm (m, 4H); 13C NMR (100.6 MHz, CD2Cl2):
d=40.0, 56.5, 62.1, 125.8, 127.0, 128.6, 146.8 ppm.
Resolution of methyl rac-3-amino-3-(1-naphthyl)propanoate 14b: Anap-
propriate quantity of freshly prepared sodium hydroxide solution (2n,
~47 mL) was added to a solutionof potassium dihydrogenphosphate
(KH2PO4; 0.5m, 200 mL), until the pH value was adjusted to 8.2. rac-14b
(4 g) and Amano Lipase PS (1.8 g) were stirred in this phosphate buffer
(120 mL) at room temperature for 24 h. The product was thenfiltered
and washed with H2O and dried over KOH under high vacuum. The
powdery product was thenstirred with EtOAc (50 mL) adn filtered.
After removal of solvent, (R)-14b was obtained in 45% (1.8 g). The resi-
due was dissolved inNaOH solution(2 n) and filtered. The filtrate was
acidified to pH 6 and the product precipitated. After filtration, washed
with H2O and dried over KOH under high vacuum, (S)-12b was obtained
in43–48% (1.6–1.8 g).
(R)-3-Amino-3-(2-naphthyl)propan-1-ol ((R)-15c): M.p. 68–698C; HPLC
(Crownpak CR(ꢀ), HClO4 (pH 2)/MeOH 90:10, flow rate 0.5 mLminꢀ1
)
>99% ee; [a]D =+17.38 (c=1 in CH2Cl2); 1H NMR (400.1 MHz,
CD2Cl2): d=1.92–1.97 (m, 2H), 2.59 (brs, 3H), 3.73–3.84 (m, 2H), 4.28
(unresolved dd, 1H), 7.44–7.51 (m, 3H), 7.75 (s, 1H), 7.83–7.85 ppm (m,
3H); 13C NMR (100.6 MHz, CD2Cl2): d=39.9, 56.5, 62.1, 124.0, 124.5,
125.7, 126.2, 127.6, 127.8, 128.3, 132.7, 133.5, 144.1 ppm; elemental analy-
sis calcd (%) for C13H15NO: C 77.58, H 7.51, N 6.96; found: C 77.46, H
7.55, N 6.69.
(S)-3-Amino-3-(4-chlorphenyl)propan-1-ol ((S)-15d): Rf =0.45 (EtOAc/
MeOH/Et3N 49:49:2); m.p. 53–568C; [a]D =ꢀ17.68 (c=0.97 inCH 2Cl2);
1H NMR (400.1 MHz, CD2Cl2): d=1.79–1.85 (m, 2H), 2.32 (brs, 3H),
3.67–3.77 (m, 2H), 4.10 (t, J=6.5 Hz, 1H),7.24–7.34 ppm (m, 4H);
13C NMR (100.6 MHz, CD2Cl2): d=40.3, 56.0, 62.1, 127.7, 128.9, 132.7,
145.6 ppm; MS (EI, 70 eV): m/z (%): 185 (1) [M]+, 184, (1) [Mꢀ1]+, 142
(32), 140 (100); HRMS (ESI+): m/z calcd for C9H12ClNO: 185.06075;
found: 185.06103.
Methyl (R)-3-amino-3-(1-naphthyl)propanoate ((R)-14b): M.p. 57–598C;
HPLC (Chiralcel OD-H, hexane/EtOH 95:5, flow rate 1.0 mLminꢀ1
>98% ee; [a]D =+48.18 (c=0.5 inMeOH);
)
1H NMR (400.1 MHz,
CD2Cl2): d=1.85 (brs, 2H), 2.68 (dd, J=15.9, 9.7 Hz, 1H), 2.87 (dd, J=
15.9, 3.4 Hz, 1H), 3.70 (s, 3H), 5.24 (dd, J=9.7, 3.4 Hz, 1H), 7.46–7.57
(m, 3H), 7.68 (d, J=7.1 Hz, 1H), 7.78 (d, J=8.1 Hz, 1H), 7.89 (d, J=
8.1 Hz, 1H), 8.18 ppm (d, J=8.3 Hz, 1H); 13C NMR (100.6 MHz,
CD2Cl2): d=43.4, 48.1, 51.6, 122.6, 122.9, 125.6, 125.6, 126.2, 127.7, 129.0,
130.6, 134.0, 140.7, 172.6 ppm.
(S)-3-Amino-3-(4-methoxyphenyl)propan-1-ol
((S)-15e):
Rf =0.3
(EtOAc/MeOH/Et3N 49:49:2); m.p. 70.5–73.58C; [a]D =ꢀ17.98 (c=0.43
inCH 2Cl2); 1H NMR (400.1 MHz, CDCl3): d=1.80–1.96 (m, J=8.92,
4.16 Hz, 2H), 2.69 (brs, 3H), 3.79 (s, 3H), 3.77–3.81 (m, 2H), 4.10 (dd,
J=8.92, 4.16 Hz, 1H), 6.87 (m, J=8.72 Hz, 2H), 7.22 ppm (m, J=
8.72 Hz, 2H); 13C NMR (100.6 MHz, CDCl3): d=39.2, 55.3, 56.0, 62.2,
114.0, 126.9, 135.7, 158.7 ppm; MS (EI, 70 eV): m/z (%): 181 (2) [M]+,
180 (2) [Mꢀ1]+, 137 (32), 136 (100), 109 (48); elemental analysis calcd
(S)-3-Amino-3-(1-naphthyl)propanoic acid ((S)-12b): M.p. 227–2298C;
HPLC (Crownpak CR(+), HClO4 (pH 2)/MeOH 90:10, flow rate
1.5 mLminꢀ1) 100% ee; [a]D =ꢀ24.18 (c=1 in0.1 n HCl), [a]D =ꢀ49.58
(c=1 in0.5 n NaOH).
Chem. Eur. J. 2006, 12, 1855 – 1874
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1867

M. Beller et al.
(%) for C10H15NO2: C 66.27, H 8.34, N 7.73; found: C 66.57, H 8.15, N
7.67.
Et3N 98:2); m.p. >808C (glassy melting); [a]D =+3.88 (c=0.55 in
CH2Cl2); H NMR (400.1 MHz, CD2Cl2): d=2.02–2.12 (m, 2H), 2.40–2.47
1
(m, 2H), 4.46–4.57 (m, 4H), 5.00 (dd, J=8.1, 5.0 Hz, 2H), 7.46–7.50 (m,
4H), 7.52 (dd, J=8.5, 1.8 Hz, 2H), 7.80–7.91 (m, 9H), 8.31 ppm (d, J=
7.9 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=29.9, 55.3, 64.3, 124.3,
125.3, 125.3, 125.6, 126.1, 127.6, 127.9, 128.1, 132.6, 133.5, 136.9, 141.7,
151.3, 155.1 ppm; MS (EI, 70 eV): m/z (%): 499 (5) [M+2]+, 498 (22)
[M+1]+, 497 (51) [M]+, 289 (24), 288 (100), 259 (22), 182 (32), 168 (29),
167 (55); HRMS (ESI+): m/z calcd for C33H27N3O2: 497.21033; found:
497.21015; elemental analysis calcd (%) for C33H27N3O2: C 79.66, H 5.47,
N 8.44; found: C 79.74, H 5.48, N 8.50.
(R)-3-Amino-4-methyl-pentan-1-ol ((R)-15 f): M.p. 70.5–73.58C; [a]D =
+19.88 (c=0.97 inCH 2Cl2); 1H NMR (400.1 MHz, CDCl3): d=0.83 (d,
J=5.4 Hz, 3H), 0.85 (d, J=5.2 Hz, 3H), 1.37–1.58 (m, 3H), 2.65 (ddd,
J=10.5, 5.0, 2.8 Hz, 1H), 2.94 (brs, 3H), 3.71–3.81 ppm (m, 2H);
13C NMR (100.6 MHz, CDCl3): d=17.3, 18.6, 34.3, 34.6, 58.5, 63.1 ppm;
MS (CI, Isobutane): m/z (%): 119 (8) [M+2]+, 118 (100) [M+1]+. MS
(EI, 70 eV): m/z (%): 74 (100), 72 (28), 56 (34), 44 (48).
Synthesis of 2,6-bis-[(4R)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyridine
((R)-4a): By general procedure A from (R)-15a and 9, (R)-4a was ob-
tained as white needles in 52% yield. Rf =0.8 (alumina, CH2Cl2/Et3N
98:2); m.p. 114.0–116.58C; [a]D =+28.38 (c=0.79 inCH 2Cl2); 1H NMR
(400.1 MHz, CD2Cl2): d=1.91–2.02 (m, 2H), 2.31–2.39 (m, 2H), 4.44–
4.52 (m, 4H), 4.80 (dd, J=8.3, 5.0 Hz, 2H), 7.24–7.31 (m, 2H), 7.34–7.40
(m, 8H), 7.83 (t, J=7.9 Hz, 1H), 8.22 ppm (d, J=7.9 Hz, 2H); 13C NMR
(100.6 MHz, CD2Cl2): d=30.4, 55.6, 64.7, 124.5, 127.0, 127.1, 128.7, 137.1,
144.6, 151.5, 155.1 ppm; MS (EI, 70 eV): m/z (%): 398 (9) [M+1]+, 397
([M]+, 30), 264 (11), 239 (18), 238 (100), 209 (20), 132 (29), 117 (31), 104
(31), 77 (44); HRMS (ESI+): m/z calcd for C25H23N3O2: 397.17902;
found: 397.17968; elemental analysis calcd (%) for C25H23N3O2: C 75.54.
H 5.83, N 10.57; found: C 76.04, H 5.79, N 10.57.
Synthesis of 2,6-bis-[(4S)-4-(4-chlorophenyl)-5,6-dihydro-4H-[1,3]oxazi-
nyl]pyridine ((S)-4d): By general procedure A from (S)-15d and 9, (S)-
4d was obtained as white needles in 79% yield. Rf =0.7 (alumina,
CH2Cl2/Et3N 98:2); m.p. 164–1698C; [a]D =ꢀ30.08 (c=0.88 inCH 2Cl2);
1H NMR (400.1 MHz, CD2Cl2): d=1.88–1.98 (m, 2H), 2.30–2.38 (m, 2H),
4.43–4.51 (m, 4H), 4.79 (dd, J=8.7, 5.0 Hz, 2H), 7.31–7.37 (m, 8H), 7.84
(t, J=7.9 Hz, 1H), 8.21 ppm (d, J=7.9 Hz, 2H); 13C NMR (100.6 MHz,
CD2Cl2): d=30.3, 55.0, 64.8, 124.6, 128.5, 128.7, 132.7, 136.1, 137.3, 143.2,
151.4, 155.3 ppm. MS (EI, 70 eV): m/z (%): 468 (8) [M+3]+, 467 (23)
[M+2]+, 466 (12) [M+1]+, 465 (30) [M]+, 274 (30), 273 (19), 272 (100),
103 (33); HRMS (ESI+): m/z calcd for C25H21N3O2Cl2: 465.10107;
found: 465.09933; elemental analysis calcd (%) for C25H21N3O2Cl2: C
64.39, H 4.54, N 9.01, Cl 15.20; found: C 64.40, H 4.71, N 8.76, Cl 15.07.
Synthesis of 2,6-bis-[(4S)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyridine
((S)-4a): By general procedure A from (S)-15a and 9, (S)-4a was ob-
tained as white needles in 52% yield. Rf =0.8 (alumina, CH2Cl2/Et3N
98:2); m.p. 115.0–116.58C; [a]D =ꢀ29.18 (c=0.77 inCH 2Cl2); 1H NMR
(400.1 MHz, CD2Cl2): d=1.91–2.02 (m, 2H), 2.31–2.39 (m, 2H), 4.44–
4.52 (m, 4H), 4.80 (dd, J=8.3, 5.0 Hz, 2H), 7.24–7.31 (m, 2H), 7.34–7.40
(m, 8H), 7.82 (t, J=7.9 Hz, 1H), 8.22 ppm (d, J=7.9 Hz, 2H); 13C NMR
(100.6 MHz, CD2Cl2): d=30.4, 55.6, 64.7, 124.5, 127.0, 127.1, 128.7, 137.1,
144.6, 151.5, 155.1 ppm; MS (EI, 70 eV): m/z (%): 398 (15) [M+1]+, 397
(47) [M]+, 264 (13), 239 (22), 238 (100), 209 (25), 132 (32), 117 (32), 104
(31), 77 (40); HRMS (ESI+): m/z calcd for C25H23N3O2: 397.17902;
found: 397.18024.
Synthesis of 2,6-bis-[(4S)-4-(4-methoxyphenyl)-5,6-dihydro-4H-[1,3]oxa-
zinyl]pyridine ((S)-4e): By general procedure A from compounds (S)-
15e and 9, (S)-4e was obtained as white needles in 26% yield. Rf =0.6
(alumina, CH2Cl2/Et3N 98:2); m.p. 164.5–1668C; [a]D =ꢀ6.08 (c=0.44 in
1
CH2Cl2); H NMR (400.1 MHz, CD2Cl2): d=1.89–1.99 (m, 2H), 2.27–2.35
(m, 2H), 3.80 (s, 6H), 4.40–4.50 (m, 4H), 4.75 (dd, J=8.3, 5.0 Hz, 2H),
6.88–6.92 (m, 4H), 7.25–7.29 (m, 4H), 7.82 (t, J=7.9 Hz, 1H), 8.20 ppm
(d, J=7.9 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=30.4, 55.0, 55.6,
64.7, 114.0, 124.4, 128.0, 136.7, 137.1, 151.5, 155.0, 158.9 ppm; MS (EI,
70 eV): m/z (%): 459 (4) [M+2]+, 458 (21) [M+1]+, 457 (61) [M]+, 269
(18), 268 (100), 162 (53), 148 (58), 147 (85); MS (EI, 70 eV): m/z (%):
468 (8) [M+3]+, 467 (23) [M+2]+, 466 (12) [M+1]+, 465 (30) [M]+, 274
(30), 273 (19), 272 (100), 103 (33); HRMS (ESI+): m/z calcd for
C27H27N3O4: 457.20016; found: 457.20275; elemental analysis calcd (%)
for C27H27N3O4: C 70.88, H 5.95, N 9.18; found: C 70.38, H 6.06, N 8.86.
Synthesis of 2,6-bis-[(4R)-4-(1-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine ((R)-4b): By General procedure A from (R)-15b and 9, (R)-4b
was obtained as white needles in 68% yield. Rf =0.9 (alumina, CH2Cl2/
Et3N 98:2); m.p. 172.5–174.08C; [a]D =+111.18 (c=0.65 inCH 2Cl2);
1H NMR (400.1 MHz, CD2Cl2): d=2.04–2.13 (m, 2H), 2.49–2.60 (m, 2H),
4.45 (ddd, J=10.9, 6.3, 3.8 Hz, 2H), 4.56 (ddd, J=11.3, 8.3, 3.0 Hz, 2H),
5.62 (dd, J=6.7, 5.6 Hz, 2H), 7.45–7.60 (m, 8H), 7.81 (dd, J=7.9, 1.4,
2H), 7.88 (t, J=7.9 Hz, 1H), 7.93 (dd, J=8.1, 1.4 Hz, 2H), 8.12 (d, J=
8.3 Hz, 2H), 8.30 ppm (d, J=7.9 Hz, 2H); 13C NMR (100.6 MHz,
CD2Cl2): d=29.4, 52.4, 64.4, 123.2, 124.6, 125.0, 125.8, 126.4, 127.8, 129.3,
130.8, 134.3, 136.1, 137.3, 139.7, 151.6, 155.8 ppm; MS (EI, 70 eV): m/z
(%): 499 (4) [M+2]+ 498 (18) [M+1]+, 497 (46) [M]+, 469 (18), 467 (13),
453 (14), 314 (12), 302 (24), 289 (21), 288 (100), 259 (31), 167 (73), 154
(45), 153 (39), 127 (34); HRMS (ESI+): m/z calcd for C33H27N3O2:
497.21033; found: 497.21041.
Synthesis of 2,6-bis-[(4R)-4-isopropyl-5,6-dihydro-4H-[1,3]oxazinyl]pyri-
dine ((R)-4 f): By general procedure A from compounds (R)-15 f and 9,
(R)-4 f was obtained as white needles in 61% yield. Rf =0.7 (alumina,
CH2Cl2/Et3N 98:2); m.p. 90–958C; [a]D =+8.98 (c=0.62 inCH 2Cl2);
1H NMR (400.1 MHz, CD2Cl2): d=0.67 (d, J=6.9 Hz, 3H), 0.75 (d, J=
6.7 Hz, 3H), 1.40–1.50 (m, 4H), 1.60–1.66 (ddt, J=13.7, 4.8, 2.8 Hz, 2H),
2.95 (ddd, J=10.7, 6.3, 4.8 Hz, 2H), 3.93–4.01 (dddd, J=11.9, 10.7, 3.0,
1.2 Hz, 2H), 4.15–4.20 (dddd, J=10.7, 4.6, 2.8, 0.6 Hz, 2H), 7.42 (t, J=
7.7 Hz, 1H), 7.77 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.6 MHz,
CD2Cl2): d=18.5, 18.7, 24.3, 33.9, 57.7, 65.3, 123.7, 136.5, 151.3,
153.5 ppm; MS (EI, 70 eV): m/z (%): 329 (2) [M]+, 314 (2), 288 (14),
287 (80), 286 (100), 203 (46); HRMS (ESI+): m/z calcd for C19H27N3O2:
329.21033; found: 329.21016; elemental analysis calcd (%) for
C19H27N3O2: C 69.27, H 8.26, N 12.76; found: C 69.15, H 8.12, N 12.46.
Synthesis of 2,6-bis-[(4S)-4-(1-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine ((S)-4b): By general procedure A from (S)-15b and 9, (S)-4b
was obtained as white needles in 59% yield. Rf =0.9 (alumina, CH2Cl2/
Et3N 98:2); m.p. 171.0–174.58C; [a]D =+111.38 (c=0.67 inCH 2Cl2);
1H NMR (400.1 MHz, CD2Cl2): d=1.94–2.04 (m, 2H), 2.43–2.51 (m, 2H),
4.36 (ddd, J=10.9, 6.1, 3.8 Hz, 2H), 4.47 (ddd, J=10.9, 8.3, 3.4 Hz, 2H),
5.53 (dd, J=6.5, 5.6 Hz, 2H), 7.36–7.51 (m, 8H), 7.72 (d, J=7.53 Hz,
2H), 7.78 (t, J=7.9 Hz, 1H), 7.84 (d, J=7.9 Hz, 2H), 8.03 (d, J=8.3 Hz,
2H), 8.22 ppm (d, 7.93 Hz, 2H); 13C NMR (100.6 MHz, CD2Cl2): d=29.4,
52.4, 64.4, 123.2, 124.6, 125.0, 125.8, 126.4, 127.8, 129.3, 130.8, 134.3,
136.1, 137.3, 139.7, 151.6, 155.8 ppm; MS (EI, 70 eV): m/z (%): 499 (5)
[M+2]+, 498 (16) [M+1]+, 497 (9) [M]+, 469 (18), 467 (14), 453 (14), 302
(22), 289 (23), 288 (100), 259 (29), 167 (70), 154 (41), 153 (32), 127 (30);
HRMS (ESI+): m/z calcd for C33H27N3O2: 497.21033; found: 497.21114;
elemental analysis calcd (%) for C33H27N3O2·H2O: C 76.87, H 5.67, N
8.15; found: C 77.11, H 5.65, N 8.05.
Synthesis of 4-substituted 2,6-pyridine dicarboxylic acids 5: 4-Substituted
2,6-pyridine dicarboxylic acids 5a–e were synthesized by literature meth-
ods.[32] 5 f was synthesized as follows:
Compound 18 (360 mg, 1.57 mmol), phenyl boronic acid (230 mg,
1.88 mmol) and P(o-Tolyl)3 (5 mol%) were dissolved inDME (8 mL).
CsF (2.5 equiv) was added and mixture was purged with argon. Pd(OAc)2
(5 mol%) was added and the mixture was refluxed for 18 h. After cooling
to room temperature, water was added and the resulting mixture was ex-
tracted with ethyl acetate (50 mL”2). The organic layer was dried over
MgSO4 and concentrated. The residue was purified by silca gel column
chromatography to give ester 19 as a white solid (220 mg, 52%). Potassi-
um carbonate (0.5 g) was added to a solution of 19 (150 mg, 0.55 mmol)
in methanol and water (2:1, 7.5 mL). The reaction mixture was stirred for
18 h at room temperature and was then poured onto a mixture of ice and
conc. HCl. A white solid precipitated, which after filtration and drying
Synthesis of 2,6-bis-[(4R)-4-(2-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine ((R)-4c): By general procedure A from (R)-15c and 9, (R)-4c
was obtained as white needles in 81% yield. Rf =0.9 (alumina, CH2Cl2/
1868
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
gave 5 f (115 mg, 86%). M.p. 218–2208C; 1H NMR (400.1 MHz,
[D6]DMSO): d=7.75 (m, 3H), 7.85 (dd, J=1.8, 8.2 Hz, 2H), 8.54 ppm (s,
2H); 13C NMR (100.6 MHz, [D6]DMSO): d=124.9, 127.5, 129.8, 130.4,
136.1, 149.5, 150.3, 165.9 ppm; MS (EI, 70 eV): m/z (%): 243 (43) [M]+,
199 (100), 181 (78), 153 (46), 126 (39), 77 (29).
7.5 Hz, 2H), 7.58 (s, 2H), 8.02 (t, J=7.9 Hz, 1H), 8.30 ppm (d, J=7.9 Hz,
2H); 13C NMR (100.6 MHz, CD3OD): d=69.6, 80.3, 126.2, 128.4, 129.1,
130.0, 130.4, 131.1, 138.1, 142.8, 149.6, 151.9, 169.4, 172.8 ppm; FAB-MS:
m/z: 670 [M]+; UV/Vis (CH2Cl2): lmax (loge)=383 (3.54), 484 nm (4.30);
elemental analysis calcd (%) for C30H21ClN4O6Ru: C 53.78, H 3.16, N
8.36; found: C 53.51, H 3.54, N 8.23.
General procedure B for the synthesis of (pybox)(pydic)ruthenium 1 or
(pyboxazine)(pydic)ruthenium 2: The synthesis of Ru{2,6-bis-[(4R)-4-(2-
naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]pyridine}(pyridine-2,6-dicarboxy-
late) (R)-(2ca) is takenas anexample.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(4-
bromopyridine-2,6-dicarboxylate)ruthenium (1ad): From general proce-
dure B by using 3a (150 mg, 0.41 mmol), [{Ru(p-cymene)Cl2}2] (124 mg,
0.20 mmol), 5d (100 mg, 0.41 mmol), and NaOH (33 mg, 0.81 mmol), a
greensolid of 1ad (251 mg, 86%) was obtained. Rf =0.19 (CH2Cl2/
MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=4.65 (m, 4H), 5.15–5.22
(m, 2H), 6.71 (d, J=6.2 Hz, 4H), 7.09 (unresolved dd, 4H), 7.21 (t, J=
6.9 Hz, 2H), 7.61 (s, 2H), 7.68 (t, J=7.5 Hz, 1H), 7.97 ppm (d, J=7.5 Hz,
2H); 13C NMR (100.61 MHz, CDCl3): d=68.0, 78.4, 124.1, 126.6, 127.4,
128.7, 129.1, 135.7, 147.2, 149.9, 167.3, 169.8 ppm; FAB-MS: m/z: 714
[M]+, 716 [M+2]+; UV/Vis (CH2Cl2) lmax (loge)=384 (3.59), 484 nm
(4.33); elemental analysis calcd (%) for C30H21BrN4O6Ru·CH3OH: C
49.88, H 3.38, N 7.50; found: C 49.56, H 3.26, N 7.79.
Synthesis of {2,6-bis-[(4R)-4-(2-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine}(pyridine-2,6-dicarboxylate)ruthenium ((R)-2ca): Disodium pyr-
idine-2,6-dicarboxylate (Na2pydic) (64 mg, 0.30 mmol) inMeOH/H 2O 1:1
(2 mL) was added via
a cannula to a solution of (R)-4a (150 mg,
0.30 mmol) and [{Ru(p-cymene)Cl2}2] (92 mg, 0.15 mmol) inMeOH
(2 mL) under Ar. The whole reaction mixture was heated to 658C for
1 h. The reactionmixture was thendiluted with CH 2Cl2 (30 mL) and
washed with H2O (30 mL). The deep orange organic layer was dried over
MgSO4, filtered, and evaporated to dryness under reduced pressure. The
reactionmixture was thensubjected to chromatography over silica gel
(70–230 mesh) with CH2Cl2/MeOH 100:2 to CH2Cl2/MeOH 100:5 as the
gradient eluent. After removal of solvent under reduced pressure, the
product was recrystallized over CH2Cl2/n-hexane to give a brown solid
(138 mg, 60%). Rf =0.09 (CH2Cl2/MeOH 100:5); 1H NMR (400.1 MHz,
CDCl3): d=1.95–2.02 (m, 2H), 2.22–2.30, (m, 2H), 3.88–3.90 (m, 2H),
4.39–4.51 (m, 4H), 6.57–6.62 (m, 3H), 6.72–6.75 (m, 4H), 7.31–7.41 (m,
6H), 7.53 (d, J=8.5 Hz, 2H), 7.63 (t, J=7.9 Hz, 1H), 7.73 (d, J=7.9 Hz,
2H), 8.10 ppm (d, J=7.9 Hz, 2H); 13C NMR (100.6 MHz, CDCl3): d=
30.7, 58.2, 63.6, 123.5, 124.2, 124.4, 125.2, 125.3, 126.0, 127.7, 127.8, 128.8,
132.3, 132.4, 132.6, 135.7, 136.7, 149.1, 152.0, 160.5, 171.4 ppm; FAB-MS:
m/z: 764 [M]+; UV/Vis (CH2Cl2) lmax (loge)=384 (3.45), 484 nm (4.27);
elemental analysis calcd (%) for C40H30N4O6Ru·H2O: C 61.45, H 4.12, N
7.17; found: C 61.19, H 4.09, N 6.81.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(4-
methoxypyridine-2,6-dicarboxylate)ruthenium (1ae): From general pro-
cedure B by using 3a (105 mg, 0.28 mmol), [{Ru(p-cymene)Cl2}2] (87 mg,
0.14 mmol), 5e (56 mg, 0.28 mmol), and NaOH (23 mg, 0.56 mmol), a
greensolid of 1ae (98 mg, 53%) was obtained. Rf =0.29 (CH2Cl2/MeOH
100:5); 1H NMR (400 MHz, CDCl3): d=3.93 (s, 3H), 4.57–4.65 (m, 4H),
5.11–5.12 (m, 2H), 6.70 (d, J=7.3 Hz, 4H), 7.04–7.07 (unresolved dd,
4H), 7.12–7.17 (m, 4H), 7.60 (t, J=7.7 Hz, 1H), 7.93 ppm (d, J=7.7 Hz,
2H); 13C NMR (100.61 MHz, CDCl3): d=56.3, 67.7, 78.4, 112.4, 124.1,
124.9, 127.3, 128.6, 136.2, 147.7, 149.8, 166.0, 167.7, 170.8 ppm; FAB-MS:
m/z: 666 [M]+; UV/Vis (CH2Cl2): lmax (loge)=366 (3.56), 483 (4.25); ele-
mental analysis calcd (%) for C30H22N4O7Ru·0.5CH2Cl2: C 53.43, H 3.56,
N 7.91; found: C 53.07, H 3.76, N 8.03.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(pyri-
dine-2,6-dicarboxylate)ruthenium (1aa): From general procedure B by
using 3a (500 mg, 1.35 mmol), [{Ru(p-cymene)Cl2}2] (414 mg, 0.68 mmol),
and disodium pyridine-2,6-dicarboxylate (286 mg, 1.35 mmol), a brown
solid of 1aa (665 mg, 78%) was obtained. Rf =0.08 (CH2Cl2/MeOH
100:5); 1H NMR (400.1 MHz, CDCl3): d=4.59–4.68 (m, 4H), 5.15–5.21
(m, 2H), 6.68 (d, J=6.8 Hz, 4H), 7.02–7.05 (unresolved dd, 4H), 7.14 (t,
J=7.0 Hz, 2H), 7.54 (m, 3H), 7.65 (t, J=7.7 Hz, 1H), 7.95 ppm (d, J=
7.7 Hz, 2H); 13C NMR (100.6 MHz, CDCl3): d=67.8, 78.5, 124.0, 125.9,
127.3, 128.6, 129.1, 133.7, 135.6, 136.0, 147.1, 149.2, 167.4, 171.1 ppm;
FAB-MS: m/z: 636 [M]+; UV/Vis (CH2Cl2): lmax (loge)=375 (3.36),
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(4-
phenylpyridine-2,6-dicarboxylate)ruthenium (1af): From general proce-
dure B by using 3a (144 mg, 0.39 mmol), [{Ru(p-cymene)Cl2}2] (119 mg,
0.20 mmol), 5 f (95 mg, 0.39 mmol), and NaOH (31 mg, 0.78 mmol), a
greensolid of 1af (272 mg, 98%) was obtained. Rf =0.12 (CH2Cl2/MeOH
100:5); 1H NMR (400 MHz, CDCl3): d=4.60–4.70 (m, 4H), 5.17 (m, 2H),
6.71 (d, J=6.7 Hz, 4H), 7.00 (unresolved dd, 4H), 7.14–7.17 (m, 2H),
7.51 (t, J=7.3 Hz, 1H), 7.56–7.59 (m, 2H), 7.65 (t, J=7.7 Hz, 1H), 7.69
(d, J=7.3 Hz, 2H), 7.75 (s, 2H), 7.96 ppm (d, J=7.7 Hz, 2H); 13C NMR
(100.61 MHz, CDCl3): d=67.9, 78.3, 123.6, 123.9, 125.8, 126.7, 127.4,
128.4, 128.9, 129.4, 129.4, 135.9, 137.5, 146.6, 147.0, 149.2, 167.3,
171.1 ppm; FAB-MS: m/z: 712 [M]+; UV/Vis (CH2Cl2): lmax (loge)=394
484 nm
(4.47);
elemental
analysis
calcd
(%)
for
C30H22N4O6Ru·0.5CH2Cl2: C 54.03, H 3.42, N 8.26; found: C 54.37, H
(3.63),
488 nm
(4.34);
elemental
analysis
calcd
(%)
for
3.79, N 8.50.
C36H26N4O6Ru·H2O: C 59.26, H 3.87, N 7.68; found: C 59.096, H 3.38, N
7.68.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(4-
hydroxypyridine-2,6-dicarboxylate)ruthenium (1ab): From General pro-
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-chloropyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1ba): From general proce-
dure B by using 3b (100 mg, 0.25 mmol), [{Ru(p-cymene)Cl2}2] (76 mg,
0.13 mmol), and disodium pyridine-2,6-dicarboxylate (52 mg, 0.25 mmol),
a greensolid of 1ba (88 mg, 53%) was obtained. Rf =0.15 (CH2Cl2/
MeOH 100:5); 1H NMR (400.1 MHz, CDCl3): d=4.60–4.69 (m, 4H),
5.17–5.18 (m, 2H), 6.66 (d, J=6.9 Hz, 4H), 7.03 (unresolved dd, 4H),
7.14 (t, J=7.1 Hz, 2H), 7.54 (m, 3H), 7.95 ppm (s, 2H); 13C NMR
(100.6 MHz, CDCl3): d=68.0, 78.7, 124.0, 126.0, 127.3, 128.7, 129.1, 132.5,
134.2, 135.7, 147.4, 149.0, 166.8, 170.9 ppm; FAB-MS: m/z: 670 [M]+;
UV/Vis (CH2Cl2): lmax (loge)=371 (3.48), 493 nm (4.29); elemental anal-
ysis calcd (%) for C30H21N4O6Ru·CH2Cl2: C 51.41, H 3.11, N 7.86; found:
C 51.08, H 3.10, N 7.93.
cedure
B by using 3a (185 mg, 0.50 mmol), [{Ru(p-cymene)Cl2}2]
(153 mg, 0.25 mmol), 5b (101 mg, 0.50 mmol), and NaOH (40 mg,
1.0 mmol), a brownsolid of 1ab (280 mg, 86%) was obtained. Rf =0.19
(CH2Cl2/MeOH 10:1); 1H NMR (400.1 MHz, CD3OD): d=4.82–4.87 (m,
4H), 5.38–5.40 (m, 2H), 6.77 (d, J=7.3 Hz, 4H), 7.05 (s, 2H), 7.10 (unre-
solved dd, 4H), 7.21 (unresolved dd, 2H), 7.92 (t, J=6.9 Hz, 1H),
8.09 ppm (d, J=6.9 Hz, 1H); 13C NMR (100.6 MHz, CD3OD): d=69.2,
80.1, 116.2, 126.6, 128.5, 128.9, 129.9, 130.3, 138.6, 149.4, 150.8, 166.7,
170.6, 173.1 ppm; FAB-MS: m/z: 652 [M]+; UV/Vis (MeOH) lmax
(loge)=359 (3.53), 472 nm (4.24); elemental analysis calcd (%) for
C30H22N4O7Ru·CH3OH: C 54.46, H 3.83, N 8.20; found: C 54.35, H 4.16,
N 7.96.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(4-
chloropyridine-2,6-dicarboxylate)ruthenium (1ac): From general proce-
dure B by using 3a (185 mg, 0.50 mmol), [{Ru(p-cymene)Cl2}2] (153 mg,
0.25 mmol), 5c (101 mg, 0.50 mmol), and NaOH (40 mg, 1.0 mmol), a
deep greencrystalline solid of 1ac (252 mg, 75%) was obtained. Rf =0.11
(CH2Cl2/MeOH 100:5); 1H NMR (400.1 MHz, CD3OD): d=4.46 (dd, J=
9.5, 11.3 Hz, 2H), 4.77 (dd, J=8.5, 11.3 Hz, 2H), 5.39 (dd, J=8.5, 9.5 Hz,
2H), 6.79 (d, J=7.1 Hz, 4H), 7.10 (unresolved dd, 4H), 7.25 (t, J=
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-(N,N-dime-
thylamino)pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1ca): From
general procedure
B by using 3c (70 mg, 0.17 mmol), [{Ru(p-cym-
ene)Cl2}2] (52 mg, 0.085 mmol), and disodium pyridine-2,6-dicarboxylate
(36 mg, 0.17 mmol), a greencrystalline solid of 1ca (74 mg, 64%) was ob-
tained. Rf =0.05 (CH2Cl2/MeOH 100:5); 1H NMR (400.1 MHz, CDCl3):
d=3.36 (s, 6H), 4.55 (dd, J=8.8, 11.0 Hz, 2H), 4.70 (unresolved dd, 2H),
5.11 (dd, J=8.8, 9.8 Hz, 2H), 6.65 (d, J=7.2 Hz, 4H), 7.00 (unresolved
Chem. Eur. J. 2006, 12, 1855 – 1874
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1869

M. Beller et al.
dd, 4H), 7.10 (t, J=7.4 Hz, 2H), 7.26 (brs, 2H), 7.33–7.36 (m, 1H), 7.42–
7.44 ppm (m, 2H); 13C NMR (100.6 MHz, CDCl3): d=40.1, 68.0, 78.2,
106.4, 125.6, 127.1, 128.3, 128.8, 131.2, 136.2, 147.1, 150.8, 150.9, 166.6,
172.0 ppm; FAB-MS: m/z: 679 [M]+; UV/Vis (CH2Cl2): lmax (loge)=388
(3.64), 505 nm (4.33); HRMS (ESI+): m/z calcd for C32H27N5O6102Ru+
H+: 679.10880; found: 679.10046.
100:5); 1H NMR (400 MHz, CD3OD): d=3.31 (dd, J=14.7, 8.3 Hz, 2H),
3.88 (dd, J=14.7, 10.1 Hz, 2H), 6.32 (dd, J=10.1, 8.3 Hz, 2H), 7.37–7.42
(m, 10H), 7.98 (t, J=7.9 Hz, 1H), 8.24 (d, J=7.9 Hz, 2H), 8.30 (dd, J=
8.7, 6.9 Hz, 1H), 8.39 (d, J=6.9 Hz, 1H), 8.39 ppm (d, J=8.7 Hz, 1H);
13C NMR (100.61 MHz, CDCl3): d=58.1, 86.1, 123.9, 126.4, 126.6, 127.2,
129.2, 129.6, 134.9, 136.8, 147.3, 150.4, 167.5, 171.7 ppm; FAB-MS: m/z:
636 [M]+; UV/Vis (CH2Cl2) lmax (loge)=377 (3.65), 480 nm (4.36); ele-
mental analysis calcd (%) for C30H22N4O6Ru·H2O: C 55.13, H 3.70, N
8.57; found: C 55.00, H 3.59, N 8.59.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-phenylpyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1da): From general proce-
dure B by using 3d (69 mg, 0.15 mmol), [{Ru(p-cymene)Cl2}2] (47 mg,
0.077 mmol),
and
disodium
pyridine-2,6-dicarboxylate
(33 mg,
Synthesis of {2,6-bis-[(4R,5S)-4,5-diphenyl-4,5-dihydrooxazol-2-yl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1ia): From general proce-
dure B by using 3i (522 mg, 1.0 mmol), [{Ru(p-cymene)Cl2}2] (306 mg,
0.50 mmol), and disodium pyridine-2,6-dicarboxylate (211 mg, 1.0 mmol),
a dark greencrystalline solid of 1ia was obtained (584 mg, 74%). Rf =
0.15 mmol), a brownsolid of 1da (50 mg, 47%) was obtained. Rf =0.20
(CH2Cl2/MeOH 100:5); 1H NMR (400.1 MHz, CDCl3): d=4.59–4.68 (m,
4H), 5.16–5.19 (m, 2H), 6.67 (d, J=7.3 Hz, 4H), 7.03 (unresolved dd,
4H), 7.14 (t, J=7.3 Hz, 2H), 7.48–7.60 (m, 6H), 7.84 (d, J=7.7 Hz, 2H),
8.19 ppm (s, 2H); 13C NMR (100.6 MHz, CDCl3): d=67.8, 78.5, 121.9,
126.0, 127.0, 127.2, 128.6, 129.1, 129.3, 129.6, 133.7, 136.0, 137.4, 139.6,
147.1, 149.3, 167.5, 171.2 ppm; FAB-MS: m/z: 712 [M]+; UV/Vis
(CH2Cl2): lmax (loge)=345 (3.62), 495 nm (4.23); HRMS (ESI+): m/z
calcd for C36H26N4O6102Ru: 712.09618; found: 712.08960.
1
0.14 (CH2Cl2/MeOH 100:5); H NMR (400 MHz, CDCl3): d=5.01 (d, J=
10.5 Hz, 2H), 5.26 (s, 1H, 0.5 CH2Cl2), 6.23 (d, J=7.5 Hz, 4H), 6.36 (d,
J=10.5 Hz, 2H), 6.71 (unresolved dd, 4H), 6.80–6.85 (m, 6H), 7.01–7.02
(m, 6H), 7.33–7.40 (m, 3H), 7.76 (t, J=7.7 Hz, 1H), 8.14 ppm (d, J=
7.7 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=71.5, 88.2, 124.3, 125.6,
125.7, 125.8, 127.7, 127.8, 128.0, 128.1, 128.2, 132.5, 133.9, 134.1, 147.1,
149.1, 167.6, 171.4 ppm; FAB-MS: m/z: 788 [M]+, 84 [CH2Cl2]+; UV/Vis
(CH2Cl2): lmax (loge)=389 (3.63), 485 nm (4.28); elemental analysis calcd
(%) for C42H30N4O6Ru·0.5CH2Cl2: C 61.48, H 3.76, N 6.75; found: C
61.27, H 3.74, N 6.76.
Synthesis of {2,6-bis-[(4S)-4-phenyl-4,5-dihydrooxazol-2-yl]-4-(1-naph-
thylpyridine}(pyridine-2,6-dicarboxylate)ruthenium (1ea): From general
procedure B by using 3e (46 mg, 0.093 mmol), [{Ru(p-cymene)Cl2}2]
(28 mg, 0.046 mmol), and disodium pyridine-2,6-dicarboxylate (20 mg,
0.093 mmol), a greencrystalline solid of 1ea (44 mg, 62%) was obtained.
Rf =0.17 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=4.62–
4.74 (m, 4H), 5.17–5.19 (m, 2H), 6.72 (d, J=6.7 Hz, 4H), 7.07 (unre-
solved dd, 4H), 7.17 (t, J=6.7 Hz, 2H), 7.58–7.65 (m, 7H), 7.99–8.01 (m,
2H), 8.03–8.04 (m, 1H), 8.13 ppm (s, 2H); 13C NMR (100.61 MHz,
CDCl3): d=67.9, 78.6, 124.8, 125.4, 125.5, 126.1, 126.5, 127.3, 127.7, 128.7,
128.8, 129.2, 129.6, 130.9, 133.8, 133.9, 135.7, 136.1, 136.4, 139.5, 146.9,
149.3, 167.5, 172.2 ppm; FAB-MS: m/z: 763 [M]+; UV/Vis (CH2Cl2): lmax
(loge)=364 (sh; 3.65), 492 nm (4.39); elemental analysis calcd (%) for
C40H28N4O6Ru·0.5H2O: C 62.33, H 3.79, N 7.27; found: C 62.36, H 3.73 N
7.35.
Synthesis of {2,6-bis-[(4R,5R)-4,5-diphenyl-4,5-dihydrooxazol-2-yl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1ja): From general proce-
dure B by using 3j (200 mg, 0.38 mmol), [{Ru(p-cymene)Cl2}2] (117 mg,
0.19 mmol), and disodium pyridine-2,6-dicarboxylate (81 mg, 0.38 mmol),
a dark brown crystalline solid of was obtained (224 mg, 75%). Rf =0.13
(CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=4.48 (d, J=
10.2 Hz, 2H), 5.85 (d, J=10.2 Hz, 2H), 6.66 (d, J=7.1 Hz, 4H), 7.02–7.05
(m, 4H), 7.14–7.18 (m, 6H), 7.30–7.34 (m, 6H), 7.47 (m, 3H), 7.70 (t, J=
7.8 Hz, 1H), 8.04 ppm (d, J=7.8 Hz, 2H); 13C NMR (100.61 MHz,
CDCl3): d=75.4, 93.6, 124.1, 125.9, 126.0, 127.3, 128.6, 128.9, 129.0, 129.2,
129.4, 133.7, 135.5, 135.7, 147.2, 149.1, 166.9, 171.2 ppm; FAB-MS: m/z:
788 [M]+; UV/Vis (CH2Cl2): lmax (loge)=374 (3.77), 486 nm (4.51); ele-
mental analysis calcd (%) for C42H30N4O6Ru: C 64.03, H 3.84, N 7.11;
found: C 64.21, H 4.05, N 7.12.
Synthesis of {2,6-bis-[(4S,5R)-8,8a-dihydro-3aH-indeno[1,2-d]oxazolyl]-
pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1 fa): From general pro-
cedure
B by using 3 f (200 mg, 0.51 mmol), [{Ru(p-cymene)Cl2}2]
(156 mg, 0.25 mmol), and disodium pyridine-2,6-dicarboxylate (107 mg,
0.57 mmol), a deep red solid of 1 fa was obtained (290 mg, 86%). Rf =
0.11 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=3.37 (dd,
J=2.2, 18.2 Hz, 2H), 3.50 (dd, J=7.3, 18.2 Hz, 2H), 4.99 (d, J=8.1 Hz,
2H), 5.83–5.87 (m, 2H), 5.95 (d, J=7.7 Hz, 2H), 7.00–7.03 (m, 2H),
7.12–7.18 (m, 4H), 7.59 (t, J=7.7 Hz, 1H), 7.86 (d, J=7.7 Hz, 2H), 8.31
(t, J=7.7 Hz, 1H), 8.57 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz,
CDCl3): d=73.7, 78.6, 87.7, 116.5, 124.2, 125.1, 125.3, 127.5, 127.9, 129.7,
135.1, 136.8, 139.2, 147.4, 152.1, 171.3, 192.7 ppm; FAB-MS: m/z: 660
[M]+; UV/Vis (CH2Cl2): lmax (loge)=383 (3.62), 484 nm (4.39); HRMS
(ESI+): m/z calcd for C36H23N4O6102Ru: 661.06538; found: 661.06610.
Synthesis of {2,6-bis-[(4S)-4-(2-chlorophenyl)-4,5-dihydrooxazol-2-yl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1ka): From general proce-
dure B by using 3k (150 mg, 0.34 mmol), [{Ru(p-cymene)Cl2}2] (105 mg,
0.17 mmol) and disodium pyridine-2,6-dicarboxylate (72 mg, 0.34 mmol),
a
deep greensolid of 1ka (130 mg, 54%) was obtained. Rf =0.14
(CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=4.57–4.61 (m,
2H), 5.12–5.22 (m, 4H), 6.76 (m, 2H), 6.98–7.00 (m, 2H), 7.07–7.09 (m,
4H), 7.63–7.64 (m, 3H), 7.67 (t, J=7.7 Hz, 1H), 7.97 ppm (d, J=7.7 Hz,
2H); 13C NMR (100.61 MHz, CDCl3): d=63.9, 77.7, 124.3, 125.9, 126.1,
128.3, 128.7, 129.1, 129.8, 132.6, 134.2, 147.0, 149.5, 168.0, 170.9 ppm;
FAB-MS: m/z: 704 [M]+; UV/Vis (CH2Cl2): lmax (loge)=374 (3.46),
484 nm (4.22); elemental analysis calcd (%) for C30H20Cl2N4O6Ru·H2O:
C 49.87, H 3.07, N 7.75; found: C 49.85, H 3.08, N 7.59.
Synthesis of {2,6-bis-[(4R)-4-(2-naphthyl)-4,5-dihydrooxazol-2-yl]-4-(1-
naphthyl-pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1ga): From
general procedure B by using 3g (235 mg, 0.50 mmol), [{Ru(p-cyme-
ne)Cl2}2] (153 mg, 0.25 mmol), and disodium pyridine-dicarboxylate
(106 mg, 0.50 mmol), a greensolid of 1ga (236 mg, 64%) was obtained.
Rf =0.31 (CH2Cl2/MeOH 10:1); 1H NMR (400 MHz, CDCl3): d=4.69
(unresolved dd, 2H), 4.83 (unresolved dd, 2H), 5.19 (unresolved dd,
2H), 6.41 (t, J=7.5 Hz, 1H), 6.66 (d, J=7.5 Hz, 2H), 6.92 (m, 4H), 7.31–
7.34 (m, 4H), 7.39–7.43 (m, 2H), 7.63–7.65 (m, 3H), 7.75 (d, J=8.1 Hz,
2H), 7.95 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=
68.4, 77.6, 123.5, 123.9, 124.3, 125.6, 126.1, 126.5, 127.4, 127.7, 127.8,
129.7, 132.4, 132.5, 133.0, 133.3, 147.0, 148.5, 167.4, 171.0 ppm; FAB-MS:
m/z: 736 [M]+; UV/Vis (CH2Cl2): lmax (loge)=369 (3.67), 486 nm (4.27);
elemental analysis calcd (%) for C38H26N4O6Ru·H2O: C 60.55, H 3.74, N
7.43; found: C 60.49, H 3.85, N 7.30.
Synthesis of {2,6-bis-[(4S)-5,5-dimethyl-4-phenyl-4,5-dihydrooxazol-2-yl]-
pyridine}-(pyridine-2,6-dicarboxylate)ruthenium (1la): From general pro-
cedure B by using 3l (71 mg, 0.17 mmol), [{Ru(p-cymene)Cl2}2] (51 mg,
0.083 mmol),
and
disodium
pyridine-2,6-dicarboxylate
(35 mg,
0.17 mmol), a greensolid of 1la (82 mg, 70%) was obtained. Rf =0.20
(CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=0.97 (s, 6H),
1.58 (s, 6H), 4.29 (s, 2H), 6.58 (d, J=7.0 Hz, 4H), 6.99–7.07 (m, 6H),
7.33 (t, J=7.6 Hz, 1H), 7.43 (d, J=7.6 Hz, 2H), 7.63 (t, J=7.9 Hz, 1H),
7.90 ppm (d, J=7.9 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=24.0,
28.6, 75.7, 93.3, 123.9, 125.5, 125.7, 127.4, 128.1, 128.4, 133.4, 133.5, 147.6,
149.6, 167.1, 171.7 ppm; FAB-MS: m/z: 692 [M]+; UV/Vis (CH2Cl2): lmax
(loge)=378 (3.57), 484 nm (4.30); elemental analysis calcd (%) for
C34H30N4O6Ru·H2O: C 57.54, H 4.54, N 7.89; found: C 57.33, H 4.41, N
7.84.
Synthesis of {2,6-bis-[(5S)-5-phenyl-4,5-dihydrooxazol-2-yl]pyridine}(pyri-
dine-2,6-dicarboxylate)ruthenium (1ha): From general procedure B by
using 3h (200 mg, 0.54 mmol), [{Ru(p-cymene)Cl2}2] (166 mg, 0.27 mmol),
and disodium pyridine-2,6-dicarboxylate (114 mg, 0.54 mmol), a brown
solid of 1ha (245 mg, 71%) was obtained. Rf =0.14 (CH2Cl2/MeOH
Synthesis of {2,6-bis-[(4S)-4-methyl-4,5-dihydrooxazol-2-yl]pyridine)(pyri-
dine-2,6-dicarboxylate)ruthenium (1ma): From general procedure B by
using 3m (245 mg, 1.0 mmol), [{Ru(p-cymene)Cl2}2] (306 mg, 0.5 mmol),
1870
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
and disodium pyridine-2,6-dicarboxylate (211 mg, 1.0 mmol), a deep red
solid of 1ma was obtained (177 mg, 79%). Rf =0.07 (CH2Cl2/MeOH
100:5); 1H NMR (400 MHz, CDCl3): d=0.74 (d, J=6.6 Hz, 6H), 3.77–
3.86 (m, 2H), 4.25–4.30 (unresolved dd, 2H), 4.87–4.92 (unresolved dd,
2H), 7.60 (t, J=7.7 Hz, 1H), 7.83 (t, J=7.7 Hz, 2H), 8.08 (t, J=7.7 Hz,
1H), 8.30 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=
18.9, 33.8, 60.0, 123.6, 126.7, 127.0, 134.8, 147.3, 151.0, 166.6, 171.5 ppm;
FAB-MS: m/z: 512 [M]+; UV/Vis (CH2Cl2): lmax (loge)=381 (3.57),
480 nm (4.30); HRMS (ESI+): m/z calcd for C20H19N4O6102Ru+H+:
513.03380; found: 513.03479.
a red crystalline solid of 1ra was obtained (58 mg, 59%). Rf =0.21
(CH2Cl2/MeOH 100:5, neutral alumina); 1H NMR (400 MHz, CD3OD):
d=2.84 (dd, J=4.8, 11.3 Hz, 2H), 3.00 (dd, J=4.1, 11.3 Hz, 2H), 3.61–
3.68 (m, 2H), 4.72 (dd, J=7.5, 8.7 Hz, 2H), 4.84–4.89 (unresolved dd,
2H), 7.82 (t, J=7.9 Hz, 1H), 8.07 (d, J=7.9 Hz, 2H), 8.18 (dd, J=6.8,
8.5 Hz, 1H), 8.26 (d, J=6.8 Hz, 1H), 8.26 ppm (d, J=8.5 Hz, 1H);
13C NMR (100.61 MHz, CD3OD): d=63.0, 67.4, 80.4, 126.0, 129.2, 136.9,
137.4, 149.6, 152.6, 169.9, 174.6 ppm; FAB-MS: m/z: 544 [M]+; UV/Vis
(CH2Cl2): lmax (loge)=383 (3.57), 476 nm (4.32); HRMS (ESI+): m/z
calcd for C20H18N4O8102Ru: 544.01827; found: 544.01678.
Synthesis of {2,6-bis-[(4S)-4-isopropyl-4,5-dihydrooxazol-2-yl]pyridine}-
(pyridine-2,6-dicarboxylate)ruthenium (1na): From general procedure B
by using 3n (201 mg, 0.66 mmol), [{Ru(p-cymene)Cl2}2] (204 mg,
Synthesis of {2,6-bis-[(4R)-4-(tert-butyl-dimethylsilanyloxymethyl)-4,5-di-
hydrooxazol-2-yl]pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1sa):
From general procedure B by using 3s (25 mg, 0.049 mmol), [{Ru(p-cym-
ene)Cl2}2] (15 mg, 0.025 mmol), and disodium pyridine-2,6-dicarboxylate
(10 mg, 0.049 mmol), a deep red solid of 1sa was obtained (24 mg, 63%).
Rf =0.17 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=ꢀ0.19
(s, 6H), ꢀ0.17 (s, 6H), 0.71 (s, 18H), 2.98–3.06 (m, 4H), 3.73–3.81 (m,
2H), 4.73–4.77 (unresolved dd, 2H), 4.80–4.85 (unresolved dd, 2H), 7.61
(t, J=7.9 Hz, 1H), 7.87 (d, J=7.9 Hz, 2H), 8.10 (t, J=7.7 Hz, 1H),
8.34 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=ꢀ5.8,
ꢀ5.7, 17.9, 25.6, 63.0, 65.5, 75.0, 124.0, 126.7, 127.1, 134.8, 147.2, 151.0,
168.0, 171.1 ppm; FAB-MS: m/z: 772 [M]+; UV/Vis (CH2Cl2): lmax (loge)
0.33 mmol),
and
disodium
pyridine-2,6-dicarboxylate
(141 mg,
0.66 mmol), a greencrystalline solid of 1na (309 mg, 82%) was obtained.
Rf =0.33 (CH2Cl2/MeOH 10:1); 1H NMR (400 MHz, CDCl3): d=0.44 (d,
J=6.8 Hz, 6H), 0.59 (d, J=7.2 Hz, 6H), 1.03–1.10 (m, 2H), 3.66–3.71 (m,
2H), 4.56–4.60 (unresolved dd, 2H), 4.64–4.68 (unresolved dd, 2H), 7.61
(t, J=7.8 Hz, 1H), 7.85 (d, J=7.8 Hz, 2H), 8.08 (t, J=7.7 Hz, 1H),
8.30 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=13.8,
18.8, 68.9, 71.0, 123.8, 126.6, 127.0, 134.7, 147.1, 150.9, 166.5, 171.5 ppm;
FAB-MS: m/z: 568 [M]+; UV/Vis (CH2Cl2) lmax (loge)=382 (3.56),
480 nm (4.30).
=
382 (3.68), 481 nm (4.26); HRMS (ESI+): m/z calcd for
C32H46N4O8102RuSi2: 772.20908; found: 772.24414.
Synthesis of {2,6-bis-[(4S)-4-tert-butyl-4,5-dihydrooxazol-2-yl]pyridine}-
(pyridine-2,6-dicarboxylate)ruthenium (1oa): From general procedure B
by using 3o (112 mg, 0.34 mmol), [{Ru(p-cymene)Cl2}2] (104 mg,
0.17 mmol), and disodium pyridine-2,6-dicarboxylate (72 mg, 0.34 mmol),
Synthesis of {2,6-bis-{(4R)-4-[1-(tert-Butyldimethylsilanyloxy)ethyl]-4,5-
dihydrooxazol-2-yl}pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1ta):
From general procedure B by using 3t (30 mg, 0.060 mmol), [{Ru(p-cym-
ene)Cl2}2] (18 mg, 0.030 mmol), and disodium pyridine-2,6-dicarboxylate
(13 mg, 0.060 mmol), a deep orange solid of 1ta was obtained (34 mg,
a
deep orange solid of 1oa was obtained (46 mg, 23%). Rf =0.18
(CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=0.40 (s, 18H),
3.02 (dd, J=3.9, 9.6 Hz, 2H), 4.51–4.55 (unresolved dd, 2H), 4.73 (dd,
J=3.9, 9.0 Hz, 2H), 7.69 (t, J=7.7 Hz, 1H), 7.90 (t, J=7.7 Hz, 2H), 8.02
(t, J=7.7 Hz, 1H), 8.29 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz,
CDCl3): d=24.9, 33.4, 71.7, 73.3, 124.7, 126.7, 126.9, 134.5, 135.5, 147.6,
152.0, 167.6, 172.1 ppm; FAB-MS: m/z: 596 [M]+; UV/Vis (CH2Cl2): lmax
(loge)=379 (3.76), 484 nm (4.32); HRMS (ESI+): m/z calcd for
C26H31N4O6102Ru+H+: 597.13052; found: 597.12872.
1
71%). Rf =0.10 (CH2Cl2/MeOH 100:5); H NMR (400 MHz, CDCl3): d=
ꢀ0.33 (s, 3H), ꢀ0.22 (s, 2H), 0.67 (d, J=5.7 Hz, 2H), 0.68 (s, 18H), 3.13–
3.19 (m, 2H), 3.72–3.77 (m, 2H), 4.69 (unresolved dd, 2H), 4.93 (dd, J=
6.5, 9.4 Hz, 2H), 7.62 (t, J=7.9 Hz, 1H), 7.88 (d, J=7.9 Hz, 2H), 8.09 (t,
J=7.7 Hz, 1H), 8.35 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz,
CDCl3): d=ꢀ5.5, ꢀ5.1, 15.6, 17.7, 25.5, 66.8, 68.3, 71.9, 124.2, 126.8,
127.1, 134.7, 147.1, 151.0, 167.6, 171.0 ppm; FAB-MS: m/z:800 [M]+.
Synthesis of {2,6-bis-[(4S,5S)-4-methyl-5-phenyl-4,5-dihydrooxazol-2-yl]-
pyridine}(pyridine-2,6-dicarboxylate)ruthenium (1pa): From general pro-
Synthesis of {2,6-bis-[(4S)-4-Methoxycarbonyl-4,5-dihydrooxazol-2-yl]pyr-
idine}(pyridine-2,6-dicarboxylate) ruthenium (1ua): From general proce-
dure B by using 3u (100 mg, 0.30 mmol), [{Ru(p-cymene)Cl2}2] (92 mg,
0.15 mmol), and disodium pyridine-2,6-dicarboxylate (63 mg, 0.30 mmol),
a deep greenbrowncrystalline solid of 1ua was obtained (32 mg, 18%).
Rf =0.46 (CH2Cl2/MeOH 100:5, neutral alumina); 1H NMR (400 MHz,
CDCl3): d=3.49 (s, 6H), 4.17 (dd, J=7.2, 9.6 Hz, 2H), 4.94 (unresolved
dd, 2H), 5.18 (unresolved dd, 2H), 7.66 (t, J=7.7 Hz, 1H), 7.96 (d, J=
7.7 Hz, 2H), 8.16 (t, J=7.7 Hz, 1H), 8.35 ppm (d, J=7.7 Hz, 2H);
13C NMR (100.61 MHz, CDCl3): d=53.7, 64.4, 73.8, 125.3, 126.2, 126.6,
135.6, 146.6, 151.1, 167.4, 169.0, 171.7 ppm; FAB-MS: m/z: 600 [M]+;
UV/Vis (CH2Cl2): lmax (loge)=371 (3.79), 488 nm (4.43); HRMS (ESI+
): m/z calcd for C22H18N4O10102Ru: 600.01109; found: 600.00665.
cedure
B by using 3p (135 mg, 0.34 mmol), [{Ru(p-cymene)Cl2}2]
(104 mg, 0.17 mmol), and disodium pyridine-2,6-dicarboxylate (72 mg,
0.34 mmol), a deep greencrystals of 1pa was obtained (177 mg, 79%).
Rf =0.16 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CD2Cl2): d=0.84
(d, J=6.7 Hz, 6H), 3.75 (dd, J=9.7, 6.7 Hz, 2H), 5.51 (d, J=9.7 Hz, 2H),
7.33–7.37 (m, 4H), 7.38–7.41 (m, 6H), 7.69 (t, J=7.9 Hz, 1H), 8.00 (d,
J=7.9 Hz, 2H), 8.08 (dd, J=7.2, 8.2 Hz, 1H), 8.23 ppm (m, 2H);
13C NMR (100.61 MHz, CD2Cl2): d=18.2, 68.1, 92.5, 124.1, 126.5, 126.9,
129.1, 129.6, 135.1, 135.8, 136.7, 147.4, 151.3, 166.5, 171.4 ppm; FAB-MS:
m/z: 664 [M]+; UV/Vis (CH2Cl2): lmax (loge)=382 (3.81), 482 nm (4.53);
elemental analysis calcd (%) for C32H26N4O6Ru: C 57.91, H 3.95, N 8.44;
found: C 57.86, H 3.84, N 8.27.
Synthesis of {2,6-bis-[(4R)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium ((R)-2aa): From general pro-
cedure B by using (R)-4a (199 mg, 0.50 mmol), [{Ru(p-cymene)Cl2}2]
(153 mg, 0.25 mmol), and disodium pyridine-2,6-dicarboxylate (106 mg,
0.50 mmol), a greensolid of ( R)-2aa (132 mg, 40%) was obtained. Rf =
0.11 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=1.80–1.85
(m, 2H), 2.25–2.33, (m, 2H), 3.74–3.76 (m, 2H), 4.33–4.39 (m, 2H), 4.42–
4.46 (m, 2H), 6.42 (d, J=7.3 Hz, 4H), 7.01 (unresolved dd, 4H), 7.11 (t,
J=7.3 Hz, 2H), 7.44–7.50 (m, 3H), 7.62 (t, J=7.9 Hz, 1H), 7.97 ppm (d,
J=7.9 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=30.4, 57.5, 62.7,
124.0, 125.4, 125.8, 126.0, 127.4, 128.6, 132.5, 139.3, 149.3, 151.8, 160.3,
171.4 ppm; FAB-MS: m/z: 664 [M]+; UV/Vis (CH2Cl2): lmax (loge)=384
Synthesis of {2,6-bis-[(4S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}(pyri-
dine-2,6-dicarboxylate)ruthenium (1qa): From general procedure B by
using 3q (100 mg, 0.25 mmol), [{Ru(p-cymene)Cl2}2] (77 mg, 0.13 mmol),
and disodium pyridine-2,6-dicarboxylate (53 mg, 0.25 mmol), a brown
solid of 1qa was obtained (141 mg, 85%). Rf =0.15 (CH2Cl2/MeOH
1
100:5); H NMR (400 MHz, CDCl3): d=2.27–2.37 (m, 4H), 3.98–4.06 (m,
2H), 4.48 (unresolved dd, 2H), 4.65 (unresolved dd, 2H), 6.74 (d, J=
7.5 Hz, 4H), 7.14–7.18 (m, 6H), 7.62 (t, J=7.9 Hz, 1H), 7.86 (d, J=
7.9 Hz, 2H), 8.14 (t, J=7.7 Hz, 1H), 8.39 ppm (d, J=7.7 Hz, 2H);
13C NMR (100.61 MHz, CDCl3): d=39.3, 65.2, 75.5, 124.0, 126.9, 127.0,
127.4, 128.6, 128.8, 135.1, 147.3, 151.1, 167.2, 171.5 ppm; FAB-MS: m/z:
664 [M]+; UV/Vis (CH2Cl2): lmax (loge)=382 (3.70), 481 nm (4.49); ele-
mental analysis calcd (%) for C32H26N4O6Ru·tBuOMe: C 59.11, H 5.09,
N 7.45; found: C 58.76, H 4.67, N 7.81.
(3.47),
482 nm
(4.23);
elemental
analysis
calcd
(%)
for
C32H26N4O6Ru·H2O: C 56.38, H 4.14, N 8.22; found: C 56.13, H 3.96, N
8.23.
Synthesis of {2,6-bis-[(4R)-4-hydroxymethyl-4,5-dihydrooxazol-2-yl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium (1ra): From general proce-
dure B by using 3r (50 mg, 0.18 mmol), [{Ru(p-cymene)Cl2}2] (55 mg,
0.09 mmol), and disodium pyridine-2,6-dicarboxylate (38 mg, 0.18 mmol),
Synthesis of {2,6-bis-[(4S)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium ((S)-2aa): From general pro-
cedure B by using (S)-4a (199 mg, 0.50 mmol), [{Ru(p-cymene)Cl2}2]
(153 mg, 0.25 mmol) and disodium pyridine-2,6-dicarboxylate (106 mg,
Chem. Eur. J. 2006, 12, 1855 – 1874
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1871

M. Beller et al.
0.50 mmol), a greensolid of ( S)-2aa (95 mg, 29%) was obtained. Rf =
0.13 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=1.80–1.84
(m, 2H), 2.24–2.32, (m, 2H), 3.73–3.75 (m, 2H), 4.32–4.38 (m, 2H), 4.41–
4.45 (m, 2H), 6.41 (d, J=7.3 Hz, 4H), 7.00 (unresolved dd, 4H), 7.10 (t,
J=7.3 Hz, 2H), 7.43–7.49 (m, 3H), 7.61 (t, J=7.9 Hz, 1H), 7.96 ppm (d,
J=7.9 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=30.4, 57.5, 62.6,
123.9, 125.3, 125.8, 126.0, 127.4, 128.6, 132.5, 139.2, 149.3, 151.8, 160.3,
171.4 ppm; FAB-MS: m/z: 664 [M]+; UV/Vis (CH2Cl2): lmax (loge)=385
(4.27); HRMS (ESI+): m/z calcd for C32H2535Cl2N4O6102Ru: 733.01947;
found: 733.01749.
Synthesis of {2,6-bis-[(4S)-4-(4-methoxyphenyl)-5,6-dihydro-4H-[1,3]oxa-
zinyl]pyridine}(pyridine-2,6-dicarboxylate)ruthenium ((S)-2ea): From
general procedure B by using (S)-4e (97 mg, 0.21 mmol), [{Ru(p-cym-
ene)Cl2}2] (65 mg, 0.11 mmol) and disodium pyridine-2,6-dicarboxylate
(45 mg, 0.21 mmol), a greensolid of ( S)-2ea (80 mg, 53%) was obtained.
Rf =0.19 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=1.81–
1.84 (m, 2H), 2.22–2.28, (m, 2H), 3.67–3.69 (m, 2H), 3.75 (s, 6H), 4.33–
4.37 (m, 2H), 4.43–4.46 (m, 2H), 6.32 (d, J=8.5 Hz, 4H), 6.51 (d, J=
8.5 Hz, 4H), 7.45–7.53 (m, 3H), 7.60 (t, J=7.8 Hz, 1H), 7.95 ppm (d, J=
7.8 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=30.7, 55.5, 57.0, 63.0,
114.2, 123.9, 125.3, 125.6, 127.2, 131.5, 132.5, 149.4, 152.0, 158.6, 160.1,
171.5 ppm; FAB-MS: m/z: 724 [M]+; UV/Vis (CH2Cl2): lmax (loge)=387
(3.45), 482 nm (4.28); HRMS (ESI+): m/z calcd for C34H31N4O8102Ru:
725.11853; found: 725.11740.
(3.47),
482 nm
(4.26);
elemental
analysis
calcd
(%)
for
C32H26N4O6Ru·H2O: C 56.38, H 4.14, N 8.22; found: C 56.34, H 4.03, N
8.07.
Synthesis of {2,6-bis-[(4R)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyri-
dine}(4-chloropyridine-2,6-dicarboxylate)ruthenium ((R)-2ac): From gen-
eral procedure B by using (R)-4a (197 mg, 0.50 mmol), [{Ru(p-cym-
ene)Cl2}2] (152 mg, 0.25 mmol), 5c (100 mg, 0.50 mmol), and NaOH
(40 mg, 1.0 mmol), a greensolid of ( R)-2ac (132 mg, 38%) was obtained.
Rf =0.16 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3): d=1.85–
1.89 (m, 2H), 2.23–2.32, (m, 2H), 3.71–3.73 (m, 2H), 4.35–4.41 (m, 2H),
4.44–4.49 (m, 2H), 6.44 (d, J=7.2 Hz, 4H), 7.05 (unresolved dd, 4H),
7.16 (t, J=7.3 Hz, 2H), 7.40 (s, 2H), 7.64 (t, J=7.9 Hz, 1H), 7.98 ppm (d,
J=7.9 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=30.5, 57.8, 63.1,
124.1, 126.0, 126.0, 127.6, 128.7, 139.2, 140.3, 150.1, 152.0, 160.4,
170.4 ppm; FAB-MS: m/z: 698 [M]+; UV/Vis (CH2Cl2): lmax (loge)=393
Synthesis of {2,6-bis-[(4R)-4-isopropyl-5,6-dihydro-4H-[1,3]oxazinyl]pyri-
dine}(pyridine-2,6-dicarboxylate)ruthenium ((R)-2 fa): From general pro-
cedure
B by using (R)-4 f (329 mg, 1.0 mmol), [{Ru(p-cymene)Cl2}2]
(306 mg, 0.50 mmol) and disodium pyridine-2,6-dicarboxylate (211 mg,
1.0 mmol), a deep greencrystalline solid of ( R)-2 fa (166 mg, 28%) was
obtained. Rf =0.05 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CD2Cl2):
d=0.46 (d, J=7.1 Hz, 6H), 0.49 (d, J=6.9 Hz, 6H), 1.17–1.25 (m, 2H),
1.85–1.98 (m, 4H), 2.51 (dd, J=4.3, 6.8 Hz, 2H), 4.46 (m, 4H), 7.65 (t,
J=7.7 Hz, 1H), 7.97 (d, J=7.7 Hz, 2H), 8.04 (t, J=7.7 Hz, 1H),
8.26 ppm (d, J=7.7 Hz, 2H); 13C NMR (100.61 MHz, CD2Cl2): d=16.4,
19.0, 21.8, 30.8, 58.3, 64.9, 124.0, 126.4, 126.8, 133.4, 151.8, 152.5, 159.5,
171.6 ppm; FAB-MS: m/z: 597 [M+H]+; UV/Vis (CH2Cl2): lmax (loge)=
395 (3.59), 481 nm (4.38); elemental analysis calcd (%) for
C26H30N4O6Ru·H2O: C 50.89, H 5.26, N 9.13; found: C 50.90, H 5.00, N
9.08.
(3.53),
485 nm
(4.32);
elemental
analysis
calcd
(%)
for
C32H25ClN4O6Ru·0.5H2O: C 54.36, H 3.71, N 7.92; found: C 54.37, H
3.66, N 8.00.
Synthesis of {2,6-bis-[(4R)-4-(1-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine}(pyridine-2,6-dicarboxylate)ruthenium ((R)-2ba): From general
procedure B by using (R)-4b (650 mg, 1.3 mmol), [{Ru(p-cymene)Cl2}2]
(400 mg, 0.65 mmol) and disodium pyridine-2,6-dicarboxylate (276 mg,
1.3 mmol), a greensolid of ( R)-2ba (488 mg, 49%) was obtained. Rf =
X-ray crystallographic studies of the complexes: Data were collected
with a STOE-IPDS diffractometer using graphite-monochromated MoKa
radiation. The structures were solved by direct methods (SHELXS-97: G.
M. Sheldrick, University of Gçttingen, Germany, 1997) and refined by
full-matrix least-squares techniques against F2 (SHELXL-97: G. M. Shel-
drick, University of Gçttingen, Germany, 1997). XP (BRUKER AXS)
was used for structure representations. CCDC-279900–279903 (1ia, 1ja,
1na, an d(S)-2aa, respectively) contain the supplementary crystallograph-
ic data for this paper. These data canbe obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1
0.11 (CH2Cl2/MeOH 100:5); H NMR (400 MHz, CDCl3): d=1.90 (d, J=
13.7 Hz, 2H), 2.39–2.45, (m, 2H), 4.40–4.54 (m, 6H), 6.20 (t, J=7.6 Hz,
1H), 6.60–6.62 (m, 4H), 7.12–7.16 (m, 2H), 7.21–7.29 (m, 6H), 7.55 (d,
J=8.3 Hz, 2H), 7.60 (d, J=8.3 Hz, 2H), 7.63 (t, J=7.9 Hz, 1H),
7.98 ppm (d, J=7.9 Hz, 2H); 13C NMR (100.61 MHz, CDCl3): d=29.0,
53.2, 62.8, 121.1, 123.9, 124.7, 125.1, 125.3, 125.8, 125.9, 126.0, 127.9,
128.3, 128.7, 130.7, 133.2, 134.3, 148.1, 151.9, 161.0, 171.1 ppm; FAB-MS:
m/z: 765 [M+H]+; UV/Vis (CH2Cl2): lmax (loge)=383 (3.39), 481 nm
(4.25); HRMS (ESI+): m/z calcd for C40H30N4O6102Ru: 764.12091; found:
764.14739.
Synthesis of {2,6-bis-[(4S)-4-(1-naphthyl)-5,6-dihydro-4H-[1,3]oxazinyl]-
pyridine}(pyridine-2,6-dicarboxylate)ruthenium ((S)-2ba): By using (S)-
4b (400 mg, 0.80 mmol), [{Ru(p-cymene)Cl2}2] (246 mg, 0.40 mmol) and
disodium pyridine-2,6-dicarboxylate (170 mg, 0.80 mmol), a green solid of
(S)-2ba (293 mg, 48%) was obtained. Rf =0.11 (CH2Cl2/MeOH 100:5);
1H NMR (400 MHz, CDCl3): d=1.89 (d, J=13.7 Hz, 2H), 2.37–2.45, (m,
2H), 4.38–4.53 (m, 6H), 6.20 (t, J=7.7 Hz, 1H), 6.59–6.62 (m, 4H), 7.12–
7.16 (m, 2H), 7.20–7.29 (m, 6H), 7.56 (d, J=8.1 Hz, 2H), 7.60 (d, J=
8.3 Hz, 2H), 7.64 (t, J=7.9 Hz, 1H), 7.99 ppm (d, J=7.9 Hz, 2H);
13C NMR (100.61 MHz, CDCl3): d=29.0, 53.2, 62.8, 121.0, 123.9, 124.7,
125.1, 125.3, 125.7, 125.9, 126.0, 127.9, 128.3, 128.6, 130.6, 133.1, 134.3,
148.2, 151.9, 160.9, 171.2 ppm; FAB-MS: m/z: 765 [M+H]+; UV/Vis
(CH2Cl2): lmax (loge)=383 (3.37), 482 nm (4.25); HRMS (ESI+): m/z
calcd for (C40H30N4O6102Ru): 764.12091; found: 764.14165.
Computational methods: All calculations were carried out by using the
Gaussian98 program. [54] All structures were optimized at B3LYP density
functional level of theory with the LANL2DZ[55] basis set, and character-
ized as energy minimum structures without imaginary number of fre-
quencies at the same level of theory (B3LYP/LANL2DZ).[56] The
B3LYP/LANL2DZ structures were further refined at the B3LYP DFT
level of theory with the LANL2DZ basis set by adding a set of polariza-
tionfunction(LANL2DZ(d)). The B3LYP/LANLDZ(d) optimized struc-
tures are used for comparisonwith the available X-ray data. To assign
the observed UV-visible adsorptionspectra, we carried out time-depen-
dent DFT calculations at the B3P86/LANL2DZ(d) DFT level with the
B3LYP/LANL2DZ(d) optimized structures.
Synthesis of {2,6-bis-[(4S)-4-(4-chlorophenyl)-5,6-dihydro-4H-[1,3]oxazi-
nyl]pyridine}(pyridine-2,6-dicarboxylate)ruthenium ((S)-2da): From gen-
eral procedure B by using (S)-4d (200 mg, 0.43 mmol), [{Ru(p-cyme-
ne)Cl2}2] (131 mg, 0.21 mmol) and disodium pyridine-2,6-dicarboxylate
(91 mg, 0.43 mmol), a greensolid of ( S)-2da (171 mg, 54%) was ob-
tained. Rf =0.25 (CH2Cl2/MeOH 100:5); 1H NMR (400 MHz, CDCl3):
d=1.80–1.85 (m, 2H), 2.22–2.30, (m, 2H), 3.70–3.73 (m, 2H), 4.28–4.34
(m, 2H), 4.43–4.48 (m, 2H), 6.36 (d, J=8.4 Hz, 4H), 6.96 (d, J=8.4 Hz,
4H), 7.62 (t, J=7.9 Hz, 1H), 7.97 ppm (d, J=7.9 Hz, 2H); 13C NMR
(100.61 MHz, CDCl3): d=30.4, 57.0, 63.0, 124.3, 125.6, 125.7, 127.3, 128.8,
132.7, 133.3, 137.7, 149.4, 151.8, 160.6, 171.3 ppm; FAB-MS: m/z: 732
[M]+, 734 [M+2]+; UV/Vis (CH2Cl2): lmax (loge)=386 (3.46), 483 nm
Acknowledgements
This work has been financed by the State of Mecklenburg-Western Pom-
merania, the Bundesministerium für Bildung und Forschung (BMBF),
and the Deutsche Forschungsgemeinschaft (SPP “Sekundäre Wechselwir-
kungen”). We thank Prof. Dr. M. Michalik, Dr. W. Baumann, C. Mewes,
H. Baudisch, A. Lehmann, and S. Buchholz (all IfOK) for their excellent
technical and analytical support. Dr. A. Kçckritz (ACA) is thanked for
general discussions. M.K.T. thanks the Alexander-von-Humboldt-Stiftung
for granting him an AvH-fellowship and Prof. L. J. Farrugia for the free-
ware Ortep-3 for Windows.[52]
1872
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1855 – 1874

Homogeneous Catalysis
FULL PAPER
salencomplexes see: h) T. Takeda, R. Irie, Y. Shinoda, T. Katsuki,
Synlett 1999, 1157–1159; i) K. Nakata, T. Takeda, J. Mihara, T.
Hamada, R. Irie, T. Katsuki, Chem. Eur. J. 2001, 7, 3776–3782.
[12] a) M. K. Tse, M. Klawonn, S. Bhor, C. Dçbler, G. Anilkumar, H.
Hugl, W. Mägerlein, M. Beller, Org. Lett. 2005, 7, 987–990; b) M. K.
Tse, C. Dçbler, S. Bhor, M. Klawonn, W. Mägerlein, H. Hugl, M.
Beller, Angew. Chem. 2004, 116, 5367–5372; Angew. Chem. Int. Ed.
2004, 43, 5255–5260; c) M. Klawonn, M. K. Tse, S. Bhor, C. Dçbler,
M. Beller, J. Mol. Catal. A 2004, 218, 13–19; d) S. Bhor, M. K. Tse,
M. Klawonn, C. Dçbler, W. Mägerlein, M. Beller, Adv. Synth. Catal.
2004, 346, 263–267; e) M. K. Tse, S. Bhor, M. Klawonn, C. Dçbler,
M. Beller, Tetrahedron Lett. 2003, 44, 7479–7483; for newly devel-
oped “pybim” ligands, see also: f) S. Bhor, G. Anilkumar, M. K. Tse,
M. Klawonn, C. Dçbler, B. Bitterlich, A. Grotevendt, M. Beller,
Org. Lett. 2005, 7, 3393–3396; g) G. Anilkumar, S. Bhor, M. K. Tse,
M. Klawonn, B. Bitterlich, M. Beller, Tetrahedron: Asymmetry 2005,
16, 3536–3561.
[13] See also references [14b,15,18c] for pioneer work of “Pybox” from
Nishiyama and co-workers.
[14] a) D. Cuervo, M. P. Gamasa, J. Gimeno, Chem. Eur. J. 2004, 10,
425–432; b) H. Nishiyama, S. Yamaguchi, M. Kondo, K. Itoh, J.
Org. Chem. 1992, 57, 4306–4309.
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Received: October 11, 2005
Published online: January 27, 2006
1874
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Chem. Eur. J. 2006, 12, 1855 – 1874