New chiral diamide ligands containing redox-active hydroquinone groups. Synthesis and results in the palladium(II)-catalyzed 1,4-diacetoxylation of 1,3-dienes

Article abstract of DOI:10.1016/j.jorganchem.2003.09.007

Chiral ligands 8-11, 22 and 23 were synthesized from different chiral diamines as a new class of ligands for the Pd(II)-catalyzed 1,4-diacetoxylation of 1,3-dienes. The synthesis from the diamines and protected benzoic acids was performed in a few simple steps and gave the ligands in high overall yields. The hydroquinone groups present in the ligands are in situ oxidized to benzoquinone to give the active ligands. Application of these ligands in the 1,4-diacetoxylation reaction afforded the oxidation product with high regio- and diastereoselectivity and an enantiomeric excess up to 42% was obtained. Possible coordination modes of the metal to the ligand are discussed, and experiments were made to investigate the coordination by varying the reaction conditions or making changes to the ligands.

Full text of DOI:10.1016/j.jorganchem.2003.09.007

Journal of Organometallic Chemistry 687 (2003) 508ꢀ517
/
www.elsevier.com/locate/jorganchem
New chiral diamide ligands containing redox-active hydroquinone
groups. Synthesis and results in the palladium(II)-catalyzed 1,4-
diacetoxylation of 1,3-dienes
Renzo C. Verboom a, Bernd J. Plietker b,1, Jan-E. Backvall a,*
¨
a Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
b Organic Chemistry II, Dortmund University, D-44221 Dortmund, Germany
Received 15 July 2003; received in revised form 4 September 2003; accepted 4 September 2003
Dedicated to Professor Jean-Pierre Geneˆt on the occasion of his 60th birthday
Abstract
Chiral ligands 8ꢀ
/11, 22 and 23 were synthesized from different chiral diamines as a new class of ligands for the Pd(II)-catalyzed
1,4-diacetoxylation of 1,3-dienes. The synthesis from the diamines and protected benzoic acids was performed in a few simple steps
and gave the ligands in high overall yields. The hydroquinone groups present in the ligands are in situ oxidized to benzoquinone to
give the active ligands. Application of these ligands in the 1,4-diacetoxylation reaction afforded the oxidation product with high
regio- and diastereoselectivity and an enantiomeric excess up to 42% was obtained. Possible coordination modes of the metal to the
ligand are discussed, and experiments were made to investigate the coordination by varying the reaction conditions or making
changes to the ligands.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Asymmetric catalysis; Oxidation; Palladium; Ligand design; Dienes
1. Introduction
Reactions of carbonꢀ
central importance in organic chemistry. A large num-
[4], halides [5], functionalized amines [6], and masked
carbon nucleophiles [7] can be added to the diene to give
the 1,4-oxidized products in high yields and with good
control of the regio- and stereoselectivity (Scheme 1).
Cyclic as well as acyclic dienes can be used, and both
intermolecular and intramolecular versions of the reac-
tions have been developed. In many cases the bis-allylic
products can be used for further synthetic transforma-
tions [5,8,9]. The versatility of the 1,4-oxidation reaction
has been demonstrated in the synthesis of a number of
/carbon double bonds are of
ber of processes have been developed for the transfor-
mation of carbonꢀcarbon double bonds, and during the
/
last two decades processes based on metal-mediated
reactions have become increasingly important. Of all
metals used for reactions of this kind, palladium has
become one of the most diverse [1].
The palladium(II)-catalyzed 1,4-oxidation of 1,3-
dienes has been shown to be useful for oxidative
functionalization of conjugated dienes, thereby introdu-
cing a large variety of nucleophiles in the 1- and 4-
positions of 1,3-dienes [2]. Carboxylic acids [3], alcohols
natural products [10ꢀ12]. We are currently working on
/
an asymmetric version of the 1,4-oxidation reaction.
A catalytic amount of p-benzoquinone (BQ) is
required in the 1,4-oxidation reaction for two reasons:
(i) benzoquinone activates the intermediate (p-allyl)pal-
ladium(II) complex towards attack by the second
nucleophile [13], and (ii) it reoxidizes the palladium(0)
formed back to palladium(II) [14]. By the use of a
stoichiometric amount of a terminal oxidant, such as
manganese dioxide [3], or molecular oxygen together
with a metal macrocyclic complex such as iron(II)
* Corresponding author. Fax: ꢁ
E-mail addresses: plietker@pop.uni-dortmund.de (B.J. Plietker),
jeb@organ.su.se (J.-E. Backvall).
/46-8-154-908.
¨
1
Fax: ꢁ49-234-755-3884.
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.09.007

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509
Scheme 1. 1,4-oxidation of dienes with different nucleophiles.
phthalocyanine (Fe(Pc)) [15], the hydroquinone formed
in this process is reoxidized to benzoquinone. Because of
the close proximity of benzoquinone to palladium, at
least during the nucleophilic attack on the (p-allyl)
intermediate, we have introduced the use of chiral
benzoquinone ligands (BQ*) to induce enantioselectivity
in the 1,4-oxidation reaction. Indeed, such ligands have
been shown to generate a moderate enantioselectivity.
Thus, chiral sulfoxide-substituted benzoquinone ligand
1b (Fig. 1) gave 45% e.e. in the 1,4-diacetoxylation
reaction [16], and C2-symmetric chiral amide 2 afforded
54% e.e in the 1,4-dialkoxylation reaction [17].
To gain further insight into the mechanism of the 1,4-
diacetoxylation reaction, we recently studied the inter-
mediate (p-allyl)palladium complexes of this reaction in
acetic acid solutions [18]. It was found that an equili-
brium exists between the diene and the two enantiomeric
trans-4-acetoxy-[h3-(1,2,3)-cyclohexenyl]palladium com-
plexes, and that the rate of this equilibrium is increased
by the addition of either acetate or methanesulfonic
acid. Treatment of racemic bis(4-acetoxy-2-phenyl-[h3-
(1,2,3)-cyclohexenyl])palladium acetate complex with a
stoichiometric amount of a chiral sulfoxide ligand 1c, in
the presence of acetate, gave the 1,4-oxidation product
in almost 50% enantiomeric excess in the very beginning
of the reaction (at low conversion), but after full
conversion the enantiomeric excess had decreased to
only 28%. This shows that the nucleophilic attack on the
(p-allyl)palladium(BQ*)-complex is faster than the ace-
tate exchange reaction via the diene. It also implies that
a fully dynamic system is not operative under the
reactions conditions and emphasizes the need for the
formation of only one of two possible diastereomeric (p-
allyl)palladium(BQ*)-complexes from the diene. With
the ligands used so far, it is unclear whether they
coordinate to the metal and exert their chiral informa-
tion throughout the entire catalytic cycle.
It is well-known that bidentate ligands can form
stable complexes upon coordination to a metal atom,
and the advantage of such complexes in catalysis is
illustrated by the increased use of bidentate ligands over
the past decades [19]. More recently, their importance in
asymmetric catalysis has increased. We envisioned that
bidentate ligands in our reaction would lead to more
stable palladium-ligand complexes that would not
release the ligands at any stage of the reaction, and
hence could provide a higher enantioselectivity. We have
therefore designed and synthesized a series of new
ligands, consisting of C2-symmetric diamides containing
redox-active hydroquinone groups. The synthesis and
the results of their use in the 1,4-diacetoxylation
reaction will be presented here.
2. Results and discussion
Amides have been used earlier as ligands for the 1,4-
oxidation reaction because of their good coordinating
properties to palladium [20,21]. Chiral C2-symmetric
diamides have a high conformational rigidity as a result
of the amide bond, where rotation about the CꢀN bond
/
is prohibited by the partial double bond character of this
bond. For practical reasons, the hydroquinone form of
the ligands was synthesized. A schematic model of the
new ligands and the in situ oxidation to the benzoqui-
none form is given in Fig. 2.
For the ligand backbones, four different C2-sym-
metric diamines were used: (ꢂ
cyclohexane, (ꢁ)-(R)-1,1?-binaphthyl-2,2?-diamine,
(ꢁ)-(11S,12S)-11,12-diamino-9,10-dihydro-9,10-etha-
noanthracene and (ꢂ)-(1S,2S)-1,2-diphenyl-1,2-etha-
/)-(1R,2R)-1,2-diamino-
/
/
/
nediamine. These diamines have dihedral angles of
approximately 60, 90, 1208 and a more variable angle,
respectively, between the two CꢀN bonds (Fig. 3). The
/
free rotation in 1,2-diphenyl-1,2-ethanediamine allows
the ligand derived from it to coordinate to palladium
with the optimal chelation angle. It is known that this
angle can have a profound effect on the enantioselec-
Fig. 1.

510
R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ
/517
Fig. 2.
tivity in for instance Pd(0)-catalyzed asymmetric allylic
alkylation reactions [22,23].
meric ratio. Ligands 8 and 11 gave an enantioselectivity
of 26 and 22%, respectively (entries 1 and 4).
The higher enantioselectivity with ligand 10 when
compared to ligands 8 and 11 is likely a result of the
The synthesis of ligands 8ꢀ11 was performed in three
/
simple steps starting from the four diamines mentioned
before and commercially available 1-bromo-2,5-di-
methoxybenzene (Scheme 2). Lithiation followed by
carboxylation gave 68% yield of 2,5-dimethoxy-benzoic
acid (3). Compound 3 was then transformed into the
corresponding acid chloride, which was directly used for
acylation of the diamines. The highest yields were
obtained when the benzoic acid chloride was used in
large excess relative to that of the diamine, and a 3.5:1
different dihedral angles between the two Cꢀ
where the larger angle of ꢀ1208 in 10 gives a higher
enantioselectivity than the ꢀ608 angle in 8, in accor-
/N bonds,
/
/
dance with the results by Trost et al. [22]. In ligand 11
the angle is variable due to free rotation around the
central CꢀC bond, which can result in good chelation of
/
palladium, but with an angle which might be insufficient
for a high enantioselectivity. The similar results with
ligands 8 and 11, however, suggest that 11 adopts a
conformation to coordinate the metal center with an
angle of approximately the same size as in 8.
One of the purposes with bidentate ligands is that the
formation of a chelate will guarantee a strong coordina-
tion of the ligand. Many studies have been performed on
the mode and strength of coordination of metals to
amides. Pd(II) is one of the most effective metal ions in
the promotion of amide hydrogen ionisation in peptides
ratio gave diamides 4ꢀ
Deprotection of the methoxy groups was performed
with excess boron tribromide [24] in CH2Cl2 at ꢂ78 8C,
and gave ligands 8ꢀ11 in 81ꢀ93% yield.
Ligands 8ꢀ11 were tested in the 1,4-diacetoxylation
/7 in more than 90% yield.
/
/
/
/
reaction with 2-phenyl-1,3-cyclohexadiene (12) as the
test substrate, using 10 mol% Pd(OAc)2, 10 mol% ligand
and 0.4 M LiOAc in HOAcꢀacetone 4:1. The above
/
mentioned Fe(Pc)/O2 system was applied for the (re)ox-
idation of hydroquinone. The results are shown in Table
[20,26ꢀ28], and a number of Pd(II)-containing amide-
/
macrocycles have been prepared and isolated, in which
the palladium ion coordinates to the amide nitrogen
atoms. In some complexes containing pyridinecarbox-
amide groups, deprotonation occurs readily and the
actual deprotonated amide nitrogens were observed
[29,30]. Fig. 4 schematically shows the chelates that
can be formed with the ligands discussed in this article.
Complexation can in principle take place both through
the amide (A) and the iminol (B) form. Based on
spectroscopy data on 14-membered tetraazamacrocyclic
complexes of Pd(II), where IR-measurements showed
the absence of the azomethine group and the presence of
1 (entries 1ꢀ4). The 1,4-diacetoxylation product (13)
was formed exclusively and none of the 1,2-oxidation
product was observed. The trans-selectivity in the 1,4-
/
addition was in the range 88ꢀ91%. The formation of 13
/
was slower than in the corresponding reaction using
benzoquinone, which can explain the moderate yields
[25]. Except for ligand 9, which gave racemic product
only, the enantiomeric excess was moderate. Ligand 10
proved best and gave 40% yield and 39% e.e. (entry 3),
very close to our ‘old record’ of 45% e.e. with sulfoxide
ligand 1b. However, 10 gave a much higher diastereo-
Fig. 3.

R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ
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511
Scheme 2. Synthesis of ligands 8ꢀ
/
11. Reagents and conditions: (a) n-BuLi, ꢂ78 8C, then CO2; (b) SOCl2, reflux; (c) diamine, Et3N, CH2Cl2, 0 8C to
/
r.t.; (d) BBr3, CH2Cl2, ꢂ78 8C.
/
metal-bonded nitrogen atoms [31], coordination
through the iminol form of the ligands can probably
be ruled out. Ionization of amide hydrogens occurs at
low pH with Pd(II) complexation, and complexes with
pKa values as low as 3.5 have been reported [26ꢀ28].
Whether Pd(OAc)2 is able to deprotonate amides in
/
Table 1
1,4-Diacetoxylation reactions in the presence of ligands 8ꢀ11
/
Entry
Ligand
[LiOAc] (M)
Yield of 13 (%) a
Trans:cis ratio b
e.e. (%) c
26
1
2
3
4
5
6
8
9
0.4
0.4
0.4
0.4
0.25
1.0
38
23
40
16
45
27
89:11
88:12
91:9
B5
/
10
11
10
10
39
22
26
42
89:11
88:12
85:15
Reactions were run on a 50-mg scale. See Section 4 details.
a
Isolated yield.
Determined by HPLC.
Determined by HPLC. In entries 1 and 4 the major enantiomer is opposite to that of the other entries.
b
c

512
R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ517
/
ligand by protecting it against acid-catalyzed degrada-
tion [16]. This was reflected by the higher yield of
diacetoxylation product 13 that was obtained with
ligand 1b (R?ꢃt
/
Bu) compared to that with 1a (R?ꢃH).
/
Thus, the ligands containing the tert-butyl substitu-
ents were synthesized as shown in Scheme 3. The
protected benzoic acid 16 was prepared from tert-
butylhydroquinone in three steps. After methylation of
the two hydroxy groups, monobromination of the
benzene ring gave 15 as the major isomer. Lithiation
and subsequent carboxylation gave 16 in an overall yield
of 43%. Following the same procedure as the acylation
Fig. 4.
acetic acid solutions as used here is not known. A higher
acetate concentration could enhance the deprotonation
and promote stronger chelate formation, resulting in
higher enantioselectivities. To investigate if this was the
case, ligand 10 was used with varying acetate concentra-
tions under otherwise similar reaction conditions. With
0.25 M LiOAc, the enantioselectivity was lower (26%
e.e., entry 5). As mentioned before, 39% e.e. was
obtained with 0.4 M LiOAc (entry 3). With 1.0 M
LiOAc a slightly higher enantioselectivity was obtained
(42% e.e.) but this was accompanied by a lower yield
as described above, 17ꢀ
/
20 were obtained in 90ꢀ98%
/
yield. The final deprotection using excess boron tribro-
mide gave ligands 22 and 23 in 93 and 80% yield,
respectively. However, this deprotection method did not
work for compounds 21 and 24.
Deprotection of 17 and 20 with BBr3 at ꢂ78 8C gave
/
only partially deprotected products. Raising the tem-
perature still gave partial deprotection (0 8C) or even led
to degradation of the products to the carboxylic acid
(room temperature). Dealkylation of the methyl ethers
of 19 with trimethylsilyl iodide [33], prepared in situ
from trimethylsilyl chloride and sodium iodide [34] in
acetonitrile at 70 8C, also failed and gave only partial
hydrolysis, even after longer reaction times (2 days).
Oxidative dealkylation of 16 and 19 with cerium(IV)
ammonium nitrate (CAN) in acetonitrile [35], a reaction
that would give the benzoquinone products, indeed
afforded these products according to TLC. However,
they could be isolated in only low yield and were
contaminated with several other products from which
they could not be separated. No further efforts were
made to deprotect these two compounds.
Compounds 22 and 23 were tested as ligands in the
diacetoxylation reaction using 0.4 M LiOAc, and the
corresponding values for the e.e. are presented in Table
2. Contrary to the expectations, the yield of 13 was not
improved when compared to the results with the ligands
without the tert-butyl groups. The diastereomeric ratio
remained unaffected and was still high, with a trans:cis
ratio up to 93:7. Ligand 23 gave 24% of product 13 but
with only 22% e.e., a decrease in enantioselectivity when
compared to ligand 10, indicating that the extra
substituent does not have a positive influence on the
and decreased diastereoselectivity [32] (trans:cisꢃ85:15)
/
(entry 6). Thus, the acetate concentration has indeed an
effect on the enantioselectivity, but concentrations
higher than 0.4 M are probably not beneficial for the
efficiency of the reaction.
If the Nꢀ
/
PdꢀN chelate is not exclusively formed,
/
other ways of interaction between the metal and the
ligand are possible. For instance, hydrogen bonding
between the amide hydrogen and the benzoquinone
oxygen would make coordination of palladium to the
amide nitrogen impossible, and thereby leave the outer,
non-substituted CꢀC double bond of the benzoquinone
/
moiety available for coordination (C in Fig. 5). With
palladium this far from the chiral center, the role of the
chiral ligand would be reduced to nothing more than a
simple source of benzoquinone. The chiral information
would not be transferred to the product, and this could
be a possible explanation for the moderate e.e. observed.
We therefore argued that steric hindrance at this outer
position could prevent coordination of palladium to this
Cꢀ
center (D). A tert-butyl substituent was therefore
introduced at the unsubstituted CꢀC double bond.
/
C double bond and force the metal to the ligand
/
Moreover, it was previously shown that such a sub-
stituent provided extra stability to the benzoquinone
Fig. 5.

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513
Scheme 3. (Attempted) synthesis of ligands 21ꢀ
/
24. Reagents and conditions: (a) K2CO3, MeI, DMF, 60 8C; (b) Br2, HOAc, r.t.; (c) n-BuLi, ꢂ
/78 8C,
then CO2; (d) SOCl2, reflux; (e) diamine, Et3N, CH2Cl2, 0 8C to r.t.; (f) BBr3, CH2Cl2, ꢂ
/
78 8C.
enantioselectivity. Ligand 22 gave racemic product as its
unsubstituted analogue 9 also did.
more electron-rich and the intramolecular hydrogen-
bonding (as shown in C) might have been enhanced.
This would also leave less benzoquinone available to
palladium and result in both lower yield and enantios-
electivity.
The lack of any enantioselectivity induced by ligands
9 and 22 could be explained by the bridge length
between the two amide groups, which is two carbons
longer than in the other ligands. The seven-membered
chelates that could be formed with these ligands are
probably weaker than their five-membered analogues,
and inefficient binding of palladium with both nitrogen
atoms would explain the loss of enantioselectivity.
The lower yield and decrease in enantiomeric excess,
from 39% with ligand 10 to only 22% with ligand 23,
caused by the introduction of tert-butyl groups to the
ligand, is evidence of a less effective coordination. The
extra substituents may indeed have rendered the ligands
more sterically crowded, preventing palladium from
coordinating to the CꢀC double bond away from the
/
amide-group, but this did not lead to a more proper
chelation of the metal. Instead, coordination may have
become simply impossible resulting in a low yield.
Moreover, the benzoquinone ring might have become

514
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/
Table 2
Diacetoxylation reactions in the presence of ligands 22 and 23
Entry
Ligand
[LiOAc] (M)
Yield of 13 (%) a
Trans:cis ratio b
e.e. (%) c
1
2
22
23
0.4
0.4
15
24
90:10
93:7
B5
22
/
Reactions were run on a 50-mg scale. See Section 4 for details.
a
Isolated yield.
Determined by HPLC.
Determined by HPLC.
b
c
3. Conclusions
Analytische Laboratorien, Lindlar, Germany. MALDI-
TOF spectra were recorded on a Bruker Biflex III
We have synthesized a series of new enantiopure
ligands for the asymmetric palladium(II)-catalyzed 1,4-
diacetoxylation of conjugated dienes. The ligands are
C2-symmetric diamides and contain hydroquinone
groups that can be oxidized in situ to benzoquinones,
which are used for the reoxidation of Pd(0) to Pd(II).
The synthesis was performed in a few simple steps from
4 different chiral diamines and gave the ligands in good
yields.
We have applied the ligands in the 1,4-diacetoxylation
reaction where they gave a moderate chiral induction.
The oxidation product was obtained with high regio-
and diastereoselectivity, and an enantiomeric excess up
to 42% was reached. In terms of yield and diastereo-
selectivity, this is a slight improvement compared to
ligands that have been developed earlier.
instrument. Merck silica gel 60 (240ꢀ400 mesh) was
/
used for flash chromatography, and analytical thin-layer
chromatography was performed on Merck precoated
silica gel 60-F254 plates. Tetrahydrofuran (THF) was
freshly distilled under nitrogen from sodium benzophe-
none ketyl prior to use. Methylene chloride (CH2Cl2)
was distilled from calcium hydride. (ꢂ
Diaminocyclohexane was purchased from Fluka, (ꢁ
(R)-1,1?-binaphthyl-2,2?-diamine from Aldrich and
(ꢂ)-(1S,2S)-1,2-diphenyl-1,2-ethanediamine from Lan-
caster in ꢁ98% optical purity. (ꢁ)-(11S,12S)-11,12-
/)-(1R,2R)-1,2-
/)-
/
/
/
Diamino-9,10-dihydro-9,10-ethanoanthracene [22] (96%
optical purity) was prepared by a Curtius degradation of
(ꢂ)-9,10,-dihydro-9,10-ethanoanthracene-11,12-dicar-
/
boxylic acid [36]. 2,5-dimethoxybenzoic acid (3) [37] and
4-tert-butyl-2,5-dimethoxybenzoic acid (16) [38] were
prepared following literature procedures, and the NMR
data were in agreement with literature. 2-Phenyl-1,3-
cyclohexadiene (12) was prepared by a method devel-
oped in our laboratories [39].
The introduction of extra substituents on the ligand,
thought to direct the metal to the amide nitrogen atoms
in the center of the ligand, was not successful and led to
a decrease in both yield and enantioselectivity.
4.1.1. (ꢁ)-(R,R)-N,N?-bis-(2?,5?-Dimethoxy-
/
4. Experimental
benzamido)-1,2-cyclohexane (4). General procedure
2,5-Dimethoxybenzoic acid (1.44 g, 7.9 mmol) was
dissolved in 5 ml thionyl chloride and the solution was
refluxed for 2 h. After cooling to room temperature
(r.t.), the solvent was evaporated in vacuo, and coeva-
4.1. General remarks
1H- (400 or 300 MHz) and 13C- (100 or 75 MHz)
NMR spectra were recorded on a Varian spectrometer.
Chemical shifts (d) are reported in ppm, using residual
solvent proton resonance or tetramethylsilane as inter-
nal standard. For all characterized compounds, the 13C-
NMR signals correspond to two carbons due to C2-
porated three times with 5 ml toluene. (ꢂ)-(1R,2R)-1,2-
/
Diaminocyclohexane (0.26 g, 2.3 mmol) was dissolved in
7 ml CH2Cl2, triethylamine (1.26 ml, 9.0 mmol) was
added and the solution was cooled to 0 8C and stirred
under argon. The acid chloride was dissolved in 3 ml
CH2Cl2 and added to the solution from a syringe during
five minutes. The solution was stirred for 14 h. Et2O (25
ml) was added, and the organic phase was washed with
water, saturated aqueous sodium bicarbonate (twice)
symmetry. Optical rotations were obtained on a Perkinꢀ
/
Elmer 241 Polarimeter. Analytical high-pressure chro-
matography (HPLC) was performed on a Waters liquid
chromatograph. Elemental analysis was performed by

R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ
/517
515
and water. The organic layer was dried over Na2SO4,
and the solvent was removed in vacuo. The residue was
7.24 (m, 10H), 7.70 (d, Jꢃ
/
3.2 Hz, 2H), 8.89ꢀ
/
8.95 (m,
2H, NH); 13C-NMR (100 MHz, CDCl3, 25 8C): d 55.77,
56.44, 59.00, 112.84, 115.71, 119.29, 121.72, 127.52,
127.78, 128.34, 139.49, 152.08, 153.69, 164.93. MALDI-
TOF MS: Calc. for C32H32N2O6: 541.2334; Found:
541.2518 [M]ꢁ.
purified by silica chromatography (petroleum etherꢀ
EtOAc 1:4) to give 977 mg (97%) of 4 as a beige solid.
[a]2D5 21.08 (c 1.76, CHCl3); 1H-NMR (400 MHz,
CDCl3, 25 8C): d 1.31ꢀ1.52 (m, 4H), 1.78ꢀ1.85 (m, 2H),
2.22ꢀ2.30 (m, 2H), 3.77 (s, 6H), 3.82 (s, 6H), 4.03ꢀ4.10
(m, 2H), 6.81ꢀ6.84 (d, Jꢃ9.2 Hz, 2H), 6.91ꢀ6.95 (dd,
Jꢃ3.2, 9.2 Hz, 2H), 7.67 (d, Jꢃ3.2 Hz, 2H), 8.10ꢀ8.16
(br d, Jꢃ
7.6 Hz, 2H, NH); 13C-NMR (100 MHz,
/
ꢁ
/
/
/
/
/
/
/
/
4.1.5. (ꢂ
benzamido)-1,2-cyclohexane (8). General procedure
(ꢁ)-(R,R)-N,N?-bis-(2?,5?-Dimethoxy-benzamido)-
/
)-(R,R)-N,N?-bis-(2?,5?-Dihydroxy-
/
/
/
/
/
CDCl3, 25 8C): d 24.92, 32.90, 53.28, 55.77, 56.37,
112.90, 115.77, 118.76, 122.18, 151.97, 153.64, 165.09.
Anal. Calc. for C24H30N2O6: C, 65.14; H, 6.83; Found:
C, 65.36; H, 6.81%.
1,2-cyclohexane (4) (856 mg, 1.93 mmol) was dissolved
in CH2Cl2 (25 ml) under an argon atmosphere and
cooled to ꢂ78 8C. Boron tribomide (3.7 ml, 38.7 mmol)
/
was added dropwise from a syringe. The solution was
stirred for 16 h and was allowed to slowly come to r.t.
during this time. The reaction was quenched by the
addition of a few ml of ether. Water and CH2Cl2 were
added and the phases were separated. The organic layer
was washed twice with water, dried (Na2SO4), and the
solvent was removed in vacuo. Column chromatography
4.1.2. (ꢁ)-(R)-N,N?-bis-(2?,5?-Dimethoxy-
/
benzamido)-2,2?-binaphthalene (5)
According to the procedure for the preparation of 4, 5
was obtained from (ꢁ)-(R)-1,1?-binaphthyl-2,2?-dia-
/
mine in 90% as a beige solid. [a]D24
CHCl3); H-NMR (300MHz, CDCl3, 25 8C): d 2.95 (s,
ꢁ13.48 (c 1.08,
/
1
(petroleum etherꢀ
a beige solid. [a]D23
(300 MHz, acetone-d6, 25 8C): d 1.36ꢀ
1.52ꢀ1.67 (m, 2H), 1.74ꢀ1.88 (m, 2H), 2.11ꢀ
2H), 2.98 (s, 2H, OH), 3.98ꢀ4.12 (m, 2H), 6.66ꢀ
Jꢃ8.7 Hz, 2H), 6.87ꢀ6.92 (dd, Jꢃ2.7, 8.7 Hz, 2H),
7.14 (d, Jꢃ2.7 Hz, 2H), 7.99 (s, 2H, OH), 8.02ꢀ8.08 (br
d, Jꢃ
6.6 Hz, 2H, NH). 13C-NMR (100 MHz, acetone-
/
EtOAc 1:4) gave 644 mg (86%) of 7 as
1
6H), 3.75 (s, 6H), 6.58ꢀ
6.90 (dd, Jꢃ3.3, 9.0 Hz, 2H), 7.02ꢀ
7.21ꢀ7.27 (ddd, Jꢃ1.3, 6.9, 8.2 Hz, 2H), 7.38ꢀ
(ddd, Jꢃ1.3, 6.9, 8.2 Hz, 2H), 7.70 (d, Jꢃ
7.92ꢀ7.96 (br d, 2H), 8.08ꢀ8.13 (d, Jꢃ
9.02ꢀ9.07 (d, Jꢃ
9.1 Hz, 2H), 9.78 (br s, 2H, NH); 13C-
/
6.62 (d, Jꢃ
/
9.0 Hz, 2H), 6.84ꢀ
/
ꢂ
/
96.48 (c 1.73, MeOH); H-NMR
1.49 (m, 2H),
2.20 (m,
6.70 (d,
/
/
7.07 (br d, 2H),
/
/
/
/
7.44
/
/
/
/
/3.3 Hz, 2H),
/
/
/
/
/9.1 Hz, 2H),
/
/
/
/
/
/
/
NMR (75 MHz, CDCl3, 25 8C): d 55.57, 55.75, 112.69,
115.39, 120.01, 120.28, 121.50, 121.75, 125.27, 127.19,
128.01, 129.44, 131.05, 132.91, 136.57, 151.71, 153.60,
163.50. Anal. Calc. for C38H32N2O6: C, 74.49; H, 5.26;
Found: C, 74.18; H, 5.37%.
/
d6, 25 8C) d 25.51, 30.63, 54.18, 113.05, 115.43, 119.10,
122.72, 150.01, 155.41, 170.85.
4.1.6. (ꢂ)-(R)-N,N?-bis-(2?,5?-Dihydroxy-
/
benzamido)-2,2?-binaphthalene (9)
According to the procedure for the preparation of 8, 9
4.1.3. (ꢁ
/
)-(11S,12S)-N,N?-bis-(2?,5?-Dimethoxy-
benzamido)-9,10-dihydro-9,10-ethanoanthracene (6)
According to the procedure for the preparation of 4, 6
was obtained from 5 in 93% as a pale brown solid. [a]D23
ꢂ
48.28 (c 1.77, MeOH); 1H-NMR (300 MHz, acetone-
/
was obtained from (ꢁ
/
)-(11S,12S)-diamino-9,10-dihy-
dro-9,10-ethanoanthracene in 93% as a beige solid. [a]D28
d6, 25 8C): d 3.04 (s, 2H, OH), 6.58-6.62 (d, Jꢃ
2H), 6.78ꢀ6.83 (dd, Jꢃ3.0, 8.7 Hz, 2H), 7.08ꢀ7.13 (br
d, 2H), 7.15 (d, Jꢃ3.0 Hz, 2H), 7.24ꢀ7.31 (ddd, Jꢃ1.5,
6.9, 8.4 Hz, 2H), 7.40ꢀ7.47 (ddd, Jꢃ1.5, 6.9, 8.4 Hz,
2H), 7.96ꢀ8.01 (br d, 2H), 8.09ꢀ8.14 (d, Jꢃ9.0 Hz,
2H), 8.45ꢀ8.49 (d, Jꢃ9.0 Hz, 2H), 9.90 (br s, 2H, OH),
10.07ꢀ
10.15 (br s, 2H, NH). 13C-NMR (75 MHz,
acetone-d6, 25 8C): d 114.94, 117.79, 118.82, 122.41,
124.14, 125.55, 125.90, 126.37, 127.68, 129.11, 130.24,
132.61, 133.67, 136.50, 150.75, 152.54, 167.41.
/
8.7 Hz,
/
/
/
1
ꢁ
/
55.98 (c 1.02, MeOH); H-NMR (300 MHz, CDCl3,
/
/
/
25 8C): d 3.52 (s, 6H), 3.79 (s, 6H), 4.34ꢀ
4.52 (d, Jꢃ3.0 Hz, 2H), 6.77ꢀ6.80 (d, Jꢃ
6.92ꢀ6.97 (dd, Jꢃ3.3, 9.0 Hz, 2H), 7.18ꢀ7.29 (m, 4H),
7.31ꢀ7.37 (m, 2H), 7.44ꢀ7.48 (m, 2H), 7.70 (d, Jꢃ3.3
Hz, 2H), 7.88ꢀ7.94 ( br d, Jꢃ
8.7 Hz, 2H, NH); 13C-
/4.40 (m, 2H),
/
/
/
/
/9.0 Hz, 2H),
/
/
/
/
/
/
/
/
/
/
/
/
/
/
NMR (75 MHz, CDCl3, 25 8C): d 49.50, 55.79, 55.99,
57.34, 112.82, 115.37, 119.37, 121.60, 124.98, 125.92,
126.38, 126.68, 139.58, 140.81, 151.79, 153.69, 164.31.
4.1.7. (ꢁ)-(11S,12S)-N,N?-bis-(2?,5?-dihydroxy-
/
4.1.4. (ꢂ
/
)-(1S,2S)-N,N?-bis-(2?,5?-Dimethoxy-
benzamido)-9,10-dihydro-9,10-ethanoanthracene (10)
According to the procedure for the preparation of 8,
benzamido)-1,2-diphenylethane (7)
According to the procedure for the preparation of 4, 7
10 was obtained from 6 in 81% as a beige solid. [a]D23
ꢁ
/
1
was obtained from (ꢂ
/)-(1S,2S)-1,2-diphenyl-1,2-etha-
117.68 (c 0.26, MeOH); H-NMR (300 MHz, acetone-
nediamine in 95% as a beige solid. [a]D27
ꢂ
/
50.38 (c 0.62,
d6, 25 8C): d 2.92 (s, 2H, OH), 4.58ꢀ
6.76 (d, Jꢃ9.0 Hz, 2H), 6.88ꢀ6.94 (dd, Jꢃ
2H), 7.10ꢀ7.12 (d, Jꢃ3.0 Hz, 2H), 7.12ꢀ7.25 (m, 4H),
7.35ꢀ7.39 (m, 2H), 7.44ꢀ7.48 (m, 2H), 7.88 (s, 2H, OH),
/
4.63 (m, 4H), 6.72ꢀ
/
1
CHCl3); H-NMR (400 MHz, CDCl3, 25 8C): d 3.76 (s,
/
/
/3.0, 9.0 Hz,
6H), 3.85 (s, 6H), 5.58ꢀ
8.8 Hz, 2H), 6.93ꢀ6.97 (dd, Jꢃ
/
5.61 (m, 2H), 6.83ꢀ
/
6.86 (d, Jꢃ
/
/
/
/
/
/
3.2, 8.8 Hz, 2H), 7.14ꢀ
/
/
/

516
R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ517
/
7.99ꢀ
/
8.07 (br d, Jꢃ
/
6.3 Hz, 2H, NH). 13C-NMR (75
[a]2D3
CDCl3, 25 8C): d 1.35 (s, 18H), 3.52 (s, 6H), 3.82 (s, 6H),
4.30-4.36 (m, 2H), 4.52 (d, Jꢃ3.2 Hz, 2H), 6.79 (s, 2H),
7.16ꢀ7.27 (m, 4H), 7.31ꢀ7.34 (m, 2H), 7.44ꢀ7.47 (m,
2H), 7.65 (s, 2H), 7.87ꢀ7.92 (d, Jꢃ8.0 Hz, 2H, NH).
ꢁ
/
112.48 (c 1.77, CHCl3); 1H-NMR (400 MHz,
MHz, acetone-d6, 25 8C): d 50.17, 56.56, 113.49, 115.52,
118.92, 122.66, 125.24, 126.71, 127.28, 127.30, 140.43,
142.83, 149.92, 155.25, 170.72. MALDI-TOF MS: Calc.
for C30H24N2O6: 509.1706; Found: 509.1727 [M]ꢁ.
/
/
/
/
/
/
13C-NMR (100 MHz, CDCl3, 25 8C): d 29.41, 35.30,
49.56, 55.58, 56.09, 57.44, 111.15, 114.18, 118.96,
124.92, 125.92, 126.35, 126.64, 139.66, 140.91, 143.51,
151.24, 152.76, 164.49.
4.1.8. (ꢂ)-(1S,2S)-N,N?-bis-(2?,5?-Dihydroxy-
/
benzamido)-1,2-diphenylethane (11)
According to the procedure for the preparation of 8,
11 was obtained from 7 in 91% as a beige solid. [a]D24
ꢂ
/
46.18 (c 1.77, MeOH); 1H-NMR (300 MHz, acetone-d6,
25 8C): d 2.95 (s, 2H, OH), 5.66ꢀ5.70 (m, 2H), 6.70ꢀ
6.74 (d, Jꢃ9.0 Hz, 2H), 6.89ꢀ6.95 (dd, Jꢃ3.0, 9.0 Hz,
2H), 7.12ꢀ7.24 (m, 6H), 7.31ꢀ7.33 (d, Jꢃ3.0 Hz, 2H),
7.35ꢀ 8.98 (m, 2H,
/
/
4.1.12. (ꢂ)-(1S,2S)-N,N?-bis-(4?-tert-Butyl-2?,5?-
/
/
/
/
dimethoxy-benzamido)-1,2-diphenylethane (20)
According to the procedure for the preparation of 17,
/
/
/
/
7.40 (m, 4H), 8.03 (s, 2H, OH), 8.93ꢀ
/
20 was obtained from (ꢂ)-(1S,2S)-1,2-diphenyl-1,2-
/
NH). 13C-NMR (75 MHz, acetone-d6, 25 8C): d 59.25,
113.44, 115.68, 119.10, 122.84, 128.26, 128.75, 129.03,
140.62, 150.16, 155.09, 170.53.
ethanediamine in 90% as a beige solid. [a]D26
1.26, CHCl3); H-NMR (300 MHz, CDCl3, 25 8C): d
ꢂ70.18 (c
/
1
1.35 (s, 18H), 3.80 (s, 6H), 3.88 (s, 6H), 5.56ꢀ
2H), 6.87 (s, 2H), 7.12ꢀ7.24 (m, 10H), 7.67 (s, 2H),
8.90ꢀ
8.95 (m, 2H, NH). 13C-NMR (75 MHz, CDCl3,
/
5.60 (m,
/
4.1.9. (ꢁ)-(R,R)-N,N?-bis-(4?-tert-Butyl-2?,5?-
dimethoxy-benzamido)-1,2-cyclohexane (17)
According to the procedure for the preparation of 4,
17 was obtained from (ꢂ
hexane and 4-tert-butyl-2,5-dimethoxybenzoic acid in
/
/
25 8C): d 29.54, 35.47, 55.70, 56.52, 58.94, 111.12,
114.53, 119.04, 127.55, 127.90, 128.40, 139.79, 143.73,
151.62, 152.80, 165.12. Anal. Calc. for C40H48N2O6: C,
73.59; H, 7.41; Found: C, 73.78; H, 7.19%.
/)-(1R,2R)-1,2-diaminocyclo-
1
96% as a white solid. [a]D22
NMR (300 MHz, CDCl3, 25 8C): d 1.35 (s, 18H), 1.35ꢀ
1.52 (m, 4H), 1.76ꢀ1.83 (m, 2H), 2.21ꢀ2.29 (m, 2H),
3.82 (s, 6H), 3.86 (s, 6H), 4.01ꢀ4.10 (m, 2H), 6.85 (s,
7.8 Hz, 2H, NH).
ꢁ
/
6.58 (c 1.59, CHCl3); H-
/
/
/
4.1.13. (ꢁ)-(R)-N,N?-bis-(4?-tert-Butyl-2?,5?-
/
/
dihydroxy-benzamido)-2,2?-binaphthalene (22)
According to the procedure for the preparation of 8,
2H), 7.65 (s, 2H), 8.13ꢀ
/
8.19 (br d, Jꢃ
/
13C-NMR (75 MHz, CDCl3, 25 8C): d 24.94, 29.43,
32.97, 35.29, 53.12, 55.59, 56.39, 111.19, 114.30, 119.34,
143.27, 151.40, 152.63, 165.17.
22 was obtained from 18 in 93% as a pale brown solid.
[a]2D4
ꢁ
75.28 (c 0.57, MeOH); 1H-NMR (300 MHz,
/
acetone-d6, 25 8C): d 1.27 (s, 18H), 2.99 (s, 2H, OH),
6.61 (s, 2H), 7.03ꢀ7.08 (br d, 2H), 7.23 (s, 2H), 7.23ꢀ
7.29 (ddd, Jꢃ1.5, 6.9, 8.3 Hz, 2H), 7.38ꢀ7.45 (ddd, Jꢃ
1.5, 6.9, 8.3 Hz, 2H), 7.95ꢀ8.00 (br d, 2H), 8.08ꢀ8.12 (br
d, 2H), 8.63ꢀ8.90 (d, Jꢃ9.0 Hz, 2H), 9.45 (br s, 2H,
/
/
4.1.10. (ꢁ)-(R)-N,N?-bis-(4?-tert-Butyl-2?,5?-
dimethoxy-benzamido)-2,2?-binaphthalene (18)
According to the procedure for the preparation of 17,
/
/
/
/
/
/
/
/
18 was obtained from (ꢁ)-(R)-1,1?-binaphthyl-2,2?-
/
OH), 9.93 (br s, 2H, NH). 13C-NMR (75 MHz, acetone-
d6, 25 8C): d 29.36, 35.44, 116.11, 116.28, 116.42, 123.36,
123.82, 125.82, 126.04, 127.61, 129.09, 130.21, 132.30,
133.79, 137.12, 143.89, 149.46, 151.10, 166.20.
diamine in 98% as a beige solid. [a]D26
CHCl3); H-NMR (300 MHz, CDCl3, 25 8C): d 1.28 (s,
ꢁ52.4 8(c 1.32,
/
1
18H), 2.97 (s, 6H), 3.80 (s, 6H), 6.61 (s, 2H), 7.01ꢀ
(d, Jꢃ7.5 Hz, 2H), 7.20ꢀ7.26 (ddd, Jꢃ1.5, 6.9, 8.4 Hz,
2H), 7.37ꢀ7.43 (ddd, Jꢃ1.5, 6.9, 8.4 Hz, 2H), 7.65 (s,
2H), 7.91ꢀ7.96 (d, Jꢃ7.5 Hz, 2H), 8.07ꢀ8.12 (d, Jꢃ9.3
Hz, 2H), 9.06ꢀ9.12 (d, Jꢃ9.3 Hz, 2H), 9.78 (br s, 2H,
/
7.06
/
/
/
/
/
/
/
/
/
/
/
4.1.14. (ꢁ)-(11S,12S)-N,N?-bis-(4?-tert-Butyl-2?,5?-
/
NH). 13C-NMR (75 MHz, CDCl3, 25 8C): d 29.29,
35.32, 55.53 (two overlapping signals of non-equivalent
carbons), 110.80, 114.13, 118.73, 120.08, 121.67, 125.13,
125.28, 127.12, 127.96, 129.38, 130.99, 132.98, 136.75,
144.18, 151.13, 152.57, 163.67.
dihydroxy-benzamido)-9,10-dihydro-9,10-
ethanoanthracene (23)
According to the procedure for the preparation of 8,
23 was obtained from 19 in 80% as a beige solid. [a]2D7 ꢁ
/
1
157.78 (c 1.20, MeOH); H-NMR (400 MHz, CDCl3,
25 8C): d 1.31 (s, 18H), 4.21ꢀ4.26 (m, 2H), 4.40 (d, Jꢃ
2.4, 2H), 5.48 (s, 2H, OH), 6.43 (s, 2H), 6.45 (s, 2H,
7.33 (m,
/
/
4.1.11. (ꢁ)-(11S,12S)-N,N?-bis-(4?-tert-Butyl-2?,5?-
/
dimethoxy-benzamido)-9,10-dihydro-9,10-
ethanoanthracene (19)
According to the procedure for the preparation of 17,
OH), 6.84 (s, 2H), 7.08ꢀ
/
7.18 (m, 4H), 7.25ꢀ
/
4H), 10.66 (s, 2H, NH). 13C-NMR (100 MHz, CDCl3,
25 8C): d 29.15, 35.09, 49.22, 57.01, 111.61, 112.63,
116.88, 124.84, 125.77, 127.04, 127.18, 138.23, 140.60,
145.09, 147.06, 154.02, 168.97.
19 was obtained from (ꢁ
/
)-(11S,12S)-diamino-9,10-
dihydro-9,10-ethanoanthracene in 93% as a beige solid.

R.C. Verboom et al. / Journal of Organometallic Chemistry 687 (2003) 508ꢀ
/517
517
[11] A. Palmgren, A.L.E. Larsson, J.-E. Backvall, J. Org. Chem. 64
¨
4.2. General procedure for the asymmetric
palladium(II)-catalyzed 1,4-diacetoxylation reaction
(1999) 836.
[12] C. Jonasson, M. Ronn, J.-E. Backvall, J. Org. Chem. 65 (2000)
¨
¨
2122.
[13] J.-E. Backvall, A. Gogoll, Tetrahedron Lett. 29 (1988) 2243.
[14] H. Grennberg, A. Gogoll, J.-E. Backvall, Organometallics 12
Diene 12 (50 mg, 0.32 mmol) was added to a solution
of Pd(OAc)2 (7.2 mg, 0.032 mmol), chiral ligand (0.032
¨
¨
(1993) 1790.
[15] J.-E. Backvall, R.B. Hopkins, H. Grennberg, M. Mader, A.K.
mmol), LiOAc×
/
2H2O (51 mg, 0.50 mmol) and Fe(Pc)
¨
(4.5 mg, 0.008 mmol) in HOAcꢀ
/acetone 4:1 (1.25 ml)
Awasthi, J. Am. Chem. Soc. 112 (1990) 5160.
[16] A. Thorarensen, A. Palmgren, K. Itami, J.-E. Backvall, Tetra-
and the solution was stirred for 18 h under an oxygen
atmosphere at r.t. Et2O was added, and the organic
phase was extracted with 1 M NaOH (ꢄ3), washed with
¨
hedron Lett. 38 (1997) 8541.
[17] K. Itami, A. Palmgren, A. Thorarensen, J.-E. Backvall, J. Org.
/
¨
brine, dried (MgSO4) and evaporated. The crude
product was purified by column chromatography
Chem. 63 (1998) 6466.
[18] H.K. Cotton, R.C. Verboom, L. Johansson, B.P. Plietker, J.-E.
Backvall, Organometallics 21 (2002) 3367.
¨
[19] P.W.N.M. van Leeuwen, P.C.J. Kamer, J.N.H. Reek, P. Dierkes,
Chem. Rev. 100 (2000) 2741.
(pentaneꢀEt2O 3:1). The diastereomeric ratio and
/
enantiomeric excess of trans-1,4-diacetoxy-2-phenyl-2-
cyclohexene (13) was determined by HPLC analysis
[20] H. Sigel, R.B. Martin, Chem Rev. 82 (1982) 385.
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Chem. 30 (1971) 421.
using a Daicel Chiralcel OD-H column (hexaneꢀ
/
2-
14.1 and
propanol 98/2, flow rate 0.5 ml minꢂ1): tRꢃ
16.2 min.
/
[22] B.M. Trost, D.L. Van Vranken, C. Bingel, J. Am. Chem. Soc. 114
(1992) 9327.
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(b) For a recent application of the optimal ligand see: B. M. Trost,
J. Dudash, Jr, O. Dirat, Chem Eur. J. 8 (2002) 259.
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(1979) 4863.
Acknowledgements
Financial support from the Swedish Research Council
is gratefully acknowledged.
[25] A slower reaction usually leads to lower yields due to aromatisa-
tion as a side-reaction. The choice for this particular aromatisa-
tion-sensitive substrate is explained by the ease of separation on
chiral HPLC.
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