A convenient protocol for the synthesis of axially chiral Br?nsted acids

Article abstract of DOI:10.1016/j.tet.2007.11.067

Partially hydrogenated binaphthol monophosphoric acids were prepared via an improved four-step sequence. It is demonstrated that typical protection and deprotection of the phenolic groups are dispensable. The vinyl-substituted derivative has been polymerized to give a novel polymerized organocatalyst.

Full text of DOI:10.1016/j.tet.2007.11.067

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 1316e1322
www.elsevier.com/locate/tet
A convenient protocol for the synthesis of axially chiral Brønsted acids
b
a
b,
Michael Bartoszek b, Matthias Beller a, , Jens Deutsch , Markus Klawonn , Angela Kockritz
*
*
,
¨
Navid Nemati a, Anahit Pews-Davtyan a
a Leibniz Institute for Catalysis at University Rostock, Albert-Einstein-Straße 3a, 18059 Rostock, Germany
b Leibniz Institute for Catalysis at University Rostock, Branch Berlin: Richard-Willstaetter-Straße 12, 12489 Berlin, Germany
Received 26 July 2007; received in revised form 1 November 2007; accepted 20 November 2007
Available online 23 November 2007
Abstract
Partially hydrogenated binaphthol monophosphoric acids were prepared via an improved four-step sequence. It is demonstrated that typical
protection and deprotection of the phenolic groups are dispensable. The vinyl-substituted derivative has been polymerized to give a novel
polymerized organocatalyst.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Brønsted acid; Organocatalysts; H8-BINOL diphosphates; Polymer
1. Introduction
Interestingly, in organotransition metal catalysis octahydro-
genated BINOL-based (H8-BINOL) compounds were reported
to induce higher enantioselectivity compared to the corre-
sponding unsaturated BINOL derivatives.16 Based on these
observations we became interested to synthesize novel organo-
catalysts with partially hydrogenated aromatic backbone. In
addition to the different steric features of these ligands we
thought they might be easier to prepare.
Asymmetric reactions catalyzed by chiral Brønsted acids
have attracted significant interest in recent years.1 In general,
the activation of the substrate is enabled via hydrogen bonding2
or formation of ion pairs, depending on the acidic strength.
Smooth transitions can be observed between both of these
edge cases.
Among the different chiral Brønsted acids, especially axial
chiral phosphoric acid diesters, e.g., BINOL derivatives, have
been shown to be useful catalysts for a wide range of reactions
like transfer hydrogenations,3 hydrophosphonylation,4 amida-
tion of imines5 and addition of C-nucleophiles to imines,6
hetero-DielseAlder reactions,7 aza-ene-type reaction,8
Strecker reaction,9 allylboration of ketones,10 MoritaeBayl-
iseHillman reactions,11 Mannich12 and Mannich-type reac-
tions,13 PicteteSpengler reaction14 and aza-FriedeleCrafts
alkylation.15 Thus, the development of new chiral Brønsted
catalysts as well as their improved preparation is of major
interest in organocatalysis.
The multi-step synthesis of the commonly known 3,30-
substituted binaphthyl-based chiral phosphates starts with pro-
tection of the hydroxy groups via methylation, bromination in
3,30-position, Suzuki coupling with arylboronic acids, removal
of the protective group, phosphorylation with phosphoryl chlo-
ride and hydrolysis of the PeCl bond. Notably, the selective
bromination in 3,30-position is difficult, which leads to tedious
purification.
Recently, Inanaga et al.17 reported the synthesis of partially
hydrogenated binaphthol monophosphoric acids and used
them for complexation with rare earth metals. H8-BINOLS
with phenyl, 3,5-bis(trifluoromethylphenyl) or mesityl substit-
uents in 3,30-position were prepared according to the above
mentioned method using Pd/phosphine catalysts.10,11a,b,18
Other procedures for the synthesis of 3,30-arylsubstituted
BINOLS make use of a Ni-catalyzed arylation with arylmag-
nesium bromides19,20 or the introduction of boronic acid
* Corresponding authors. Tel.: þ49 381 1281113; fax: þ49 381 128151113
(M.B.); tel.: þ49 30 63924325; fax: þ49 30 63924454 (A.K.).
E-mail addresses: matthias.beller@catalysis.de (M. Beller), angela.
koeckritz@catalysis.de (A. Kockritz).
¨
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.11.067

M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
1317
Br
Br2
H2,Pd/C
OH
OH
OH
OH
OH
OH
Br
1
2
3
Ar
Ar
O
POCl3/H+/H2O
O
Ar-B(OH)2, Pd cat.
OH
OH
P
OH
O
Ar
Ar
4
5
Scheme 1. Synthesis of the chiral Brønsted acids 5.
groups in 3,30-position followed by Suzuki cross-coupling
with aryl bromides.19,21,22 Both routes need protecting/depro-
tecting steps.
Interestingly, the 1H NMR spectrum of 4k in CHCl3
showed four signals for the OH group at 4.76, 4.77, 4.81
and 4.86, which disappeared by D2O exchange. However, in
DMSO-d6 a downfield shift of a singlet signal to 7.45 ppm
was recorded. We interpret this observation as a possible inter-
action through the space of sterically adjacent protons. The
short dista0nce between the OH proton and the hydrogen at
2. Results and discussion
Here, we report the synthesis of some new H8-binaphthyl-
substituted phosphates as well as an improved procedure for
the preparation of such chiral Brønsted acids in only four steps
in gram-scale (Scheme 1). The (R)-binaphthol 1 was always
used as educt.
H10 or H10 of 2.5 A can be observed at the modelled structure
˚
of 4k (Fig. 1). A NOESY spectrum of compound 4k in CHCl3
supports this modelling and showed a correlation between the
OH0 hydrogen atoms and the aromatic hydrogen atoms H10 and
H10 of the phenanthryl groups due to their close-by position.
The appearance of the hydroxyl groups as four singlets
should be caused by the hindrance of the rotation of the
phenanthryl moieties leading to rotamers. A coupling of an
OH hydrogen atom with neighbouring hydrogen atoms can
be ruled out because the HETCOR and COSY spectra of 4k
did not indicate such behaviour.
Esterification proceeded with phosphoryl chloride and sub-
sequent hydrolysis led to the diphosphates 5 in good to excellent
yield (Table 2). Notably, in case of 4c more vigorous conditions
were needed to hydrolyze the intermediately formed chloro-
phosphate to 5c. Due to steric hindrance the yields of 4c and
5c are the lowest of all investigated compounds.
Exploratory investigations showed that the protection of the
phenolic groups in the Suzuki coupling is not necessary and so
is the cleavage of the OMe group with BBr3 omitted. The bromi-
nation of 2 which we have prepared by hydrogenation on 100 g
scale to 3 can be carried out directly at low temperature
(ꢀ30 ꢁC), similar to the procedure reported by Cram et al.23 Test-
ing different palladium catalysts for the Suzuki couplingof3 with
phenylboronic acid, good results were achieved with Pd(OAc)2/
BuPAd2(n-butyl-di-1-adamantyl-phosphine;CataCXiumA)cata-
lyst (Table 1, entry 1).24,25 This commercially available cat-
alyst can be easily used with various arylboronic acids
without special precautions. As shown in Table 1 the corre-
sponding coupling products were obtained in general in 70
to >90% yield. Compared to other catalysts in similar cou-
pling reactions the coupling products 4aek were observed
in higher yield.22
In addition to standard spectroscopic characterization of new
products, LSIMS (Liquid Secondary Ion Mass Spectrometry)
was used as a soft ionization method. All spectra were recorded
with the so-called ‘magic bullet’ matrix (a mixture of
Table 1
Coupling products of 3 with arylboronic acids to 4 ((R)-enantiomers)
T
Entry
No.
AreB(OH)2
Reaction time [h]
Yield [%]
Mp [ꢁC]
[a]D (T [ꢁC], c, solvent)
1
4a
4b
4c
4d
4e
4f
C6H5e
2-Naphthyle
Mesityl
12
2.5
15
2
70
72
185
ꢀ29.5 (29.5, 0.5, CHCl3)
ꢀ150.5 (29.4, 0.5, CHCl3)
ꢀ36.2 (29.3, 0.4, CHCl3)
ꢀ29.2 (29.0, 0.5, CHCl3)
ꢀ168.2 (24.8, 0.4, CHCl3)
ꢀ34.6 (23.8, 0.49, CHCl3)
ꢀ28.3 (28.3, 0.39, CHCl3)
ꢀ32.8 (27.9, 0.4, CHCl3)
ꢀ35.3 (26.8, 0.4, CHCl3)
ꢀ42.7 (29.2, 0.48, CHCl3)
ꢀ45.3 (23.0, 0.5, CHCl3)
2
205e206
121e123
195e196
185e187
133e135
187e188
167e169
102e105
179e181
193e195
3
61
96
4
3,5-((CF3)2eC6H3)e
4-(CH2]CHeC6H4)e
3,5-(F2eC6H3)e
4-(FeC6H4)e
5
2
81
99
6
1
7
4g
4h
4i
4
81
76
8
4-(CH3OeC6H4)e
4-(C6H5OeC6H4)e
9-Anthracenyle
9-Phenanthryle
8
9
8
71
58
10
11
4j
4k
3.5
1
>99

1318
M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
O
OH
O
P
O
O
O
AIBN
PVA
P
OH
O
n
6
5e
Scheme 2. Formation of the polymeric Brønsted acid 6.
5e was polymerized according to a radical pathway described
for styrene monomers (Scheme 2).26
The obtained solid product is insoluble in organic solvents. It
exhibited a very small BET surface of 3.63 m2/g. The particle
size and surface texture is shown in the TEM image in Figure 2.
The particle size shows a broad distribution between 4.5 and
100 mm. The image originates from the border area of a poly-
meric agglomerate which consists of adhered smaller units.
The size of primary particles could not be determined. The
measurement of the particle size showed a definite dependence
of the size distribution from the time of dispersion under ultra-
sound conditions. This fact argues for agglomeration as well
Figure 1. HyperChem structure of 4k.
dithioerythritol and dithiothreitol). As expected, 4aek and the
majority of the phosphoric acid esters 5 gave expected spectra
mostly with [M]þ as base peaks accompanied by [Mþ1]þ. Sur-
prisingly, abundant cluster peaks were the base peaks in the
spectra of 5c, 5e and 5i, where potassium ions were added to
the phosphoric ester molecules to generate [MþK]þ peaks.
Normally, [MþNa]þ peaks which are accompanied by [Mþ1]
peaks are expected in such spectra. Since comparable prepara-
tion and cleaning procedures were applied the different behav-
iour should be caused by the different aryl substituents.
Whereas phenyl, naphthyl, anthracenyl and phenanthryl as
well as fluorophenyl and methoxyphenyl substituents led to
protonation in the LSIMS ionization process, mesityl, phen-
oxyphenyl, styryl and even trifluoromethylphenyl groups
supported the formation of [MþK]þ ions. These results can
be interpreted as an indication for an increased ability of cation
complexation of the corresponding ligands 5c, 5e and 5i.
With regard to application a convenient separation of chiral
Brønsted acids in catalytic reactions is desirable. Therefore,
a strategy for the synthesis of a polymeric acid was also devel-
oped. Here, vinylphenylboronic acid was used as coupling
agent to obtain 4e. After phosphorylation, the vinyl group of
Figure 2. TEM image of the polymer 6.
Table 2
Phosphoric acid diesters 5 ((R)-enantiomers)
Yield [%]a
Mp [ꢁC]
[a]D (T [ꢁC], c, solvent)
T
Entry
No.
Ar
Reaction time [h]
1
5a
5b
5c
5d
5e
5f
C6H5e
2-Naphthyle
Mesityl
1.5
1.5
2.5
1.5
2
99
93
63
99.9
87
90
73
71
77
94
98
290b
ꢀ283.8 (28.4, 0.4, CHCl3)
ꢀ297.3 (27.5, 0.4, CHCl3)
ꢀ181.3 (28.1, 0.35, CHCl3)
ꢀ192.7 (25.5, 0.38, CHCl3)
ꢀ250.4 (29.7, 0.5, CHCl3)
ꢀ267.6 (26.8, 0.4, CHCl3)
ꢀ224.8 (26.8, 0.4, CHCl3)
ꢀ217.9 (27.7, 0.39, CHCl3)
ꢀ233.8 (28.3, 0.38, CHCl3)
ꢀ173.4 (27.9, 0.4, CHCl3)
ꢀ160.1 (22.4, 0.5, CHCl3)
2
350b
3
174e176b
167e169
456b
293e295b
277e279b
241e243b
261e264b
244e246b
252e255b
4
3,5-((CF3)2eC6H3)e
4-(CH2]CHeC6H4)e
3,5-(F2eC6H3)e
4-(FeC6H4)e
5
6
2
7
5g
5h
5i
2.5
2.5
2.5
2
8
4-(CH3OeC6H4)e
4-(C6H5OeC6H4)e
9-Anthracenyle
9-Phenanthryle
9
10
11
a
5j
5k
2
Isolated yield.
Decomposition.
b

M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
1319
as for the above described morphology of the powder. Typical
vinyl bands (C]C, wagging und rocking CH), e.g., at
1626 cmꢀ1, disappeared or became less intensive in the
FTIR and Raman spectra. The band at 1107 cmꢀ1 related to
PO vibrations was slightly switched to 1096 cmꢀ1. These re-
sults provide a strong indication for the formation of
a polymer.
chromatography (eluent hexane/ethyl acetate). Yield 95e
100%. Mp: 142 ꢁC. The melting point, NMR and MS data
were in accordance with literature23 results.
4.3. 3,30-Diaryl-5,6,7,8,50,60,70,80-octahydro-
(1,10-binaphthalene)-2,20-diols 4
General procedure: 10 mg Pd(OAc)2 (2 mol %) and 20 mg
(adamantyl)2-butyl-phosphine (2.5 mol %) were added in an
inert atmosphere to a solution of 1 g of 3 (2.2 mol) and 2.5e
3 equiv of the corresponding boronic acid, dissolved in 1,2-di-
methoxyethane and 10 ml 1 M K2CO3 solution. The mixture
was heated up to 95 ꢁC for 1e15 h (TLC control, eluent hex-
ane/CH2Cl2 1:1). After cooling down the organic phase was
separated, diluted with CH2Cl2, washed with saturated NH4Cl
solution as well as with H2O and dried with Na2SO4. Then
the solvent was evaporated and the solid residue was purified
by column chromatography (eluent hexane/CH2Cl2).
3. Conclusions
New H8-BINOL phosphoric acid diesters were prepared
according to a convenient four-step reaction sequence. The
typical protection of the OH groups of the BINOL before fur-
ther functionalization is not necessary. Pd(OAc)2/BuPAd2
serves as an efficient catalyst for Suzuki coupling reactions
of the bishydroxynaphthol derivative. This simplifies the prep-
aration of this class of interesting organocatalysts. In addition,
a heterogeneous phosphoric acid diester was prepared via
a styryl-substituted monomer. Catalytic investigations of the
novel Brønsted acids are in progress.
4.3.1. Compound 4a11b
White solid; 1H NMR (CDCl3) d 1.75 (m, 8H), 2.26 (m, 2H),
2.41 (m, 2H), 2.80 (t, 4H, J¼6.2), 4.89 (s, 2H, OH), 7.15 (s, 2H,
ArH, BINOL), 7.32 (m, 2H, ArH), 7.42 (m, 4H, ArH), 7.59 (m,
4H, ArH); 13C NMR (CDCl3) d 23.1, 27.2, 29.3, 120.1, 126.0,
127.1, 128.4, 129.2, 130.2, 131.7, 136.6, 137.9, 148.1; MS
(FAB pos.) m/z 446.1 [M]þ, 447.1 [MþH]þ. Anal. Calcd for
C32H30O2: C, 86.06; H, 6.77. Found: C, 86.12; H, 6.23.
4. Experimental
4.1. General
The octahydro binaphthol 2 was prepared according to a liter-
ature procedure.27 Elemental analyses were determined by the
ICP-OES method using an Optima 3000 XL (Perkin Elmer)
and an EA 1110 (CE Instruments). 1H, 13C, 31P and 19F NMR
spectra were recorded on a Varian UNITYPLUS 300 and 500
(300 and 500 MHz). Chemical shifts are given in parts per
million with respect to TMS (1H, 13C), H3PO4 (31P) or CFCl3
(19F), coupling constants are reported in hertz. Optical rotations
were measured on a Perkin Elmer 241 polarimeter. Mass spectra
were obtained onan Autospec(Micromass). Raman spectrawere
received on a fibre-optic RXN spectrometer (Kaiser Optical Sys-
tems, laser 785 nm, laser power 30 mW). The FTIR spectra
were recorded on a Nicolet Avatar 370 (Thermo Electron, di-
amond ATR, resolution 4, 32 scans). FTIR and Raman values
are given in cmꢀ1. TEM images were obtained with a CM-20
Phillips at 200 kW acceleration voltages. The particle size of
polymer was measured in water with HeeNe-Laser on
a Fritsch Particle Sizer Analysette 22.
4.3.2. Compound 4b
White solid; 1H NMR (CDCl3) d 1.77 (m, 8H), 2.31 (m, 2H),
2.47 (m, 2H), 2.84 (m, 4H), 5.01 (s, 2H, OH), 7.27 (s, 2H, ArH,
BINOL), 7.48 (m, 4H, ArH), 7.75 (dd, 2H, J¼8.45, 1.45, ArH),
7.87 (m, 6H, ArH), 8.06 (s, 2H, ArH); 13C NMR (CDCl3) d 23.1,
27.2, 29.3, 120.2, 125.9, 126.0, 126.1, 127.6, 127.8, 127.9,
128.1, 130.4, 132.0, 132.5, 133.5, 135.5, 136.8, 148.3; MS
(FAB) m/z 547.5 [MþH]þ. Anal. Calcd for C40H34O2: C,
87.88; H, 6.27. Found: C, 87.60; H, 6.21.
4.3.3. Compound 4c20
White solid; 1H NMR (CDCl3) d 1.76 (m, 8H), 2.00 (3s, 18H,
6CH3), 2.32 (m, 4H), 2.76 (t, 4H, J¼6.2), 4.53 (s, 2H, OH), 6.80
(s, 2H, ArH, BINOL), 6.93 (2s, 4H, ArH); 13C NMR (CDCl3)
d 19.7, 20.4, 21.0, 23.1, 27.0, 29.1, 120.3, 124.5, 128.1, 128.2,
129.6, 131.0, 133.6, 135.8, 136.9, 147.8; MS (FAB) m/z 530.1
[M]þ. Anal. Calcd for C38H42O2: C, 85.99; H, 7.98. Found: C,
86.32; H, 8.38.
4.2. 3,30-Dibromo-5,6,7,8,50,60,70,80-octahydro-
(1,10-binaphthalene)-2,20-diol 3
Compound 2 of 8.83 g (30 mmol) was dissolved in 300 ml
CH2Cl2 and cooled down to ꢀ30 ꢁC. Under stirring, 11 g bro-
mine (69 mmol) was added in one portion. The stirring was
continued at ꢀ30 ꢁC for 30 min (TLC control, eluent hexane/
CH2Cl2 1:1). Then 400 ml of a saturated solution of NaHSO3
was added and the reaction mixture was slowly warmed up to
room temperature. The organic phase was subsequently washed
with saturated NaHCO3 solution and with cold H2O, dried over
Na2SO4 and finally the solvent was evaporated. The crude prod-
uct was recrystallized from heptane or purified by column
4.3.4. Compound 4d11b
White solid; 1H NMR (CDCl3) d 1.76 (m, 8H), 2.32 (m, 4H),
2.83 (m, 4H), 4.93 (s, 2H, OH), 7.22 (s, 2H, ArH, BINOL), 7.82
(s, 2H, ArH), 8.09 (s, 4H, ArH); 13C NMR (CDCl3) d 22.8, 27.3,
29.2, 119.3, 120.6, 123.3, 123.5 (q, JCF¼272.6), 129.4, 130.7,
131.2, 131.4 (q, JCF¼33.1), 131.5, 138.5, 139.9, 148.3; 19F
NMR (CDCl3) d ꢀ63.3; MS (FAB pos.) m/z 718.2 [M]þ,
719.2 [MþH]þ. Anal. Calcd for C36H26F12O2: C, 60.17; H,
3.65. Found: C, 60.40; H, 3.64.

1320
M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
4.3.5. Compound 4e
132.1, 132.5, 136.7, 147.1; MS (FAB pos.) m/z 647.4
[MþH]þ. Anal. Calcd for C48H38O2: C, 89.13; H, 5.92.
Found: C, 89.43; H, 5.97.
1
White solid; H NMR (CDCl3) d 1.74 (m, 8H), 2.24 (m,
2H), 2.40 (m, 2H), 2.80 (t, 4H, J¼6.1), 4.91 (s, 2H, OH),
5.25 (dd, 2H, J¼11.5, w1, eCH]CH2), 5.77 (dd, 2H,
J¼17.6, 0.7, eCH]CH2), 6.74 (dd, 2H, J¼17.5, 11,
eCH]CH2), 7.16 (s, 2H, ArH, BINOL), 7.47 and 7.57
(dd, 4H, J¼8.3, 1.7, ArH); 13C NMR (CDCl3) d 23.0, 27.2,
29.3, 113.8, 120.1, 125.7, 126.2, 129.3, 130.3, 131.6, 136.3,
136.5, 136.7, 137.4, 148.2; MS (EI) m/z 498.4 [M]þ. Anal.
Calcd for C36H34O2: C, 86.71; H, 6.87. Found: C, 86.23; H,
6.41.
4.3.11. Compound 4k
White solid; 1H NMR (DMSO-d6) d 1.74 (m, 8H), 2.50 (m,
4H), 2.76 (m, 4H), 6.94 (m, 2H, ArH, BINOL), 7.33 (d, 1H,
J¼2.5, ArH), 7.45 (m, 12H, ArH, OH), 7.96 (m, 3H, ArH),
8.87 (m, 4H, ArH); 13C NMR (DMSO-d6) d 22.8, 22.9, 23.0,
27.0, 28.8, 122.7, 123.0, 123.3 (d), 123.6, 123.8, 124.8, 125.0,
125.2, 126.4 (d), 126.5, 126.8 (d), 127.0, 127.5 (d), 127.6,
127.6, 127.7, 127.8, 128.0, 128.5, 129.5 (d), 129.9 (dd), 130.7,
130.9, 131.3 (d), 131.5 (d), 135.8, 136.0, 136.2, 136.3, 149.8,
150.0; MS (FAB pos.) m/z 647.4 [MþH]þ. Anal. Calcd for
C48H38O2: C, 89.13; H, 5.92. Found: C, 88.52; H, 5.74.
4.3.6. Compound 4f
White solid; 1H NMR (CDCl3) d 1.75 (m, 8H), 2.23 (m, 2H),
2.34 (m, 2H), 2.80 (m, 4H), 4.88 (s, 2H, OH), 6.75 (m, 2H, ArH),
7.16 (m, 6H, ArH and ArHeBINOL); 13C NMR (CDCl3) d 22.9,
27.2, 29.2, 102.3 (t, JCF¼25.4), 112.1 (q, JCF¼17.4, 8.0), 119.6,
124.0, 130.9, 131.8, 137.8, 141.0 (t, JCF¼9.9), 148.1, 162.8 (dd,
JCF¼247.2, 13.1); 19F NMR (CDCl3) d ꢀ111.1 (m); MS (FAB
pos.) m/z 518.1 [M]þ, 519.1 [MþH]þ. Anal. Calcd for
C32H26F4O2: C, 74.12; H, 5.05. Found: C, 73.62; H, 4.93.
4.4. 3,30-Diaryl-5,6,7,8,50,60,70,80-octahydro-1,10-
binaphthyl-2,20-diyl-hydrogenphosphates 5
General procedure: to a solution of 1 mmol 4 in 2 ml dry
pyridine a solution of 1.5e2 mmol freshly distilled phospho-
rus oxychloride in 1 ml dry pyridine was added at room tem-
perature over a period of 10 min. The mixture was stirred at
80 ꢁC until no educt could be observed in an accompanying
thin layer chromatogram (eluents CH2Cl2/hexane 5:2;
CH2Cl2/EtOH 10:1, 7:1). The solution was allowed to cool
down to 40 ꢁC, then 1 ml H2O and after 10 min 5 ml 6 N
HCl were added dropwise. The resulting mixture was heated
to 100 ꢁC for 5 min (5c 30 min), cooled down and filtrated.
The isolated solid was reprecipitated from ethanol/6 N HCl,
washed with H2O and reprecipitated again from CH2Cl2/hex-
ane. If necessary, the product was finally purified by column
chromatography.
4.3.7. Compound 4g
White solid; 1H NMR (CDCl3) d 1.75 (m, 8H), 2.31 (m, 4H),
2.80 (t, 4H, J¼5.9), 4.85 (s, 2H, OH), 7.10 (m, 6H, ArH), 7.57
(m, 4H, ArH); 13C NMR (CDCl3) d 22.9, 23.0, 27.1, 29.2, 115.0
(d, J¼21.4), 119.8, 125.1, 130.4, 130.8, 130.9, 131.8, 133.8,
133.84, 136.6, 148.1, 160.4 (d, J¼246.3); 19F NMR (CDCl3)
d ꢀ116.1 (m); MS (FAB) m/z 482.1 [M]þ, 483.2 [MþH]þ.
Anal. Calcd for C32H28F2O2: C, 79.65; H, 5.85. Found: C,
79.91; H, 6.09.
4.3.8. Compound 4h
White solid; 1H NMR (CDCl3) d 1.74 (m, 8H), 2.31 (m, 4H),
2.79 (t, 4H, J¼6.2), 3.84 (s, 3H, OCH3), 4.88 (s, 2H, OH), 7.03
(m, 6H, ArH), 7.52e7.53 (m, 4H, ArH); 13C NMR (CDCl3)
d 23.1, 27.1, 29.3, 55.3 (OCH3), 113.8, 114.2, 120.1, 125.6,
127.7, 130.1, 130.3, 131.4, 136.0, 148.1, 158.8; MS (FAB) m/z
506.2 [M]þ, 507.2 [MþH]þ. Anal. Calcd for C34H34O4: C,
80.60; H, 6.76. Found: C, 80.97; H, 7.12.
4.4.1. Compound 5a28
White solid; 1H NMR (DMSO-d6) d 1.58 (m, 2H), 1.77 (m,
6H), 2.21 (m, 2H), 2.64 (m, 2H), 2.85 (m, 4H), 7.21 (s, 2H, ArH,
BINOL), 7.37 (m, 6H, ArH), 7.62 (d, 4H, J¼7.6, ArH); 13C
NMR (DMSO-d6) d 22.1, 27.3, 28.5, 127.1 (d, JCP¼3.3),
128.1, 129.3, 130.8, 130.9 (d, JCP¼3.7), 134.4 (d, JCP¼1.2),
136.6, 137.1, 143.2 (d, JCP¼9.2); 31P NMR (DMSO-d6)
d ꢀ0.5 (s); MS (FAB neg.) m/z 507.2 [MeH]ꢀ. Anal. Calcd
for C32H29O2P: C, 75.58; H, 5.75; P, 6.09. Found: C, 75.73;
H, 5.63; P, 5.82.
4.3.9. Compound 4i
White solid; 1H NMR (CDCl3) d 1.74 (m, 8H), 2.31 (m, 4H),
2.80 (t, 4H, J¼5.6), 4.89 (s, 2H, OH), 7.29 (m, 20H); 13C NMR
(CDCl3) d 23.0, 27.1, 29.2, 30.3, 118.1, 118.3, 118.6, 118.9,
119.0, 119.1, 120.0, 123.2, 123.3, 123.33, 125.4, 128.2, 129.4,
129.7, 129.8, 130.3, 130.5, 131.7, 132.8, 135.6, 136.4, 148.1,
156.4, 156.6, 157.1, 157.15, 157.2; MS (FAB) m/z 630.2
[M]þ, 631.2 [MþH]þ. Anal. Calcd for C44H38O4: C, 83.78;
H, 6.07. Found: C, 84.13; H, 6.41.
4.4.2. Compound 5b29
1
White solid; H NMR (DMSO-d6) d 1.62 (m, 2H), 1.81 (s,
6H), 2.29 (m, 2H), 2.69 (m, 2H), 2.89 (m, 4H), 7.36 (s, 2H,
ArH, BINOL), 7.52 (m, 4H, ArH), 7.81 (m, 2H, ArH), 7.94
(m, 6H, ArH), 8.14 (s, 2H, ArH); 13C NMR (DMSO-d6)
d 22.1, 27.4, 28.5, 126.1 (d, JCP¼4.9), 127.3, 127.4, 127.7,
128.0, 130.9 (d, JCP¼3.1), 131.0, 132.0, 132.9, 134.6, 134.7,
136.9, 143.4 (d, JCP¼9.2); 31P NMR (DMSO-d6) d ꢀ1.0 (s);
MS (FAB neg.) m/z 607.6 [MꢀH]ꢀ, (FAB pos.) m/z 609
[MþH]þ, 631.4 [MþNa]þ, 647.4 [MþK]þ. Anal. Calcd for
C40H33O4P: C, 78.93; H, 5.46; P, 5.09. Found: C, 78.63; H,
5.64; P, 5.18.
4.3.10. Compound 4j
1
White solid; H NMR (CDCl3) d 1.70 (m, 8H), 2.21 (m,
4H), 2.80 (m, 4H), 5.11 (s, 2H, OH), 7.28 (m, 2H, ArH,
BINOL), 7.54 (m, 8H, ArH), 8.45 (m, 4H, ArH), 8.50 (m,
6H); 13C NMR (CDCl3) d 22.7, 22.74, 26.9, 29.0, 122.1,
122.3, 125.6, 127.0, 127.1, 127.6, 128.6, 130.5, 131.5,

M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
1321
4.4.3. Compound 5c
1
White solid; H NMR (CDCl3) d 1.65 (m, 2H), 1.82 (m,
4.4.7. Compound 5g28
White solid; 1H NMR (CDCl3) d 1.63 (m, 2H), 1.80
(m, 6H), 2.34 (m, 2H), 2.67 (m, 2H), 2.83 (m, 4H), 7.11 (m,
10H); 13C NMR (CDCl3) d 22.5, 22.6, 27.8, 29.2, 114.7 (d,
JCF¼21.3), 126.9, 130.6, 131.0, 131.1, 132.9, 135.4, 137.6,
142.9 (d, JCP¼9.1), 160.5 (d, JCF¼245.7); 31P NMR (CDCl3)
d 2.0 (s); 19F NMR (CDCl3) d ꢀ116.4 (s); MS (FAB) m/z
545.1 [MþH]þ. Anal. Calcd for C32H27F2O4P: C, 70.58; H,
5.00; P, 5.69. Found: C, 70.82; H, 5.39; P, 5.99.
6H), 2.01 (3s, 18H, 6CH3), 2.29 (m, 2H), 2.82 (m, 2H), 2.84
(m, 4H), 6.93 (m, 6H, ArH); 13C NMR (CDCl3) d 21.0,
21.02, 21.1, 21.3, 22.5, 22.6, 27.7, 27.8, 29.2, 29.3, 126.5,
126.53, 126.6, 126.7, 127.5, 128.2, 128.4, 128.7, 129.4 (d,
JCP¼4.8), 130.7, 130.8, 132.2, 132.3, 132.4, 132.43, 132.5
(d, JCP¼1.8), 132.7, 132.72, 135.6, 135.7, 135.89, 135.9,
136.2, 136.25, 136.3, 136.34, 136.96, 136.98, 137.0 (d,
JCP¼2.8), 137.04, 137.1, 142.9 (d, JCP¼10.7), 143.5 (d,
JCP¼12.2); 31P NMR (CDCl3) d 6.6 (s); MS (FAB) m/z
593.3 [MþH]þ, 631.3 [MþK]þ. Anal. Calcd for C38H41O4P:
C, 77.00; H, 6.97; P, 5.23. Found: C, 77.27; H, 7.19; P,
5.58.
4.4.8. Compound 5h
1
White solid; H NMR (CDCl3) d 1.61 (m, 2H), 1.79 (m,
6H), 2.33 (m, 2H), 2.82 (m, 2H), 2.84 (m, 4H), 3.63 (s, 6H,
2ꢂOCH3), 6.80 (s, 4H, ArH), 7.12 (s, 2H, ArH), 7.44 (d,
4H, ArH); 13C NMR (CDCl3) d 22.5, 22.6, 29.2, 29.7, 55.1
(OCH3), 113.6, 126.9, 129.1, 130.4, 131.1, 135.3, 136.9,
142.7 (d, JCP¼9.2), 158.9; 31P NMR (CDCl3) d 2.5 (s); MS
(FAB) m/z 569.2 [MþH]þ. Anal. Calcd for C34H33O6P: C,
71.82; H, 5.85; P, 5.45. Found: C, 72.17; H, 6.11; P, 5.79.
4.4.4. Compound 5d
White solid; 1H NMR (CDCl3) d 1.66 (m, 2H), 1.87 (m, 6H),
2.39 (m, 2H), 2.70 (m, 2H), 2.89 (m, 4H), 6.46 (s, 2H, OH), 7.11
(s, 2H, ArH, BINOL), 7.61 (s, 2H, ArH), 7.87 (s, 4H, ArH); 13
C
NMR (CDCl3) d 22.3, 22.4, 27.9, 29.1, 121.0 (d, J¼3.5), 123.3
(q, JCF¼272.6), 126.9 (d, J¼1.5), 129.2 (d, JCP¼3.4), 129.6 (d,
J¼1.9), 131.2, 131.3 (q, JCF¼33.3), 136.2 (d, JCP¼1.8), 138.8,
139.2, 142.4 (d, JCP¼9.2); 31P NMR (CDCl3) d 0.6 (s); 19F
NMR (CDCl3) d ꢀ63.6; MS (FAB neg.) m/z 779.3 [MꢀH]ꢀ,
(FAB pos.) m/z 761.3 [MꢀF]þ, 781.3 [MþH]þ, 803.3
[MþNa]þ, 819.3 [MþK]þ. Anal. Calcd for C36H25F12O4P: C,
55.4; H, 3.23; P, 3.97. Found: C, 55.00; H, 3.10; P, 4.20.
4.4.9. Compound 5i30
White solid; 1H NMR (CDCl3) d 1.62 (m, 2H), 1.80 (s, 6H),
2.26 (m, 2H), 2.65 (m, 2H), 2.91 (m, 4H), 7.25 (m, 20H); 13C
NMR (CDCl3) d 22.5, 22.6, 27.8, 29.2, 118.6, 118.8, 119.0,
119.1, 122.8, 123.3, 127.0 (d, JCP¼2.2), 128.2, 129.6, 129.8,
130.8, 131.0, 131.1 (d, JCP¼3.6), 131.8, 135.5 (d, JCP¼2.1),
135.6, 137.3 (d, JCP¼1.5), 142.7 (d, JCP¼9.1), 156.4, 156.6,
157.3; 31P NMR (CDCl3) d 2.8 (s); MS (FAB) m/z 693.4
[MþH]þ, 715.4 [MþNa]þ; 731.4 [MþK]þ. Anal. Calcd for
C44H37O6P: C, 76.29; H, 5.38; P, 4.47. Found: C, 76.57; H,
5.73; P, 4.89.
4.4.5. Compound 5e
White solid; 1H NMR (DMSO-d6) d 1.57 (m, 2H), 1.76 (m,
6H), 2.18 (m, 2H), 2.64 (m, 2H), 2.85 (m, 4H), 5.02 (br s, 2H,
OH), 5.28 (d, 2H, J¼11.2, eCH]CH2), 5.87 (d, 2H, J¼17.6,
eCH]CH2), 6.76 (dd, 2H, J¼17.8, 11, eCH]CH2), 7.23 (s,
2H, ArH, BINOL), 7.51 and 7.62 (d, 4H, J¼8.3, ArH); 13C
NMR (DMSO-d6) d 22.1, 27.3, 28.5, 114.3, 125.9, 127.2 (d,
JCP¼1.7), 129.5, 130.5 (d, JCP¼3.4), 130.6, 134.4, 135.9,
136.3, 136.7 (d, JCP¼3.7), 143.3 (d, JCP¼9.5); 31P NMR
(DMSO-d6) d ꢀ0.5 (s); MS (FAB neg.) m/z 558.6 [Mꢀ2H]ꢀ,
559.6 [MꢀH]ꢀ, 560.6 [M]ꢀ, (FAB pos.) m/z 599.2 [MþK]þ;
FTIR (KBr) n 1627, 1605, 1288, 1235, 1106, 988, 902,
843; Raman (KBr) n 1627, 1607, 1412. Anal. Calcd for
C36H33O4P: C, 77.13; H, 5.93; P, 5.52. Found: C, 77.49; H,
5.88; P, 5.26.
4.4.10. Compound 5j
1
White solid; H NMR (CDCl3) d 1.81 (m, 8H), 2.34 (m,
2H), 2.68 (m, 2H), 2.84 (m, 4H), 7.12 (s, 2H, ArH, BINOL),
7.46 (m, 10H, ArH), 7.84 (m, 8H, ArH); 13C NMR (CDCl3)
d 125.8, 126.9, 127.1, 127.8, 128.0, 129.3, 131.1 (d, JPC¼3.3),
131.6, 133.4, 135.3, 136.7, 137.4, 142.7 (d, JPC¼9.1); 31P
NMR (CDCl3) d 2.3 (s); MS (FAB pos.) m/z 708.2 [MþH]þ.
Anal. Calcd for C48H37O4P: C, 81.34; H, 5.26; P, 4.37. Found:
C, 81.87; H, 5.41; P, 4.19.
4.4.6. Compound 5f
1
White solid; H NMR (CDCl3) d 1.68 (m, 2H), 1.87 (m,
4.4.11. Compound 5k30
White solid; 1H NMR (DMSO-d6) d 1.84 (m, 8H), 2.50 (m,
2H), 2.90 (m, 6H), 7.23 (s, 2H, ArH, BINOL), 7.63 (m, 10H,
ArH), 7.90 (m, 4H, ArH), 8.86 (m, 4H, ArH); 13C NMR
(DMSO-d6) d 22.2, 22.3, 27.6, 28.6, 122.8, 123.1, 125.9,
126.2, 126.4, 126.5, 126.8, 126.9, 127.3, 127.5, 128.6, 128.7,
129.4, 129.5, 129.7 (d, JCP¼2.1), 130.2, 130.6, 130.8, 131.0,
131.8, 132.2, 132.8, 133.8 (d, JCP¼5.8), 134.7, 136.8, 137.2,
144.0, 144.2 (d, JCP¼9.1); 31P NMR (DMSO-d6) d 0.5 (s);
MS (FAB neg.) m/z 707.2 [MꢀH]ꢀ, (FAB pos.) m/z 709.2
[MþH]þ. Anal. Calcd for C48H37O4P: C, 81.34; H, 5.26; P,
4.37. Found: C, 81.91; H, 5.47; P, 3.94.
6H), 2.41 (m, 2H), 2.71 (m, 2H), 2.90 (m, 4H), 6.34 (tt, 2H,
ArH), 6.95 (m, 4H, ArH), 7.14 (s, 2H, ArHeBINOL), 8.41
(s, 2H, OH); 13C NMR (CDCl3) d 22.4, 22.5, 27.8, 29.2, 102.5
(t, JCF¼25.4), 112.4 (q, JCF¼17.3, 8.2), 127.1 (d, JCP¼1.5),
130.0 (d, JCP¼2.1), 130.8, 135.8 (d, JCP¼1.9), 138.5, 139.8
(t, JCF¼10.2), 142.5 (d, JCP¼9.2), 162.6 (dd, JCF¼247.6,
13.2); 31P NMR (CDCl3) d 3.2 (s); 19F NMR (CDCl3)
d ꢀ111.1 (m); MS (FAB pos.) m/z 581.3 [MþH]þ. Anal.
Calcd for C32H25F4O4P: C, 66.21; H, 4.34; P, 5.34. Found:
C, 65.47; H, 4.02; P, 5.48.

1322
M. Bartoszek et al. / Tetrahedron 64 (2008) 1316e1322
11. (a) McDougal, N. T.; Trevellini, W. L.; Rodgen, S. A.; Klimax, L. T.;
4.5. Polymerization of 5e
Schaus, S. E. Adv. Synth. Catal. 2004, 346, 1231; (b) McDougal, N. T.;
Schaus, S. E. J. Am. Chem. Soc. 2003, 125, 12094;(c) Rodgen, S. A.; Schaus,
S. E. Angew. Chem., Int. Ed. 2006, 45, 4929.
To a stirred solution of 206 mg of 5e (0.36 mmol) and
7.5 mg azobisisobutyronitrile in 4 ml of a benzene/THF mix-
ture (1.5:1), was added a warm (45 ꢁC) aqueous solution of
polyvinyl alcohol (12 mg in 1.2 ml, Mw 85,000e124,000,
87e89% hydrolyzed). After vigorously stirring at room tem-
perature for 15 min to homogenize the particle size, the tem-
perature was slowly raised up to 75e80 ꢁC and the stirring
was continued at this temperature until the educt spot disap-
peared during TLC control (ca. 10 h). The heterogeneous mix-
ture was filtered and washed with hot water, ethanol/water,
ethanol, THF, ethanol and hexane. White polymer beads of
6 were obtained in quantitative yield after drying under high
vacuum. FTIR (KBr) n 1626, 1603, 1235, 1096, 1005, 827;
Raman (KBr) n 1607, 1433; elemental analysis found: C,
63.91; H, 5.76; P, 3.13.
12. (a) Terada, M.; Sorimachi, K.; Uraguchi, D. Synlett 2006, 133; (b)
Uraguchi, D.; Terada, M. J. Am. Chem. Soc. 2004, 126, 5356.
13. (a) Akiyama, T.; Itoh, J.; Yokota, K.; Fuchibe, K. Angew. Chem., Int. Ed.
2004, 43, 1566; (b) Akiyama, T.; Saitoh, Y.; Morita, H.; Fuchibe, K. Adv.
Synth. Catal. 2005, 347, 1523.
14. Seayad, J.; Seayad, A. M.; List, B. J. Am. Chem. Soc. 2006, 128, 1086.
15. Uraguchi, D.; Sorimachi, K.; Terada, M. J. Am. Chem. Soc. 2004, 126,
11084.
16. (a) Zeng, Q.; Liu, H.; Cui, X.; Mi, A.; Jiang, Y.; Li, X.; Choi, M. C. K.;
Chan, A. S. C. Tetrahedron: Asymmetry 2002, 13, 115; (b) Chan, A. S. C.;
Zhang, F.-Y.; Yip, C.-W. J. Am. Chem. Soc. 1997, 119, 4080; (c) Boiteau,
J.-G.; Imbos, R.; Minnaard, A. J.; Feringa, B. L. Org. Lett. 2003, 5, 681;
(d) Hu, A.-G.; Fu, Y.; Xie, J.-H.; Zhou, H.; Wang, L.-X.; Zhou, Q.-L.
Angew. Chem., Int. Ed. 2002, 41, 2348.
17. (a) Furuno, H.; Hayano, T.; Kambara, T.; Sugimoto, Y.; Hanamoto, T.;
Tanaka, Y.; Jin, Y. Z.; Kagawa, T.; Inanaga, J. Tetrahedron 2003, 59,
10509; (b) Furuno, H.; Kambara, T.; Tanaka, Y.; Hanamoto, T.; Kagawa,
T.; Inanaga, J. Tetrahedron Lett. 2003, 44, 6129; (c) Furuno, Y.; Inanaga,
J. EP Patent 1,038,877, 2000; Chem. Abstr. 2000, 133, 266975e.
18. Chen, Y.; Yekta, S.; Yudin, A. K. Chem. Rev. 2003, 103, 3155.
19. Wipf, P.; Jung, J.-K. J. Org. Chem. 2000, 65, 6319.
Acknowledgements
The authors acknowledge gratefully the financial support of
the Ministry of Economics of the state Mecklenburg-Vorpom-
mern (project V230-630-08-TIFA-419). Thanks are dedicated
to Dr. E. Grundemann, Dr. M.-M. Pohl, Dr. U. Bentrup, D.
¨
Michalik, Mrs. H. Gehrmann and Mrs. C. Domke for the exe-
cution of NMR, TEM, FTIR, Raman and ICP-OES analyses.
20. Schrock, R. R.; Jamieson, J. Y.; Dolman, S. J.; Miller, S. A.; Bonitatebus,
P. J., Jr.; Hoveyda, A. H. Organometallics 2002, 21, 409.
21. Yu, H.-B.; Hu, Q.-S.; Pu, L. J. Am. Chem. Soc. 2000, 122, 6500.
22. Cox, P. J.; Wang, W.; Snieckus, V. Tetrahedron Lett. 1992, 33, 2253.
23. Cram, D. J.; Helgeson, R. C.; Peacock, S. C.; Kaplan, L. J.; Domeier,
L. A.; Moreau, P.; Koga, K.; Mayer, J. M.; Chao, Y.; Siegel, M. G.;
Hoffman, D. H.; Sogah, G. D. Y. J. Org. Chem. 1978, 43, 1930.
24. Frisch, A. C.; Zapf, A.; Briel, O.; Kayser, B.; Shaikh, N.; Beller, M.
J. Mol. Catal. 2004, 214, 231.
References and notes
25. For some other applications of this ligand in coupling reactions, see: (a)
Zapf, A.; Ehrentraut, A.; Beller, M. Angew. Chem. 2000, 112, 4315; (b)
Zapf, A.; Beller, M. Chem. Commun. 2005, 431; (c) Klaus, S.; Neumann,
1. Akiyama, T.; Itoh, J.; Fuchibe, K. Adv. Synth. Catal. 2006, 348, 999.
2. Schreiner, P. R. Chem. Soc. Rev. 2003, 289.
3. (a) Rueping, M.; Sugiono, E.; Azap, C.; Theissmann, T.; Bolte, M. Org.
Lett. 2005, 7, 3781; (b) Rueping, M.; Antonchick, A. P.; Theissmann, T.
Angew. Chem., Int. Ed. 2006, 45, 3683; (c) Rueping, M.; Antonchick,
A. P.; Theissmann, T. Angew. Chem., Int. Ed. 2006, 45, 6751.
4. Akiyama, T.; Morita, H.; Itoh, J.; Fuchibe, K. Org. Lett. 2005, 7, 2583.
5. Rowland, G. B.; Zhang, H.; Rowland, E. B.; Chennamadhavuni, S.; Wang,
Y.; Antilla, J. C. J. Am. Chem. Soc. 2005, 127, 15696.
H.; Zapf, A.; Strubing, D.; Hubner, S.; Almena, J.; Riermeier, T.; Gross,
¨ ¨
P.; Sarich, M.; Krahnert, W. R.; Rossen, K.; Beller, M. Angew. Chem.
2006, 118, 161; Angew. Chem., Int. Ed. 2006, 45, 154; (d) Michalik,
D.; Kumar, K.; Zapf, A.; Tillack, A.; Arlt, M.; Heinrich, T.; Beller, M.
Tetrahedron Lett. 2004, 45, 2057; (e) Tewari, A.; Hein, M.; Zapf, A.;
Beller, M. Synthesis 2004, 935; (f) Datta, A.; Plenio, H. Chem. Commun.
2003, 1504; (g) Benedi, C.; Bravo, F.; Uriz, P.; Fernandez, E.; Claver, C.;
Castillon, S. Tetrahedron Lett. 2003, 44, 6073; (h) Ehrentraut, A.; Zapf,
A.; Beller, M. Adv. Synth. Catal. 2002, 344, 209; (i) Ehrentraut, A.;
Zapf, A.; Beller, M. Synlett 2000, 1589.
6. (a) Dixon, D.; Tillman, A. L. Synlett 2005, 2635; (b) Uraguchi, D.;
Sorimanchi, K.; Terada, M. J. Am. Chem. Soc. 2005, 127, 9360.
7. (a) Itoh, J.; Fuchibe, K.; Akiyama, T. Angew. Chem. 2006, 118, 4914;
(b) Long, J.; Hu, J.; Shen, X.; Ji, B.; Ding, K. J. Am. Chem. Soc. 2002,
124, 10; (c) Akiyama, T.; Tamura, Y.; Itoh, J.; Morita, H.; Fuchibe, K.
Synlett 2006, 141; (d) Tonoi, T.; Mikami, K. Tetrahedron Lett. 2005,
46, 6355; (e) Akiyama, T.; Morita, H.; Fuchibe, K. J. Am. Chem.
Soc. 2006, 128, 13070.
26. Sellner, H.; Faber, C.; Rheiner, P. B.; Seebach, D. Chem.dEur. J. 2000, 6,
3692.
27. Korostylev, A.; Tararov, V. I.; Fischer, C.; Monsees, A.; Borner, A. J. Org.
¨
Chem. 2004, 69, 3220.
28. Chen, X.-H.; Xu, X.-Y.; Liu, H.; Cun, L.-F.; Gong, L.-Z. J. Am. Chem.
Soc. 2006, 128, 1402.
29. Liu, H.; Cun, L.-F.; Mi, A.-Q.; Jiang, Y.-Z.; Gong, L.-Z. Org. Lett. 2006,
8, 6023.
8. Terada, M.; Machioka, K.; Sorimachi, K. Angew. Chem., Int. Ed. 2006, 45,
2254.
9. Rueping, M.; Sugiono, E.; Azap, C. Angew. Chem., Int. Ed. 2006, 45,
2617.
30. Rueping, M.; Sugiono, E.; Theissmann, T.; Kuenkel, A.; Kockritz, A.;
¨
10. Lou, S.; Moquist, P. N.; Schaus, S. E. J. Am. Chem. Soc. 2006, 128, 12660.
Pews-Davtyan, A.; Nemati, N.; Beller, M. Org. Lett. 2007, 9, 1065.