Sterically demanding planar chiral P,N ligands by diastereoselective ortho lithiation of pentaphenylferrocenyloxazolines and their application to palladium-catalyzed substitutions with cyclic allylic acetates

Article abstract of DOI:10.1021/om500049f

Functionalized 1′,2′,3′,4′,5′- pentaphenylferrocenes are known as valuable ligands and catalysts. Planar chiral derivatives - e.g. Fu's pentaphenylferrocene fused pyridines or palladacycles developed in our group - have previously been described to be very efficient asymmetric catalysts for a number of applications. Nevertheless, protocols for diastereoselective ortho lithiations of 1′,2′,3′,4′, 5′-pentaphenylferrocenes are still unknown. Such protocols could significantly increase the arsenal of accessible planar chiral pentaphenylferrocenes. In this full paper, we describe such diastereoselective ortho lithiations of pentaphenylferrocenyloxazolines. Both possible diastereomers can be produced in almost diastereomerically pure form depending on the choice of a Lewis base additive, which is required in the lithiation step for a sufficient reactivity. This development was utilized to prepare a set of planar chiral pentaphenylferrocene-based phosphino-oxazoline ligands. The latter were investigated in Pd-catalyzed allylic substitution reactions with cyclic allylic acetates to allow for a first comparison with related planar chiral ligands and provided good enantioselectivity with this challenging substrate class.

Full text of DOI:10.1021/om500049f

Article
pubs.acs.org/Organometallics
Sterically Demanding Planar Chiral P,N Ligands by Diastereoselective
Ortho Lithiation of Pentaphenylferrocenyloxazolines and Their
Application to Palladium-Catalyzed Substitutions with Cyclic Allylic
Acetates
Marta Ayerbe Garcia, Wolfgang Frey, and Rene Peters*
́
Institut fur Organische Chemie, Universitat Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
̈
̈
S
* Supporting Information
ABSTRACT: Functionalized 1′,2′,3′,4′,5′-pentaphenylferro-
cenes are known as valuable ligands and catalysts. Planar
chiral derivativese.g. Fu’s pentaphenylferrocene fused
pyridines or palladacycles developed in our grouphave
previously been described to be very efficient asymmetric
catalysts for a number of applications. Nevertheless, protocols
for diastereoselective ortho lithiations of 1′,2′,3′,4′,5′-penta-
phenylferrocenes are still unknown. Such protocols could
significantly increase the arsenal of accessible planar chiral
pentaphenylferrocenes. In this full paper, we describe such
diastereoselective ortho lithiations of pentaphenylferrocenyloxazolines. Both possible diastereomers can be produced in almost
diastereomerically pure form depending on the choice of a Lewis base additive, which is required in the lithiation step for a
sufficient reactivity. This development was utilized to prepare a set of planar chiral pentaphenylferrocene-based phosphino-
oxazoline ligands. The latter were investigated in Pd-catalyzed allylic substitution reactions with cyclic allylic acetates to allow for
a first comparison with related planar chiral ligands and provided good enantioselectivity with this challenging substrate class.
configured or the epimeric Rp-configured product is obtained
with excellent diastereoselectivity starting from the same
oxazoline substrate. The diastereoselective lithiations have
served to prepare planar chiral phosphino-oxazoline hybrid
ligands. The latter were used to synthesize Pd(II)-P,N
complexes. To allow for a first comparison with the
corresponding pentamethylferrocene oxazoline ligands,11c they
have been investigated in allylic substitution reactions of cyclic
allylic acetates.14,15
INTRODUCTION
■
Planar chiral ferrocenyl ligands have proven to be one of the
most efficient ligand classes for asymmetric catalysis and are
also extensively utilized on an industrial scale.1,2 A key step in
the preparation of planar chiral ferrocene ligands is usually a
diastereoselective ortho lithiation to introduce and control the
element of planar chirality.1 A number of complementary
ortho-lithiation approaches have been developed, which make
use of a variety of ortho-directing groups such as amines,3
oxazolines,4 sulfoxides,5 acetals,6 hydrazones,7 imidazolines,8
oxazaphospholidineoxides9 and amides.10 To increase the steric
demand of the ferrocene core, 1′,2′,3′,4′,5′-pentamethylferro-
cenes have also been studied in diastereoselective ortho
metalations.11 In contrast, diastereoselective ortho lithiations
of 1′,2′,3′,4′,5′-pentaphenylferrocenes have not been reported
yet. Previous attempts toward lithiations of chiral pentaphe-
nylferrocenes have been unsuccessful due to insufficient
reactivity.12,11d,f As a consequence, the corresponding planar
chiral P,N ligands have thus far not been accessible for catalytic
applications. Given the peculiar efficiency of pentaphenylferro-
cene-derived asymmetric catalysts in a diverse range of
applications,13 the diastereoselective ortho lithiation of chiral
pentaphenylferrocenes could be an attractive tool to access new
catalyst structures.
RESULTS AND DISCUSSION
■
Development of a Diastereoselective Ortho Metal-
ation of Pentaphenylferrocenyloxazolines. Pentaphenyl-
ferrocenyloxazolines derived from valinol and tert-leucinol were
prepared according to a published procedure.11f A number of
ortho-lithiation conditions were then studied to allow for
suitable reactivity and are summarized in Table 1. No reactivity
was observed with n-, s-, or t-BuLi in ethereal solvents at −78
°C (entries 1−4). At 0 °C the ortho-methylated product 2a was
formed in low yield and with low diastereoselectivity using n-
BuLi as base, after trapping of the generated carbanion with
methyl iodide (entry 5). Essential for a satisfactory reactivity
was the use of N,N,N′,N′-tetramethylethylenediamine
(TMEDA) as activating Lewis basic additive. With 1.5 equiv
Herein, we now report two protocols for the highly
diastereoselective ortho lithiation of pentaphenylferrocenylox-
azolines. Depending on the protocol used, either the Sp-
Received: January 16, 2014
Published: February 6, 2014
© 2014 American Chemical Society
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Article
metallocene backbone, thus resulting in an increased repulsion
with the oxazoline substituent, the Rp,S-configured product is
almost exclusively produced.
Table 1. Development of the Diastereoselective Ortho
Lithiation of 1a
The optimized lithiation conditions (Table 1, entry 7) were
then applied to the formation of different types of ortho-
functionalized products (Table 2). Next to the ortho
methylation of 1a (entry 1), the ortho silylation (entry 4),
and various ortho phosphinylations (entries 5 and 7−9) also
provided the desired diastereomerically pure planar chiral
products in useful yields under the same conditions. For good
conversion it was necessary that the reaction of the generated
organolithium species with the corresponding electrophile be
allowed to proceed at room temperature overnight. For the
ortho iodination both iodine and diiodoethane gave no desired
product under the standard conditions. However, sufficient
reactivity was achieved by the addition of LiClO4 as an additive
to activate diiodoethane as an electrophile (entry 3).
The oxazoline 1b derived from tert-leucinol was investigated
in the ortho methylation (Table 2, entry 2) and phosphiny-
lation (with Ph2PCl, entry 6) and also provided diastereomeri-
cally pure products, even though the repulsive interaction
between the tert-butyl residue R and the C5Ph5 ligand should be
further increased.
base (X
equiv)
additive (Y
equiv)
T1
t1
yield
a
b
entry
1
solvent (°C) (h)
(%)
dr
n-BuLi
(2.0)
THF
THF
THF
Et2O
Et2O
Et2O
Et2O
−78
−78
−78
−78
0
3
3
3
3
3
4
4
0
2
3
4
5
6
7
s-BuLi
(2.0)
0
t-BuLi
(2.0)
0
n-BuLi
(2.0)
0
n-BuLi
(2.0)
33
61
3:1
n-BuLi
(1.5)
TMEDA
(1.5)
−78
−78
>50:1
>50:1
n-BuLi
(1.5)
TMEDA
(3)
70
Epimeric products with the opposite sense of the element of
planar chirality may be prepared with high diastereoselectivity,
if the lithiation additive TMEDA is replaced by bis(2-tert-
butoxyethyl) ether (Scheme 1). This methodology has recently
a
b
Yield of isolated product after column chromatography. Determined
by H NMR of the crude product.
1
of n-BuLi in combination with 1.5 equiv of TMEDA, the ortho
lithiation could be performed at −78 °C to provide
diastereomerically pure 2a (entry 6). With double the amount
of TMEDA the yield of 2a could be further increased (entry 7).
The major isomer of product 2a has been formed with an
Rp,S configuration (for the determination of the absolute
configuration, see below),16 which is in harmony with a
stereochemical model presented by Richards for ortho
lithiations of ferrocenyl oxazolines.4a This model claims that
the substituent at the stereocenter next to the oxazoline
nitrogen atom should point toward the endo position (i.e.,
toward the metallocene) in order to minimize steric
interactions with the N-coordinated alkyllithium base, since
the latter adopts a position exo to the iron atom. Although a
C5Ph5 ligand should add much to the steric hindrance of a
Scheme 1. Formation of an Epimeric 1,2-Disubstituted
Pentaphenylferrocene
been developed for the diastereoselective ortho lithiation of
ferrocenyloxazolines bearing an unsubstituted Cp spectator
Table 2. Diastereoselective Ortho Functionalization of Pentaphenylferrocene Oxazolines 1
a
b
entry
product
R
EX
E
yield (%)
dr
1
2
3
4
5
6
7
8
9
2a
2b
3a
4a
5a
5b
6a
7a
8a
iPr
tBu
iPr
iPr
iPr
tBu
iPr
iPr
iPr
MeI
MeI
Me
70
50
75
85
80
88
68
91
39
>50:1
>50:1
>50:1
>50:1
>50:1
>50:1
>50:1
>50:1
>50:1
Me
(ICH2)2/LiClO4
Me3SiOTf
I
Me3Si
Ph2P
Ph2P
Ph2PCl
Ph2PCl
(4-MeOC6H4)2PCl
(4-F3CC6H4)2PCl
(3,5-(F3C)2C6H3)2PCl
(4-MeOC6H4)2P
(4-F3CC6H4)2P
(3,5-(F3C)2C6H3)2P
a
b
1
Yield of isolated product after column chromatography. Determined by H NMR of the crude product.
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Table 3. Formation of Pd−Allyl Complexes 9−12
a
b
entry
product
R
Ar
yield (%)
dr
1
2
3
4
5
9a
iPr
tBu
iPr
iPr
iPr
Ph
Ph
>99
>99
>99
>99
>99
1.3:1
>50:1
1.3:1
1.5:1
1.4:1
9b
10a
11a
12a
4-MeOC6H4
4-F3CC6H4
3,5-(F3C)2C6H3
a
b
1
Yield of isolated product. Determined by H NMR.
Scheme 2. Complexation of epi-5a to the Pd−Allyl Fragment
ligand and is also applicable to pentaphenylferrocenes as
showcased for the synthesis of the P,N ligand (epi)-5a.17
Formation and Structural Elucidation of η3-Allyl Pd−
P,N Complexes. To investigate the coordination behavior, we
employed the P,N ligands 5−8 to prepare cationic Pd-allyl
complexes 9−12 in a two-step, one-pot procedure via
successive treatment with [Pd(C3H5)Cl]2 and AgSbF6 (Table
3).11c All of these complexations proceeded with quantitative
yields. Whereas 5a equipped with a PPh2 donor group and
bearing an iPr residue at the oxazoline 4-position gave a ca. 1:1
mixture of isomers (entry 1, exo and endo allyl isomers; vide
infra), the related 5b, in which the iPr is formally replaced by a
tBu group, provided exclusively the exo isomer (entry 2), which
might be more favorable for steric reasons in that case. In
addition, the coordination of the other iPr-substituted oxazoline
derivatives 6a−8a resulted in almost equal amounts of both
isomers (entries 3−5).
bond lengths are significantly different, with the carbon atom
trans to phosphorus having the longer distance (9a, Pd−C =
2.211(5) Å; 9b, Pd−C = 2.251(3) Å) in comparison to that
trans to nitrogen (9a, Pd−C = 2.116(5) Å; 9b, Pd−C =
2.120(3) Å), indicating the higher trans influence of the
phosphino moiety.20 The interplanar tilt angles between the
allyl fragments and the P−Pd−N coordination planes are
56.5(7) and 68.4(8)° (9a, exo and endo, respectively) and
55.3(3)° (9b). The center distance of the Cp rings in one
ferrocene fragment is 3.35 Å, which is similar to the case for
other pentaphenylferrocenes.10 13j The interplanar angles
f,
between the Cp ring and the attached phenyl moieties are in
an interval of 37.0(2)−69.3(2)° (9a) and of 44.8(1)−68.3(1)°
(9b), which is an expected behavior. The endo phenyl rings on
the P atom and the isopropyl or tert-butyl residues connected
to the oxazoline rings are both in close contact with phenyl
substituents of the C5Ph5 ligand. To optimize these contact
distances, both Cp rings of a ferrocene unit are significantly
tilted toward each other (angle between ring planes 9.8(3)°
(9a) and 9.2(2)° (9b)) to increase the distances between the
C5Ph5 ligand and the iPr/tBu and P-Ph residues.21 For the
same reason the Cp-C atoms connected to the P moieties are
considerably pyramidalized (sum of bond angles at the Cp-C
atom for 9a, 355.2(4)°; sum of bond angles at the Cp-P atom
for 9b, 355.4(2)°). Overall this results in a situation in which
the Pd center is located 0.98(1) Å (9a) and 0.986(6) Å (9b)
above the upper Cp plane. To minimize contacts, the Cp rings
are also screwed out of the face-to-face orientation charac-
terized by an average torsion angle (Cp1−Cp2) of −16.1° (9a)
and −16.6° (9b).
Complexation of the P,N ligand epi-5a with the opposite
sense of planar chirality was achieved in a similar manner in
nearly quantitative yield (Scheme 2). In that case a 2.8:1
mixture of isomers was formed.
The constitution and the Sp configuration of complexes 9a,b
have been determined by X-ray crystal structure analysis
(Figure 1).18 In the case of 9a, the crystal contained a 55:45
mixture of an exo and an endo isomer. Only the exo isomer is
depicted in Figure 1 (top). In contrast, the crystal of 9b
contained only the exo isomer (Figure 1, bottom). Both solid-
state structures reveal a just slightly distorted square planar
coordination geometry around the palladium centers. The Pd−
ligand bond lengths and angles are similar to those found in
related pentamethylferrocene-based Pd(II) complexes by
Helmchen containing oxazoline and phosphine donors11c and
[(η3-allyl)(PHOX)Pd] complexes.19 As expected, both Pd−C
The cyclohexenylium complex 13 is accessible in quantitative
yield in a way similar to that for 9−12 (Scheme 3). Both in
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Figure 1. (top) X-ray single-crystal structure analysis of 9a. Color code: C (gray); N (blue); O (red); P (yellow-orange); Fe (orange); Pd
(magenta). Hydrogen atoms, the SbF6 counterion, and dichloromethane (two per unit cell) are omitted for clarity in the ORTEP plot (ellipsoids at
the 50% probability level). Two different views are shown for the exo isomer (the endo isomer is not depicted). Selected bond lengths (Å) and
angles (deg): N−Pd, 2.086(4); P−Pd, 2.2608(13); C(trans to P)−Pd, 2.211(5); C(cis to P)−Pd, 2.116(5); N−Pd−P, 95.07(11); C(trans to P)−
Pd−N, 101.76(19); C(trans to P)−Pd−C(cis to P), 67.8(2); C(cis to P)−Pd−P, 94.94(19); N−Pd−C(cis to P), 169.3(2); P−Pd−C(trans to P),
160.64(16). (bottom) X-ray single-crystal structure analysis of 9b. Color code: C (gray); N (blue); O (red); P (yellow-orange); Fe (orange); Pd
(magenta). Hydrogen atoms, the SbF6 counterion, and diethyl ether (one per unit cell) are omitted for clarity in the ORTEP plot (ellipsoids at the
50% probability level). Two different views are shown. Selected bond lengths (Å) and angles (deg): N−Pd, 2.104(3); P−Pd, 2.2626(8); C(trans to
P)−Pd, 2.251 (3); C(cis to P)−Pd, 2.120(3); N−Pd−P, 95.92(7); C(trans to P)−Pd−N, 102.15(11); C(trans to P)−Pd−C(cis to P), 66.61(11);
C(cis to P)−Pd−P, 93.65(9); N−Pd−C(cis to P), 168.39(11); P−Pd−C(trans to P), 152.71(9).
solution and in the solid state a single isomer has been
detected.
The X-ray crystal structure analysis of 13 revealed an exo
configuration (Figure 2), which should be strongly favored to
minimize repulsion of the cyclic allylic ligand with the
pentaphenylferrocene core. The structure is otherwise quite
similar to that of 9a with a slightly distorted square planar
coordination sphere of the palladium centers. Both Pd−C bond
lengths are again significantly different, with the carbon atom
trans to phosphorus having the longer distance (Pd−C =
2.2682(17) Å) in comparison to that trans to nitrogen (Pd−C
= 2.1286(15) Å), in agreement with the greater trans influence
of the phosphino moiety.20 The interplanar tilt angle between
the allyl fragment and the P−Pd−N coordination plane is
70.6(1)°, and the center distance of the Cp rings in one
ferrocene fragment is 3.34 Å. In addition, in that case both Cp
rings of one ferrocene unit are tilted toward each other with an
angle between ring planes of 10.0(1)°. The Cp-C atom
connected to the P atom is considerably pyramidalized (sum of
bond angles at the Cp-C atom 355.3(1)°), resulting in a
structure in which the Pd center is located 0.722(3) Å above
the upper Cp plane.22
Scheme 3. Formation of the Pd−Allyl Complexes 13
Pd-Catalyzed Allylic Substitutions Using Cyclic Sub-
strates. Complexes 9−12 were investigated in Pd-catalyzed
asymmetric allylic substitutions with cycloalkenyl acetate
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Figure 2. X-ray single crystal structure analysis of 13. Color code: C (gray); N (blue); O (red); P (yellow-orange); Fe (orange); Pd (magenta).
Hydrogen atoms, the SbF6 counterion, and diethyl ether (one per unit cell) are omitted for clarity in the ORTEP plot (ellipsoids at the 50%
probability level). Two different views are shown. Selected bond lengths (Å) and angles (deg): N−Pd, 2.1100(12); P−Pd, 2.2794(5); C(trans to
P)−Pd, 2.2682(17); C(cis to P)−Pd, 2.1286(15); N−Pd−P, 94.31(4); C(trans to P)−Pd−N, 103.80(5); C(trans to P)−Pd−C(cis to P), 65.36(7);
C(cis to P)−Pd−P, 96.13(5); N−Pd−C(cis to P), 167.41(6); P−Pd−C(trans to P), 161.37(4).
Table 4. Catalytic Asymmetric Allylic Alkylation of Cycloalkenyl Acetate Substrates
a
b
entry
n
R′
catalyst
R
Ar
X
base
NaH
solvent
T (°C)
t (h)
yield (%)
ee (%)
1
2
3
4
5
6
7
1
1
1
1
1
1
1
1
1
1
1
0
0
2
H
9a
iPr
iPr
iPr
tBu
iPr
iPr
iPr
iPr
iPr
iPr
iPr
iPr
iPr
iPr
Ph
Ph
Ph
Ph
Ph
Ph
Ph
4
1
1
4
1
1
1
1
1
1
1
1
1
1
THF
22
22
1
1
>99
>99
19
71
78
77
51
82
84
78
87
83
H
H
H
H
H
H
H
H
H
Me
H
H
H
9a
BSA/KOAc
BSA/KOAc
BSA/KOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
BSA/NaOAc
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
9a
−20
22
12
15
1
9b
15
9a
22
>99
>99
61
9a
22
1
(epi)-9a
10a
11a
12a
9a
THF
22
12
1
c
8
4-MeOC6H4
4-F3CC6H4
3,5-(F3C)2C6H3
Ph
THF
22
67
9
THF
22
1
20
10
11
12
13
14
THF
22
1
0
THF
22
12
1
>99
>99
>99
80
74
d
9a
Ph
THF
22
91
d
10a
4-MeOC6H4
THF
22
12
12
91
9a
Ph
THF
22
90
a
b
c
d
Yield of isolated product. Determined by GC. The catalyst was preformed prior to use. Determined by 1H NMR using Eu(hfc)3 as chiral shift
reagent.
substrates and dimethyl malonate (Table 4).14,15 This reaction
type was chosen to allow for a direct comparison with the
structurally similar pentamethylferrocene-derived phosphino-
oxazoline hybrid ligands described by Helmchen et al.11c They
had demonstrated that the large steric demand of a
1′,2′,3′,4′,5′-pentamethylferrocene backbone allowed for high
levels of enantioselection with these challenging substrates,
whereas previously investigated Pd(II) complexes of planar
chiral phosphino-oxazoline ligands required a stereogenic
phosphino donor for high asymmetric induction.15a In general,
enantioselectivity using cyclic allylic substrates is still difficult to
control. This has been explained by the lower steric demand of
their syn substituents in comparison to that for acyclic
substrates, because the syn substituents are assumed to play a
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key role in the stereodifferentiation in the η3-allyl Pd
intermediates.14
reactivity. A possible explanation for these observations might
be that with less electron-rich phosphines in combination with
the large steric demand of the pentaphenylferrocene core the
complexes are more prone to undergo a Pd decomplexation,
thus resulting in lower reactivity and reduced enantioselectivity.
In contrast, the complexes of more electron rich phosphines
might be more stable in terms of loss of Pd. In addition, with
these complexes the regioselectivity for malonate attack is still
high, but the reactivity is decreased in comparison to 9a due to
a less electrophilic allylic system. Interesting and unexpected is
the fact that the use of (epi)-9a provided the same major
enantiomer as the use of 9a. This might suggest either that with
(epi)-9a the P,N-chelate complex is not the catalytically most
relevant species or that planar chirality has a smaller effect and
that the oxazoline substituent dictates also in the present
system the exo/endo configuration of the allyl complexes.
If not mentioned otherwise, in our catalytic investigations the
Pd complexes were prepared in situ from [Pd(η3-C3H5)Cl]2
and the corresponding ligand (1.1 equiv per Pd). Initial
attempts were performed with cyclohexenyl acetate in THF
using NaH as a base and 4 mol % of catalyst 9a. The yield was
quantitative after 1 h at 22 °C, but the enantioselectivity was
only moderate (Table 4, entry 1). Switching from NaH in THF
to KOAc/N,O-bis(trimethylsilyl)acetamide (BSA) in CH2Cl2
slightly improved the enantioselectivity, and the product was
formed in quantitative yield after 1 h at 22 °C with a reduced
catalyst loading of 1 mol % of 9a (entry 2). Despite this high
rate at 22 °C, at −20 °C the reaction was too slow for
preparatively useful yields (entry 3). Moreover, the enantiose-
lectivity was not improved by a lower temperature. With
catalyst 9b carrying the tert-butyl residue R, the reactivity was
poor even at 22 °C (entry 4). Using 9a again with NaOAc for
KOAc (entry 5) and THF for CH2Cl2 (entry 6) further
improved the enantioselectivity.
Under the optimized conditions the other Pd complexes
prepared in this study have also been investigated. In contrast
to our initial expectations, the use of diarylphosphine moieties
with increased π acidity did not result in higher reactivity and
enantioselectivity. Increased π acidity should result in a higher
electrophilicity of the allylic C atom in the trans position.14
However, with p-CF3 substituents the product was formed in
low yield and the enantioselectivity was even somewhat
reduced (Table 4, entry 9).
With CF3 substituents at positions 3 and 5 on the P-aryl
moieties, there was no product formation at all (Table 4, entry
10). In contrast, with a p-OMe donor substituent the best
enantioselectivity was attained, but the reactivity was lower than
that with 9a (entry 8). (epi)-9a is also notably less active than
9a and is also inferior in terms of enantioselection (entry 7).
Since catalyst 9a is thus the most active catalyst in this study,
it was utilized for three additional cycloalkenyl acetates. A
cyclohexenyl acetate with a tetrasubstituted C atom at the 5-
position was significantly less reactive, but a quantitative yield
could be obtained with a prolonged reaction time of 12 h
(Table 4, entry 11). The increased steric bulk of the substrate
has also a negative impact on the enantioselectivity. High
reactivity and enantioselectivity was observed with cyclo-
pentenyl acetate using catalysts 9a and 10a (entries 12 and
13). The corresponding cycloheptenyl substrate was less
reactive, but good yield and enantioselectivity were attained
after a reaction time of 12 h (entry 14).
A comparison with the results by Helmchen reveals that the
reactivity and selectivity data are similar for pentamethyl- and
pentaphenylferrocenes. An advantage of the latter systems is
the greater stability of the pentaphenylferrocene core toward
oxidative decomposition, since acceptor substituents increase
the oxidation potential of ferrocenes, whereas donor sub-
stituents lead to a greater sensitivity toward oxidation.23
The stereochemical outcome of the reactions can be easily
explained by the preferred exo configuration of the cyclo-
alkenylium complexes and the expected regioselective nucleo-
philic attack of the malonate trans to the P donor as a result of
the trans effect.14 The screening of electronically different
phosphines showed that higher π acidity of the phosphines did
not lead to higher enantioselectivity and reactivity, as was
initially expected. Moreover, an electron-rich phosphine even
gave the highest enantioselectivity, yet at the cost of lower
CONCLUSION
■
In conclusion, we have described the first diastereoselective
ortho lithiations of chiral enantiopure 1′,2′,3′,4′,5′-pentaphe-
nylferrocenes. Oxazoline moieties were used as efficient ortho-
directing groups. By the choice of the lithiation conditions,
both possible diastereomers with regard to the element of
planar chirality can be accessed as single diastereomers.
Trapping of the planar chiral organolithium species was
achieved with a number of electrophiles. Using diarylphosphino
chlorides, a small set of P,N ligands was prepared and then
employed to form the corresponding Pd-allyl complexes. The
latter were investigated in the allylic substitution of cyclic allylic
acetates, and some of them allowed for good enantioselection
with this challenging substrate class.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were performed in oven-
dried glassware under a positive pressure of nitrogen. All glassware
used was washed with demineralized water to remove any traces of
chloride. THF was dried under N2 over molecular sieves in a solvent
purification system. The solvents dichloromethane, chloroform,
methanol, and ethyl acetate were used as purchased from commercial
suppliers. Solvents were usually removed at 30−40 °C by rotary
evaporation at 600−10 mbar pressure, and nonvolatile compounds
were dried in vacuo at 0.1 mbar. 1a and the starting material for 1b
were prepared according to the literature.11f Yields refer to isolated,
pure compounds and are calculated in mole percent of the used
starting material. NMR spectra were recorded at 21 °C operating at
300 or 500 MHz (1H), 125 MHz (13C), and 235 MHz (19F). Chemical
shifts are referred in terms of ppm, and J coupling constants are given
in Hz. Abbreviations for multiplicities are as follows: s (singlet), d
(doublet), t (triplet), m (multiplet), b (broad signal). IR spectra were
recorded on an ATR unit, and the signals are given in wavenumbers
(cm−1). Optical rotation was measured at the sodium D line in a cell
with 100 mm path length. Melting points were measured in open glass
capillaries and are uncorrected. Mass spectra were measured on an ESI
spectrometer. Single-crystal X-ray analysis was performed by Dr.
Wolfgang Frey (Universitat Stuttgart).
̈
( S ) - N - ( 1 - H y d r o x y - 3 - d i m e t h y l b u t a n - 2 - y l ) -
pentaphenylferrocenylamide.11f To a suspension of pentaphenyl-
ferrocenecarboxylic acid (391 mg, 0.6 mmol, 1 equiv) in DCM (10
mL) and DMF (ca. 5 μL, ca. 0.1 equiv) at room temperature was
added oxalyl chloride (80 μL, 0.9 mmol, 1.5 equiv) in two portions
within 5 min. Warning: significant amounts of CO and corrosive HCl
are released, with pressure exchange via balloon. When all of the solid
had dissolved, stirring was continued for 30 min, and then all volatiles
were removed under reduced pressure. The resulting dark red solid
residue was dissolved in DCM (8 mL) and triethylamine (101 mg, 130
μL, 1 mmol, 2 equiv), the solution was cooled to 0 °C, and a solution
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of (L)-leucinol (80 μL, 0.6 mmol, 1 equiv) in DCM (2 mL) was added
in one portion. Stirring was continued at room temperature overnight,
and then all volatiles were removed under reduced pressure and the
red-orange residue was purified by column chromatography (pentane/
EtOAc 3/1 → pure EtOAc) to yield the title product as an orange
(C47H41FeNO·6H2O): C, 75.70; H, 6.35; N, 1.88. Found: C, 76.02;
H, 6.09; N, 1.98.
1-[(4S)-tert-Butyl-2-oxazolin-2-yl]-2-(Rp)-(methyl)-1′,2′,3′,4′,5′-
pentaphenylferrocene (2b). Following GP1 a red solid was obtained
and isolated in a yield of 50% (dr > 50:1).
23
C48H43FeNO, mol wt: 705.71. Mp: 146.8−147.2 °C. [α]D
=
solid (391 mg, 0.55 mmol, 86%).
C47H43FeNO2, mol wt: 709.69. Mp: 166.5−167.7 °C. [α]D
1
+112.9° (c = 0.106 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.15−6.99 (m, 25 H, HPh), 4.72 (m, 1 H, HFc), 4.19 (m, 2 H,
HFc), 3.83 (t, J = 8.4, 1 H, OCH2), 3.70 (t, J = 8.2, 1 H, OCH2), 3.53
(t, J = 9.2, 1 H, NCH), 2.02 (s, 3 H, CH3C5H3R), 0.78 (s, 9 H,
C(CH3)3). 13C NMR (125 MHz, CDCl3, 21 °C): δ 134.1, 131.5,
125.9, 125.1, 86.6, 76.7, 75.2, 74.8, 73.8, 66.6, 32.3, 29.9, 28.6, 25.6,
25.0, 11.5, 1.2. IR (solid): ν 3086, 3057, 3028, 2958, 2925, 2852, 2245,
1727, 1646, 1600, 1502, 1478, 1443, 1409, 1362, 1301, 1260, 1195,
1178, 1155, 1077, 1028, 1012, 970, 954, 906, 846, 799, 727, 698, 647,
620, 572, 557. HRMS (ESI): m/z calcd for [M]+ C48H43FeNO,
706.2768; found, 706.2758. A sufficient microanalysis could not be
obtained due to solvent inclusion.
23
=
1
−40.0° (c = 0.836 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.17−7.05 (m, 25 H, HPh), 5.70 (d, J = 6.0, 1 H, NH), 4.82 (b,
1 H, HFcCCO), 4.48 (b, 1 H, HFcCCO), 4.40 (t, J = 3.0, 2 H, HFc),
3.66 (b, 2 H, CH2OH), 3.37 (q, J = 6.0, 1 H, HNCHC), 1.74 (b, 1 H,
OH), 0.92 (s, 9 H, C(CH3)3). 13C NMR (125 MHz, CDCl3, 21 °C): δ
168.8, 148.7, 142.4, 142.0, 134.9, 132.2, 129.4, 127.2, 127.0, 126.5,
126.1, 91.7, 88.1, 81.4, 78.1, 75.3, 72.0, 62.9, 60.5, 33.5, 27.1, 21.4. IR
(solid): ν 3056, 3028, 2976, 2932, 2871, 2359, 2249, 1722, 1612, 1502,
1468, 1444, 1425, 1379, 1361, 1333, 1279, 1170, 1132, 1078, 1029,
972, 938, 909, 876, 813, 784, 767, 728, 698, 658, 577. HRMS
(MALDI): m/z calcd for [M]+ C47H43FeNO2, 732.2536; found,
732.2526. A sufficient microanalysis could not be obtained due to
solvent inclusion.
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp)-(iodo)-1′,2′,3′,4′,5′-pen-
taphenylferrocene (3a). Following GP1, 1a (24 mg, 0.034 mmol) and
TMEDA (0.015 mL, 0.1 mmol) were treated with n-butyllithium (15%
in hexane, 0.030 mL, 0.053 mmol) at −78 °C. The solution was stirred
for 4 h before warming to 0 °C. Then LiClO4 (11 mg, 0.1 mmol) and
ICH2CH2I (30 mg, 0.1 mmol) were added. The reaction was then
warmed to room temperature and stirred overnight. Compound 3a
(206 mg, 0.025 mmol, 75%, dr > 50:1) was isolated as a red-yellow
(S)-4-Isopropyl-2-pentaphenylferrocenyl-4,5-dihydrooxa-
zole (1b). (S)-N-(1-Hydroxy-3-dimethylbutan-2-yl)-
pentaphenylferrocenylamide (393 mg, 0.55 mmol, 1 equiv) was
dissolved in DCM (3 mL) and triethylamine (230 μL, 1.6 mmol, 3
equiv). DMAP (ca. 7 mg, 0.05 mmol, 0.1 equiv) and p-tosyl chloride
(131 mg, 0.7 mmol, 1.25 equiv) were added and the mixture was
stirred at room temperature overnight. All volatiles were subsequently
removed under reduced pressure, and the residue was purified by
column chromatography (pentane/EtOAc 4/1) to yield the title
solid.
23
C46H38FeINO, mol wt: 803.55. Mp: 102.3−103.9 °C. [α]D
=
−61.9° (c = 0.46 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.17−7.03 (m, 25 H, HPh), 4.81 (m, 1 H, HFc), 4.51 (m, 1 H,
HFc), 4.37 (t, J = 7.8, 1 H, HFc), 3.87−3.79 (m, 1 H, NCH), 3.70−3.65
(m, 2 H, OCH2), 1.42 (m, 1 H, CH3CHCH3), 0.97 (d, J = 6.7, 3 H,
CH3CHCH3), 0.77 (d, J = 6.8, 3 H, CH3CHCH3). 13C NMR (75
MHz, CDCl3, 21 °C): δ 134.0, 132.5, 127.1, 126.4, 88.8, 83.2, 78.4,
74.9, 72.8, 69.3, 48.7, 32.5, 29.7, 19.5, 18.2, 2.2. IR (solid): ν 2955,
2924, 2869, 2852, 2359, 1658, 1640, 1600, 1502, 1443, 1409, 1374,
1346, 1248, 1158, 1137, 1074, 1028, 978, 935, 908, 865, 844, 823, 800,
783, 742, 699. HRMS (ESI): m/z calcd for [M]+ C46H38FeINO,
804.1421; found, 804.1405. A sufficient microanalysis could not be
obtained due to the instability of the molecule.
1
product 1b as a bright orange solid (334 mg, 0.48 mmol, 87% yield).
23
C47H41FeNO, mol wt: 691.68. Mp: 157.7−158.9 °C. [α]D
=
−27.5° (c = 0.6 g dL−1, CHCl3). 1H NMR (300 MHz, CDCl3, 21 °C):
δ 7.12−7.01 (m, 25 H, HPh), 4.80 (m, 1 H, HFc), 4.71 (m, 1 H, HFc),
4.32 (m, 1 H, HFc), 4.29 (m, 1 H, HFc), 3.80 (m, 2 H, OCH2), 3.45 (t,
J = 12.0, 1 H, NCH), 0.76 (s, 9 H, C(CH3)3). 13C NMR (125 MHz,
CDCl3, 21 °C): δ 162.8, 135.2, 132.4, 127.0, 126.1, 88.1, 74.7, 74.1,
67.7, 33.3, 26.0. IR (solid): ν 3109, 3086, 3056, 3030, 2951, 2901,
2865, 2244, 1652, 1600, 1576, 1502, 1482, 1443, 1411, 1393, 1378,
1363, 1327, 1302, 1266, 1209, 1179, 1156, 1117, 1074, 968, 908, 869,
848, 825, 800, 783, 766, 731, 699, 648, 621, 575, 558. HRMS
(MALDI): m/z calcd for [M]+ C47H41FeNO, 692.2611; found,
692.2594. A sufficient microanalysis could not be obtained due to
solvent inclusion.
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp)-(trimethylsilyl)-
1′,2′,3′,4′,5′-pentaphenylferrocene (4a). Following GP1 a reddish
solid was obtained and isolated in a yield of 85% (dr > 50:1).
C49H47FeNOSi, mol wt: 749.83 g mol−1. Mp: 125.9−126.6 °C.
General Procedure for the Diastereoselective Ortho
Functionalization of 1 (GP1). A solution of the corresponding
oxazoline 1 (1 equiv) and TMEDA (3 equiv) in Et2O (1 mL per 30
mg of 1) was cooled to −78 °C and was then treated dropwise with n-
BuLi (1.5 equiv). The resulting solution was stirred for 4 h at −78 °C
and then warmed to 0 °C and treated with the corresponding
electrophile (3 equiv). The reaction mixture was then warmed to room
temperature, and stirring was continued overnight. The mixture was
subsequently filtered over Celite and the solvent removed in vacuo.
The crude product was purified by column chromatography (silica,
PE/EtOAc, 95/5).
23
1
[α]D = +1291.9° (c = 0.12 g dL−1, CHCl3). H NMR (300 MHz,
CDCl3, 21 °C): δ 7.16−7.03 (m, 25 H, HPh), 5.01 (m, 1 H, HFc), 4.48
(t, J = 3.0, 1 H, HFc), 4.40 (m, 1 H, HFc), 4.04 (dd, J = 6.0, J = 3.0, 1 H,
OCH2), 3.78 (t, J = 9.0, 1 H, NCH), 3.56 (m, 1 H, OCH2), 1.64 (m, 1
H, CH3CHCH3), 1.02 (d, J = 6.0, 3 H, CH3CHCH3), 0.82 (d, J = 9.0,
3 H, CH3CHCH3), 0.04 (s, 9 H, (CH3)3Si). 13C NMR (75 MHz,
CDCl3, 21 °C): δ 164.3, 135.4, 132.8, 132.5, 127.1, 126.3, 88.2, 83.6,
80.0, 79.3, 78.1, 73.0, 69.4, 33.0, 20.0,18.3, 0.8. IR (solid): ν 3087,
3056, 3029, 2955, 2924, 2894, 2870, 2850, 2245, 1946, 1881, 1806,
1648, 1600, 1576, 1502, 1468, 1443, 1410, 1383, 1366, 1314, 1288,
1243, 1179, 1155, 1139, 1122, 1063, 1027, 986, 906, 881, 833,
800,783, 727, 697, 648, 620, 571, 556. HRMS (ESI): m/z calcd for
[M]+ C49H47FeNOSi, 750.2850; found, 750.2844. Anal. Calcd for
C49H47FeNOSi: C, 78.49; H, 6.32; N, 1.87. Found: C, 78.63; H, 6.28;
N, 1.98.
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Rp)-(methyl)-1′,2′,3′,4′,5′-
pentaphenylferrocene (2a). Following GP1 a red solid was obtained
and isolated in a yield of 70% (dr > 50:1).
C47H41FeNO, mol wt: 691.68. Mp: 99.4−100.5 °C. [α]D23 = −17.6°
1
(c = 0.475 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21 °C): δ
7.16−7.04 (m, 25 H, HPh), 4.69 (m, 1 H, HFc), 4.20 (m, 2 H, HFc),
3.87−3.75 (m, 2 H, OCH2), 3.62−3.59 (m, 1 H, NCH), 2.07 (s, 3 H,
CH3C5H3R), 1.36−1.25 (m, 1 H, CH3CHCH3), 0.99−0.97 (d, J = 6.5,
3 H, CH3CHCH3), 0.75 (d, J = 6.6 Hz, 3 H, CH3CHCH3). 13C NMR
(125 MHz, CDCl3, 21 °C): δ 163.9, 135.4, 135.2, 132.6, 132.4, 127.1,
126.1, 88.0, 87.7, 77.9, 75.9, 74.9, 74.4, 73.2, 69.1, 32.9, 27.0, 20.6,
19.9, 18.7, 12.8. IR (solid): ν 3086, 3056, 3028, 2956, 2923, 2870,
2851, 2851, 2361, 1986, 1967, 1739, 1648, 1600, 1502, 1466, 1443,
1364, 1260, 1179, 1155, 1074, 1027, 973, 953, 910, 825, 800, 783, 742,
699, 661, 621, 573. HRMS (MALDI): m/z calcd for [MH]+
C47H42FeNO, 692.2611; found, 692.2598. Anal. Calcd for
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp)-(diphenylphosphino)-
1′,2′,3′,4′,5′-pentaphenylferrocene (5a). Following GP1 an orange-
red solid was obtained and isolated in a yield of 80% (dr > 50:1).
C58H48FeNOP, mol wt: 861.83. Mp: 143.5−144.5 °C. [α]D
23
=
+87.7° (c = 1 g dL−1, CHCl3). 1H NMR (300 MHz, CDCl3, 21 °C): δ
7.40−6.93 (m, 35 H, HPh), 4.96 (m, 1 H, HFc), 4.44 (m, 1 H, HFc),
4.17 (m, 1 H, HFc), 3.56−3.30 (m, 2 H, OCH2), 3.14−3.02 (t, J = 7.9,
1 H, NCH), 1.19 (m, 1 H, CH3CHCH3), 0.67 (d, J = 6.7, 3 H,
CH3CHCH3), 0.35 (d, J = 6.6, 3 H, CH3CHCH3). 13C NMR (75
MHz, CDCl3): δ 136.7, 136.3, 134.6, 132.8, 132.5, 132.3, 128.4, 127.1,
126.2, 88.0, 72.3, 26.9, 22.8, 19.4, 17.5. 31P NMR (121.5 MHz, CDCl3,
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21 °C): δ −27.7 (s). IR (solid): ν 3086, 3054, 3028, 2956, 2928, 2869,
2244, 1948, 1808, 1640, 1600, 1502, 1476, 1445, 1432, 1410, 1382,
1344, 1311, 1274, 1254, 1181, 1127, 1093, 1074, 1027, 982, 950, 907,
875, 848, 829, 800, 783, 739, 697, 647, 621, 572. HRMS (ESI): m/z
calcd for [MH]+ C58H49FeNOP, 862.2897; found, 862.2877. Anal.
Calcd for C58H48FeNO2P·(n-pentane)·CH2Cl2: C, 74.28; H, 6.04; N,
1.35. Found: C, 74.48; H, 5.84; N, 1.63.
1-[(4R)-Isopropyl-2-oxazolin-2-yl]-2-(Rp)-(diphenylphosphino)-
1′,2′,3′,4′,5′- pentaphenylferrocene (epi-5a). Following GP1 but
using diethylene glycol dibutyl ether instead of TMEDA, 1a (22 mg,
0.033 mmol) and diethylene glycol dibutyl ether (0.024 mL, 0.1
mmol) were treated with n-butyllithium (15% in hexane, 0.03 mL, 0.05
mmol) at −78 °C. The solution was stirred for 4 h before warming to
0 °C. Then ClPPh2 (0.02 mL, 0.1 mmol) was added. The reaction
mixture was warmed to room temperature and stirred overnight. The
mixture was subsequently filtered over Celite and the solvent removed
in vacuo. The crude product was purified by column chromatography
(silica, PE/EtOAc, 95/5) to yield the product as an orange-red solid
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp)-(bis[4-(trifluoromethyl)-
phenyl]phosphino)-1′,2′,3′,4′,5′-pentaphenylferrocene (7a). Fol-
lowing GP1 an orange-red solid was obtained and isolated in a yield
of 91% (dr > 50:1).
C60H46F6FeNOP, mol wt: 997.82. Mp: 140.2−141.1 °C. [α]D
23
=
1
+123.1° (c = 0.5 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.54−6.94 (m, 33 H, HPh), 5.01 (m, 1 H, HFc), 4.56 (m, 1 H,
HFc), 4.14 (m, 1 H, HFc), 3.43 (m, 2 H, OCH2), 3.15 (t, J = 7.5, 1 H,
NCH), 1.14 (m, 1 H, CH3CHCH3), 0.64 (d, J = 6.7, 3 H,
CH3CHCH3), 0.33 (d, J = 6.8, 3 H, CH3CHCH3). 13C NMR (125
MHz, CDCl3, 21 °C): δ 136.8, 136.6, 134.3, 132.6, 132.5, 132.3, 127.0,
126.4, 125.1, 88.3, 78.8, 78.0, 72.2, 68.9, 31.7, 18.9, 17.1. 31P NMR
(121.5 MHz, CDCl3, 21 °C): δ −28.5 (s). 19F NMR (235 MHz,
CDCl3, 21 °C): δ −62.84 (s), −62.89 (s). IR (solid): ν 3087, 3058,
3029, 2959, 2870, 2245, 1723, 1641, 1603, 1502, 1477, 1444, 1395,
1321, 1275, 1166, 1125, 1105, 1058, 1030, 1015, 980, 951, 906, 875,
826, 800, 783, 727, 696, 648, 621, 602, 572, 557. HRMS (ESI): m/z
calcd for [MH]+ C60H47F6FeNOP, 998.2624; found, 998.2622. A
sufficient microanalysis could not be obtained due to solvent inclusion.
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp )-(bis[3,5-
(trifluoromethyl)phenyl]phosphino)-1′,2′,3′,4′,5′-pentaphenylferro-
cene (8a). Following GP1 an orange-red solid was obtained and
(249 mg, 0.029 mmol, 90%, dr > 50:1).
23
C58H48FeNOP, mol wt: 861.83. Mp: 139.8−140.9 °C. [α]D
=
1
+37.7° (c = 0.15 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.16−6.89 (m, 35 H, HPh), 5.24 (m, 1 H, HFc), 4.53 (t, J = 2.2,
1 H, HFc), 4.40 (m, 1 H, HFc), 3.70 (m, 1 H, NCH), 3.11 (dd, J = 3.0, J
= 9.0, 1 H, OCH2), 2.65 (dd, J = 6.0, J = 12, 1 H, OCH2), 1.81 (m, 1
H, CH3CHCH3), 0.75 (d, J = 6.0, 3 H, CH3CHCH3), 0.61 (d, J = 6.0,
3 H, CH3CHCH3). 13C NMR (75 MHz, CDCl3, 21 °C): δ 134.4,
133.3, 132.5, 132.3, 128.8, 128.3, 127.4, 127.1, 127.0, 126.6, 126.4,
89.3, 88.8, 88.1, 71.2, 70.6, 70.1, 55.8, 53.4, 31.7, 27.2, 26.9, 19.2, 13.9.
31P NMR (121.5 MHz, CDCl3, 21 °C): δ −31.4 (s). IR (solid): ν
isolated in a yield of 39% (dr > 50:1).
23
C62H44F12FeNOP, mol wt: 1133.82. Mp: 121.9−122.6 °C. [α]D
=
1
−53.3° (c = 0.24 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.89 (s, 1 H, F3CCHPh), 7.73 (d, J = 7.0, 2 H, F3CCHPh), 7.66
(s, 1 H, F3CCHPhCF3), 7.52 (d, J = 7.0, 2 H, F3CCHPh), 7.14−6.97
(m, 25 H, HPh), 5.06 (m, 1 H, HFc), 4.64 (t, J = 2.7, 1 H, HFc), 4.15 (m,
1 H, HFc), 3.61 (t, J = 8.3, 1 H, NCH), 3.33 (m, 1 H, OCH), 3.15 (m,
1 H, OCH), 1.58 (m, 1 H, CH3CHCH3), 0.70 (d, J = 6.5, 3 H,
CH3CHCH3), 0.41 (d, J = 6.5, 3 H, CH3CHCH3). 13C NMR (125
MHz, CDCl3, 21 °C): δ 161.8, 144.0, 143.8, 136.1, 134.0, 132.4, 132.0,
131.8, 127.1, 126.6, 124.1, 121.9, 88.5, 79.2, 79.1, 78.8, 73.0, 69.4, 32.1,
19.1, 17.8. 31P NMR (121.5 MHz, CDCl3, 21 °C): δ −26.8. 19F NMR
(235 MHz, CDCl3, 21 °C): δ −62.6 (s), −62.8 (b), −63.0 (s). IR
(solid): ν 3058, 2961, 1656, 1601, 1502, 1444, 1352, 1275, 1173, 1119,
1092, 1028, 980, 945, 896, 843, 800, 783, 741, 699, 680, 619, 573, 557,
535, 522. HRMS (ESI): m/z calcd for [M]+ C62H44F12FeNOP,
1134.2393. A sufficient microanalysis could not be obtained due to
solvent inclusion.
3053, 2958, 2928, 2870, 1893, 1731, 1646, 1600, 1501, 1444, 1433,
1409, 1373, 1324, 1254, 1181, 1156, 1095, 1073, 1027, 982, 920, 848,
829, 800, 783, 740, 696, 620, 571, 556. HRMS (ESI): m/z calcd for
[MH]+ C58H49FeNOP, 862.2897; found, 862.2911. A sufficient
microanalysis could not be obtained due to solvent inclusion.
1-[(4S)-tert-Butyl-2-oxazolin-2-yl]-2-(Sp)-(diphenylphosphino)-
1′,2′,3′,4′,5′-pentaphenylferrocene (5b). Following GP1 an orange-
red solid was obtained and isolated in a yield of 88% (dr > 50:1).
23
C59H50FeNOP, mol wt: 875.85. Mp: 176.5−177.7 °C. [α]D
=
1
+47.2° (c = 0.216 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.35−6.98 (m, 35 H, HPh), 5.00 (m, 1 H, HFc), 4.47 (m, 1 H,
HFc), 4.22 (m, 1 H, HFc), 3.42−3.24 (m, 3 H, OCH2CHCN), 0.48 (s,
9 H, (CH3)3C). 13C NMR (125 MHz, CDCl3, 21 °C): δ 163.2, 136.8,
136.6, 134.8, 132.8, 132.2, 129.4, 128.4, 128.35, 128.30, 128.2, 127.7,
127.0, 126.2, 88.2, 83.4, 79.9, 78.3, 77.9, 67.9, 33.0, 25.9. 31P NMR
(121.5 MHz, CDCl3, 21 °C): δ −28.3 (s). IR (solid): ν 3086, 3055,
3029, 2957, 2920, 2851, 2244, 1742, 1646, 1600, 1502, 1477, 1444,
1433, 1411, 1364, 1331, 1303, 1260, 1206, 1179, 1131, 1073, 1027,
983, 908, 828, 800, 783,731, 698, 647, 620, 572. HRMS (ESI): m/z
calcd for [MH]+ C59H51FeNOP, 876.3054; found, 876.3027. A
sufficient microanalysis could not be obtained due to solvent inclusion.
1-[(4S)-Isopropyl-2-oxazolin-2-yl]-2-(Sp)-(bis(4-methoxyphenyl)-
phosphino)-1′,2′,3′,4′,5′-pentaphenylferrocene (6a). Following GP1
an orange-red solid was obtained and isolated in a yield of 68% (dr >
General Procedure for the Synthesis of the Pd−Allyl
Complexes 9−12 (GP2). A mixture of [Pd(η3-C3H5)Cl]2 (0.05
mmol), the corresponding ligand (0.1 mmol, 2.0 equiv), and dry
CH2Cl2 (2 mL per 0.1 mmol of ligand) was stirred for 10 min at room
temperature. Then a solution of AgSbF6 (2.0 equiv) in dry methanol
(0.5 mL per 0.1 mmol of AgSbF6) was added, and the reaction mixture
was stirred for an additional 1 h. Filtration through Celite and
evaporation of the solvent gave the pure product.
(η3-Allyl)[1-[(4S)-isopropyl-2-oxazolin-2-yl]-2-(Sp)-(diphenylphos-
phino)-1′,2′,3′,4′,5′-pentaphenylferrocene]palladium Hexafluor-
oantimonate (9a). Following GP2 a red crystalline solid was isolated
in quantitative yield (dr = 1.3:1).
C61H53F6FeNOPPdSb, mol wt: 1245.07. Mp: 131.8−132.0 °C dec.
23
1
[α]D = −657.0° (c = 0.206 g dL−1, CHCl3). H NMR (500 MHz,
CDCl3, 21 °C): mixture of two isomers in a ratio of 1.3:1 (called a and
b), δ 7.63−6.96 (m, 50 H, HPh), 6.82 (b, 10 H, PCCHPh, isomer b),
6.75 (b, 10 H, PCCHPh, isomer a), 5.89 (m, 1 H, Hallyl, isomer a), 5.52
(m, 1 H, HFc, isomer a), 5.49 (m, 1 H, HFc, isomer b), 5.40 (m, 1 H,
Hallyl, isomer b), 5.04 (m, 1 H, HFc, isomer b), 5.00 (m, 1 H, HFc,
isomer a), 4.91 (m, 1 H, HFc, isomer a), 4.90 (m, 1 H, Hallyl, isomer a),
4.72 (m, 1 H, Hallyl, isomer b), 4.47 (t, J = 9.0, 1 H, NCH, isomer a),
4.41 (t, J = 9.0, 1 H, NCH, isomer b), 4.25 (m, 2 H, OCH2, isomer a),
4.05 (q, J = 7.0, 1 H, Hallyl, isomer a), 4.00 (m, 1 H, Hallyl, isomer b),
3.77 (m, 2 H, OCH2, isomer b), 3.43 (d, J = 7.0, 1 H, Hallyl, isomer a),
50:1).
23
C60H52FeNO3P, mol wt: 921.88. Mp: 160.9−161.3 °C. [α]D
=
+86.2° (c = 0.291 g dL−1, CHCl3). H NMR (300 MHz, CDCl3, 21
°C): δ 7.33−6.90 (m, 29 H, HPh), 6.80 (d, 2 H, J = 8.5, HPhCCOMe),
6.68 (d, 2 H, J = 8.4, HPhCCOMe), 4.92 (m, 1 H, HFc), 4.42 (m, 1 H,
HFc), 4.16 (m, 1 H, HFc), 3.79 (s, 3 H, COCH3), 3.67 (s, 3 H,
COCH3), 3.50 (m, 1 H, OCH2), 3.33 (m, 1 H, NCH), 3.15 (t, J = 8.1,
1 H, OCH2), 1.23 (m, 1 H, CH3CHCH3), 0.67 (d, J = 6.4, 3 H,
CH3CHCH3), 0.36 (d, J = 6.7, 3 H, CH3CHCH3). 13C NMR (75
MHz, CDCl3, 21 °C): δ 137.7, 137.5, 134.7, 132.7, 126.8, 126.0, 113.9,
87.9, 55.0., 26.9, 19.1, 17.2. 31P NMR (121.5 MHz, CDCl3, 21 °C): δ
−32.03 (s). IR (solid): ν 3054, 2955, 2869, 2834, 1641, 1592, 1567,
1497, 1441, 1401, 1345, 1281, 1246, 1125, 1091, 1074, 1028, 981, 949,
919, 875, 826, 797, 7416, 698. HRMS (ESI): m/z calcd for [MH]+
C60H53FeNO3P, 922.3109; found, 922.3119. A sufficient microanalysis
could not be obtained due to solvent inclusion.
1
3.37 (d, J = 4.5, 1 H, Hallyl, isomer b), 2.69 (d, J = 13.8, 1 H, Hallyl
,
isomer b), 2.32 (d, J = 12.0, 1 H, Hallyl, isomer a), 1.93 (m, 1 H,
CH3CHCH3), 1.41 (m, 1 H, CH3CHCH3), 0.93 (d, J = 7.0, 3 H,
CH3CHCH3, isomer a), 0.88 (d, J = 7.0, 3 H, CH3CHCH3, isomer b),
0.34 (d, J = 7.0, 3 H, CH3CHCH3, isomer a), 0.26 (d, J = 7.0, 3 H,
CH3CHCH3, isomer b). 13C NMR (125 MHz, CDCl3, 21 °C): δ
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169.7, 136.0, 135.9, 135.6, 135.5, 133.4, 133.3, 132.1, 131.1, 131.0,
130.9, 130.8, 129.6, 129.5, 129.4, 129.3, 129.2, 127.8, 127.7, 127.4,
127.4, 89.8, 89.7, 69.7, 68.9, 32.0, 31.0, 30.9, 30.2, 29.8, 20.3, 19.8,
16.5, 15.2, 14.2, 14.1, 1.0. 31P NMR (121.5 MHz, CDCl3, 21 °C): δ
16.2 (s), 15.2 (s). IR (solid): ν 3057, 2924, 2854, 1724, 1600, 1503,
1480, 1441, 1410, 1383, 1267, 1246, 1172, 1100, 1076, 1028, 998, 834,
802, 784, 740, 699, 657, 622, 569, 622, 569, 546. HRMS (ESI): m/z
calcd for [M − SbF6]+ = C61H53FeNOPPd, 1008.2266; found,
1008.2257. Anal. Calcd for C61H53F6FeNOPPdSb·6H2O: C, 54.14; H,
4.84; N, 1.04. Found: C, 54.05; H, 4.65; N, 0.86.
isomer a), 4.85 (m, 1 H, HFc, isomer b), 4.73 (t, J = 7.8, 1 H, NCH,
isomer b), 4.49 (t, J = 9.4, 1 H, OCH, isomer a), 4.41 (t, J = 9.6, 1 H,
OCH, isomer a), 4.25 (t, J = 8.2, 1 H, OCH, isomer b), 4.21 (t, J = 8.6,
1 H, OCH, isomer b), 4.10 (d, J = 7.3, 2 H, Hallyl, isomer a), 3.89 (s, 3
H, OCH3, isomer a), 3.88 (s, 3 H, OCH3, isomer b), 3.77 (s, 3 H,
OCH3, isomer a), 3.76 (s, 3 H, OCH3, isomer b), 3.46 (d, J = 4.5, 1 H,
Hallyl, isomer a), 3.38 (d, J = 5.5, Hallyl, isomer b), 3.04 (d, J = 11.9,
Hallyl, isomer b), 2.02 (m, 1 H, CH3CHCH3, isomer b), 1.52 (m, 1 H,
CH3CHCH3, isomer a), 0.93 (d, J = 6.9, 3 H, CH3CHCH3, isomer a),
0.88 (d, J = 6.9, 3 H, CH3CHCH3, isomer b), 0.33 (d, J = 6.2, 3 H,
CH3CHCH3, isomer a), 0.24 (d, J = 6.9, 3 H, CH3CHCH3, isomer b).
13C NMR (63 MHz, CDCl3, 21 °C): δ169.8, 162.8, 161.4, 137.5,
(η3-Allyl)[1-[(4R)-isopropyl-2-oxazolin-2-yl]-2-(Rp)-(diphenylphos-
phino)-1′,2′,3′,4′,5′-pentaphenylferrocene]palladium Hexafluor-
oantimonate (epi-9a). Following GP2 a red crystalline solid was
isolated in quantitative yield (dr = 2.8:1).
137.4, 137.0, 136.9, 133.5, 133.4, 132.9, 132.8, 132.7, 132.5, 132.1,
127.7, 127.6, 127.3, 124.3, 123.8, 120.6, 120.5, 119.8, 119.7, 119.3,
119.1, 115.4, 115.3, 115.2, 115.1, 115.0, 114.9, 111.3, 89.8, 89.6, 83.5,
83.5, 83.3, 81.8, 81.4, 80.9, 90.6, 78.0, 75.8, 69.5, 68.8, 63.1, 58.3, 57.0,
55.8, 55.6, 53.5, 50.9, 30.7, 30.1, 29.8, 20.3, 19.7, 16.3, 15.0. 31P NMR
(121.5 MHz, CDCl3, 21 °C): δ 13.5, 12.2. IR (solid): ν 2957, 2918,
2849, 1592, 1566, 1538, 1500, 1462, 1441, 1408, 1381, 1286, 1256,
1179, 1095, 1074, 1022, 955, 917, 829, 801, 741, 698, 655, 571, 548.
HRMS (ESI): m/z calcd for [M − SbF6]+ = C63H57FeNO3PPd,
1068.2478; found, 1068.2466. A sufficient microanalysis could not be
obtained due to instability.
23
C61H53F6FeNOPPdSb, mol wt: 1245.07. Mp: > 190 °C dec. [α]D
= 186.5° (c = 0.73 g dL−1, CHCl3). H NMR (500 MHz, CDCl3, 21
1
°C): mixture of two isomers in a ratio of 2.8:1 (called a and b), δ
7.28−7.17 (m, 11 H, HPh), 6.97 (m, 16 H, HPh), 6.83−6.78 (m, 17 H,
HPh), 6.70−6.63 (m, 2 H, HPh), 5.79 (m, 1 H, Hallyl, isomer a), 5.60
(m, 1 H, Hallyl, isomer b), 5.25 (m, 2 H, HFc, isomer b), 4.92 (m, 2 H,
HFc, isomer a), 4.73 (m, 1 H, Hallyl), 4.71 (m, 1 H, Hallyl), 4.44 (t, J =
9.9, 1 H, NCH, isomer a), 4.25 (d, J = 4.0, 1 H, Hallyl, isomer a), 4.22
(d, J = 4.5, 1 H, Hallyl, isomer b), 4.05 (m, 1 H, HFc, isomer a), 4.01 (m,
1 H, HFc, isomer b), 3.82 (dd, J = 10.4, J = 3.8, 2 H, OCH2, isomer a),
3.66 (d, J = 5.2, 1 H, Hallyl, isomer a), 3.58 (t, J = 6.2, 1 H, NCH,
isomer b), 3.50 (d, J = 8.0, 1 H, Hallyl, isomer b), 3.26 (dd, J = 5.6, J =
2.0, 2 H, OCH2, isomer b), 3.02 (d, J = 12.2, 1 H, Hallyl, isomer b), 2.90
(d, J = 12.9, 1 H, Hallyl, isomer a), 1.88 (m, 1 H, CH3CHCH3), 1.66
(m, 1 H, CH3CHCH3), 0.84 (d, J = 6.0, 3 H, CH3CHCH3, isomer b),
0.76 (d, J = 7.8, 3 H, CH3CHCH3, isomer a), 0.14 (d, J = 6.0, 3 H,
CH3CHCH3, isomer b), −0.14 (d, J = 6.9, 3 H, CH3CHCH3, isomer
a). 13C NMR (125 MHz, CDCl3, 21 °C): δ 168.6, 135.0, 134.9, 134.3,
133.4, 133.2, 132.7, 132.3, 132.1, 132.0, 131.9, 131.8, 129.7, 129.6,
129.4, 129.3, 127.8, 127.7, 127.6, 89.7, 83.1, 82.5, 80.4, 79.0, 76.1, 75.1,
75.0, 72.7, 72.4, 68.0, 55.2, 48.2 31.9, 31.5, 29.9, 18.5, 18.1, 13.3, 12.8,
9.4. 31P NMR (121.5 MHz, CDCl3, 21 °C): δ 15.6 (s), 14.8 (s). IR
(solid): ν 3057, 2961, 2925, 2852, 1600, 1578, 1544, 1502, 1480, 1463,
1439, 1410, 1384, 1312, 1279, 1261, 1244, 1172, 1101, 1075, 1027,
998, 908, 801, 783, 727, 697, 657, 571, 547. HRMS (ESI): m/z calcd
for [M − SbF6]+ = C61H53FeNOPPd, 1008.2266; found, 1008.2266. A
sufficient microanalysis could not be obtained due to solvent inclusion.
(η3-Allyl)[1-[(4S)-tert-butyl-2-oxazolin-2-yl]-2-(Sp)-(diphenylphos-
phino)-1′,2′,3′,4′,5′-pentaphenylferrocene]palladium Hexafluor-
oantimonate (9b). Following GP2 a red crystalline solid was isolated
in quantitative yield (dr > 50:1).
(η3-Allyl)[1-[(4S)-isopropyl-2-oxazolin-2-yl]-2-(Sp)-(bis[4-
( t r i fl u o r o m e t h y l ) p h e n y l p h o s p h i n o ) - 1 ′ , 2 ′ , 3 ′ , 4 ′ , 5 ′ -
pentaphenylferrocene]palladium Hexafluoroantimonate (11a).
Following GP2 a red crystalline solid was isolated in quantitative
yield (dr = 1.5:1).
23
C63H51F12FeNOPPdSb, mol wt: 1381.06. Mp: >190 °C dec. [α]D
= −451.7° (c = 0.176 g dL−1, CHCl3). 1H NMR (300 MHz, CDCl3, 21
°C): mixture of two isomers 1.5:1 (called a and b), δ 7.59 (m, 4 H,
HPhCCCF3CHPh, isomer a), 7.596(m, 4 H, HPhCCCF3CHPh, isomer
b), 7.17 (t, J = 3.8, 10 H, HPh), 6.99 (q, J = 6.9, 20 H, HPh), 6.88 (d, J =
8.1, 10 H, HPh, isomer b), 6.76 (d, J = 7.5, 10 H, HPh, isomer a), 5.88
(m, 1 H, Hallyl, isomer a), 5.60 (m, 1 H, HFc, isomer a), 5.55 (m, 1 H,
HFc, isomer b), 5.48 (m, 1 H, Hallyl, isomer b), 5.11 (m, 1 H, HFc,
isomer b), 5.04 (m, 1 H, HFc, isomer a), 4.98 (m, 1 H, HFc, isomer a),
4.97 (m, 1 H, Hallyl, isomer a), 4.96 (m, 1 H, HFc, isomer b), 4.82 (m, 1
H, Hallyl, isomer b), 4.52 (t, J = 8.5, 1 H, NCH, isomer a), 4.43 (t, J =
9.0, 1 H, NCH, isomer b), 4.27 (q, J = 8.5, 2 H, OCH2, isomer a), 4.09
(m, 1 H, Hallyl, isomer a), 4.08 (m, 1 H, Hallyl, isomer b), 3.88 (q, J =
12.0, 2 H, OCH2, isomer b), 3.38 (m, 2 H, Hallyl), 3.37 (m, 1 H, Hallyl),
2.66 (d, J = 12.0, 1 H, Hallyl, isomer b), 2.37 (d, J = 12.0, 1 H, Hallyl
,
isomer a), 1.91 (m, 1 H, CH3CHCH3, isomer a), 1.90 (m, 1 H,
CH3CHCH3, isomer b), 0.94 (d, J = 6.0, 3 H, CH3CHCH3, isomer a),
0.89 (d, J = 6.0, 3 H, CH3CHCH3, isomer b), 0.35 (d, J = 7.0, 3 H,
CH3CHCH3, isomer a), 0.26 (d, J = 7.0, 3 H, CH3CHCH3, isomer b).
13C NMR (125 MHz, CDCl3, 21 °C): δ 169.8, 136.2, 133.2, 133.1,
132.0, 131.7, 131.6, 131.59, 131.5, 127.79, 127.72, 127.6, 127.5, 90.2,
90.0, 78.2, 78.0, 77.6, 76.6, 75.9, 69.9, 69.0, 31.1, 30.3, 29.8, 20.4, 19.8,
16.6, 15.1. 31P NMR (202.5 MHz, CDCl3, 21 °C): δ 16.9 (s), 15.7 (s).
19F NMR (235 MHz, CDCl3, 21 °C): δ −62.85 (b), −62.90 (b),
−63.01 (s), −63.07 (s), −63.25 (b), −63.26 (b). IR (solid): ν 3058,
2958, 2923, 2851, 1727, 1600, 1502, 1465, 1014, 955, 919, 875, 832,
801, 740, 698, 656, 621, 600, 571, 559. HRMS (ESI): m/z calcd for
[M − SbF6]+ = C63H51F6FeNOPPd, 1144.2014; found, 1144.2019. A
sufficient microanalysis could not be obtained due to instability.
(η3-Allyl)[1-[(4S)-isopropyl-2-oxazolin-2-yl]-2-(Sp)-(bis[3,5-
t r i fl u o r o m e t h y l ) p h e n y l p h o s p h i n o ) - 1 ′ , 2 ′ , 3 ′ , 4 ′ , 5 ′ -
pentaphenylferrocene]palladium Hexafluoroantimonate (12a).
Following GP2 a red crystalline solid was isolated in quantitative
yield (dr = 1.4:1).
23
C62H55F6FeNOPPdSb, mol wt: 1259.10. Mp: > 170 °C dec. [α]D
= −225.5° (c = 0.21 g dL−1, CHCl3). 1H NMR (500 MHz, CDCl3, 21
°C): δ 7.78−6.68 (m, 35 H, HPh), 5.74 (m, 1 H, Hallyl), 5.63 (m, 1 H,
HFc), 5.28 (m, 1 H, Hallyl), 5.01 (m, 1 H, Hallyl), 4.92 (m, 1 H, Hallyl),
4.88 (m, 1 H, HFc), 4.61 (m, 1 H, NCH), 4.21 (m, 2 H, OCH2), 3.97
(m, 1 H, Hallyl), 3.22 (m, 1 H, Hallyl), 0.60 (s, 9 H, C(CH3)3). 13C
NMR (125 MHz, CDCl3, 21 °C): δ 133.2, 132.3, 131.0, 130.9, 129.3,
129.3, 127.6, 127.4, 90.2, 29.7, 26.1, 1.0. 31P NMR (121.5 MHz,
CDCl3, 21 °C): δ 18.5 (s). IR (solid): ν 3056, 2985, 1723, 1600, 1502,
1482, 1438, 1383, 1365, 1290, 1243, 1172, 1102, 1075, 1027, 988, 952,
908, 830, 802, 785, 735, 696, 654, 560, 542. HRMS (ESI): m/z calcd
for [M − SbF6]+ = C62H55FeNOPPd, 1022.2423; found, 1022.2418. A
sufficient microanalysis could not be obtained due to solvent inclusion.
(η3-Allyl)[1-[(4S)-isopropyl-2-oxazolin-2-yl]-2-(Sp)-(bis(4-
methoxyphenyl)phosphino)-1′,2′,3′,4′,5′-pentaphenylferrocene]-
palladium Hexafluoroantimonate (10a). Following GP2 a red
crystalline solid was isolated in quantitative yield (dr = 1.3:1).
C63H57F6FeNO3PPdSb, mol wt: 1305.12. Mp: 160.6−161.6 °C dec.
C65H49F18FeNOPPdSb, mol wt: 1517.06. Mp: 197.7−198.0 °C dec.
23
1
[α]D = −379.8° (c = 0.193 g dL−1, CHCl3). H NMR (300 MHz,
CDCl3, 21 °C): mixture of two isomers 1.34:1 (called a and b), δ
7.20−7.15 (m, 9 H, HPh), 7.02−6.95 (m, 20 H, HPh), 6.84−6.75 (m,
26 H, HPh), 6.59−6.49 (m, 4 H, HPh), 5.88 (m, 1 H, Hallyl, isomer a),
5.50 (m, 1 H, Hallyl, isomer b), 5.48 (m, 1 H, HFc, isomer a), 5.44 (m, 1
H, HFc, isomer b), 5.03 (m, 1 H, HFc, isomer b), 4.98 (m, 1 H, HFc,
isomer a), 4.88 (t, J= 6.0, 1 H, NCH, isomer a), 4.86 (m, 1 H, HFc,
23
1
[α]D = −425.6° (c = 0.265 g dL−1, CHCl3). H NMR (500 MHz,
CDCl3, 21 °C): mixture of two isomers in a ratio of 1.4:1 (called a and
b), δ 8.17 (m, 3 H, HPhCCCF3), 7.89 (m, 1 H, HPhCCCF3, isomer a),
7.87 (m, 1 H, HPhCCCF3, isomer b), 7.67 (d, J = 11.5, 1 H,
HPhCCCF3, isomer a), 7.56 (d, J = 11.5, 1 H, HPhCCCF3, isomer b),
7.19−6.68 (m, 50 H, HPh), 5.92 (m, 1 H, Hallyl, isomer a), 5.72 (m, 1
H, HFc, isomer a), 5.67 (m, 1 H, HFc, isomer b), 5.60 (m, 1 H, Hallyl
,
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isomer a), 5.15 (m, 1 H, HFc, isomer a), 5.14 (m, 1 H, HFc, isomer b),
5.08 (t, J = 6.3, 1 H, Hallyl, isomer a), 4.98 (t, J = 8.0, 1 H, Hallyl, isomer
b), 4.92 (m, 1 H, HFc, isomer b), 4.86 (m, 1 H, HFc, isomer a), 4.53
(m, 1 H, Hallyl, isomer a), 4.45 (m, 1 H, Hallyl, isomer b), 4.31−4.28 (m,
3 H, OCH2, NCH, isomer a), 4.15 (m, 2 H, OCH2, isomer b), 3.89 (t,
J = 11.5, 1 H, NCH, isomer b), 3.40 (m, 1 H, Hallyl, isomer b), 3.39 (d,
J = 7.7, 1 H, Hallyl, isomer a), 2.74 (d, J = 12.4, 1 H, Hallyl, isomer b),
2.57 (d, J = 12.2, 1 H, Hallyl, isomer a), 1.56 (m, 2 H, CH3CHCH3),
0.87 (d, J = 7.8, 3 H, CH3CHCH3, isomer b), 0.86 (d, J = 6.9, 3 H,
CH3CHCH3, isomer a), 0.31 (d, J = 7.8, 3 H, CH3CHCH3, isomer a),
0.23 (d, J = 6.9, 3 H, CH3CHCH3, isomer b). 13C NMR (125 MHz,
CDCl3, 21 °C): δ 169.6, 136.4, 136.0, 132.78, 132.70, 131.9, 127.9,
127.88, 127.85, 127.7, 125.3, 121.4, 121.1, 120.8, 90.7, 90.4, 88.1, 82.9,
70.5, 70.1, 66.1, 58.1, 34.2, 31.1, 30.6, 29.8, 22.5, 20.5, 20.0, 17.1, 15.9,
15.4, 14.1. 31P NMR (121.5 MHz, CDCl3, 21 °C): δ 20.3 (s), 19.1 (s).
19F NMR (235 MHz, CDCl3, 21 °C): δ −62.5 (s), −63.0 (b), −63.3
5.49−5.47 (m, 1 H, HCCH), 3.71 (s, 3 H, OCH3), 3.70 (s, 3 H,
OCH3), 3.25 (d, J = 9.5, 1 H, OCHCCO), 2.90−3.84 (m, 1 H,
H2CHCH), 1.98−1.91 (m, 2 H, CH2), 1.77−1.65 (m, 2 H, CH2),
1.58−1.49 (m, 1 H, CH2), 1.37−1.30 (m, 1 H, CH2). 13C NMR (125
MHz, CDCl3, 21 °C): δ 168.8, 168.7, 129.6, 127.2, 56.7, 52.3, 52.2,
35.3, 26.5, 24.8, 20.8. The analytical data are in agreement with
literature data.26
(R)-Dimethyl 3-cyclopentenylmalonate: yield >99%, colorless oil;
91% ee (R)25 as determined by H NMR (300 MHz, C6D6) using
1
(+)-Eu(hfc)3 as a chiral shift reagent.
C10H14O4, mol wt: 198.22. [α]D23 = +73.5 (c 0.89 g dL−1, CHCl3).
1H NMR (500 MHz, CDCl3, 21 °C): δ 5.82−5.80 (m, 1 H, HCCH),
5.64−5.62 (m, 1 H, HCCH), 3.71 (s, 6 H, OCH3), 3.37−3.34 (m, 1
H, H2CHCH), 3.26 (d, J = 9.5, 1 H, OCHCCO), 2.36−2.29 (m, 2 H,
CH2), 2.14−2.08 (m, 1 H, CH2), 1.60−1.55 (m, 1 H, CH2). 13C NMR
(125 MHz, CDCl3, 21 °C): δ 169.1, 169.0, 133.0, 131.3, 56.6, 52.4,
52.3, 45.4, 31.7, 27.7. The analytical data are in agreement with
literature data.26
(s). IR (solid): ν 2959, 2923, 2851, 1711, 1600, 1503, 1465, 1443,
1355, 1278, 1187, 1122, 1095, 1028, 906, 844, 801, 741, 699, 681, 655,
621. HRMS (ESI): m/z calcd for [M − SbF6]+ = C65H49F12FeNOPPd,
1280.1763; found, 1280.1777. A sufficient microanalysis could not be
obtained due to instability.
(R)-Dimethyl 3-cycloheptenylmalonate: yield 80%, colorless oil;
90% ee (R)25 as determined by GC (HRCG MEGA 2 serie HT system
with a Bondex-UN-alpha+beta column; length of the column 20 m, i.d.
0.30 mm; film thickness 0.25 μm; carrier gas 0.4 bar of H2; method
100 °C isotherm); Rt = 90.9 min (R) and 93.7 min (S).
[η3-2-Cyclohexen-1-yl][[(4S)-isopropyl-2-oxazolin-2-yl]-2-
(Sp)-(diphenylphosphino)-1′,2′,3′,4′,5′-pentaphenylferrocene]-
palladium Hexafluoroantimonate (13). A mixture of [Pd(η3-
C6H9)Cl]2 (8.8 mg, 0.02 mmol, 1 equiv),24 7a (34 mg, 0.04 mmol, 2
equiv), and dry CH2Cl2 (1 mL) was stirred for 10 min at room
temperature. Then a solution of AgSbF6 (14 mg, 0.04 mmol, 2 equiv)
in dry methanol (0.25 mL) was added and the mixture was stirred for
an additional 1 h. Filtration through Celite and evaporation of the
solvent gave the product as a red crystalline solid (51.4 mg, 0.04 mmol,
>99%, dr > 50:1).
C12H18O4, mol wt: 226.27. [α]D23 = +6.6° (c = 1.0 g dL−1, CHCl3).
1H NMR (500 MHz, CDCl3, 21 °C): δ 5.82−5.77 (m, 1 H, HCCH),
5.57−5.54 (m, 1 H, HCCH), 3.71 (s, 3 H, OCH3), 3.69 (s, 3 H,
OCH3), 3.44 (d, J = 8.5, 1 H, OCHCCO), 3.03−2.99 (m, 1 H,
H2CHCH), 2.12−2.10 (m, 2 H, CH2), 1.93−1.89 (m, 1 H, CH2),
1.66−1.56 (m, 3 H, CH2), 1.37−1.28 (m, 2 H, CH2). 13C NMR (125
MHz, CDCl3, 21 °C): δ 169.1, 168.9, 132.8, 132.7, 56.7, 52.3, 52.2,
39.6, 30.9, 30.1, 28.3, 26.2. The analytical data are in agreement with
literature data.26
23
C64H57F6FeNOPPdSb, mol wt: 1285.13. Mp: >162.8 °C dec. [α]D
= −614.8° (c = 0.185 g dL−1, CHCl3). 1H NMR (300 MHz, CDCl3, 21
°C): δ 7.66−6.58 (m, 33 H, HPh), 5.9 (m, 1 H, Hallyl), 5.80 (t, J = 7.8, 1
H, Hallyl), 5.54 (m, 1 H, HFc), 4.94 (m, 1 H, HFc), 4.48 (m, 1 H, HFc),
4.56 (t, J = 9.0, 1 H, OCH2), 4.31(m, 1 H, Hallyl), 4.26 (t, J = 8.5, 1 H,
CNCH), 4.08 (m, 1 H, OCH2), 2.01 (m, 1 H, CH2), 1.26 (m, 1 H,
CH3CHCH3), 1.02 (m, 1 H, CH2), 0.96 (d, J = 6.5, 3 H,
CH3CHCH3), 0.86 (m, 3 H, CH2), 0.62 (m, 1 H, CH2), 0.32 (d, J
= 6.0, 3 H, CH3CHCH3). 13C NMR (125 MHz, CDCl3, 21 °C):
δ169.9, 136.3, 136.2, 133.3, 133.1, 132.2, 132.1, 131.0, 130.9, 130.3,
129.7, 129.6, 129.0, 128.9, 127.79, 127.72, 127.4, 127.3, 109.7, 109.6,
98.8, 98.6, 89.6, 82.2, 80.7, 80.6, 78.4, 76.5, 75.2, 72.5, 72.4, 69.2, 30.8,
29.8, 28.19, 28.15, 27.4, 26.8, 24.7, 22.8, 21.7, 20.2, 19.7, 18.4, 16.1,1.2
(R)-Dimethyl 2-(5,5-dimethylcyclohex-2-en-1-yl)malonate: yield
>99%, colorless oil; 74% ee as determined by GC (HRCG MEGA 2
serie HT system with a Bondex-UN-alpha+beta column; length of the
column 20 m, i.d. 0.30 mm; film thickness 0.25 μm; carrier gas 0.4 bar
of H2, method 50 °C 1 min, ramp @ 10 °C min−1 until 110 °C,
isotherm hold 1 min); Rt = 44.7 min (S) and 45.6 min (R).
C13H20O4, mol wt: 240.30. [α]D23 = +2.1° (c = 1.0 g dL−1, CHCl3).
1H NMR (300 MHz, CDCl3, 21 °C): δ 5.72−5.68 (m, 1 H, HCCH),
5.50−5.47 (m, 1 H, HCCH), 3.748 (s, 3 H, OCH3), 3.743 (s, 3 H,
OCH3), 3.25 (d, J = 9.0, 1 H, OCHCCO), 2.98−2.86 (m, 1 H,
H2CHCH), 1.83−1.75 (m, 2 H, CH2), 1.43−1.39 (m, 1 H, CH2), 1.16
(m, 1 H, CH2), 0.95 (s, 1 H, CH3), 0.91 (s, 1 H, CH3). 13C NMR (125
MHz, CDCl3, 21 °C): δ169.1, 128.3, 126.0, 56.7, 52.5, 39.7, 38.8, 34.5,
.
31P NMR (121.5 MHz, CDCl3, 21 °C): δ 17.5 (s), 12.1 (s). IR
(solid): ν 3088, 3057, 3029, 2961, 2925, 2852, 2365, 1721, 1599, 1502,
1481, 1441, 1410, 1383, 1313, 1283, 1246, 1169, 1101, 1075, 1044,
1028, 998, 954, 908, 848, 801, 728, 697, 658, 620. HRMS (ESI): m/z
calcd for [M − SbF6]+ = C64H57FeNOPPd, 1048.2580; found,
1048.2573. Anal. Calcd for C64H57F6FeNOPPdSb: C, 59.81; H, 4.47;
N, 1.09. Found: C, 59.83; H, 4.74; N, 1.07.
General Procedure for the Allylic Alkylation of Cyclic Allylic
Acetates (GP3). A mixture of [Pd(η3-C3H5)Cl]2 (0.5 mol %) and the
corresponding ligand 5−8 (1.1 mol %) in dry THF (1 mL per mmol
of substrate) was stirred for 15 min at room temperature. The
corresponding allylic acetate was added, and the resulting mixture was
stirred for 10 min at room temperature. Then dimethyl malonate (1
equiv) and BSA (1 equiv) were added. The reaction was started by the
addition of NaOAc (0.03 equiv). After it was stirred for 1 h at 22 °C,
the reaction mixture was filtered over Celite and the solvent removed
in vacuo. The residue was subjected to column chromatography (silica,
PE/Et2O, 9/1).
32.0, 29.7, 25.2. HRMS (ESI): m/z calcd for [M + Na]+
=
C13H20NaO4, 263.1254; found, 263.1263.
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures giving NMR spectra of new compounds and
determinations of enantiomeric excesses and CIF files giving
crystallographic data for 9a,b and 13. This material is available
free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for R.P.: rene.peters@oc.uni-stuttgart.de.
(R)-Dimethyl 3-cyclohexenylmalonate: yield >99%, colorless oil;
87% ee (R)25 as determined by GC (HRCG MEGA 2 serie HT system
with a Bondex-UN-alpha+beta column; length of the column 20 m, i.d.
0.30 mm; film thickness 0.25 μm; carrier gas 0.4 bar of H2; method 50
°C 1 min, ramp @ 10 °C min−1 until 80 °C, isotherm hold 1 min): Rt
= 103.9 min (S) and 106.4 min (R).
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
23
C11H16O4, mol wt: 212.24. [α]D = +32.1 (c 1.0 g dL−1, CHCl3).
Notes
1H NMR (500 MHz, CDCl3, 21 °C): δ 5.76−5.72 (m, 1 H, HCCH),
The authors declare no competing financial interest.
1077
dx.doi.org/10.1021/om500049f | Organometallics 2014, 33, 1068−1078

Organometallics
Article
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ACKNOWLEDGMENTS
■
This work was financially supported by F. Hoffmann-La Roche.
We thank B.Sc. Mario Cicac-
̌
Hudi for experimental contribu-
tions during a research internship.
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