Chiral phosphane alkenes (PALs): Simple synthesis, applications in catalysis, and functional hemilability

Article abstract of DOI:10.1002/chem.200501470

A simple synthesis of a chiral phosphane alkene (PAL) involves: 1) palladium-catalyzed Suzuki coupling of 10-bromo-5H-dibenzo[a,d]cyclohepten-5-ol (1) with phenylboronic acid to give quantitatively 10-phenyl-5H-dibenzo[a,d] cyclohepten-5-ol (2); 2) reacti

Full text of DOI:10.1002/chem.200501470

FULL PAPER
DOI: 10.1002/chem.200501470
Chiral Phosphane Alkenes (PALs): Simple Synthesis, Applications in
Catalysis, and Functional Hemilability
Elisabetta Piras, Florian Läng, Heinz Rüegger, Daniel Stein, Michael Wçrle, and
Hansjçrg Grützmacher*[a]
Dedicated to Dr. Herbert Hugl
Abstract: A simple synthesis of a chiral
phosphane alkene (PAL) involves:
1) palladium-catalyzed Suzuki coupling
C
hep
G
U
G
U
A
the hydrogenation of various nonfunc-
tionalized and functionalized olefins
(turnover frequencies (TOFs) of up to
4000 hꢀ1) and moderate enantiomeric
excesses have been achieved (up to
67% ee). [Ir(PhtroppPh)2]OTf reversibly
takes up three equivalents of H2. The
highly reactive octahedral [Ir(H)2-
of 10-bromo-5H-dibenzo
ten-5-ol (1) with phenylboronic acid to
give quantitatively 10-phenyl-5H-di-
benzo[a,d]cyclohepten-5-ol (2); 2) reac-
ACHTRE[UNG a,d]ACHERTUcNG ycloACHRTEhUNG ep-
A
G
A
G
E
G
G
N
tion of 2 with Ph2PCl under acidic con-
ditions to give a racemic mixture of the
(CH2Cl2)(H2-PhtroppPh)2] could be
ACHRTUNEG(OTf)ACHTREUGN
phosphane oxide (10-phe
zo[a,d]cyclohepten-5-yl)di
phane oxide (PhtroppoPh, 3), which is
A
N
isolated and contains two hydrogenated
monodentate H2-PhtroppPh phosphanes,
one CH2Cl2 molecule, one triflate
anion, and two hydrides. Based on this
structure and extensive NMR spectro-
scopic studies, a mechanism for the hy-
drogenation reactions is proposed.
A
G
U
G
U
G
G
G
N
G
separated into enantiomers by using
high-pressure liquid chromatography
(HPLC) on a chiral column; 3) reduc-
tion with trichlorosilane to give the
enantiomerically pure phosphanes (R)-
and (S)-(10-pheACHTREUNGnyl-5H-diACHTREUNbG enACHETRzUNG oAHCERT[GNU a,d]ACHTREcUNG y-
Introduction
Alkenes have become recognized as steering ligands in cat-
alysis. Lemaire and co-workers[1] proposed various h4-1,5-cy-
clooctadienerhodium(i) and -iridium(i) complexes, [M-
ACHTREUNG
(cod)L2]+, to be the active catalysts in transfer hydrogena-
tion reactions.[2] Chiral ligands A–D in which the stereogenic
centers result from asymmetric substitution of a coordinated
alkene (Scheme 1) were recently introduced by Hayashi[3]
and Carreira[4] and their co-workers as well as by our
group[5] and proved to be effective in a wide variety of ho-
[a] Dipl.-Chem. E. Piras, Dr. F. Läng, Dr. H. Rüegger,
Dipl.-Chem. D. Stein, Dr. M. Wçrle, Prof. Dr. H. Grützmacher
Department of Chemistry and Applied Biology
ETH-Hçnggerberg
Scheme 1. Chiral alkenes used as steering ligands in enantioselective cat-
8093 Zürich (Switzerland)
alysis. nbd=norbornadiene; Ph-bnd=2,6-diphenylbicycloACHTREUNG
Fax : (+41)44-633-14-18
diene; dbcot=dibenzoACHTREUNG
E-mail: gruetzmacher@inorg.chem.ethz.ch
norbornene.
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5849

mogeneously catalyzed reactions [1,4-addition of arylboron-
ic acids to a,b-unsaturated carbonyls (Hayashi–Miyaura re-
action), allylic alkylation reactions, kinetic racemate resolu-
tion of allyl carbonates, and hydrogenation, transfer hydro-
genation, and hydroboration reactions].
phosphanes (S)-PhtroppPh ((S)-4) and (R)-PhtroppPh ((R)-4) in
an excellent overall yield (85% based on 1).
The structure of rac-4 was determined by using X-ray
crystallography and the resulting structure is displayed in
Figure 1.[14]
As we have pointed out, phosphane alkene ligands
(PALs) are especially interesting because they are topo-
graphically related to tripod ligands (six-electron donors)
but serve only as four-electron donors.[6,7] 5-Phosphanyl-5H-
dibenzoACHTREUNG
[a,d]cycloheptenes, R1troppR (R denotes the phos-
phorus atom, R1 the C=C-bonded substituent) have been in-
troduced as a new class of very rigid concave-shaped
PALs.[8] A patent has been granted that describes the utility
of this ligand in cyclocarbonylation reactions.[9] We found
tropp-type phosphanes to be excellent ligands in the cross-
coupling of aryl halides with arylboronic acids (Suzuki–
Miyaura coupling)[10] and chiral tropp derivatives E have
been employed in the iridium-catalyzed enantioselective hy-
drogenation of imines.[6] Very recently, the use of the chiral
PAL ligand F in the RhI-catalyzed enantioselective Haya-
shi–Miyaura reaction, which gives biologically active com-
pounds, was reported.[11]
Figure 1. ORTEP view of the S enantiomer of 4. The thermal ellipsoids
are drawn at the 50% probability level. The hydrogen atoms have been
ꢀ
ꢀ
omitted for clarity. Selected bond lengths [Š]: P1 C1 1.894(2), C4 C5
In this paper we describe a compact, simple synthesis of
an enantiomerically pure PAL, its application in enantiose-
lective catalyses, and, in particular, its function as a hemila-
bile ligand.[12]
ꢀ
1.344(2), C4 C16 1.491(2). The bite angle of 4 is 75.58.
The racemic mixture of PhtroppPh (rac-4) was allowed to
react with a variety of rhodium(i) or iridium(i) precursor
complexes (Scheme 3) to give the complexes [Rh-
Results and Discussion
A
ACHTREUNG
Syntheses: In a palladium-catalyzed Suzuki reaction, 10-
ACHTREUNG
bromo-5H-dibenzo
A
tropp complex [Ir(PhtroppPh)2]OTf, which was obtained as a
racemic mixture of the homochiral complexes (S,S)-6 and
(R,R)-6. The ease of the latter reaction is remarkable in
view of the steric encumbrance of the free ligand (cone
angle ꢁ2408).
with phenylboronic acid to give 10-phenyl-5H-dibenzo-
ACHTREUNG[a,d]cyclohepten-5-ol (2) on a multigram scale in 97% yield
(Scheme 2).[13] The subsequent reaction of 2 with Ph2PCl
under acidic conditions gave the oxophosphorane PhtroppoPh
(rac-3), in an Arbuzov-type rearrangement. The enantio-
The S-configured enantiomer (S)-4 was used to synthesize
the chiral complexes (S)-5c and (S,S)-6. All the complexes
were obtained in excellent yields (90–97%) and are crystal-
line stable materials. Note that 5a–c and 6 are examples of
very rare triaryl-substituted alkene complexes. NMR spec-
troscopic data show that the C=
ACHTREUNGmers were very easily separated by using high-pressure
liquid chromatography (HPLC) on a cellulose tris(3,5-dime-
thylphenylcarbamate) (OD-H) column, and subsequent re-
duction with HSiCl3 under standard conditions gave the
Ctrop unit is coordinated to the
rhodium center in 5a–c. This is,
for example, indicated by the
significant coordination shift
(Dd=dcomplexꢀdligand
)
observed
for the tertiary =13CH nucleus
in (S)-5c (DdCH =ꢀ75.6 ppm).
In the bis-tropp iridium com-
plex 6, the C=C double bonds
are less strongly bonded
(DdCH =ꢀ48.6 ppm) as is also
indicated by the results of an
X-ray
structure
analysis
(Figure 2, performed on
single crystal containing a race-
a
Scheme 2. Synthesis of chiral PALs (S)-PhtroppPh ((S)-4) and (R)-PhtroppPh ((R)-4).
5850
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Chiral Phosphane Alkenes
FULL PAPER
ꢀ
AHCTREUNG
have typical lengths (2.267(4) Š).
Catalyzed 1,4-addition of arylboronic acids to a,b-unsaturat-
ed ketones: The enantiomerically pure complex (S)-[Rh
2ACHTREUNG(m2-
OH)2(PhtroppPh)2] (derived in situ from [Rh
2A(m2-Cl)2A(C2H4)4]
and (S)-4 in dioxane/KOH/H2O) is the precursor of the
enantioselective catalyst for the Hayashi–Miyaura reaction
(Scheme 4) and cyclohex-2-enone (7) was converted cleanly
to 3-phenylcyclohexanone (9) (1–5mol% catalyst, 55 8C,
Scheme 3. Synthesis of chiral (PhtroppPh) RhI (5a–c) and IrI complexes
(6). coe=cyclooctene.
Scheme 4. Enantioselective Hiyashi–Miyaura reactions using (S)-
[Rh(PhtroppPh)] complexes as catalysts.
2 h, >85% conversion) and N-benzylmaleimide (8)
(0.1 mol%, 558C, 2 h, >98% conversion) to 1-benzyl-3-phe-
nylpyrrolidine-2,5-dione (10). In both cases, the R-config-
ured products (95% ee for (R)-9, 79% for (R)-10) were ob-
tained in accord with the suggested intermediate I in which
the strongly s-donating phenyl group binds highly stereose-
lectively in the trans position with respect to the p-accepting
C=Ctrop moiety.[3,11,15]
Hydrogenation reactions: We were also interested in the
performance of the [M(PhtroppPh)] complexes as catalysts in
hydrogenation reactions. In previous work we showed that
a
saturated, dihydrogenated di
AHCTREUNG
ACHTREbUNG enACHTUEGzRN oACHTRE[UNG a,d]ACHRTUNEGcyACHERTcUNG loACHTUEGhRN epACHTREUNGtanACHTREUNGyl-
Figure 2. ORTEP plot of (S,S)-[Ir(PhtroppPh)2]OTf ((S,S)-6). The thermal
ellipsoids are shown at the 30% probability level. The R,R isomer, the
hydrogen atoms, the triflate anion, and two molecules of dichloro-
phosphane, H2-tropp, which binds as a monodentate ligand
via the phosphorus atom, may only be dehydrogenated to a
chelating bidentate tropp ligand within the coordination
sphere of RhI and IrI complexes.[16] We also demonstrated
that with strained ligand systems the C=Ctrop unit may be hy-
drogenated in IrI complexes.[17] The RhI complexes 5a–c
showed no detectable reaction with H2, however, the iridium
complex [Ir(PhtroppPh)2]OTf (6) does react readily. Various
NMR spectroscopic experiments have allowed us to make
some suggestions with respect to the rather complicated re-
action sequence that is shown in Scheme 5.
1) In CH2Cl2 as solvent and under conditions in which the
H2 concentration in solution is low, two new 31P resonances
at d=62.5and 39 ppm were detected, in addition to a reso-
nance from unreacted 6 (d=52.9 ppm), which are typical for
the k1,h2- and k1 binding modes, respectively, of the tropp
ACHTREUNGmethane have been omitted for clarity. Selected bond lengths [Š] and
ꢀ
ꢀ
ꢀ
ꢀ
angles [8]: Ir P1 2.263(3), Ir P2 2.271(3), Ir C4 2.40(1), Ir C52.29(1),
ꢀ
ꢀ
ꢀ
ꢀ
Ir C19 2.47(1), Ir C20 2.34(1), Ir ct1 2.24(1), Ir ct2 2.30(1) (ct1=cent-
ꢀ ꢀ
ꢀ ꢀ
roid of C4=C5, ct2=centroid of C19=C20); P1 Ir ct1 88.6(1), ct1 Ir ct2
ꢀ ꢀ
95.1(1), ct2 Ir P2 88.6(1).
ꢀ
mic mixture of 6). The Ir C bonds are quite long, especially
ꢀ
to the quaternary carbon atoms =CPh: Ir1 C4 2.40(1) Š,
ꢀ
Ir1 C19 2.47(1) Š.
Both phosphorus centers adopt a cis position within the
mildly tetrahedrally distorted coordination sphere of the IrI
center (f=248; the angle at the intersection between the
planes running through iridium, phosphorus, and the cen-
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5851

H. Grützmacher et al.
hydride resonances are observed at d=ꢀ13.5(ddd,
2J
A
2J
G
2J
(H,H)=2.5Hz)
and
ꢀ15.3 ppm (ddd, 2J
(P,H)=18.0, 2J(P,H)=9.8, 2J
2.5Hz). The coupling constants indicate that the two hy-
drides adopt a cis position with respect to each 31P nucleus
and to each other. Two-dimensional 13C{1H} HMQC correla-
tion experiments showed that the 1H signals at 2.80 (Hc),
4.33 (Hb), and 4.82 ppm (Ha) (integrating one proton each)
are bonded to sp3 carbon atoms. The related 13C chemical
shifts are 39.8 ppm for CHbHc and 48.2 ppm for CHa. That
is, the C=Ctrop unit of the k1-bonded ligand is hydrogenated.
The other PhtroppPh ligand is unchanged as is evidenced by
1
the singlet in the H NMR spectrum at d=5.18 ppm for the
olefinic proton in the CH=CPh unit. The corresponding 13C
signal appears at 93.5ppm. These spectroscopic data led us
to propose the structure III for this compound. Again, an
additional ligand L (solvent, OTfꢀ) likely occupies the sixth
coordination site in this IrIII cis-dihydride complex.
3) At yet higher H2 concentrations (reached by shaking
the reaction mixtures at 1–4 bar H2), a third species was de-
tected (step c in Scheme 5). At room temperature, a broad
singlet at d=45.0 ppm was observed in the 31P NMR spec-
1
trum and one very broad resonance at ꢀ30.52 ppm in the H
NMR spectrum indicating the presence of hydrides. A two-
dimensional 13C{1H} HMQC experiment clearly showed that
ꢀ
both C=Ctrop units are hydrogenated. In the CPhHa CHbHc
unit, the Ha proton is observed as a broad singlet at d=
3.81 ppm, Hb exhibits a doublet at d=3.22 ppm (2J
ACHTREUNG
2.44 ppm (2J(Hb,Hc)=15.1, 3J
ACHTREGUN ACHRTEU(GN Ha,Hc)=5.5 Hz). Each signal
Scheme 5. Reaction of 6 with H2. L stands for loosely bound unspecified
ligands (solvent molecules) and a, b, c and a’, b’, c’ denote protons in the
hydrogenated PhtroppPh ligand. The racemic mixture of 6 was used for
these experiments and only the S,S isomer is shown. The five steps (a–e)
are mentioned in the main text.
integrates for two protons. The 13C NMR spectrum shows a
resonance at d=39.9 ppm for the CHbHc carbon atom and
at d=47.3 ppm for the CHa unit. The observed line broad-
1
ening in the 31P and H NMR spectra indicate dynamic phe-
1
nomena. Notably, in a two-dimensional H{1H} NOESY cor-
relation experiment, exchange between Ha, Hb, and the hy-
drides was observed. This finding gives a first indication that
the hydrogenation of the C=Ctrop units is reversible. On the
basis of these spectroscopic data, we propose structure 11a
for this complex. Again, labile solvent molecules or the
OTfꢀ anion likely complete the coordination sphere of this
IrIII dihydride diphosphane complex and their exchange
causes the NMR resonances to broaden.
ligand (step a in Scheme 5). The large value of 2J
ACHTRE(UNG P,P)=
316 Hz indicates that both phosphorus centers are in a trans
position. Furthermore, a broad resonance at d=ꢀ13.5ppm
1
in the H NMR spectrum indicates the presence of two hy-
drides. We assigned the structure II to this complex. It is
likely that another ligand L occupies the sixth coordination
site in this IrIII complex and this may be a solvent molecule
or the OTfꢀ counteranion. Exchange of L, a possible mutual
displacement of the C=Ctrop units, and the reversibility of
the H2 addition step (see below) explain the highly fluxional
behavior and the broadened NMR spectroscopy resonances
that made further characterization of II impossible.
4) Decreasing the temperature of solutions of 11a from
298 to 190 K led to significant but reversible changes in the
NMR spectra. A new species, 11b, was reversibly formed
1
(Scheme 5, step d). In the H NMR spectrum, the broad res-
onance at about ꢀ30 ppm at 298 K is replaced by two mul-
2
2) At slightly higher H2 concentrations, another species
III was observed which exhibits two well-resolved doublets
in the 31P NMR spectrum at d=58.2 and 34.9 ppm with a
tiplets at ꢀ29.12 and ꢀ26.33 ppm (2J
(P,H)=14.5, J
G
9.9 Hz). The coupling constants indicate that, again, both
hydrides are in a cis position with respect to the phosphorus
nuclei and to each other. Two separated sets of signals for
Hb, Hc, Hbenz and Hb’, Hc’, Hbenz’ are observed and demon-
strate the nonequivalence of the hydrogenated tropp ligands,
H2-PhtroppPh, at 190 K (Hbenz denotes the benzylic proton in
the a position to the phosphorus atom; the nonequivalence
of the ligands is also clearly seen in the 13C NMR spectrum).
2J
ACHTREUNG(P,P) value of 274 Hz (step b in Scheme 5). Again, the
chemical shifts indicate that the complex contains one tropp
ligand binding in a k1,h2 mode and one ligand coordinated
only via the phosphorus atom in a k1 mode. The P,P cou-
pling constant indicates that the phosphorus centers adopt a
1
trans position. In the H NMR spectrum, two well-resolved
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Chiral Phosphane Alkenes
FULL PAPER
In a 31P{1H} HMQC experiment, long-range coupling of Ha’
to the phosphorus nuclei was observed. These spectroscopic
data suggest that 11b results from 11a by the substitution of
were added as hydrogen scavengers, 6 was recovered in
>90% yield (Scheme 5, step e). That is, the hydrogenation
of the C=Ctrop bonds in 6 is fully reversible and 11c is able
to deliver the three equivalents of hydrogen initially taken
up in the hydrogenation reactions.
ꢀ
one ligand L by an agostic Ir Ha’ interaction. A mutual Ha/
Ha’ displacement is an obvious dynamic process and the
likely reason why these protons are observed as a broad-
ened singlet. That only a singlet at d=49.0 ppm is observed
in the 31P NMR spectrum of 11b is likely due to the fact
that both phosphorus nuclei are fortuitously isochronous.
The structures shown in Scheme 5, especially of 11a, are
strongly supported by the results of a single-crystal X-ray
analysis of the yellow complex 11c (Figure 3), which was ob-
tained by slow diffusion of n-hexane into a hydrogen-satu-
Enantioselective hydrogenation reactions: Therefore 11a–c
are efficient catalysts for the hydrogenation of alkenes and
at 1 bar of H2, room temperature, and with a substrate-to-
catalyst ratio (S/C) of 4000, 1-octene and cyclooctene are
converted to octane and cyclooctane with turnover frequen-
cies (TOFs) of >4000 and 3500 hꢀ1, respectively.[19] The effi-
cacy of the enantiomerically pure complex (S,S)-6 was
tested under comparable conditions in the enantioselective
hydrogenation of itaconic acid (12a) and its esters 12b,c and
14 (Scheme 6 and Table 1). These substrates have previously
been found difficult to hydrogenate with iridium com-
plexes.[20]
By using S/C=10000, an 85% conversion of the dimethyl
ester 12b to dimethyl succinate 13b was achieved after 2 h,
(CH2Cl2)(H2-PhtroppPh)2]
Figure 3. ORTEP plot of (S,S)-[Ir(H)2ACTHERNGU(OTf)ACHTREUGN
(11c); thermal ellipsoids are shown at the 30% probability level. The
R,R isomer, the hydrogen atoms of the H2-PhtroppPh ligands, and a mole-
cule of CH2Cl2 have been omitted for clarity. The hydrogen atoms
bonded to the iridium are shown in calculated positions. Selected bond
ꢀ
ꢀ
ꢀ
lengths [Š] and angles [8]: Ir1 P1 2.315(2), Ir P2 2.313(2), Ir Cl1
ꢀ
ꢀ ꢀ
ꢀ ꢀ
ꢀ ꢀ
2.550(3), Ir O1 2.260(6); O1 Ir P2 92.1(2), O1 Ir P1 94.7(2), P2 Ir P1
ꢀ ꢀ
ꢀ ꢀ
ꢀ ꢀ
172.7(1), O1 Ir Cl1 88.2(2), P2 Ir Cl1 93.5(1), P1 Ir Cl1 89.2(1).
rated solution of 11a.[15] All structural features deduced
from the NMR spectra are observed in the structure of 11c.
That is, two hydrogenated, very bulky H2-PhtroppPh ligands
(cone angle ꢁ2708) bind via the phosphorus centers to an
iridiumACHTREUNG(iii) center and reside in the trans positions of the oc-
tahedral coordination sphere. The two hydrides H1 and H2
(placed in calculated positions) are in cis positions with re-
spect to the phosphorus centers and to each other. The re-
maining two coordination sites in the basal plane are occu-
ꢀ
pied by one of the oxygen atoms of the triflate anion (Ir O
2.260(6) Š) and one of the chlorine atoms of a CH2Cl2 mol-
ecule. The structure shows only minor distortions from an
ideal octahedral form. Complex 11c is only the second ex-
ample of an iridium–methylene chloride complex and the
long Ir···Cl distance (2.551(3) Š) indicates that the CH2Cl2 is
loosely bound.[18]
5) The complexes 11a–c are highly reactive. When solu-
tions of 11a were repeatedly purged with argon at room
temperature, the starting complex 6 was formed after some
time and when simple alkenes like 1-octene or cyclooctene
Scheme 6. Proposed mechanism for the catalytic hydrogenation of al-
kenes with (S,S)-6 as catalyst precursor. L stands for loosely bound un-
specified ligands (solvent molecules).
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5853

H. Grützmacher et al.
Table 1. Substituents X,Y in functionalized olefins and eeꢁs in enantiose-
lective hydrogenation reactions with catalyst (S,S)-6.
Experimental Section
X
Y
ee [%] (configuration)
General techniques: All syntheses were performed in dried glassware
under argon using standard Schlenk techniques. Solvents were freshly dis-
tilled from sodium/benzophenone (THF), sodium/tetraglyme/benzophe-
none (hexane, toluene), or calcium hydride (dichloromethane) prior to
use. Air-sensitive compounds were stored and weighed in an argon-filled
glove box (Braun MB 150 B-G system) and small-scale reactions were
12, 13a
12, 13b
12, 13c
14, 15
CH2COOH
CH2COOMe
CH2COOnBu
NHCOMe
COOH
30 (R)
60 (R)
67 (R)
39 (S)
COOMe
COOnBu
COOMe
performed directly in the glove box. 10-Bromo-5H-di
hepten-5-one was synthesized from dibenzosuberenone following a re-
ported procedure.[21]
ACHTREbUNG enACTHREzUNG oACHTREUNG[a,d]ACHTREUNGcyACHTREUNGclo-
G
ACHTREUNG
with an enantiomeric excess (ee) of 60%. With the same S/
C ratio, the free acid 12a (39% conversion) and the n-butyl
ester 12c (23% conversion) were found to have lower activ-
ities and the products 13a and 13c were obtained with 30
and 67% ee, respectively (see also Table 2 in the Experi-
mental Section). The a-dehydroamino acid ester 14 was con-
verted with a conversion of >99% to 15 at S/C=100, but at
lower catalyst loadings the activity drops to give 23% (S/
C=4000) or 7% conversion (S/C=10000). The enantiose-
lectivity remained unchanged at a moderate 39% ee in
favor of the S-configured isomer.
Characterization: NMR spectra were recorded with Bruker Avance 500,
300, or 250 spectrometers. The chemical shifts (d) were measured accord-
ing to procedures set out by IUPAC and are expressed in ppm relative to
1
tetramethylsilane (TMS) for H and 13C NMR spectra and H3PO4 for 31P
NMR spectra.[22] The exception is for 103Rh, with the frequency reference
X=3.16 MHz. Coupling constants J are given in hertz (Hz) as absolute
values unless specifically stated otherwise. Where a first-order analysis is
appropriate, the multiplicity of the signals is indicated as s, d, t, q, or m
for singlets, doublets, triplets, quartets, or multiplets, respectively. Other-
wise the spin systems are specified explicitly. The abbreviation br is given
for broadened signals. Quaternary carbon atoms are indicated as Cquat
,
quaternary aromatic carbon atoms as Car, and aromatic units as CHar and
CHar unless noted otherwise.
A model explaining the preference for the formation of
the R isomers of 13a–c and the S isomer of 15 is shown at
the bottom of Scheme 6 and was constructed on the basis of
the structure of the [Ir(H)2(H2-PhtroppPh)2] fragment of 11c.
We assume that in the reactive conformation of intermedi-
ate IV, the C=C bond of the substrate lies in the plane with
the hydrides in the C2-symmetric bipyramidal structure of
X-ray crystallographic measurements were performed by using a Bruker
SMART Apex and CCD1k as well as with Stoe IPDS I and IPDS II
area-detector diffractometers. Refinement was carried out using
SHELXL-97[26]
.
IR spectra were recorded with a Perkin–Elmer-Spectrum 2000 FTIR-
Raman spectrometer equipped with a KBr beam splitter (range 500–
4000 cmꢀ1). Solution spectra were measured in a 0.5mm KBr cell; for
solid compounds the ATR technique was applied. The absorption bands
are described as follows: strong (s), very strong (vs), medium (m), weak
(w), or broad (br).
the catalyst. The sterically more demanding
X group
(CH2COOR for 12a–c, NHCOMe for 14) is expected to be
more comfortably placed in the relatively open space below
UV/Vis spectra were measured with the UV/Vis Lambda 19 spectrome-
ter in 0.5cm quartz cuvettes (range 200–600 nm).
ꢀ ꢀ
the phenyl group Ph1 which is coplanar with the P Ir P
The mass spectra of organic compounds were recorded on a Finnigan
MAT SSQ 7000 mass spectrometer.
vector. This assumption is also in accord with the increase in
ee in the order R=H<R=Me<R=nBu observed for the
itaconate esters 12a–c. Rapid oxidative addition of H2 to
the intermediate V, a solvated bis-phosphane iridium com-
plex with the monodentate phosphanes in trans positions,
completes the catalytic cycle.
Gas chromatograms were recorded with a HP Series 6890 gas chromato-
graph on an Agilent 19091J-413 HP-5%5 phenyl methyl siloxane
column (30.0 m, 320 mm, 0.25 mm) or on a Lipodex-E MN 723368.25
chiral column (25.0 m, 259 mm, 0.21 mm).
Melting points were determined with a Büchi melting-point apparatus
and are uncorrected. Samples were prepared in open-glass capillaries.
Syntheses and spectroscopic data
ACHTRE[UGN a,d]cyclohepten-5-ol ( A 500 mL
BrtropOH) (1):
Conclusion
10-Bromo-5H-dibenzo
round-bottomed flask was charged with 10-bromo-5H-dibenzo-
AHCTRE[UNG a,d]cyclohepten-5-one (20.0 g, 70 mmol) and MeOH (200 mL). The solu-
tion was cooled to 08C and subsequently NaBH4 (1.3 g, 35mmol) and a
solution of NaOH (140 mg, 3.5mmol) in water (5mL) was added. The
reaction mixture was allowed to warm to room temperature and stirred
for 18 h. H2O (100 mL) was added to the mixture, leading to the precipi-
tation of 1. Filtration and crystallization from a Et2O/n-hexane (1:2) gave
19.9 g (99% yield) of colorless crystals.
M.p. 126–1318C; 1H NMR (300.1 MHz, CDCl3, 258C, TMS): d=2.46
(brs, 1H; OH), 5.36 (brs, 1H; CHbenz), 7.20–7.35(m, 4H; C Har +CHolefin),
7.39–7.50 (m, 3H; CHar), 7.62–7.90 ppm (m, 3H; CHar); 13C{1H} NMR
(300.1 MHz, CDCl3, 258C, TMS): d=70.3 (br; CHbenz), 121.0 (br; CHar),
121.5(br; CHar), 126.4 (br; CHar), 126.7 (br; CHar), 127.3 (br; CHar),
129.0 (br; CHar), 130.17 (s; CHar), 131.4 (br; Cquat), 132.1 (br; Cquat), 133.8
(br; Cquat), 141.1 (br; Cquat), 141.8 ppm (br; Cquat). The signal for the fifth
quaternary carbon was not observed.
In the reactions described in this work, PALs served as func-
tional hemilabile ligands in the catalytic hydrogenation of
alkenes. Classical hemilabile ligands stabilize a reactive
metal fragment through a rapid intramolecular “on”–“off”
equilibrium,[12]
[M
N
A
(D=inert
donor, Z=labile donor), but their chemical composition re-
mains intact. This is not the case with PALs in hydrogena-
tion reactions. When the activation barriers involved in the
chemical transformation of the ligand are sufficiently high,
an advantage of such chemically functional hemilabile be-
havior may be that the substrate does not have to compete
with the intramolecular donor Z for the vacant coordination
sites at the (catalytically) reactive metal site.
10-Phenyl-5H-dibenzo
round-bottomed flask was charged with 1 (4.0 g, 13.9 mmol) and dime-
thoxyethane (DME) (100 mL). Pd(OAc)2 (93 mg, 0.4 mmol), Ph3P
(349 mg, 1.3 mmol), a degassed aqueous solution of Na2CO3 (9 mL, 2m),
ACHTRE[UGN a,d]cyclohepten-5-ol ( A 250 mL
PhtropOH) (2):
AHCTREUNG
5854
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 5849 – 5858

and PhB(OH)2 (2.0 g, 16.6 mmol) were added to this solution. The reac-
tion mixture was stirred under reflux for 18 h. Then, H2O (30 mL) was
added and 2 was extracted with AcOEt (3”30 mL). The combined or-
ganic phases were dried with Na2SO4, filtered, and all volatile materials
were removed under reduced pressure. The resulting solid was purified
by using flash chromatography (AcOEt/n-hexane 2:8) to give 3.9 g (97%
yield) of the pure product.
M.p. 122–1248C; 1H NMR (250.1 MHz, CDCl3, 258C, TMS): d=2.61
(brs, 1H; OH), 5.44 (s, 1H; CHbenz), 7.05–7.95 ppm (brm, 14H; CHar,
CHolefin); 13C{1H} NMR (75.5 MHz, CDCl3, 258C, TMS): d=70.9 (br;
CHbenz), 120.9 (br; CHar), 125.9 (br; CHar), 126.1 (br; CHar), 127.72
(CHar), 127.9 (br; CHar), 128.34 (CHar), 128.45( CHar), 128.92 (CHar),
129.1 (br, CHar), 129.97 (br; CHar), 132.4 (br; Cquat), 133.6 (br; Cquat),
141.8 (br; Cquat), 142.6 (br; Cquat), 143.3 (br; Cquat), 143.57 ppm (Cquat); MS
(70 eV): m/z (%): 284.0 (100) [M+], 255.0 (44), 207.0 (29) [M+ꢀPh],
179.0 (41).
G
U
Chiral Phosphane Alkenes
FULL PAPER
2
4
4J
144.0 (s; Ctrop), 144.6 ppm (s; Car); 31P{1H} NMR (121.5MHz, CDCl 3,
258C, H3PO4): d=ꢀ13.8 ppm (s); MS (70 eV): m/z (%): 452.3 (5) [M+],
267.2 (100) [Phtrop+], 183.1 (15) [Ph2P+], 77.1 (<4) [C6H5+]; ATR IR
(neat): n˜ =3054–3011 (w; CH stretch), 1481 (s), 1430 (s; C=C stretch),
1095(w), 1025(w), 774 (s), 739 (vs), 695cm ꢀ1 (vs).
CH2Cl2 (1 mL) was added dropwise to a solution of [RhACHTREUNG
(0.08 g, 0.17 mmol) in CH2Cl2 (2 mL). The red solution was stirred for
30 min at room temperature and then the volatile materials were re-
moved under reduced pressure. The red solid was dissolved in CH2Cl2
and layered with n-hexane. After 18 h at room temperature, 0.13 g (90%
yield) of red crystals were isolated.
1
(10-Phenyl-5H-dibenzo
(
A
oxide
M.p. 170–1758C; H NMR (300.1 MHz, CDCl3, 258C, TMS): d=1.42 (m,
PhtroppoPh) (3): A 150 mL Schlenk tube was charged with 2 (3.8 g,
1H; CHcod), 1.65–1.87 (m, 2H; CHcod), 1.99 (m, 1H; CHcod), 2.22–2.67
(m, 4H; CHcod), 3.70 (d, 3J(P,H)=6.1 Hz, 1H; CHolefincod), 3.83 (d, 3J-
ACHTREUNG
13.0 mmol) and THF (70 mL). CF3COOH (3.0 g, 27 mmol) and freshly
distilled Ph2PCl (3.1 g, 14.3 mmol) were added to this solution. The reac-
tion mixture was then stirred at room temperature for 20 h. The reaction
was quenched with a saturated aqueous NaCl/Na2CO3 solution (40 mL).
The phosphine oxide rac-3 was then extracted with THF (3”20 mL). The
organic phase was dried with Na2SO4, filtered, and the volatile materials
removed under reduced pressure. The colorless oil was purified by using
flash chromatography on silica gel (AcOEt/n-hexane 6:4) to provide a
colorless solid in 97% yield (6.3 g).
A
ACHTREUNG
3
CHar), 7.10 (d, JACHTREUNG
7.63 (s, 2H; CHar), 7.82 (d, J=7.9 Hz, 1H; CHar), 7.85–7.95 ppm (m, 2H;
CHar); 13C{1H} NMR (75.5 MHz, CDCl3, 258C, TMS): d=25.9 (s;
CH2,cod), 28.5(s; CH2,cod), 31.4 (s; CH2,cod), 34.5(s; CH2,cod), 56.3 (d, 1J-
ACHRTEUGN ACHTREUNG
(P,C)=21.6 Hz; CHbenz), 82.7 (d, 2J
A
ACHTREUNG
The two enantiomers were separated by preparative high-performance
liquid chromatography (HPLC) (OD-H (cellulose triphenylcarbamate)
column; flow rate: 0.8 mLminꢀ1; eluent: n-hexane/isopropanol 98:2; re-
tention times: (R)-3: 8.0 min, [a]2D0 =ꢀ27.8; (S)-3: 10.4 min, [a]2D0 =20.9).
AHCTREUNG
G
ACHTREUNG
U
+
AHCTREUNG
M.p. 95–1008C; 1H NMR (250.1 MHz, CDCl3, 258C, TMS): d=5.20 (d,
G
JACHTREUNG
2J
ACHTREUNG
AHCTREUNG
A
ACHTREUNG
AHCTREUNG
A
ACHTREUNG
AHCTREUNG
A
ACHTREUNG
AHCTREUNG
ACHTREUNG
n˜ =3049 (w; CH stretch), 2916–2841 (m; CH stretch), 1486 (m), 1436 (m;
A
ACHTREUNG
CC stretch), 1259 (s), 1148 (s), 1028 (vs), 764 (s), 697 (vs), 635 cmꢀ1 (vs).
G
ACHTREUNG
[Rh
ACHTREUNG
A
ACHTREUNG
with [Rh CTHREUNG
A
ACHTREUNG
TlPF6 (72 mg, 0.20 mmol), and CH3CN (3 mL). Immediate evolution of
CO and precipitation of white TlCl were observed. The resulting orange
suspension was then filtered through dry Celite. The filtrate was concen-
trated under reduced pressure yielding an orange solid which was washed
with n-hexane to give 156 mg of 5b (95% yield).
A
JACHTREUNG
ACHTREUNG
31P{1H} NMR (101.3 MHz, CDCl3, 258C, H3PO4): d=26.4 ppm (s); MS
(70 eV): m/z (%): 468.3 (18) [M+], 267.2 (100) [Phtrop+], 77.1 (<4)
[C6H5+]; ATR IR (neat): n˜ =3052–3016 (w; CH stretch), 1597 (w), 1490
(s), 1436 (vs), 1186 (m; P=O stretch), 1112 (s), 695 (vs), 551 cmꢀ1 (vs).
1
M.p. 152–1578C; H NMR (300.1 MHz, CD3CN, 258C, TMS): d=5.80 (d,
2J(P,H)=15.9 Hz, 1H; CHbenz), 6.97–7.06 (m, 2H; CHar), 7.23 (d, 2J-
ACHTREUNG
(10-Phenyl-5H-dibenzo
ACHTREUNG[a,d]cyclohepten-5-yl)diphenylphosphane
AHCTREUNG
(
PhtroppPh) (4): A 250 mL Schlenk tube was charged with (S)-3 (2.0 g,
4.3 mmol) and toluene (100 mL). HSiCl3 (11.5g, 85.0 mmol) was added
to this solution. The reaction mixture was warmed to 908C and stirred
for 18 h. The reaction was quenched with a degassed 20% aqueous
NaOH (6.3m) solution (70 mL) and then the phosphane was extracted
with toluene (3”20 mL). The organic phase was dried with Na2SO4 and
filtered under the exclusion of air. The volatile materials were removed
under reduced pressure and the phosphane was crystallized from CH2Cl2/
n-hexane (1:5). After 18 h at room temperature, 1.75 g (90% yield) of
colorless crystals of (S)-4 precipitated.
AHCTREUNG
3
3
A
ACHTRE(UNG P,C)=11.0 Hz;
AHCTREUNG
A
ACHTREUNG
G
ACHTREUNG
G
ACHTREUNG
M.p. 175–1808C; 1H NMR (300.1 MHz, CDCl3, 258C, TMS): d=4.91 (d,
C
ipsoP), 137.0 (s; Ctrop), 142.1 ppm (s; Car); 31P{1H} NMR (121.5MHz,
CD3CN, 258C, H3PO4): d=ꢀ144.4 (sept, 1J
ACHTRE(UNG P,F)=706.5Hz, 1P; PF 6),
2J
ACHTREUNG(P,H)=5.9 Hz; CHbenz), 6.90 (s; CHar), 6.93 (s; CHar), 7.00–7.23 (m, 9H;
93.8 ppm (d, 1J(Rh,P)=158.2 Hz); 103Rh NMR (12.6 MHz, CD3CN,
ACHTREUNG
CHar), 7.29 (s, 1H; CHolefin), 7.30–7.35(m, 2H; C Har), 7.37–7.57 ppm (m,
258C): d=596.2 ppm (dd, 1J(Rh,P)=158.2, 2J
ACHTERNGU ACHTRE(UNG Rh,H)=2.9 Hz); UV/Vis
10H; CHar); 13C{1H} NMR (75.5 MHz, CDCl3, 258C, TMS): d=56.9 (d,
1J
CHar), 127.7 (d, 3J
(P,C)=6.7 Hz; CHmetaP), 128.3 (s; CHar), 128.6 (s; CHar), 129.0 (s; CHar),
129.6 (d, J(P,C)=3.0 Hz; CHtrop), 129.7 (d, J(P,C)=1.8 Hz; CHtrop), 129.8
(d, J(P,C)=3.2 Hz; CHtrop), 130.7 (d, J
(P,C)=1.7 Hz; CHtrop), 133.5(d, 2J-
ACHTREUNG
(THF): l=284.0 nm; ATR IR (neat): n˜ =3049–2929 (w; CH stretch),
1575 (w), 1484 (m), 1436 (m), 1285 (brs), 1099 (m), 831 (vs), 741 (s),
697 cmꢀ1 (s).
ACHTREUNG
ACHTREUNG
A
N
A
N
(MeCN)(PhtroppPh)] (5c): A mixture
ACHTREUNG
N
G
2A(m2-Cl)2A(C2H4)4] (9 mg, 23 mmol) and (S)-4 (21 mg, 46 mmol) in
Chem. Eur. J. 2006, 12, 5849 – 5858
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5855

H. Grützmacher et al.
THF (1 mL) was stirred for 1 h at room temperature. The solvent was re-
moved and [Rh2A
(m2-Cl)2(PhtroppPh)2] was precipitated from CH2Cl2/n-
1H NMR (500.2 MHz, CD2Cl2, ꢀ838C, TMS): d=ꢀ29.12 (q, 2J
ACHTREUNG
N
14.5, 2J
G
(P,H)=14.5, 2J
ACHRTEUNG ACHTREUNG
hexane (1:5) as an orange powder (25 mg, 93%). The NMR spectra were
recorded in CD3CN, which caused the formation of [RhCl-
9.9 Hz, 1H; Hhydride), 1.98 (d, J=13.5Hz, 1H; C Hc’), 2.15(d, J=12.8 Hz,
1H; CHc), 3.01 (d, J=10.4 Hz, 1H; CHb’), 3.19 (d, J=10.7 Hz, 1H; CHb),
3.33 (s, 2H; CHa’ +CHa), 5.50 (brs, 1H; CHbenz’), 5.67 ppm (brs, 1H;
CHbenz); 13C NMR (125.8 MHz, CD2Cl2, ꢀ838C, TMS): d=39.5(s, 1C;
CHCHb’Hc’), 40.7 (s, 1C; CHCHbHc), 47.1 (s, 1C; CHCHa+CHa’), 55.9 (1C;
CHbenz), 56.7 ppm (1C; CHbenz’); 31P{1H} NMR (202.5MHz, CD 2Cl2,
ꢀ838C, H3PO4): d=49.0 ppm (s).
ACHTREUNG
(CD3CN)(PhtroppPh)].
1H NMR (300.1 MHz, CDCl3, 5 % CDCN, 258C, TMS): d=4.81 (d, 2J-
3
ACHTREUNG
AHCTREUNG
JACHTREUNG
5
%
J
A
Catalyses
3
AHCTREUNG
1,4-Addition of PhB(OH)2 to cyclohex-2-enone (7): A solution of [Rh2-
ACHRTE(UNG m2-Cl)2ACHTREU(GN C2H4)4] (10 mg, 26 mmol) and (S)-4 (24 mg, 53 mmol) in 1,4-diox-
A
ACHTREUNG
ane (3 mL) was stirred for 15min at room temperature and then KOH
(0.3 mL of a 1.7m solution, 0.5mmol) was added and the mixture stirred
for a further 5min. PhB(OH) 2 (370 mg, 3.0 mmol) was added to the re-
sulting orange solution and after 5min of stirring cyclohex-2-enone ( 7)
(103 mg, 1.0 mmol) was added. The mixture was kept at 558C for 2 h
whereby the conversion was followed by GC (capillary HP-5: 90 8C for
A
ACHTREUNG
G
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
140.4 (m; Car), 140.8 (m; Car), 148.0 ppm (Car). The quaternary olefinic
carbon atom was not observed. 31P{1H} NMR (121.5MHz, CDCl 3, 5 %
3 min, then heating to 1808C at
a ; flow rate:
rate of 38Cminꢀ1
1.6 mL H2 minꢀ1; retention times: 7: 2.93 min; 9: 18.6 min). Under these
conditions, the following conversions were obtained for various catalyst
loadings: 5mol%: 86%; 3 mol%: 81%; 1 mol%: 51%. From the experi-
ment with 5mol% catalyst loading the product was isolated as follows:
addition of saturated aqueous NaHCO3 (5mL), extraction with tert-butyl
methyl ether (TBME; 3”10 mL), drying with MgSO4, and concentration
under reduced pressure left a brown oil that was purified by using flash
chromatography (silica gel, hexane/TBME 1:0.6) to provide 420 mg of 9
as a slightly yellow oil (yield 82%).
CD3CN, 258C, H3PO4): d=99.3 ppm (d, J
[Ir(PhtroppPh)2]OTf (6): A solution of (S)-4 (403 mg, 0.89 mmol) in THF
(5mL) was added dropwise to a solution of [Ir 2A(m2-Cl)2A(coe)4] (200 mg,
0.22 mmol) in THF (5mL). The mixture was stirred for 1 h until the
color of the solution changed from deep red to a very intense dark red.
AgOTf (114 mg, 0.45mmol) was added and the mixture was stirred for
an additional 5h. The suspension was then filtered and the filtrate was
concentrated under reduced pressure. The resulting solid was dissolved in
CH2Cl2 and layered with n-hexane. After 20 h at room temperature,
540 mg (97% yield) of dark-red crystals were obtained.
ACHTRE(UNG Rh,P)=197 Hz).
C
CHTREUNG
The enantiomeric excess (ee 92–95%) was determined by chiral HPLC
(Chiralcel OD-H; eluent: n-hexane/iPrOH 98:2; retention times: (R)-9:
26.3 min; (S)-9: 31.3 min). The major product had the R configuration, as
judged by a comparison with the reported optical rotation: [a]2D0 =+17.3
1
M.p. 168–1738C; H NMR (300.1 MHz, CD2Cl2, 258C, TMS): d=5.18 (m,
2J(P,H)+4J
ACHTREUNG ACHTREUNG(P’,H)=14.0 Hz, 2H; CHbenz), 6.10 (d, J=7.0 Hz, 2H; CHar),
6.27 (t, J=8.8 Hz, 2H; CHar), 6.33 (s, 2H; CHolefintrop), 6.44–6.75(m, 10H;
CHar), 6.89–7.92 ppm (m, 32H; CHar); 13C{1H} NMR (75.5 MHz, CD2Cl2,
(c=0.75in CHCl ).[23]
3
258C, TMS): d=57.3 (m, 1J
(P,Ccis)+2J
6.6 Hz; Colefintrop), 126.5(s; CHar), 127.3–127.6 (m; CHorthoP +CHar), 127.8
(s; CHar), 128.2 (s; CHar), 128.3 (d, J(P,C)=1.4 Hz; CHar), 128.5(s;
CHar), 129.0 (s; CHar), 129.1 (d, 2J
(P,C)=13.8 Hz; CHorthoP), 129.3 (s;
CHar), 129.6 (s; CHar), 129.8 (s; CHar), 130.9 (s; CHar), 131.3 (s; CHar),
132.3 (t, 3J(P,C)=4.3 Hz; CHmetaP), 133.9 (t, 3J
(P,C)=4.8 Hz; CHmetaP),
134.3 (s; CHar), 135.2 (d, J(P,C)=4.1 Hz; Ctrop), 135.3 (d, J(P,C)=3.7 Hz;
Ctrop), 135.6 (d, 1J
(P,C)=12.3 Hz; CipsoP), 137.0 (d, J(P,C)=0.9 Hz; Ctrop),
143.3 ppm (d, J
(P,C)=0.9 Hz; Car); 31P{1H} NMR (121.5MHz, CD 2Cl2,
(P,C)+3J(P’,C)=27.6 Hz; CHbenz), 88.1 (t, 2J-
ACHRTEUNG ACHTREUGN
1,4-Addition of PhB(OH)2 to N-benzylmaleimide (1-benzylpyrrole-2,5-
dione) (8): A solution of [Rh2ACHTRENGU(m2-Cl)2ACHTREU(NG C2H4)4] (5mg, 13 mmol) and (S)-4
(13 mg, 28 mmol) in 1,4-dioxane (2.5mL) was stirred for 15min at room
temperature and then KOH (0.25mL of a 1.0 m solution, 0.25mmol) was
G
ACHTREUNG ACHETRUNG ACHTRE(NUG P,Ctrans)=
(P,Ctrans)=10.6 Hz; CHolefintrop), 115.0 (t, 2J(P,Ccis)+2J
AHCTREUNG
AHCTREUNG
added. The mixture was stirred for
a further 5min. Subsequently
PhB(OH)2 (185mg, 1.5mmol) was added to the orange solution and
then, after 5min of stirring, N-benzylmaleimide (8) (97 mg, 0.5mmol)
was added. The mixture was kept at 558C for 2 h. GC analysis (capillary
HP-5: 90 8C for 3 min, then heating to 1808C at a rate of 48Cminꢀ1; flow
rate: 1.6 mL H2 minꢀ1; retention times: 8: 23.1 min; 10: 34.1 min) of the
crude reaction mixture indicated complete conversion (>98%). Saturat-
ed aqueous NaHCO3 (5mL) was then added. Extraction with TBME
(3”10 mL), drying with MgSO4, and concentration under reduced pres-
sure gave a brown oil which was purified by using flash chromatography
(silica gel, hexane/TBME 1:0.8) to provide 1-benzyl-3-phenylpyrrolidine-
2,5-dione (10) as a colorless solid (isolated yield: 93%). Complete con-
version within 2 h at 558C was also observed with a catalyst loading of
only 0.1 mol%.
G
ACHTREUNG
R
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
258C, H3PO4): d=52.9 ppm (s); UV/Vis (THF): l=368.5nm; ATR IR
(neat): n˜ =3053 (m; CH stretch), 1575 (w), 1481 (m), 1439 (m; CC
stretch), 1263 (s), 1136 (s), 1030 (s), 694 (s), 635(s), 514 cm
ꢀ1
(s).
[Ir(H)2(L2)(H2-PhtroppPh)2] 11a,b (L=CH2Cl2 and/or OTf and/or agostic-
H): Compound rac-6 (20 mg, 0.016 mmol) was dissolved in CD2Cl2
(0.4 mL) in a resealable J-young NMR tube. The tube was cooled in
liquid N2 and the argon atmosphere was replaced with 1 bar of H2. Upon
warming to room temperature (CAUTION: the tube was under approxi-
mately 4 bar of H2), the sample was vigorously shaken and the color of
the solution gradually changed from deep red to yellow. The selected
chemical shifts for 11a listed below were assigned on the basis of two-di-
mensional 13C{1H} HMQC, HMBC, and 31P{1H} COSY NMR experi-
ments.
The enantiomeric excess ee (80%) was determined by means of chiral
HPLC (Chiralcel OD-H: n-hexane/iPrOH 90:10; retention times: (S)-10:
21.1 min; (R)-10: 25.3 min). The major product had the R configuration,
as judged by a comparison with the reported optical rotation:[24] [a]D20
ꢀ50.1 (c=0.82 in CHCl3).
=
1H NMR (500.2 MHz, CD2Cl2, 258C, TMS): d=ꢀ30.52 (brs, 2H;
Hydrogenation of itaconic acid (2-methylenesuccinic acid) (12a): Under
the conditions specified in Table 2, a 50 mL Teflon-sealed Schlenk tube
was charged with a mixture of itaconic acid (131 mg, 1.00 mmol), the sol-
vent (0.6 mL) (see Table 2), and catalyst (S,S)-6 in CH2Cl2 (0.5mL) (for
S/C ratios see Table 2). This mixture was frozen in liquid N2. The reaction
flask was evacuated and purged with 1 bar of H2. Upon warming to room
temperature, whereby the pressure of H2 increased to about 2.5bar, the
color of the solution changed from dark brown to pale yellow. After 2 h
of stirring the solution at room temperature, the conversion was checked
2
3
2
Hhydride), 2.44 (dd, JACHTREUNG(H,H)=15.1, JACHTRE(UGN H,H)=5.5 Hz, 2H; CHc), 3.22 (d, J-
ACHTREUNG
ACHTREUNG
1C; CHCHbHc), 47.3 (s, 1C; CHCHa), 58.6 ppm (d, 1J
ACHTRE(UNG P,C)=60.6 Hz, 1C;
CHbenz); 31P{1H} NMR (202.5MHz, CD 2Cl2, 258C, H3PO4): d=45.0 ppm
(s).
Compound 11b was formed in CD2Cl2 from 11a at low temperatures.
The selected chemical shifts given below were assigned on the basis of
13C{1H} HMQC, HMBC, and 31P{1H} COSY experiments at 190 K.
1
with H NMR spectroscopic analysis by integration of representative sig-
nals of 12a and 13a in [D6]DMSO.
5856
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 5849 – 5858

Chiral Phosphane Alkenes
FULL PAPER
Table 2. Solvent, reaction time, S/C ratio, conversion, and ee for the cata-
lyzed hydrogenation reactions of 12a–c and 14 using (S,S)-6 as catalyst at
a hydrogen pressure of ꢁ2.5bar and T=298 K.
tiomeric excess of 58–67%. The R configuration was the major isomer to
be obtained.
Hydrogenation of 2-acetamidoacrylic acid methyl ester (14): Under the
conditions specified in Table 2, a 50 mL Teflon-sealed Schlenk tube was
charged with 2-acetamidoacrylic acid methyl ester 14 (143 mg, 1.0 mmol),
CH2Cl2 (1.5mL), and various amounts of ( S,S)-6 (100 mmol, 2.5 mmol,
1 mmol, entries 11–13) in CH2Cl2 (0.5mL). The mixture was frozen in
liquid N2 and the flask evacuated and purged with 1 bar of H2. Upon
warming to room temperature, the color of the solution changed from
dark brown to pale yellow. After 2 h of stirring the solution at room tem-
perature, yields and enantioselectivities were determined by means of
Entry
Solvent
t [min]
S/C ratio
Conversion [%]
ee [%]
reactions with itaconic acid (12a)
1
2
3
4
MeOH
THF
MeOH
MeOH
120
120
120
120
200
200
4000
10000
>99
>99
74
30
21
23
39
n.d.[a]
reactions with 2-methylenesuccinic acid dimethyl ester (12b)
5CH
6
2Cl2
CH2Cl2
60
1200
4000
10000
90
8560
60
GC (chiral capillary: Lipodex-E; 808C (3 min); heating rate: 38Cminꢀ1
;
final temperature: 1708C; flow rate: 0.8 mL H2minꢀ1; retention times:
(S)-15: 23.2 min; (R)-15: 23.8 min; 14: 22.6 min).
reactions with 2-methylenesuccinic acid dibutyl ester (12c)
7
8
9
10
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
120
120
120
120
200
500
2000
10000
>99
>99
>99
23
67
n.d.[a]
58
The configuration of the major product was S (by comparison with a
sample of N-acetyl-d-alanine methyl ester (R)-15 purchased from
Bachem).
n.d.[a]
reactions with 2-acetamidoacrylic acid methyl ester (14)
11
12
13
CH2Cl2
CH2Cl2
CH2Cl2
120
120
120
100
4000
10000
>99
23
39
39
39
7
[a] n.d.=not determined.
Acknowledgements
The enantiomeric excess was determined by using the corresponding 2-
methylsuccinic acid dimethyl ester (13b), which was obtained by methyl-
ation of 13a with TMSCHN2 in MeOH/benzene, by GC (chiral capillary:
Lipodex-E, 708C, heating rate: 18Cminꢀ1; final temperature: 1108C; flow
This work was supported by LANXESS AG and the Swiss National Sci-
ence Foundation.
rate: 0.8 mL H2 minꢀ1
; retention times: (S)-13b: 18.6 min; (R)-13b:
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J. Am. Chem. Soc. 1998, 120, 1441.
19.2 min; 12b: 23.7 min).[25] The major isomer had the R configuration.
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Hydrogenation of dimethyl itaconate (2-methylenesuccinic acid dimethyl
ester) (12b): Under the conditions specified in Table 2, a 300 mL Teflon-
sealed Schlenk tube was charged with 12b (entry 5: 316 mg, 2 mmol;
entry 6: 790 mg, 5mmol), CH 2Cl2 (9.5mL), and ( S,S)-6 (0.5mL of a 1m m
solution in CH2Cl2). The solution was frozen in liquid N2 and the argon
atmosphere replaced by 1 bar of H2. Upon warming to room tempera-
ture, whereby the pressure of H2 increased to about 2.5bar, the solution
changed from dark red to colorless. After the indicated reaction times,
yields and enantioselectivities were determined by using GC.
The configuration of the major product was R (by comparison with a
sample of (R)-2-methylsuccinic acid dimethyl ester purchased from
Fluka).
Hydrogenation of dibutyl itaconate (2-methylenesuccinic acid dibutyl
ester) (12c): Under the conditions specified in Table 2, a 50 mL Teflon-
sealed Schlenk tube was charged with dibutyl itaconate (12c) (242 mg,
1.0 mmol), CH2Cl2 (0.5mL), and various amounts of ( S,S)-6 (50 mmol,
20 mmol, 5 mmol, 1 mmol, entries 7–10) in CH2Cl2 (0.5mL). The mixture
was frozen in liquid N2 and the flask evacuated and purged with 1 bar of
H2. Upon warming to room temperature, the color of the solution
changed from dark brown to pale yellow. After 2 h of stirring the solution
at room temperature, the conversion was checked by 1H NMR spectro-
scopic analysis by integration of representative signals of 12c and 13c in
CDCl3. In one experiment (entry 7), the solvent was evaporated and the
resulting orange oil was distilled at 0.02 mbar to provide 2-methylsuccinic
acid dibutyl ester as a colorless liquid (isolated yield: 224 mg, 92%).
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24, 2997.
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1H NMR (300.1 MHz, CDCl3, 258C, TMS): d=0.86 (t, 3J
6H; CH3(Bu)), 1.17 (d, 3J
(H,H)=7.1 Hz, 3H; CH3), 1.21–1.36 (m, 4H;
CH2(Bu)), 1.42–1.55 (m, 4H; CH2(Bu)), 2.29 (dd, 2J(H,H)=16.5, 3J-
(H,H)=5.7 Hz, 1H; CH2), 2.82 (dd, 2J(H,H)=16.5, 3J
(H,H)=8.5Hz,
ACHTRE(UNG H,H)=7.4 Hz,
AHCTREUNG
AHCTREUNG
A
N
ACHTREUNG
1H; CH2), 2.95–3.08 (m, 1H; CH), 4.00–4.13 ppm (m, 2H; OCH2(Bu));
13C{1H} NMR (75.5 MHz, CDCl3, 258C, TMS): d=13.5(CH 3(Bu)), 16.9
(CH3), 19.1 (CH2(Bu)), 30.7 (CH2(Bu)), 35.9 (CH), 37.6 (CH2), 64.0
(OCH2(Bu)), 64.1 (OCH2Bu), 171.3 (C=O), 174.6 ppm (C=O).
To determine the enantiomeric excess, 13c was converted into 13a by
saponification with KOH/H2O in boiling EtOH which was subsequently
methylated with TMSCHN2 to give 13b. The resulting product 13b was
analyzed by means of GC (for conditions, see above), showing an enan-
[9] B. Junghans, M. Scalone, T. A. Zeibig, EP 1078923A2, 2001.
[10] C. Thoumazet, L. Ricard, H. Grützmacher, P. Le Floch, Chem.
Commun. 2005, 1592.
Chem. Eur. J. 2006, 12, 5849 – 5858
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5857

H. Grützmacher et al.
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285365 ((S)-4), CCDC-284999 ((S,S)-6), and CCDC-285000 ((S,S)-
11c) contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/
cif.
[15] In contrast, with the less selective complex [RhACTHERNGU(solv)2ACHTREUNG(
Phdbcot)]+
[13] We applied a slightly modified procedure which gives 1 in a quanti-
tative (>97%) isolated yield; see the Experimental Section for de-
tails.
(see D in Scheme 1) only 63% ee was obtained under comparable
conditions (see ref. [5]).
[16] S. Deblon, L. Liesum, J. Harmer, H. Schçnberg, A. Schweiger, H.
Grützmacher, Chem. Eur. J. 2002, 8, 601.
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Grützmacher, Inorg. Chim. Acta 2004, 357, 1931.
[14] Crystal structure of (S)-4: C33H25P; orthorhombic; space group
P212121; a=11.4415(7), b=13.6491(9), c=15.3552(9) Š; V=
2398(1) Š3; Z=4; 1calcd =1.253 Mgmꢀ3
; crystal dimensions 0.58”
0.51”0.32 mm; Bruker SMART Apex diffractometer; MoKa radia-
tion; 200 K; 2qmax =56.568; 19578 reflections, 5965 independent
(Rint =0.0223), direct methods; full-matrix least-squares refinement
versus F2 with SHELXTL (version 6.12) and SHELXL-97; 307 pa-
rameters, 0 restraints; R1 =0.0389 and wR2 (all data)=0.0971; max/
min residual electron density=0.313/ꢀ0.191 eŠꢀ3. Crystal structure
of (S,S)-6: C67H50F3IrO3P2S; monoclinic; space group P21/n; a=
21.465(5), b=14.328(3), c=22.546(5) Š; b=114.37(1)8; V=
[18] The Ir···Cl distance in [Ir(Cp)ACHERTU(GN CH3)ACHRETGNU(CH2Cl2)(PACHTRE(UNG CH3)3)]BARF is
2.462(3) Š: B. A. Arndtsen, R. G. Bergman, Science 1995, 270, 1970.
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621, 26; b) T. Focken, G. Raabe, C. Bolm, Tetrahedron: Asymmetry
2004, 15, 1693; c) E. Guimet, M. Dieguez, A. Ruiz, C. Claver, Tetra-
hedron: Asymmetry 2004, 15, 2247; d) X. B. Jiang, M. van den Berg,
A. J. Minnaard, B. L. Feringa, J. G. de Vries, Tetrahedron: Asymme-
try 2004, 15, 2223.
[21] G. N. Walker, A. R. Engle, J. Org. Chem. 1972, 37, 4294.
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P. Granger, Pure Appl. Chem. 2001, 73, 1795.
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[24] G. Bettoni, C. Franchini, F. Morlacchi, N. Tangari, V. Tortorella, J.
Org. Chem. 1976, 41, 2780.
6316(2) Š3; Z=4; 1calcd =1.489 Mgmꢀ3
; crystal dimensions 0.31”
0.22”0.18 mm; Bruker SMART Apex diffractometer; MoKa radia-
tion; 200 K; 2qmax =43.948; 26029 reflections, 7679 independent
(Rint =0.0526); direct methods; full-matrix least-squares refinement
versus F2 with SHELXTL (version 6.12) and SHELXL-97; 714 pa-
rameters; 923 restraints; R1 =0.0751 and wR2 (all data)=0.2135;
ꢀ3
max/min residual electron density=4.110/ꢀ1.673 eŠ
.
Crystal
structure of (S,S)-11c: C68H58Cl2F3IrO3P2S; monoclinic; space group
P21/c; a=25.555(4), b=10.265(2), c=25.414(4) Š; b=109.14(1)8;
V=6298(1) Š3; Z=4; 1calcd =1.500 Mgmꢀ3; crystal dimensions 0.4”
0.2”0.1 mm; Bruker SMART PLATFORM diffractometer equip-
ped with CCD Detector; MoKa radiation; 293 K; 2qmax =39.568;
32855 reflections, 5689 independent (Rint =0.1092); direct methods;
empirical absorption correction SADABS (version 2.03); full-matrix
least-squares refinement versus F2 with SHELXTL (version 6.12);
748 parameters; 984 restraints; R1 =0.0418 and wR2 (all data)=
0.0897; max/min residual electron density=0.79/ꢀ0.51 eŠꢀ3. CCDC-
[25] N. Hashimoto, T. Aoyama, T. Shiori, Chem. Pharm. Bull. 1981,
29(5), 1475.
[26] G. M. Sheldrick, SHELXL-97, A program for crystal structure re-
finement, University of Gçttingen (Germany), 1997, release 97-2.
Received: November 27, 2005
Revised: January 12, 2006
Published online: May 23, 2006
5858
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 5849 – 5858