Synthesis of phospholane-phosphoramidite ligands and their application in asymmetric catalysis

Article abstract of DOI:10.1002/cctc.201500070

A set of phospholane-phosphoramidite ligands, which possess four elements of chirality, has been synthesized through a modular diastereoselective process. The ligands were applied in the Rh-catalyzed asymmetric C =C hydrogenation of several functionalized olefins with enantioselectivities of up to 99 % ee and a turnover frequency of up to 12 000 h^-1, in the Rh-catalyzed hydroformylation of vinyl arenes with enantioselectivities of up to 79 % ee, and in the Ir-catalyzed asymmetric C =N hydrogenation of different aryl imines with enantioselectivities of up to 79 % ee. New P,P′ hybrid ligands: A set of phospholane-phosphoramidites (quinaphoslane) with four elements of chirality are synthesized through a modular diastereoselective process and applied in the Rh-catalyzed hydrogenation of functionalized olefins with up to 99 % ee and a turnover frequency (TOF) of up to 12 000 h^-1, in the Rh-catalyzed hydroformylation of vinyl arenes with regioselectivities of up to 99 % and up to 79 % ee, and in the Ir-catalyzed hydrogenation of imines with up to 79 % ee.

Full text of DOI:10.1002/cctc.201500070

DOI: 10.1002/cctc.201500070
Full Papers
Synthesis of Phospholane–Phosphoramidite Ligands and
their Application in Asymmetric Catalysis
Tim Hammerer, Walter Leitner,* and Giancarlo Franciò*[a]
Dedicated to Prof. Albrecht Salzer on the occasion of his 70th birthday
A set of phospholane–phosphoramidite ligands, which possess
four elements of chirality, has been synthesized through a mod-
ular diastereoselective process. The ligands were applied in the
Rh-catalyzed asymmetric C=C hydrogenation of several func-
tionalized olefins with enantioselectivities of up to 99% ee and
a turnover frequency of up to 12000 hÀ1, in the Rh-catalyzed
hydroformylation of vinyl arenes with enantioselectivities of up
to 79% ee, and in the Ir-catalyzed asymmetric C=N hydrogena-
tion of different aryl imines with enantioselectivities of up to
79% ee.
Introduction
Several P,P’ hybrid compounds have been introduced as a new
powerful class of chiral ligands for asymmetric transition-
metal-catalyzed transformations.[1] Within bidentate electroni-
cally unequal phosphorous ligands, phosphine-phosphorami-
dites play a prominent role, and several examples of this class
of ligands based on various backbones have been reported
(Figure 1).[1–4]
in 2001.[6a] Phosphine-phospholane ligands based on a chromi-
um arene backbone,[6b] on a substituted 1,1’-ferrocene,[6c] and
on a thiophene[6d,e] have been reported.
Up to now there are only two examples of P,P’ ligands that
comprise a phospholane moiety and a nonphosphine donor.
The first example was a benzothiophene-based phospholane–
phosphonite ligand related to the ButiPhane family reported
by Salzer et al. (Figure 2).[7] More recently, Clarke et al. intro-
Figure 1. Examples of phosphine-phosphoramidite ligands.
Figure 2. Examples of P,P’ hybrid ligands that contain a phospholane moiety.
The phosphine-phosphoramidite ligand quinaphos, intro-
duced by Leitner, Faraone et al. in 2000, demonstrated the ver-
satility and the efficiency of this class of P,P’ ligands.[3a] Follow-
ing an original protocol,[5] quinaphos ligands are accessible as
a diastereomeric mixture through a one-pot synthesis that
started from 8-bisarylphosphinoquinoline. Recently, a general
separation procedure was developed to enable the isolation of
diastereomerically pure quinaphos on a gram scale.[3d]
duced phospholane–phosphite ligands and demonstrated their
utility in the asymmetric hydroformylation of alkyl alkenes[8a]
and vinyl arenes.[8b]
We set out to prepare a new class of chiral hybrid P,P’ li-
gands that combine the two extremely successful structural
motifs: phospholane and phosphoramidite. This results in
a pronounced electronic differentiation between the two
donor atoms (electron-rich phospholane versus the phosphor-
amidite unit with p-acceptor character). The chiral phospho-
lane 8-[(2R,5R)-2,5-dimethylphospholan-1-yl]-quinoline ((RCP,RCP)-
1) reported recently by Bçrner et al.[9] was selected as the ideal
starting material to accomplish the synthesis of the target li-
gands following the protocol established for quinaphos.[3] We
refer to this ligand type as “quinaphoslane”. Notably, the addi-
tion of lithium organyls at the 1,2-position of the chiral starting
material (RCP,RCP)-1[9] proceeded with full diastereoselectivity.
Both chiral diols and achiral diol/alcohols were attached at the
phosphoramidite moiety. The application of these quinaphos-
lane ligands in various metal-catalyzed reactions is reported.
In contrast, the number of P,P’ ligands that contain one
phospholane moiety is rather small.[6] Most of them are combi-
nations of a phospholane and a phosphine group such as the
first example Me-UCAP-Ph (Figure 2) described by Stelzer et al.
[a] Dr. T. Hammerer, Prof. Dr. W. Leitner, Dr. G. Franciò
Institut für Technische Chemie und Makromolekulare Chemie
RWTH Aachen University
Worringerweg 2, 52074 Aachen (Germany)
E-mail: francio@itmc.rwth-aachen.de
leitner@itmc.rwth-aachen.de
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201500070.
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Results and Discussion
Table 1. 31P NMR data of quinaphoslane ligands (CDCl3).
Ligand
R
Chirality Diol/alcohol
at C2
dP[a]
dP[b]
JPP’
Ligand synthesis and structure
[ppm] [ppm] [Hz]
Following the synthetic protocol established for the quinaphos
ligand family,[3,5] the target ligands were synthesized from
(RCP,RCP)-1[9] (Scheme 1). In the first step, a fully stereoselective
L1
nBu
RC2
134.9
138.4
135.4
135.3
À5.9 177.8
À10.1 138.6
À5.6 188.7
À10.3 153.3
L2
L3
L4
nBu
RC2
1-naph SC2
1-naph SC2
L5
1-naph SC2
138.9
À6.1 199.2
L6
L7
1-naph SC2
1-naph SC2
125.2
128.1
À9.8 168.1
À8.9 162.3
Scheme 1. Reaction sequence for the synthesis of quinaphoslane ligands.
1,2-addition of the lithium organyl to (RCP,RCP)-1 was observed
using both nBuLi or 1-naphthyllithium as nucleophiles.[10] Upon
in situ reaction of the resulting key chiral lithium amide inter-
mediates 2a and 2b, respectively, with the phosphorochlori-
dite from (Sa)- or (Ra)-(1,1’-binaphthalene)-2,2’-diol (Scheme 1,
route 1) single diastereomeric phospholane–phosphoramidite
compounds L1–L4 were obtained, as evidenced by 31P NMR
spectroscopy (Table 1).
[a] Phosphoramidite; [b] phospholane.
Accordingly, in each reaction sequence, two doublets were
detected as major signals. Akin to the quinaphos ligands,[3] the
chemical shifts and the coupling constants in the 31P NMR
spectra are significantly affected from the relative configura-
tion of the binaphthol moiety, whereas the influence of the
nature of the substituent at the 2-position of the dihydro-
quinoline ring is rather marginal. Thus, L1 and L3, which have
the same spatial arrangement,[11] show similar P,P’ coupling
constants (J=177.8 and 188.7 Hz) and chemical shifts for the
Pphospholane (d=À5.9 and À5.6 ppm) and the Pphosphoramidite (d=
134.9 and 135.4 ppm). In comparison, L2 and L4 display
a smaller P,P’ coupling constant (J=138.6 and 153.3 Hz), an
almost coincident upfield shift for the Pphospholane peaks (d=
À10.1 and À10.3 ppm), and slightly different chemical shifts
for Pphosphoramidite (d=138.4 and 135.3 ppm). The quinaphoslane
synthesis through route 1 led to the formation of side products
(ꢀ15%) that could not be removed during the work-up by dif-
ferent purification methods. In the crude mixture, besides the
desired species described above, two additional singlets were
observed in the 31P NMR spectra, one at d=144.9 ppm, which
belongs to the pyrophosphite 4 reported by Bçrner et al. and
Figure 3. Identified side products from synthesis route 1.
Faraone et al.,[12] and a second at d=À18.4 ppm, which arises
from the phospholane amine 5 (Figure 3). Both side products
result from adventitious water present in the reaction mixture.
The formation of the side products described above could
be suppressed effectively through the use of route 2 for the
synthesis of the quinaphoslane ligands (Scheme 1).[5] In this se-
quence, the lithium amide 2 is first quenched with an excess
of PCl3 to result in the formation of the corresponding PCl2
compound 3 as confirmed by 31P NMR spectroscopy. Unexpect-
edly, the signal of the phospholane P atom underwent a signifi-
cant downfield shift and appears at d=63.8 ppm, whereas the
R2NÀPCl2 signal lies at d=83.1 ppm, a very unusual upfield
shift compared to that of similar compounds (dꢀ150–
170 ppm).[5,13] With a value of JP,P’ = 356 Hz, the coupling con-
stant is within the range reported for phosphine-dichlorophos-
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phine compounds.[14] The condensation of PCl2 compound 3
with (Ra)- and (Sa)-(1,1’-binaphthalene)-2,2’-diol in the presence
of NEt3 resulted in the clean formation of L3 and L4, respec-
tively.
This modular procedure was exploited to access diastereo-
merically pure ligand structures that comprise a tropos diol
such as 3,3’-di-tert-butyl-5,5’-dimethoxy-(1,1’-biphenyl)-2,2’-diol
(L5) or even achiral aryl alcohol moieties such as 3,5-bis(tri-
fluoromethyl)phenol (L6) and 3,5-dimethylphenol (L7). The
latter two ligands, which lack stabilization from the chelate
effect, were particularly prone to hydrolysis, and no suitable
purification procedure could be established without extensive
decomposition. Thus, L6 and L7 were used in catalysis as ob-
tained after filtration through a short plug of Al2O3 with ꢀ90%
purity (31P NMR).
To establish the absolute configuration at the C2-position of
the dihydroquinoline backbone of the ligands, the structures
of both possible diastereomers (SC2,Ra)-L3 and (RC2,Ra)-L3 were
calculated by DFT methods (M062X/def2-SVP) and are shown
in Figure 4. The distances between the protons H-2, H-3, and
H-4 of the 1,2-dihydroquinoline backbone and the protons
H-3A and H-4A of the binaphthyl skeleton are decisive in the as-
signment of the absolute configuration of quinaphos-type li-
gands.[15] For (SC2,Ra)-L3, the calculated distances between H-3A
and H-2, H-3 and H-4, as well as H-4A and H-3 are all below 4 Š
(Table 2) and thus a NOE between these protons can occur. In
Table 2. Relevant atomic distances [Š] of both diastereomers of L3
obtained from DFT calculation.
Figure 4. Optimized geometries for (SC2,Ra)-L3 (a) and (RC2,Ra)-L3 (b) obtained
from DFT calculation (M062X/def2-SVP).
(SC2,Ra)-L3
(RC2,Ra)-L3
H-3
H-2
H-3[b]
H-4[c]
H-2
H-4
8.03
H-3A
H-4A
3.11
4.07
3.17
3.51
3.93
5.09
3.88
5.24
6.19
8.53
10.37
Accordingly, the 1,2-addition of the organometallic reagent
occurs always from the re-face of 8-[(2R,5R)-2,5-dimethylphos-
pholan-1-yl]quinoline, which results in the same spatial ar-
rangement for all of the quinaphoslane ligands synthesized
here (Figure 6). In contrast, the stereodescriptors following the
Cahn–Ingold–Prelog (CIP) rules will depend on the priority of
the substituent at the C2 of the dihydroquinoline backbone
(SC2 for the 1-naphthyl and RC2 for the n-butyl derivatives).[11]
Notably, the 1,2-addition proceeded diastereoselectively in
the temperature range between À788C and +508C. The chiral
phospholane unit could direct the stereoselective addition
either by precoordination of the Li ion in which the lone pair
at P guides the attack of the nucleophile or by an effective
steric shielding of one face of the quinoline backbone. To
verify the coordination hypothesis, (RCP,RCP)-1 was oxidized with
Se to engage the free electron pair at the phospholane unit.
The reaction with elementary Se in CH2Cl2 proceeded to com-
the case of (RC2,Ra)-L3, only protons H-3A and H-2 reside at a cal-
culated distance below 4 Š (3.88 Š), whereas the other struc-
turally relevant proton pairs reside more than 4 Š apart, and
therefore, no NOE interaction is possible.
The measured 2D NOE NMR spectrum of L3 (Figure 5)
shows intense cross peaks between the binaphthyl proton
H-3A and the quinoline protons H-2 and H-3. The comparison
of these findings with the calculated proton distances (Table 2)
clearly indicates that the diastereomer formed has the absolute
configuration (SC2,Ra). This assignment is in full agreement with
the trend observed for the through-space P,P’ coupling con-
stants of L3 (J=188.3 Hz) and L4 (J=153.3 Hz), which fits per-
fectly with the values measured for the structurally related
(SC2,Ra)-1-naphquinaphos (J=209.6 Hz) and (RC2,Ra)-1-naph-
quinaphos (J=151.5 Hz).[3d]
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Table 3. 31P{1H} NMR data of [Rh(cod)L]BF4 complexes.
dP
JPRh
dP
JP’Rh
JPP’
phosphoramidite
phospholane
Ligand
[ppm]
[Hz]
[ppm]
[Hz]
[Hz]
L3
L4
L5
L6
L7
138.6
144.3
138.9
128.1
126.6
264
260
261
267
255
44.8
31.9
41.9
41.8
41.9
132
138
134
130
136
54
49
54
49
48
tained as yellow to orange solids in 63–73% yield. The
31P{1H} NMR spectroscopic data of the synthesized complexes
are listed in Table 3.
The chemical shift of the Pphosphoramidite atom in the Rh com-
plex differs very little from that of the free ligand. In contrast,
a large coordination shift for the Pphospholane peaks is observed,
all of which appear in the range d=41.8–44.8 ppm. The only
exception is the complex [Rh(cod)L4]BF4 in which Pphospholane
has a chemical shift of d=31.9 ppm. The through-bonds P,P’
coupling constants are in the range of JP,P’ = 48–54 Hz, which is
significantly smaller than the through-space coupling con-
stants of the free ligands (JP,P’ = 153–199 Hz). Both the
PphospholaneÀRh and PphosphoramiditeÀRh coupling constants are in
the expected range (J=130–138 and 255–267 Hz, respective-
ly).
Figure 5. NOESY spectrum of L3.
pletion overnight and the corre-
sponding phospholane selenide
(RCP,RCP)-1-Se could be isolated in
a pure form from hot methanol as
colorless needles in 95% yield. The
31P{1H} NMR spectrum shows a sin-
glet at d=+67.9 ppm and a dou-
blet centered at d=+67.9 ppm
Figure 6. Stereochemistry of
the addition of organolithium
compounds to (RCP,RCP)-1.
with a coupling constant of JSe,P
=
689 Hz. In comparison with other
phospholane selenides,[16] the 71Se-
Rh-catalyzed asymmetric C=C hydrogenation
31P coupling constant is significantly smaller, which indicates
a more pronounced s character of the free electron pair and
thus an higher basicity of the phospholane donor. The addition
of 1-naphthyllithium to (RCP,RCP)-1-Se at À788C in THF proceed-
ed with full diastereoselectivity (as confirmed by 31P NMR)
along with the formation of unidentified side products. Hence,
(RCP,RCP)-1-Se is also able to direct the 1,2-addition effectively,
which indicates that the stereoselectivity is caused by steric
control rather than Li precoordination. Thus, the access of the
quinaphoslane diastereomers with opposite configuration at
the C2-position in the ortho position to the N atom is preclud-
ed by the routes used.
The quinaphos ligands led to extremely efficient Rh catalysts
for the asymmetric hydrogenation of functionalized olefins in
batch[3] and continuous-flow processes.[17] Thus, the quina-
phoslane ligands were first benchmarked in the same applica-
tion, which is one of the most useful methods to prepare opti-
cally active compounds.[18] Dimethyl itaconate was selected as
the prototypical olefinic substrate to compare the ability of
L3–L7 in the Rh-catalyzed asymmetric hydrogenation (Table 4).
Except for L5, all of the ligands resulted in very active hydro-
genation catalysts that led to full conversion within 1 h under
standard conditions (entries 1–5: CH2Cl2, pH2 =10 bar, sub-
strate/Rh=1000). Significant synergistic effects between the
stereogenic center at C2 and the chirality of the atropoisomer-
ic 1,1’-bi-2-naphthol (BINOL) moiety are evident for L3 and L4
(cf. entries 1 and 2). Although a very high enantioselectivity
(98% enantiomeric excess; ee) towards the R product was ob-
tained with L3, a modest ee value of 23% in favor of the oppo-
site enantiomer was obtained with L4. The hydrogenation with
[Rh(cod)L5]BF4 was quite sluggish with only 13% conversion
after 1 h and an enantioselectivity of 43% ee (entry 3). The S
product was formed preferentially, which suggests that the bi-
phenol moiety probably adopts an Sa conformation in the
complex. The results obtained with L6 and L7, which bear un-
Synthesis and characterization of Rh complexes
The cationic complexes [Rh(cod)(quinaphoslane)]BF4 (cod=cy-
clooctadiene) were synthesized from [Rh(cod)(acac)] (acac=
acetylacetonate) and the corresponding ligands L3–L7 by the
standard procedure depicted in Scheme 2. The Rh precursor
was dissolved in THF, and HBF4·Et2O was added. A solution of
the desired ligand in the same solvent was added dropwise to
the resulting light yellow solvatocomplex to result in a deep
orange mixture. The crude complexes were purified by recrys-
tallization either from CH2Cl2/pentane or THF/Et2O and ob-
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Table 4. Rh-catalyzed asymmetric of hydrogenation of dimethyl itaconate
with quinaphoslane ligands.[a]
Entry
Ligand
solvent
pH2 [bar]
TOF [hÀ1
]
ee [%]
1
2
3
4
5
6
7
8
L3
L4
L5
L6
L7
L3
L3
L3
L3
L3
L3
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
EtOAc
THF
MeOH
CH2Cl2
CH2Cl2
CH2Cl2
10
10
10
10
10
10
10
10
1
ꢁ1000
ꢁ1000
130
ꢁ1000
ꢁ1000
ꢁ1000
ꢁ1000
ꢁ1000
20
98 (R)
23 (S)
46 (S)
84 (R)
54 (R)
96 (R)
94 (R)
93 (R)
99 (R)
98 (R)
98 (R)
9
10
11[b]
50
54
ꢁ1000
ꢁ12000
[a] Substrate=1.5 mmol, substrate/catalyst=1000, solvent=2 mL, t=1 h,
RT; [b] Substrate=6.0 mmol, substrate/catalyst=4000, t=40 min.
Figure 7. Substrate scope of [Rh(cod)L3]BF4 in the asymmetric olefin hydro-
genation. [a] Reaction conditions: substrate=1.5 mmol, CH2Cl2 (2 mL),
t=1 h, RT, 10 bar H2, substrate/catalyst=1000; [b] MeOH (2 mL).
linked achiral phenol derivatives at the phosphoramidite
moiety, are notable. Both catalysts generated the R product
predominantly, and a remarkable ee value of 84% was ob-
tained with L6, which is decorated with electron-withdrawing
CF3 groups (entry 4), whereas 54% ee was achieved with L7,
which features a more electron-rich phosphoramidite donor
(entry 5).
tion of an electron-donating methoxy group in the para posi-
tion led to a decrease in enantioselectivity to 77% ee (S).
Thus, most of the substrates investigated were hydrogenat-
ed with similarly high enantioselectivities and activities as
achieved with the related phosphine-phosphoramidite quina-
phos, which indicates that the phospholane–phosphoramidite
combination is a valuable alternative.
The influence of the solvent and the hydrogen pressure was
investigated for the catalyst [Rh(cod)L3]BF4. Diminished enan-
tioselectivities were observed if the polarity of the reaction
medium was increased in the order CH2Cl2 >EtOAc>THF>
MeOH with ee values of 98, 96, 94, and 93%, respectively (en-
tries 1 and 6–8). A decrease of the hydrogen pressure from 10
to 1 bar led to an increase in enantioselectivity to 99% R, how-
ever, at a strongly decreased reaction rate (Table 4, entry 9).
Conversely, an increase of the pressure to 50 bar showed no
observable effect on the enantioselectivity (entry 1 vs. 10). To
estimate the activity of [Rh(cod)L3]BF4, the pressure drop
during the hydrogenation of dimethylitaconate in CH2Cl2 at
a substrate-to-Rh ratio of 4000 and an initial pH2 of 52 bar was
recorded (Supporting Information). Within 20 min the pressure
reached a constant level of 39 bar, which corresponds to an
average turnover frequency (TOF) of 12000 hÀ1.
Rh-catalyzed asymmetric hydroformylation of vinyl arenes
The phosphoramidite-phospholane ligands L3–L7 were evalu-
ated in the hydroformylation of styrene (Scheme 2) under stan-
dard conditions (substrate/catalyst=1000; pCO/H2 =30 bar,
608C, 16 h). The best result of the series was obtained with L3,
which led to 39% conversion, a branched-to-linear ratio (b/l) of
96:4, and 79% ee (Table S1). L3 was used in the hydroformyla-
tion of other vinyl arenes, in which the nature of the substitu-
ents had a pronounced effect on the enantioselectivity and
varied from 10% ee for the electron-poor p-bromostyrene to
72% ee for the electron-rich p-tert-butylstyrene. For all sub-
strates, high to excellent regioselectivities of up to 99:1
b/l were obtained (Table S1).
The substrate scope of [Rh(cod)L3]BF4 as a catalyst in the
asymmetric hydrogenation was evaluated for various function-
alized olefins (Figure 7).
The hydrogenation of dehydroamino acids (Z)-acetamido
cinnamic acid and acetamido acrylic acid as well as their corre-
sponding methyl esters led to full conversion and very good
enantioselectivities of 94–97% ee. Poor enantioselectivities of
24 and 10% ee were achieved in the hydrogenation of 1-(tri-
fluoromethyl)vinyl acetate and 1-(dimethoxyphosphoryl)vinyl
benzoate. Excellent results were obtained in the hydrogenation
of N-(1-phenylvinyl)acetamide with full conversion and an
enantioselectivity of >99% ee in favor of the S product. The
related substrate substituted in the para position with an elec-
tron-withdrawing bromide was hydrogenated with the same
excellent level of enantioselectivity. In contrast, the introduc-
Scheme 2. Rh-catalyzed hydroformylation of vinyl arenes.
Although the stereoselectivity obtained with quinaphoslane
(up to 79% ee) is slightly superior to that achieved with quina-
phos (up to 74% ee),[3a] other phosphine-phosphoramidite[19]
and phospholane–phosphite[8b] ligands are clearly superior in
this transformation.[20]
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Ir-catalyzed asymmetric C=N hydrogenation of imines
Thus, we showed that ligands based on the combination of
phospholane and phosphoramidite motifs constitute a new
valuable entry in the class of P,P’ hybrid ligands and can be
complementary to established ligand classes especially for
asymmetric hydrogenation.
Quinaphoslane ligands L3–L5 were applied in the Ir-catalyzed
hydrogenation of prochiral aryl imines (Scheme 3). The cata-
lysts were generated in situ from [Ir(cod)Cl]2, two equivalents
of the respective ligand, and 5 mol% iodine. In all experiments,
full conversion was obtained under standard conditions
(0.5 mol% catalyst loading, 40 bar, 16 h). The model substrate
N-(1-phenylethyliden)aniline was chosen to benchmark the
ligand performances. Quinaphoslane L3 formed the most ste-
reoselective catalyst to lead to 71% ee (S). Various other imine
derivatives that bear electron-donating and -withdrawing sub-
stituents could be hydrogenated with the same catalyst
system with enantioselectivities that ranged from 44–79% ee
(see Tables S2 and S3 for comprehensive data). Higher enantio-
selectivities in this transformation were obtained, for example,
with phosphine-phosphoramidite (PEAPhos) ligands described
recently.[21]
Experimental Section
General
All reactions were performed under an inert atmosphere of dry
and oxygen-free argon either with the use of standard Schlenk
1
techniques or in a glovebox. H, 13C, and 31P NMR spectra were re-
corded by using Bruker AV 300 and AV 400 spectrometers. The op-
erating frequencies of these spectrometers for NMR measurements
were 300.1 MHz for 1H, 75.5 MHz for 13C, and 121.5 MHz for 31P
1
with the AV 300 spectrometer and 400.1 MHz for H, 100 MHz for
1
13C, and 162 MHz for 31P with the AV 400 spectrometer. For H and
13C{1H} NMR spectroscopy, the chemical shifts (d) are given in ppm
with use of the residual solvent signals as internal standards. For
31P NMR spectroscopy the chemical shift values (d) are given in
ppm relative to 85% phosphoric acid as external standard. The
multiplicities of the signals were assigned by assuming that the
spectra were of first order. The coupling constants (J) are given in
Hertz. For the description of the multiplicity of the signals the fol-
lowing symbols are used: s=singlet, d=doublet, t=triplet, m=
multiplet, br=broad. The signals were assigned based on two-di-
mensional NMR spectra (31P-1H HMBC, 1H-1H COSY, 13C-1H HMBC,
13C-1H HSQC). Mass spectra were recorded by using a Varian 1200 L
Quadrupole GC–MS, Finnigan MAT 8200 (MS and HRMS-EI), or
a Bruker FTICR-Apex III spectrometer (ESI-HRMS). HRMS measure-
ments were performed by using a Finnigan-MAT 95 spectrometer
(EI, 70 eV). The mass of the molecular ion is given. Optical rotations
were measured by using a Jasco P-1020 polarimeter. The concen-
trations used for measuring specific rotations are given as
g/100 mL. Dichloromethane, toluene, and pentane were dried over
alumina with a solvent purification system from Innovative Tech-
nology. THF, Et2O, MeOH, and acetonitrile were distilled and then
dried over molecular sieves. All other organic solvents were
purged with argon for 2 h before use. Deuterated solvents were
degassed through freeze–pump–thaw cycles and stored over mo-
lecular sieves. The compounds (Ra)- or (Sa)-1,1’-binaphthyl-2,2’-di-
oxychlorophosphine,[5] (2R,5R)-1-chloro-2,5-dimethylphospholane,[9]
and 8-[(2R,5R)-2,5-dimethylphospholan-1-yl)quinoline[9] were syn-
thesized according to literature procedures. All other chemicals
were purchased from Sigma–Aldrich, Acros, or Alfa Aesar and used
as received.
Scheme 3. Ir-catalyzed hydrogenation of aryl imines.
Conclusions
A new class of chiral bidentate hybrid phosphorous ligands
that comprises a phospholane and a phosphoramidite donor
has been synthesized from 8-[(2R,5R)-2,5-dimethylphospholan-
1-yl]quinoline through a diastereoselective procedure. We fol-
lowed the synthetic protocol established for the quinaphos li-
gands, and the 1,2-addition of lithium organyls proceeded ex-
clusively from the re-face. The phosphoramidite moiety is then
obtained from the in situ reaction of the resulting lithium
amide with PCl3 followed by condensation with 1,1’-bi-2-naph-
thol or achiral unlinked phenol derivatives in the presence of
a base. The quinaphoslane ligands have been fully character-
ized, and the absolute configuration was assigned by NMR
spectroscopy and DFT calculation.
The application of these ligands in the Rh-catalyzed asym-
metric hydrogenation of 10 different olefins produced good to
excellent enantioselectivities of up to >99% ee with high ac-
tivities with average turnover frequencies of up to 12000 hÀ1.
Notably, even the ligands that lack the additional axial chirality
from the binaphthol backbone at the phosphoramidite site re-
sulted in significant enantioselectivities of up to 84% ee. Prom-
ising results have been obtained in the Rh-catalyzed hydro-
formylation of vinyl arenes (turnover frequency up to 57 hÀ1,
regioselectivity up to 99:1, ee values up to 79%) and in the Ir-
catalyzed asymmetric hydrogenation of acyclic imines with
good activities and enantioselectivities up to 79% ee. Distinc-
tive synergistic effects have been observed between the chiral-
ity at the phospholane moiety and the axial chirality, and
(RCP,RCP,SC2,Ra)-L3 resulted in the same diastereomer in all inves-
tigated applications.
(2R)-8-{(2R,5R)-2,5-Dimethylphospholan-1-yl]-1-[(11bR)-di-
naphtho[2,1-d:1’,2’-f][1,3,2]dioxaphosphepin-4-yl}-2-(butyl-1-
yl)-1,2-dihydroquinoline (L1)
A solution of n-butyllithium (0.64 mL, 1.02 mmol, c=1.6m in
hexane) was added to a solution of 8-[(2R,5R)-2,5-dimethylphos-
pholan-1-yl]quinoline (247.6 mg, 1.02 mmol) in THF (10 mL) over
15 min at À788C. After additional stirring for 1 h at 08C, the reac-
tion mixture was cooled to À208C, and a solution of (Ra)-1,1’-bi-
naphthyl-2,2’-dioxychlorophosphine (357.7 mg, 1.02 mmol) in THF
(4 mL) was added over 20 min by using a syringe pump. The reac-
tion mixture was stirred overnight at RT and then filtered through
a PTFE syringe filter (with luer lock) to remove the lithium chloride.
The volatiles were removed under reduced pressure, and the re-
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maining solid was dried in vacuo to give the title compound
(purity ꢀ90% based on 31P NMR). All attempts to further purify the
compound led to decomposition. Yield: 93% (584 mg,
151.14 ppm (Cq); 31P{1H} NMR (CDCl3, 162 MHz): d=À5.55 (d, JPP
=
188.7 Hz, phospholane), 135.39 ppm (d, JPP =188.7 Hz, phosphor-
amidite); HRMS (EI): m/z: calcd (%) for C45H37NO2P2: 685.22941;
found: 685.22942; [a]2D4 =À799.76 (c=0.5, CH2Cl2).
0.949 mmol). 31P{1H} NMR (CDCl3, 121 MHz): d=À5.94 (d, JPP
=
177.8 Hz, phospholane), 134.99 ppm (d, JPP =177.8 Hz, phosphor-
amidite).
(2S)-8-[(2R,5R)-2,5-Dimethylphospholan-1-yl]-1-{(11bS)-di-
naphtho[2,1-d:1’,2’-f][1,3,2]dioxaphosphepin-4-yl}-2-(naph-
thalen-1-yl)-1,2-dihydroquinoline (L4)
(2R)-8-{(2R,5R)-2,5-Dimethylphospholan-1-yl)-1-((11bS)-di-
naphtho[2,1-d:1’,2’-f][1,3,2]dioxaphosphepin-4-yl}-2-(butyl-1-
yl)-1,2-dihydroquinoline (L2)
A solution of 1-naphthyllithium (1 equiv., 2.7 mL, c=0.312m in
THF) was added at 08C by using a syringe pump to a solution of
The synthesis was performed according to the procedure for L1
using (Sa)-(À)-1,1’-binaphthyl-2,2’-dioxychlorophosphine (purity
ꢀ85% based on 31P NMR). All attempts to further purify the com-
pound led to decomposition. Yield: 89% (559 mg, 0.908 mmol).
31P{1H} NMR (CDCl3, 121 MHz): d=À10.06 (d, JPP =138.6 Hz, phos-
pholane), 138.40 ppm (d, JPP =138.6 Hz, phosphoramidite).
8-[(2R,5R)-2,5-dimethylphospholan-1-yl]quinoline
(310 mg,
0.835 mmol) in THF (10 mL). The reaction mixture was stirred for
1 h at RT and cooled to 08C before a solution of PCl3 (568.3 mg,
4.175 mmol, 5 equiv.) in THF (10 mL) was added by using a syringe
pump. After 1 h stirring at RT, the solvent was removed under re-
duced pressure. The remaining PCl3 traces were removed by azeo-
tropic distillation with toluene (3”10 mL). The resulting PCl2 inter-
mediate 3 was dissolved in CH2Cl2 (5 mL) and added at 08C to a so-
lution of (Sa)-1,1’-binaphthyl-2,2’-diol (227.1 mg, 0.793 mmol,
0.95 equiv.) and NEt3 (422.5 mg, 4.175 mmol, 5 equiv.) in CH2Cl2
(5 mL). After stirring for 1 h at RT, the solvent was removed, and
the crude product was dissolved in THF (10 mL), and filtered
through a plug of basic alumina (20 mL). The volatiles were re-
moved under reduced pressure, and the remaining solid was dried
in vacuo to give the title compound (purity ꢀ85% based on
31P NMR). Yield: 81% (462.8 mg, 0.675 mmol). Analytically pure
product was obtained after column chromatography (pentane/
ethyl acetate 9:1, Rf =0.48), yield: 15% (85.7 mg). Both materials
with different purities have been applied in catalysis, which led to
(2S)-8-[(2R,5R)-2,5-Dimethylphospholan-1-yl]-1-{(11bR)-di-
naphtho[2,1-d:1’,2’-f][1,3,2]dioxaphosphepin-4-yl}-2-(naph-
thalen-1-yl)-1,2-dihydroquinoline (L3)
A solution of 1-naphthyllithium (1 equiv., 1.7 mL, c=0.280m in
THF) was added at 08C by using a syringe pump to a solution of
8-[(2R,5R)-2,5-dimethylphospholan-1-yl]quinoline
(114.5 mg,
0.48 mmol) in THF (10 mL). The reaction mixture was stirred for 1 h
at RT and cooled to 08C before a solution of PCl3 (329.6 mg,
2.40 mmol, 5 equiv.) in THF (10 mL) was added by using a syringe
pump. After stirring for 1 h at RT, the solvent was removed under
reduced pressure. The remaining PCl3 traces were removed by
azeotropic distillation with toluene (3”10 mL; a KOH trap and
a cold trap were used in series to protect the vacuum pump from
HCl/PCl3). The resulting PCl2 intermediate 3 was dissolved in CH2Cl2
(5 mL) and added at 08C to a solution of (Ra)-1,1’-binaphthyl-2,2’-
diol (134.7 mg, 0.47 mmol, 0.98 equiv.) and NEt3 (242.9 mg,
2.4 mmol, 5 equiv.) in CH2Cl2 (5 mL). After stirring for 1 h at RT, the
solvent was removed, and the crude product was dissolved in THF
(10 mL) and filtered through a plug of basic alumina (20 mL). The
volatiles were removed under reduced pressure, and the remaining
solid was dried in vacuo to give the title compound (purity ꢀ90%
based on 31P NMR). Yield: 90% (296.2 mg, 0.432 mmol). Analytically
pure product was obtained after washing the solid with Et2O (2”
10 mL), yield: 30% (98.7 mg). Both materials with different purities
have been applied in catalysis, which led to the same activity and
1
the same activity and selectivity. H NMR (CDCl3, 400 MHz): d=1.02
(t, JHH =JPH =8.2 Hz, 3H, CH3), 1.26–1.36 (m, 1H, CH), 1.40 (dd, JHH
=
7.0 Hz, JPH =18.1 Hz, 3H, CH3), 1.55–1.67 (m, 1H, CH2), 2.02–2.18 (m,
2H, CH2), 2.35–2.52 (m, 1H, CH), 2.53–2.69 (m, 1H, CH2), 5.92–5.97
(m, 1H, CH), 5.98–6.04 (m, 1H, CH), 6.05–6.11 (m, 1H, CH), 6.15–
6.21 (m, 1H, Ar-H), 6.56–6.64 (m, 1H, Ar-H), 6.66–6.73 (m, 1H, Ar-
H), 6.84–6.89 (m, 1H, Ar-H), 6.90–6.95 (m, 1H, Ar-H), 6.99–7.11 (m,
5H, Ar-H), 7.16–7.26 (m, 4H, Ar-H), 7.28–7.36 (m, 1H, Ar-H), 7.37–
7.44 (m, 2H, Ar-H), 7.49–7.54 (m, 1H, Ar-H), 7.61–7.65 (m, 1H, Ar-
H), 7.68–7.77 (m, 2H, Ar-H), 7.79–7.83 ppm (m, 1H, Ar-H);
13C{1H} NMR (CDCl3, 150 MHz): d=18.54 (dd, JCP =3.7 Hz, JCP
16.3 Hz, CH3), 19.82 (d, JCP =36.7 Hz, CH3), 33.50 (d, JCP =8.4 Hz,
CH), 36.27 (d, JCP =5.9 Hz, CH2), 38.43 (d, JCP =1.5 Hz, CH), 41.32
(dd, JCP =13.2 Hz, JCP =17.6 Hz, CH), 51.20 (d, JCP =3.7 Hz, CH),
=
121.23 (CH), 122.30 (CH), 122.62 (CH), 122.73 (CH), 123.54 (d, JCP
=
selectivity. 1H NMR (CDCl3, 400 MHz): d=0.99 (dd, JHH =7.0, JPH
=
3.6 Hz, CH), 124.16 (CH), 124.41 (CH), 124.87 (CH), 125.35 (CH),
125.50 (CH), 125.70 (CH), 126.09 (CH), 126.66 (CH), 127.06 (CH),
127.55 (CH), 128.22 (CH), 128.34 (CH), 128.47 (CH), 128.78 (CH),
129.29 (Cq), 130.33 (CH), 130.53 (Cq), 131.47 (Cq), 132.03 (Cq), 132.95
(Cq), 133.64 (Cq), 136.75 (CH), 139.93 (Cq), 149.01 (Cq), 149.07 (Cq),
15.3 Hz, 3H, CH3), 1.22 (dd, JHH =7.0, JPH =24.9 Hz, 3H, CH3), 1.29–
1.43 (m, 1H, CH), 1.51–1.65 (m, 1H, CH), 2.01–2.21 (m, 2H, CH2),
2.37–2.59 (m, 2H, CH2), 5.66–5.74 (m, 1H, CH), 5.76–5.86 (m, 1H,
CH), 6.12–6.19 (m, 1H, CH), 6.30–6.38 (m, 1H, Ar-H), 6.39–6.47 (m,
1H, Ar-H), 6.89–7.33 (m, 10H, Ar-H), 7.35–7.52 (m, 5H, Ar-H), 7.54–
7.61 (m, 1H, Ar-H), 7.69–7.82 (m, 2H, Ar-H), 7.92–8.00 (1H, Ar-H),
8.01–8.09 ppm (m, 1H, Ar-H); 13C{1H} NMR (CDCl3, 75 MHz): d=
19.08 (dd, JCP =4.2 Hz, JCP =16.5 Hz, CH3), 19.77 (d, JCP =36.3 Hz,
CH3), 33.76 (d, JCP =8.9 Hz, CH), 36.39 (d, JCP =7.2 Hz,CH2), 38.34
149.11 ppm (Cq); 31P{1H} NMR (CDCl3, 162 MHz): d=À10.1 (d, JPP
=
150.9 Hz, phospholane), 135.5 ppm (d, JPP =150.9 Hz, phosphorami-
dite); HRMS (EI): m/z: calcd (%)for C45H37NO2P2: 685.22941; found:
685.22977; [a]D24 =À300.35 (c=0.5, CH2Cl2).
(CH2), 40.34 (dd, JCP =12.8 Hz, JCP =19.3 Hz, CH), 51.49 (d, JCP
=
2.9 Hz, CH), 122.13 (d, JCP =2.2 Hz, CH), 122.36 (CH), 123.23 (CH),
123.28 (CH), 123.50 (CH), 124.39 (Cq), 124.47 (CH), 125.38 (CH),
125.45 (CH), 125.71 (CH), 126.03 (CH), 126.63 (CH), 126.83 (CH),
127.01 (CH), 127.39 (CH), 127.70 (CH), 128.11 (CH), 128.35 (Cq),
128.66 (CH), 128.72 (CH), 128.79 (CH), 129.83 (CH), 130.13 (CH),
130.93 (CH), 131.35 (Cq), 131.94 (Cq), 132.96 (Cq), 133.40 (Cq), 133.75
(Cq), 136.97 (CH), 139.44 (Cq), 144.82 (d, JCP =3.8 Hz, Cq), 149.76 (Cq),
(S)-1-(4,8-Di-tert-butyl-2,10-dimethoxydibenzo[d,f][1,3,2]di-
oxaphosphepin-6-yl)-8-[(2R,5R)-2,5-dimethylphospholan-1-
yl]-2-(naphthalen-1-yl)-1,2-dihydroquinoline (L5)
Triethylamine (344 mL, 2.49 mmol) was added to a solution of 3,3’-
di-tert-butyl-5,5’-dimethoxybiphenyl-2,2’-diol (178 mg, 0.497 mmol)
in CH2Cl2 (8 mL) and stirred for 30 min at RT. Subsequently, a solu-
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tion of (S)-1-(dichlorophosphino)-8-[(2R,5R)-2,5-dimethylphospho-
lan-1-yl]-2-(naphthalen-1-yl)-1,2-dihydroquinoline (257.9 mg,
Bis(3,5-dimethylphenyl)-(S)-8-[(2R,5R)-2,5-dimethylphospho-
lan-1-yl]-2-(naphthalen-1-yl)quinolin-1(2H)-ylphosphonite
(L7)
3
0.546 mmol) in CH2Cl2 (8 mL) was added to the reaction mixture
with a syringe within 30 min. The reaction mixture was stirred for
additional 1 h at RT. After removal of the solvent under reduced
pressure, THF (15 mL) was added to the residual solid and it was
flushed through a plug of basic alumina (1=2 cm, h=3 cm). The
volatiles were removed under reduced pressure, and the remaining
solid was dried in vacuo to give the title compound (purity ꢀ87%
based on 31P NMR). Yield: 75%. Analytically pure product could be
obtained after column chromatography (CH2Cl2/n-pentane 1:1, Rf =
0.48), yield: 10% (41.4 mg). Materials of both purities have been
applied in catalysis to obtain the same activity and selectivity.
1H NMR (CDCl3, 400 MHz): d=1.01 (t, JHH =JHP =15.3 Hz, 3H, CH3),
1.09 (s, 9H, CH3), 1.22 (s, 9H, CH3), 1.23–1.33 (m, 1H, CH), 1.26 (dd,
Triethylamine (970 mL, 6.99 mmol) was added to a solution of 3,5-
dimethylphenol (324.5 mg, 2.656 mmol) in CH2Cl2 (10 mL) and
stirred for 30 min at RT. Subsequently, a solution of 3 (660 mg,
1.398 mmol) in CH2Cl2 (10 mL) was added to the reaction mixture
with a syringe within 30 min. The reaction mixture was stirred for
an additional 1 h at RT. After removing the solvent under reduced
pressure, THF (15 mL) was added to the residual solid and it was
flushed through a plug of alumina (1=2 cm, h=3 cm). The vola-
tiles were removed under reduced pressure, and the remaining
solid was dried in vacuo to give the title compound (purity ꢀ90%
based on 31P NMR). Yield: 72% (647 mg, 1.006 mmol). All attempts
to purify the ligand led to decomposition. 31P{1H} NMR (CDCl3,
162 MHz): d=À8.9 (d, JPP =162.3 Hz, phospholane), 128.1 ppm (d,
J
HH =7.0 Hz, JHP =18.3 Hz, 3H, CH3), 1.53–1.62 (m, 1H, CH2), 2.04–
2.19 (m, 2H, CH2), 2.29–2.44 (m, 1H, CH), 2.46–2.59 (m, 1H, CH),
3.67 (s, 3H, OCH3), 3.89 (s, 3H, OCH3), 5.81 (dd, JHH =6.1 Hz, JHH
J
PP =162.3 Hz, phosphoramidite).
=
9.4 Hz, 1H, CH), 5.87 (m, 1H, CH), 6.18 (d, JHH =9.4 Hz, 1H, CH),
6.55 (d, JHH =3.0 Hz, 1H, CH), 6.65 (d, JHH =3.0 Hz, 1H, CH), 6.72 (d,
J
HH =3.0 Hz, 1H, CH), 6.83–6.94 (m, 3H, CH), 7.01–7.09 (m, 2H, CH),
8-[(2R,5R)-2,5-Dimethylphospholanselenid-1-yl]quinoline
((RCP,RCP)-1-Se)
7.14–7.28 (m, 2H, CH), 7.35 (d, JHH =7.3 Hz, 1H, CH), 7.42–7.49 (m,
2H, CH), 7.61 ppm (d, JHH =8.3 Hz, 1H, CH); 13C{1H} NMR (CDCl3,
Elemental Se (98 mg, 1.25 mmol) was added to a solution of
1 (234 mg, 0.97 mmol) in CH2Cl2 (4 mL). The reaction mixture was
stirred for 16 h at RT. After removal of the excess Se by filtration,
the solvent was removed under reduced pressure. The residual
solid could be purified by recrystallization from hot methanol
150 MHz): d=19.2 (dd, JCP =4.4 Hz, JCP =16.9 Hz, CH3), 19.9 (d, JCP
37.7 Hz, CH3), 30.7 (d, JCP =5.1 Hz, tBu), 31.1 (tBu), 32.8 (d, JCP
9.5 Hz, CH), 36.3 (d, JCP =7.3 Hz, CH2), 37.9 (CH2), 39.6 (dd, JCP
14.7 Hz, JCP =24.9 Hz, CH), 52.4 (d, JCP =3.1 Hz, CH), 55.7 (s, OCH3),
55.9 (s, OCH3), 111.9 (s, CH), 112.3 (s, CH), 113.1 (s, CH), 114.1 (s,
CH), 114.9 (s, CH), 115.4 (s, CH), 122.2 (s, CH), 123.1 (s, CH), 123.7 (d,
=
=
=
1
(3 mL) to result in colorless needles. Yield: >99%. H NMR (CDCl3,
400 MHz): d=0.90 (dd, JHH =7.2, JHP =18.9 Hz, 3H, CH3), 1.16 (dd,
J
CP =5.9 Hz, CH), 123.8 (s, CH), 124.9 (s, CH), 125.3 (s, CH), 125.7 (s,
J
HH =6.9, JHP =19.7 Hz, 3H, CH3), 1.79–1.94 (m, 1H, CH2), 2.12–2.40
CH), 126.9 (s, CH), 127.8 (s, CH), 128.4 (s, Cq), 128.5 (s, CH), 128.7 (s,
CH), 133.2 (d, JCP =3.4 Hz, Cq), 133.5 (d, JCP =2.8 Hz, Cq), 133.6 (s,
Cq), 136.3 (s, CH), 139.1 (s, Cq), 140.0 (s, Cq), 143.1 (s, Cq), 143.4 (d,
(m, 2H, CH2), 2.55–2.69 (m, 1H, CH2), 2.99–3.18 (m, 1H, CH), 3.59–
3.75 (m, 1H, CH), 7.46–7.53 (m, 1H, Ar-H), 7.69–7.78 (m, 1H, Ar-H),
7.97–8.05 (m, 1H, Ar-H), 8.22–8.29 (m, 1H, Ar-H), 8.89–8.95 (m, 1H,
Ar-H), 9.05–9.19 ppm (m, 1H, Ar-H); 31P{1H} NMR (CDCl3, 121 MHz):
d=68.4 (s), 68.4 ppm (d, JPSe =689 Hz).
J
CP =3.0 Hz, Cq), 143.6 (s, Cq), 143.8 (s, Cq), 143.9 ppm (s, Cq);
31P{1H} NMR (CDCl3, 162 MHz): d=À6.1 (d, JPP =199.2 Hz, phospho-
lane), 138.9 ppm (d, JPP =199.2 Hz, phosphoramidite); HRMS (EI):
m/z: calcd (%) for C47H53NO4P2: 757.34444; found: 757.34470;
[a]2D0 =À148,77 (c=0.5, CH2Cl2).
General procedure for the synthesis of quinaphoslane rhodi-
um complexes
HBF4·Et2O (48 mL, 0.12 mmol, 1 equiv.) was added to a solution of
Bis[3,5-bis(trifluoromethyl)phenyl]-(S)-8-[(2R,5R)-2,5-dime-
thylphospholan-1-yl]-2-(naphthalen-1-yl)quinolin-1(2H)-yl-
phosphonite (L6)
(acetylacetonato)-(1,5-cyclooctadiene)rhodium(I)
(36.9 mg
(0.12 mmol, 1 equiv.) in THF (1.5 mL) at RT. The resulting yellow so-
lution was stirred for an additional 15 min at RT followed by the
dropwise addition of a solution of quinaphoslane ligand (1 equiv.)
in THF (1.5 mL). After 30 min additional stirring at RT, the reaction
mixture was added dropwise into n-pentane (30 mL). The resulting
orange solid was filtered, washed with n-pentane (3”20 mL), and
dried under reduced pressure. Quinaphoslane rhodium complexes
were achieved as yellow-orange solids.
Triethylamine (653 mL, 4.715 mmol) was added to a solution of 3,5-
bis(trifluoromethyl)phenol (423 mg, 1.839 mmol) in CH2Cl2 (10 mL)
and stirred for 30 min at RT. Subsequently, a solution of 3 (445 mg,
0.943 mmol) in CH2Cl2 (10 mL) was added to the reaction mixture
with a syringe within 30 min. The reaction mixture was stirred for
additional 1 h at RT. After removal of the solvent under reduced
pressure, THF (15 mL) was added to the residual solid and it was
flushed through a plug of alumina (1=2 cm, h=3 cm). The vola-
tiles were removed under reduced pressure, and the remaining
solid was dried in vacuo to give the title compound (purity ꢀ89%
based on 31P NMR). Yield: 75% (608 mg, 0.707 mmol). All attempts
to purify the ligand led to decomposition. 31P{1H} NMR (CDCl3,
162 MHz): d=À9.84 (d, JPP =168.1 Hz, phospholane), 125.16 ppm
(d, JPP =168.1 Hz, phosphoramidite); 19F{1H} NMR (CDCl3, 100 MHz):
d=À62.9 (s, CF3), À63.2 ppm (s, CF3).
[Rh(cod)L3]BF4
The title compound was synthesized according to the procedure
above. Yield: 105 mg (0.107 mmol, 73%). 31P{1H} NMR (CDCl3,
121 MHz): d=44.8 (dd, JPP =54.5 Hz, JPRh =131.8 Hz), 138.6 ppm
(dd, JPP =54.2, JPRh =263.9 Hz).
[Rh(cod)L4]BF4
The title compound was synthesized according to the procedure
above. Yield: 98 mg (0.099 mmol, 70%). 31P{1H} NMR (CDCl3,
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Full Papers
121 MHz): d=31.9 (dd, JPP =49.3 Hz, JPRh =137.7 Hz), 144.3 ppm
(dd, JPP =49.3, JPRh =259.5 Hz).
(1.68 mg, 2.5 mmol), the desired ligand (5.5 mmol), and toluene
(2 mL). After 10 min stirring, the resulting solution was transferred
to the autoclave. The autoclave was pressurized with hydrogen
(40 bar) and stirred at RT for 16 h. The pressure was released care-
fully, and the conversion and ee value were determined by HPLC.
[Rh(cod)L5]BF4
The title compound was synthesized according to the procedure
above. Yield: 75 mg (0.071 mmol, 63%). 31P{1H} NMR (CDCl3,
121 MHz): d=41.9 (dd, JPP =54 Hz, JPRh =134 Hz), 138.9 ppm (dd,
Acknowledgements
J
PP =54, JPRh =261 Hz).
We like to thank Dr. Renat Kadyrov (Evonik) and W. C. Heraeus
GmbH for the generous donation of (2R,5R)-1-trimethylsilyl-2,5-di-
methylphospholane and precious metal complexes, respectively,
Dianjun Chen and Ghazi Ghattas for providing various sub-
strates, Ms Brigitte Pütz for the measurement of MS data, Ms
Julia Wurlitzer and Ms Hannelore Eschmann for GC and HPLC
measurements, and Markus Hoelscher for DFT calculations. The
research leading to these results has received funding from the
European Community’s Seventh Framework Program (FP7/2007–
2013) under grant agreement number 246461.
[Rh(cod)L6]BF4
The title compound was synthesized according to the procedure
above. Yield: 76 mg (0.066 mmol, 68%). 31P{1H} NMR (CDCl3,
121 MHz): d=41.9 (dd, JPP =54 Hz, JPRh =134 Hz), 138.9 ppm (dd,
J
PP =54, JPRh =261 Hz).
[Rh(cod)L7]BF4
The title compound was synthesized according to the procedure
above. Yield: 84 mg (0.089 mmol, 75%). 31P{1H} NMR (CDCl3,
121 MHz): d=41.8 (dd, JPP =49 Hz, JPRh =130 Hz), 128.1 ppm (dd,
Keywords: asymmetric catalysis · hydrogenation · iridium · p
ligands · rhodium
J
PP =49 Hz, JPRh =267 Hz).
[1] A. Bçrner, Phosphorus Ligands in Asymmetric Catalysis, Wiley-VCH, Wein-
heim, 2008.
General procedure for asymmetric C=C hydrogenation
[2] J. Wassenaar, J. N. H. Reek, Org. Biomol. Chem. 2011, 9, 1704–1713.
[3] a) G. Franciò, F. Faraone, W. Leitner, Angew. Chem. Int. Ed. 2000, 39,
1428–1430; Angew. Chem. 2000, 112, 1486–1488; b) S. Burk, G. Franciò,
W. Leitner, Chem. Commun. 2005, 3460–3462; c) G. Franciò, F. Faraone,
W. Leitner in Asymmetric Synthesis with Chemical and Biological Methods
(Eds.: D. Enders, K.-E. Jaeger), Wiley-VCH, Weinheim, 2007, pp. 250–
277; d) T. Pullmann, B. Engendahl, Z. Zhang, M. Hçlscher, A. Zanotti-
Gerosa, A. Dyke, G. Franciò, W. Leitner, Chem. Eur. J. 2010, 16, 7517–
7526.
[4] For selected examples see: a) J.-D. Huang, X.-P. Hu, Z.-C. Duan, Q.-H.
Zeng, S.-B. Yu, J. Deng, D.-Y. Wang, Z. Zheng, Org. Lett. 2006, 8, 4367–
4370; b) K. A. Vallianatou, I. D. Kostas, J. Holz, A. Bçrner, Tetrahedron
Lett. 2006, 47, 7947–7950; c) J. Wassenaar, J. N. H. Reek, Dalton Trans.
2007, 3750–3753; d) J. Wassenaar, S. van Zutphen, G. Mora, P. Le Floch,
M. A. Siegler, A. L. Spek, J. N. H. Reek, Organometallics 2009, 28, 2724–
2734; e) M. Eggenstein, A. Thomas, J. Theuerkauf, G. Franciò, W. Leitner,
Adv. Synth. Catal. 2009, 351, 725–732; f) T. M. Konrad, P. Schmitz, W.
Leitner, G. Franciò, Chem. Eur. J. 2013, 19, 13299–13303.
A 10 mL stainless-steel autoclave equipped with a glass inlet and
a magnetic stirring bar was charged under an argon atmosphere
with the substrate (1.5 mmol). The desired Rh complex (1.5 mmol)
was added by syringe as a stock solution in CH2Cl2 or MeOH. The
total amount of solvent was adjusted to 2 mL by the addition of
the appropriate quantity of the same solvent, and the autoclave
was pressurized with hydrogen. The reaction was started by
switching on the stirrer. The reaction mixture was stirred at RT for
the desired reaction time, and then the pressure was released care-
1
fully. The conversion was determined by H NMR spectroscopy of
the concentrated reaction mixture. The ee value was determined
by chiral GC or HPLC analysis after filtration through a plug of
silica. The absolute configurations of the hydrogenation products
were assigned by comparison of the sign of optical rotation with
those reported in the literature.
[5] G. Franciò, C. G. Arena, F. Faraone, C. Graiff, M. Lanfranchi, A. Tiripicchio,
Eur. J. Inorg. Chem. 1999, 1219–1227.
General procedure for asymmetric hydroformylation
[6] a) K. W. Kottsieper, U. Kühner, O. Stelzer, Tetrahedron: Asymmetry 2001,
12, 1159–1169; b) W. Braun, B. Calmuschi, J. Haberland, W. Hummel, A.
Liese, T. Nickel, O. Stelzer, A. Salzer, Eur. J. Inorg. Chem. 2004, 2235–
2243; c) S. Basra, J. G. de Vries, D. J. Hyett, G. Harrison, K. M. Heslop,
A. G. Orpen, P. G. Pringle, K. von der Luehe, Dalton Trans. 2004, 1901–
1905; d) R. Kadyrov, R. M. Koenigs, C. Brinkmann, D. Voigtlaender, M.
Rueping, Angew. Chem. Int. Ed. 2009, 48, 7556–7559; Angew. Chem.
2009, 121, 7693–7696; e) K. Matsumura, H. Shimizu, T. Saito, H. Kumo-
bayashi, Adv. Synth. Catal. 2003, 345, 180–184.
[7] U. Berens, U. Englert, S. Geyser, J. Runsink, A. Salzer, Eur. J. Org. Chem.
2006, 2100–2109.
[8] a) G. M. Noonan, J. A. Fuentes, C. J. Cobley, M. L. Clarke, Angew. Chem.
Int. Ed. 2012, 51, 2477–2480; Angew. Chem. 2012, 124, 2527–2530;
b) G. M. Noonan, C. J. Cobley, T. Mahoney, M. L. Clarke, Chem. Commun.
2014, 50, 1475–1477.
A 10 mL stainless-steel autoclave equipped with a glass inlet and
a magnetic stirring bar was charged under an argon atmosphere
with [Rh(CO)2(acac)] (0.5 mL of a 4.0 mm stock solution in toluene,
2.0 mmol) and the desired ligand (8.0 mmol) and stirred at RT for
30 min. Then, the substrate (2.0 mmol) was added by syringe and
the autoclave pressurized with syngas (30 bar, H2:CO 1:1). After
16 h, the autoclave was cooled to RT, and the pressure was re-
1
leased carefully. The conversion was determined by H NMR spec-
troscopy of the concentrated reaction mixture. The ee value and
l/b ratio were determined by chiral GC.
General procedure for asymmetric C=N hydrogenation
[9] J. Holz, A. Monsees, R. Kadyrov, A. Bçrner, Synlett 2007, 2007, 0599–
0602.
A 10 mL stainless-steel autoclave equipped with a glass inlet and
a magnetic stirring bar was charged under an argon atmosphere
with the imine (0.5 mmol) and iodine (0.025 mmol). A Schlenk flask
equipped with magnetic stirring bar was charged with [Ir(cod)Cl]2
[10] For the enantioselective addition of organometallic reagents to quino-
line see: a) F. Amiot, L. Cointeaux, E. J. Silve, A. Alexakis, Tetrahedron
2004, 60, 8221–8231; b) L. Cointeaux, A. Alexakis, Tetrahedron: Asymme-
try 2005, 16, 925–929.
ChemCatChem 2015, 7, 1583 – 1592
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Full Papers
[11] According to the CIP rules, the butyl- and 1-naphthyl-substituted li-
gands have different stereodescriptors at C2 but the same spatial ar-
rangement.
[12] a) A. Korostylev, D. Selent, A. Monsees, C. Borgmann, A. Bçrner, Tetrahe-
dron: Asymmetry 2003, 14, 1905–1909; b) G. Calabrò, D. Drommi, G.
Bruno, F. Faraone, Dalton Trans. 2004, 81–89.
[17] a) U. Hintermair, G. Franciò, W. Leitner, Chem. Eur. J. 2013, 19, 4538–
4547; b) U. Hintermair, T. Hofener, T. Pullmann, G. Franciò, W. Leitner,
ChemCatChem 2010, 2, 150–154; c) Z. Zhang, G. Franciò, W. Leitner,
ChemCatChem, 2015 10.1002/cctc.201500295.
[18] J. G. de Vries, C. J. Elsevier, Handbook of Homogeneous Hydrogenation,
Wiley-VCH, Weinheim, 2007.
[13] E. J. Amigues, C. Hardacre, G. Keane, M. E. Migaud, Green Chem. 2008,
10, 660–669.
[14] E. Zuidema, P. E. Goudriaan, B. H. G. Swennenhuis, P. C. J. Kamer,
P. W. N. M. van Leeuwen, M. Lutz, A. L. Spek, Organometallics 2010, 29,
1210–1221.
[19] Y. Yan, X. Zhang, J. Am. Chem. Soc. 2006, 128, 7198–7202.
[20] S. H. Chikkali, J. I. van der Vlugt, J. N. H. Reek, Coord. Chem. Rev. 2014,
262, 1–15.
[21] Q. Li, C.-J. Hou, X.-N. Liu, D.-Z. Huang, Y.-J. Liu, R.-F. Yanga, X.-P. Hu, RSC
Adv. 2015, 5, 13702–13708.
[15] C. J. Diez-Holz, C. Bçing, G. Franciò, M. Hçlscher, W. Leitner, Eur. J. Org.
Chem. 2007, 2995–3002.
[16] a) J. Holz, O. Zayas, M. Axel, R. Kadyrov, A. Bçrner, Chem. Eur. J. 2006,
12, 5001–5013; b) V. Bilenko, A. Spannenberg, W. Baumann, I. Komarov,
A. Bçrner, Tetrahedron: Asymmetry 2006, 17, 2082–2087; c) T. Hammer-
er, A. Dämbkes, W. Braun, A. Salzer, G. Franciò, W. Leitner, Synthesis
2012, 44, 2793–2797.
Received: January 26, 2015
Revised: March 16, 2015
Published online on April 27, 2015
ChemCatChem 2015, 7, 1583 – 1592
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