Olefins as steering ligands for homogeneously catalyzed hydrogenations

Article abstract of DOI:10.1002/chem.200400441

Iridium(I) complexes containing a (5H-dibenzo[a,d]cyclohepten-5-yl)- phosphane (tropp^R; R = phosphorus-bound substituent = Ph, Cyc) as a rigid, concave-shaped, mixed phosphane olefin ligand were prepared and tested as catalyst precursors in the

Full text of DOI:10.1002/chem.200400441

FULL PAPER
Olefins as Steering Ligands for Homogeneously Catalyzed Hydrogenations
Pascal Maire, Stephan Deblon, Frank Breher, Jens Geier, Carsten Bˆhler, Heinz R¸egger,
Hartmut Schˆnberg, and Hansjˆrg Gr¸tzmacher*[a]
Abstract: Iridium(i) complexes contain-
ing (5H-dibenzo[a,d]cyclohepten-5-
the olefinic unit in the dibenzo[a,d]cy-
cloheptenyl moiety with (R)- or (S)-
mentholate gave mixtures of diaster-
eomers that could be separated and
isolated in enantiomerically pure form.
Iridium(i) complexes with these ligands
are rare examples of side-on bonded
enolether complexes. In catalytic imine
hydrogenations, complete conversion
(>98%) was reached in all cases (con-
ditions: p[H2] = 50 bar, T = 508C, t =
2 h, substrate/catalyst 100:1). The best
enantiomeric excess (ee
S isomer) was reached with PhN=
CMePh as substrate and the R,R form
=
86%
a
yl)-phosphane (troppR; R = phospho-
rus-bound substituent = Ph, Cyc) as a
rigid, concave-shaped, mixed phos-
phane olefin ligand were prepared and
tested as catalyst precursors in the hy-
drogenation of imines. With the com-
plex [Ir(troppCyc)(cod)]OTf, turnover
frequencies (TOFs) of >6000 hꢀ1 were
reached in the hydrogenation of N-
phenyl-benzylidenamine, PhN=CHPh.
Lower activities (TOF>80 hꢀ1) are ob-
served with N-phenyl-(1-phenylethyli-
of
the
(10-menthyloxy-5H-diben-
zo[a,d]cyclohepten-5-yl)diphenylphos-
phane ligand. The iridium(i) complex
containing the same phosphane gave a
60% ee (S isomer) with the enamide
N-(1-phenylvinyl)acetamide as sub-
strate (conditions: p[H2] = 4 bar, T =
508C, t = 18 h, substrate/catalyst =
50:1). These reactions constitute the
first examples in which chiral olefins
have been used as steering ligands in
catalytic enantioselective hydrogena-
tions.
Keywords:
enantioselectivity
¥
dene)amine,
PhN=CMePh.
Chiral
homogeneous catalysis ¥ hydrogena-
tion ¥ imines ¥ iridium ¥ olefins
tropp-type ligands were prepared in
few simple steps. Monosubstitution of
Introduction
sequently, olefin hydrogenation profits from the poor bind-
ing quality of alkanes to transition metals, from which they
escape by diffusion. When this diffusion process is sup-
pressed, might olefins then be used as steering ligands for
Many scientists would probably not enthusiastically recom-
mend the use of olefins as steering ligands, especially not in
transition-metal-catalyzed hydrogenations of unsaturated
bonds. Indeed, olefins are either subject to chemical changes
or are kinetically labile place holders for so-called ™vacant∫
coordination sites;in either case they are displaced from the
transition metal. However, calculations show that the iridi-
um trihydride olefin complex [Ir(H)3(PH3)2(C2H4)] (I) is
about 65 kJmolꢀ1 more stable than the iridium alkyl com-
plex [Ir(H)2(PH3)2(C2H5)] (II), the first intermediate on the
hydrogenation pathway taken in olefin insertion into one
5]
catalytic hydrogenations?[2
Olefins have interesting electronic properties (that is,
their donor acceptor properties can be varied over a wide
range) and a useful spatial extension for creating asymmetry.
As shown in Scheme 1, binding of a bischelate with an un-
symmetrically substituted olefin H2C=CHR, as in A, will
create a chiral complex. The alternative formulation of such
a metal olefin complex as a metallacyclopropane relates this
situation to chiral tripod complexes B containing three dif-
ferent donor centers.[6] However, while tripod ligands con-
ꢀ
Ir H bond. Note that the product state [IrH(C2H6)(PH3)2]
(III) is even 130 kJmolꢀ1 higher in energy than I, but very
labile towards dissociation into [IrH(PH3)2] + C2H6.[1] Con-
[a] P. Maire, S. Deblon, Dr. F. Breher, J. Geier, C. Bˆhler, H. R¸egger,
H. Schˆnberg, Prof. Dr. H. Gr¸tzmacher
Department of Chemistry and Applied Biosciences
ETH-Hˆnggerberg
Wolfgang-Pauli-Strasse, 8093 Z¸rich (Switzerland)
Fax : (+41)-1-633-103
E-mail: gruetzmacher@inorg.chem.ethz.ch
Scheme 1. Topographical similarity between a bidentate donor-olefin
complex A with dn + 4 valence electrons and a tripod complex B with
dn + 6 valence electrons.
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DOI: 10.1002/chem.200400441
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4198 4205
Table 1. Comparison of TOFs for the hydrogenation of imines 4 and 5 to
the corresponding amines 6 and 7 with catalyst precursors 3a and 3b.
tribute six electrons to the valence electron configuration
and often electronically saturate a metal complex, the ligand
sphere in A acts only as a four-electron donor.
cat: 3a (R = Ph)
cat: 3b (R = Cyc)
In previous work we reported the easily achieved dehy-
drogenation reaction of the phosphane 5-diphenylphosphan-
TOF (4!6) [hꢀ1
TOF (5!7) [hꢀ1
]
]
>2000
82
>6000
76
yl-10,11-dihydro-5H-dibenzo[a,d]cycloheptene,
H2troppPh,
with iridium(i) complexes to give quantitative yields of com-
plexes with the unsaturated 5-diphenylphosphanyl-5H-di-
benzo[a,d]cycloheptene (troppR 1, R = Ph = phosphorus-
bound substituent) as ligand (Scheme 2).[7]
catalyst containing the P,P-di(cyclohexyl)-substituted ligand
troppCyc. A rather low activity–not unusual for imine hy-
drogenations, however–was observed when phenyl(1-phe-
nylethylidene)amine 5 was hydrogenated with 3a or 3b as
catalyst, indicating a marked steric effect on the reaction
rate.
Chiral tropp ligands with unsymmetrically substituted
C=C units were prepared in a few simple steps (Scheme 4).
First, 10-bromodibenzo[a,d]cyclohepten-5-one (8) was trans-
formed with potassium (R)-mentholate into 10-[(1R)-men-
thoxy]dibenzo[a,d]cyclohepten-5-one (90%), which was con-
verted with NaBH4/MeOH into a mixture of the (5R/5S)-
diastereomers of 10-[(1R)-menthoxy]-5H-dibenzo[a,d]cyclo-
hepten-5-ol (94%), and subsequently into a mixture of the
diastereoisomers of the chloro compound, (R,R)-12 and
(S,R)-12. Without further purification, these compounds
were treated with diphenylphosphane to yield the mixture
of diastereoisomers of the menthoxytroppPh phosphanes (R,R)-
13 and (S,R)-13 (81%). To prevent phosphane oxygenation,
the diastereomers were converted into the BH3 adducts, and
these were separated by column chromatography. The free
phosphanes were obtained after deprotection with morpho-
line and crystallization from acetonitrile, as colorless crystals
in enantiomerically pure form (96% (R,R)-13 and 95%
(S,R)-13). The same reaction sequence with potassium (S)-
mentholate gave the phosphanes (R,S)-13 and (S,S)-13.
The enantiomerically pure tetracoordinated 16-electron
complexes (R,R)-15 or (R,S)-15, or their enantiomers
(S,S)-15 and (S,R)-15, respectively (Scheme 5), were ob-
tained quantitatively by treatment of the corresponding
menthoxytroppR phosphanes 13 with [Ir(cod)2]SO3CF3 (2). The
rhodium complex (S,R)-17 was prepared in a similar way
(Scheme 5).
Scheme 2. Dehydrogenation of H2troppR with iridium(i) complexes.
To answer the question motivating this study, iridium
tropp complexes were synthesized and tested as catalyst pre-
cursors in catalytic hydrogenations.
Results
The iridium troppR complexes 3a and 3b were synthesized
in a straightforward and quantitative reaction (Scheme 3,
top) as deep red crystalline substances. For a first check of
As with 3a, cod was cleanly hydrogenated with complexes
15 as catalyst precursors. Enantioselective hydrogenations
were investigated with phenyl(1-phenylethylidene)amine 5
and 18 as substrates. Complete conversion was achieved in
all cases under the given conditions. With (R,R)-15 as cata-
lyst, the S-configured isomer (S)-7 is formed (entry 1,
Table 2) and the observed enantiomeric excess (86% ee) is
in the upper range obtained for this substrate.[5] When the
menthoxy substituent is shifted to the other carbon atom of
the C=Ctrop unit–that is, the stereochemistry at the 5-posi-
tion of the tropp ligand is reversed–and (S,R)-15 is em-
ployed as catalyst, (S)-7 is again obtained, although with a
lower ee. The R-configured amine (R)-7 was obtained with
identical ee values (entries 3, 4, Table 2) when the enantiom-
ers (S,S)-15 and (R,S)-15 containing the S-configured men-
thoxy substituent were used as catalysts. This experiment in-
dicates that the complexes 15 are indeed the precursors to
the catalytic active species. With N-(1-phenylvinyl)aceta-
mide 18 (which has better storage properties than 5) as sub-
Scheme 3. Synthesis of iridium complexes 3a and 3b and catalyzed hy-
drogenations of imines 4 and 5. [a] s/c 1000, p[H2]=50 bar, T=508C,
[s]=1m, THF.
catalytic activity, 3a was dissolved in a THF/cod mixture
(1:1 v/v, cod = 1,5-cyclooctadiene), and under 5 atm H2
complete conversion of cod to cyclooctane was observed.
The C=Ctrop bond remained unaffected and the solution with
the catalyst could be recycled without loss of activity.
Subsequently, the homogeneously catalyzed hydrogena-
j]
tion of the imines[8a 4 and 5 (Scheme 3, bottom) was inves-
tigated, and the results are listed in Table 1.
Excellent activity was found in the hydrogenation of ben-
zylidene aniline 4 to N-phenyl-benzylamine 6 with 3b as the
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H. Gr¸tzmacher et al.
FULL PAPER
strate, the S-configured isomer
(S)-19 was again obtained as
the major product (60% ee)
with the (R,R)-configured cata-
lyst (entry 5, Table 2). However,
in contrast to the previously de-
scribed experiments with 5, the
R-configured isomer (R)-19 was
obtained in 24% ee when the
diastereomer (S,R)-15 served as
catalyst precursor (entry 6,
Table 2).
The rhodium complex 17
showed no catalytic activity
under the given experimental
conditions. After prolonged re-
action times (days), only de-
composition under formation of
rhodium black occurred.
Solid-state and solution struc-
tures
X-ray diffraction studies: To
gain some information about
the conformations of the chiral
ligands in their non-coordinated
and coordinated forms, the
Scheme 4. Syntheses of enantiomerically pure tropp ligands (R,R)-13, (S,R)-13, (S,S)-13, and (R,S)-13. In the
designation of the stereochemistry, the configuration at the benzylic carbon in the dibenzo[a,d]cycloheptene
moiety is given first and the configuration at the ether carbon of the menthoxy group second.
Table 2. Reaction conditions and enantiomeric excesses (ees) obtained in
homogeneously catalyzed imine hydrogenations with complexes 15.
Entry
Cat.
Solvent Substrate
t [h] Yield [%][b] % ee[c]
/product
1[a]
2[a]
3
4
5
(R,R)-15
(S,R)-15
(S,S)-15
(R,S)-15
(R,R)-15
(S,R)-15
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
5
5
5
5
18
18
2
2
2
2
18
18
>98/7
>98/7
>98/7
>98/7
>98/19
>98/19
86 (S)
45 (S)
86 (R)
45 (R)
60 (S)
24 (R)
6
[a] Identical results with isolated and in situ prepared catalyst precursors
from 2 and (R,R)-15 or (S,R)-15. [b] Determined by GC analysis. [c] De-
termined by GC analysis with a chiral stationary phase (Lipodex E).
structures of the phosphanes (R,R)-13 and (S,R)-13 and of
the iridium complex (R,R)-15 were determined by X-ray
structure analysis.[9] We did not obtain suitable crystals of
(S,R)-15, but the structure of the rhodium complex (S,R)-17
was investigated. The results are shown in Figure 1. Structur-
ally characterized examples of vinyl ether complexes of the
late transition metals are rare.[10] While the C4=C5trop unit in
the complex (R,R)-15 binds almost symmetrically to the iri-
ꢀ
ꢀ
dium center (Ir C4 228(1) pm, Ir C5 223.1(9) pm), in the
Scheme 5. Enantioselective catalytic imine hydrogenations with the iridi-
um complexes (R,R)-15, (S,R)-15, (S,S)-15, and (R,S)-15. In the designa-
tion of the stereochemistry, the configuration at the benzylic carbon in
the dibenzo[a,d]cycloheptene moiety is given first and the configuration
at the ether carbon of the menthoxy group second. [a] s/c 100, p[H2]=
50 bar, T=508C. [b] s/c 50, p[H2]=50 bar, T=508C.
ꢀ
rhodium complex 17 the C4 C5 unit of the (R,S)-13 diaster-
eomer is bonded at much longer distances and in a highly
ꢀ
unsymmetrical fashion to the rhodium center (Rh1 C4
231.6(3) pm, Rh1 C5 306.0(1) pm). The 13C NMR data
ꢀ
imply that such a slipping of the metal towards the CH of
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Homogeneously Catalyzed Hydrogenations
4198 4205
Figure 1. A) Structure of the phosphane (R,R)-13. B) Structure of the iridium(i) complex (R,R)-15. C) Structure of the phosphane (S,R)-13. D) Structure
of the rhodium(i) complex 17. Thermal ellipsoids at 30% probability. Selected bond lengths [pm] and angles [8]. Ct1, Ct2, and Ct3 denote the centroids
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
of the coordinated C=Ccod bonds (Ct1, Ct2) or the coordinated C4 C5 bond (Ct3). A) (R,R)-13: P1 C1 190.1(3), C4 C5 132.8(4), C4 O1 137.2(4), O1
ꢀ
ꢀ
ꢀ
C16 143.4(3), H11 H23 ꢁ250, H11 H25 ꢁ350, H5 H21 ꢁ240, H5 H16 ꢁ200; ꢀ8(P) 301.5(1). B) (R,R)-15: Ir P1 226.5(2), Ir C4 228(1), Ir C5
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
223.1(9), Ir Ct1 204(1), Ir Ct2 216(1), Ir Ct3 213(1), P1 C1 187(1), C4 C5 1.46(1), C4 O1 139(1), O1 C16 149(1);P1-Ir-Ct1 93.7(5), Ct1-Ir1-Ct2
83.7(5), Ct2-Ir-Ct3 95.6(5), P1-Ir1-Ct3 92.2(5), C4-O1-C16 116.0(7), ꢀ8(P) 317.6. C) The average of two independent molecules in the unit cell are given
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
for (S,R)-13: P1 C1 188.8(3), C4 C5 134.0(4), C5 O1 136.4(3), O1 C16 144.1(3), H4 H16 ꢁ190, H4 H21 ꢁ265;C5-O1-C16 120.2(2), ꢀ8(P) 301.8(1).
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
17: Rh1 P1 226.9(1), Rh1 C4 231.6(3), Rh1 C5 306.0(1), Rh1 Ct1 201.7(1), Rh1 Ct2 216.5(1), Rh1 Ct3 262.3(1), C4 C5 139.5(4), C5 O1 135.0(3),
ꢀ
ꢀ
ꢀ
O1 C16 145.5(3), H4 H16 ꢁ220, H4 H21 ꢁ200;P1-Rh1-Ct1 92.6(1), Ct1-Rh1-Ct2 85.2(1), Ct2-Rh-Ct3 101.6(1), Ct3-Rh1-P1 80.4(1), C5-O1-C16
122.8(2), ꢀ8(P) 315.5(1).
the CH=COR unit may easily happen in all complexes in
solution. The coordination shift Dd13C (usually to lower fre-
quency) is marginal for the =COR carbon nucleus (<7 ppm,
see data in Table 3), while Dd13C is significantly larger for
=CH (24 31 ppm).
for the phosphanes (R,R)-13 and (S,R)-13 and the rhodi-
um(i) complex (S,R)-17. The NMR data for the iridium com-
plex (S,R)-15 fit nicely with the solid-state structure of the
rhodium complex (S,R)-17;that is, the conformation of the
(S,R)-13 phosphane ligand is probably very similar in both
compounds. For the iridium complex (R,R)-15, however, the
NOESY spectrum indicates the presence of two conformers
in solution. Only the minor component has the structure
shown in Figure 1B, indicated by a weak cross-peak for the
H11 H16 interaction. For the major conformer, a strong
NOE is seen between the olefinic H5 proton and the me-
thine ether proton H16. While this observation is compati-
ble with a structure in which the menthoxy group has rotat-
ed counter-clockwise to a conformation seen in (S,R)-15 and
17, the absence of any contacts between the isopropyl pro-
tons to H5 or the cod protons (which are present in (S,R)-15
and 17) make this conformation unlikely. Weak NOEs are
observed between the iPr protons and the benzo group
proton H11, and this, together with the strong H5 H16
NOE, indicates a structure in which the menthoxy group
has rotated clockwise in order to minimize the steric interac-
tion between the iPr group and the Ir(cod) unit.
Table 3. Selected NMR data for the C=Ctrop units in (R,R)-13, (S,R)-13,
(R,R)-15 , (S,R)-15 , and (S,R)-17.
d
(R,R)-13
(S,R)-13
(R,R)-15
(S,R)-15
(S,R)-17
=CH
=CH
=COR
6.40
105.5
154.6
6.47
108.0
152.8
6.78
74.7
152.7
6.78
80.4
146.4
6.66
84.1
155.5
NMR spectroscopy: With regard to the catalytic reactions, it
was of interest to examine the structures in solution and to
compare them with the solid-state structures. In the 1H
NOESY spectra, intense cross-peaks were found for the
proton proton interactions indicated by dashed lines in
Figure 1, which indicate that the structures of (R,R)-13,
(S,R)-13, and (S,R)-17 are essentially retained in solution.
Furthermore, only one conformer is observed in each case
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H. Gr¸tzmacher et al.
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Lambda 19 spectrometer in 0.5 cm quartz cuvettes. Mass spectra were
taken on a Finnigan MAT SSQ 7000 in the EI (70 eV) mode.
Conclusion
Syntheses
It is evident from the above experiments that the unsym-
metrical substitution at the C=Ctrop bond and the stereogenic
centers in the menthoxy group have an influence on the
stereochemistry in the hydrogenations. The NOESY experi-
ments suggest that the complexes with the (S,R)-configured
ligand 13 are rather rigid and that the iPr group of the men-
thoxy substituent is in proximity to the metal center. Hence,
it may be that the stereochemistry in reactions with the
(S,R)-13 ligand is controlled by the chirality of the menthoxy
group and that the R configuration favors the S configura-
tion in the product (entry 2, Table 2) or at least diminishes
the ee for the R configuration in the product (entry 6,
Table 2). However, the fact that the stereochemistry may be
controlled by the configuration at the coordinated C=Ctrop
bond is clearly demonstrated by the experiments reported in
entries 5 and 6 in Table 2;specifically in complexes with the
R,R-configured ligand, in which the orientation of the men-
thoxy group is more flexible and, importantly, the iPr group
is located away from the metal center. A more detailed
analysis must await a better understanding of iridium-cata-
lyzed hydrogenations.
[Ir(cod)(troppph)]CF3SO3 (3a): A solution of 5-diphenylphosphanyl-5H-
dibenzo[a,d]cycloheptene (troppph, 1a,[7a] 188 mg, 0.50 mmol) in CH2Cl2
(3 mL) was added with vigorous stirring to a solution of [Ir(cod)2]CF3SO3
(2, 278 mg, 0.50 mmol) in CH2Cl2 (3 ml). The resulting dark brown solu-
tion was stirred for an additional 5 min and was then layered with n-
hexane (10 mL). After one day, the product 3a started to crystallize as
deep red, lustrous needles. Yield: 360 mg (88%). M.p.: 190 1958C
1
(decomp); H NMR (300.1 MHz, CD2Cl2): d = 7.64 7.58 (m, 2H;C Har),
7.53 7.43 (m, 2H;C Har), 7.40 7.28 (m, 10H;C Har), 7.15 7.08 (m, 2H;
CHar), 6.98 6.86 (m, 2H;C Har), 6.32 (d, JP, H = 0.7 Hz, 2H;C Htropp), 5.80
2
(d, JP, H = 14.6 Hz, 1H;C HP), 5.57 (brs, 2H;C Hcod), 4.27 (brs, 2H;
CHcod), 2.57 (brm, 4H;C H2cod), 2.11 1.77 (brm, 4H;C H2cod) ppm; 13C
NMR (75.5 MHz, CD2Cl2): d = 136.4 (d, JP, C = 8.2 Hz, 2C; Cquart), 134.1
(d, JP, C = 9.2 Hz, 4C; CHar), 132.4 (d, JP, C = 1.5 Hz, 2C; Cquart), 131.7 (d,
JP, C = 2.4 Hz, 2C; CHar), 130.2 (d, JP, C = 6.1 Hz, 2C; CHar), 129.7 (d, JP, C
= 1.8 Hz, 2C; CHar), 129.5 (2C; CHar), 128.8 (d, JP, C = 10.2 Hz, 4C;
1
CHar), 128.6 (d, JP, C = 1.5 Hz, 2C; CHar), 126.2 (d, JP, C = 53.0 Hz, 2C;
CipsoPh), 109.4 (d, JP, C = 11.3 Hz, 2C; CHcod), 82.7 (2C; CHcod), 80.4 (2C;
CHtropp), 52.1 (d, JP, C = 27.7 Hz, 1C; CHP), 32.5 (d, JP, C = 3.0 Hz, 2C;
CH2cod), 30.3 (brs, 2C; CH2cod) ppm; 31P NMR (121.5 MHz, CD2Cl2): d =
62.4 (s) ppm;IR: n˜
=
2921(w), 1482(w), 1435(w), 1259vs (SO3ꢀ),
1223(m), 1155(s), 1098(w), 1028(vs), 898(w), 865(w), 804(w), 749(m),
694(m), 634(s), 572(w), 559(w) cmꢀ1;UV/Vis (CH 2Cl2): lmax = 320 nm.
[Ir(cod)(troppcyc)]CF3SO3 (3b): A solution of 5-dicyclohexylphosphanyl-
5H-dibenzo[a,d]cycloheptene (troppcyc, 1b, 195 mg, 0.50 mmol) in CH2Cl
(3 mL) was added with vigorous stirring to a solution of [Ir(cod)2]CF3SO3
(2;278 mg, 0.50 mmol) in CH 2Cl2 (3 mL). After layering of the reaction
solution with n-hexane (10 mL), the product 3b crystallized as deep red
needles. Yield: 350 mg (84%). M.p.: 175 1798C (decomp); 1H NMR
(300.1 MHz, CD2Cl2): d = 7.81 7.78 (m, 4H;C Har), 7.64 7.36 (m, 4H;
The experiments described in this work were performed
in an attempt to expand the classes of ligands known to be
usable for homogeneously catalyzed reactions. The question
raised at the beginning can be answered in combination
4]
with Hayashi×s and Carreira×s recent results:[3, yes, olefins
1
CHar), 6.45 (s, 2H;C Htropp), 6.24 (d, JP, H = 13.0 Hz, 1H;C HP), 5.49
can be used as steering ligands in catalysis, even for catalyzed
hydrogenations. The ligands presented here are certainly not
the best choice with respect to their performance. Since,
however, olefins show an enormous electronic flexibility,
like almost no other class of ligands, and furthermore are
present as potential binding sites in many natural products
not yet explored for the purposes of organometallic chemis-
try, a large pool of ligands with potentially better properties
remains to be explored.
5.42 (m, 4H;C Hcod), 2.54 2.19 (m, 8H;C H2cod) 1.75 1.05 (m, 20H;
CH2cyc), 0.50 0.44 (m, 2H;C Hcyc) ppm; 13C NMR (75.5 MHz, CD2Cl2):
d = 136.5 (d, JP, C = 6.3 Hz, 2 C; Cquart), 133.0 (2C; Cquart), 129.7 (2C;
CHar), 129.6 (2C; CHar), 129.3 (d, JP, C = 6.4 Hz, 2C; CHar), 128.8 (2C;
CHar), 106.6 (d, JP, C = 10.7 Hz, 2C; CHcod), 80.9 (2C; CHtropp), 78.5 (2C;
1
1
CHcod), 45.9 (d, JP, C = 24.1 Hz, 1C; CHP), 37.5 (d, JP, C = 24.1 Hz, 2C;
PCHcyc), 33.5 (d, JP, C = 2.9 Hz, 2C; CH2cyc), 30.8 [brs, 2C; CH2cod), 29.8
(brs, 2C; CH2cod), 28.8 (d, JP, C = 3.7 Hz, 2 C; CH2cyc), 27.3 (d, JP, C
=
11.1 Hz, 2C; CH2cyc), 26.7 (d, JP, C = 9.8 Hz, 2 C; CH2cyc), 25.4 (brs, 2C;
CH2cyc) ppm; 31P NMR (121.5 MHz, CD2Cl2): d = 66.4 (s) ppm;IR: n˜ =
2924(m), 2854(w), 1488(w), 1448(w), 1331(w), 1262(s), 1224(m),
1138(s), 1039(s), 853(w), 803(w), 758(m), 634(s), 572(m) cmꢀ1;UV/Vis
ꢀ
(CH2Cl2): lmax = 345 nm;MS (FAB, m/z, %): 689 (100) [M Otf], 581
ꢀ
ꢀ
(10) [M Otf cod].
10-[(1R)-Menthyloxy]-dibenzo[a,d]cyclohepten-5-one (9): 10-Bromodi-
benzo[a,d]cyclohepten-5-one (8; 12.00 g, 42.1 mmol)[11] and potassium
(R)-menthoxylate (8.99 g, 46.3 mmol, freshly prepared from 1.2 equiv
(R)-menthol and 1.1 equiv potassium at 1008C in 1,4-dioxane) were dis-
solved in 1,4-dioxane (150 mL). Gentle warming of the reaction mixture
occurred, and it turned reddish-brown. It was then heated to 1008C and
stirred for 3 h. Subsequently, all volatile components were evaporated
under vacuum (P = 10ꢀ2 Torr). The residue was dissolved in tert-butyl
methyl ether (TBME, 250 mL), and the solution was washed with satu-
rated aqueous NaCl. The separated organic phase was dried over MgSO4
and all volatile components were evaporated under reduced pressure to
leave a yellow oil, which was purified by flash chromatography (FC)
(silica, ethyl acetate (EE)/hexane 1:9). Yield: 13.66 g (90%), yellow oil.
Thin-layer chromatography (TC) (silica, EE/hexane: 1/9): Rf = 0.53; 1H
NMR (300.1 MHz, CDCl3): d = 8.09 (dd, J = 7.9 Hz, 1.3 Hz, 1H;C Har),
8.02 7.96 (m, 2H;C Har), 7.68 7.34 (m, 5H;C Har), 6.47 (s, 1H;C Htropp),
Experimental Section
General: All syntheses were performed under argon by use of standard
Schlenk techniques. All solvents were dried and purified by standard pro-
cedures and were freshly distilled under argon from sodium/benzophe-
none (THF), from sodium/diglyme/benzphenone (n-hexane, toluene), or
from calcium hydride (CH2Cl2) prior to use. Air-sensitive compounds
were stored and weighed in a glovebox (Braun MB 150 B-G system), and
reactions on small scales were performed directly in the glovebox. NMR
spectra were recorded on Avance DPX 300 or Avance DPX 250 systems.
The chemical shifts are given as d values and were referenced against tet-
ramethylsilane (TMS) for 1H and 13C, 85 % H3PO4 for 31P, BF 3¥Et2O for
11B, and CFCl3 for 19F NMR spectra. Coupling constants J are given in
Hertz [Hz] as positive values regardless of their real individual signs. The
multiplicity of the signals is indicated as s, d, t, q, or m for singlets, dou-
blets, triplets, quartets, or multiplets, respectively. The abbreviation br. is
given for broadened signals. Quaternary carbon atoms are indicated as
Cquart, aromatic units as CHar when not noted otherwise. The olefinic pro-
tons and 13C atoms of the C=Ctropp unit in the central seven-membered
ring are indicated as CHtropp and CHtropp, respectively. IR spectra were
measured on a Perkin Elmer 2000 FT-IR spectrometer with a KBr
beamsplitter. The UV/Vis spectra were measured with a UV/Vis/NIR
3
3
3
4.19 (ddd, JH,H = 10.3 Hz, JH,H = 10.3 Hz, JH,H = 4.0 Hz, 1H;OC H),
2.34 2.24 (m, 2H;C Hmenthyl, CH2menthyl), 1.83 0.82 (m, 7H;C Hmenthyl
,
3
3
CH2menthyl), 0.98 (d, JH,H
=
7.0 Hz, 3H;C H3menthyl), 0.94 (d, JH,H
=
3
6.5 Hz, 3H;C H3menthyl), 0.83 (d, JH,H = 7.0 Hz, 3H;C H3menthyl) ppm; 13C
NMR (62.9 MHz, CDCl3):
d
=
195.0 (C=O), 152.8 (=COquart),
138.8(Cquart), 137.1 (Cquart), 134.2 (Cquart), 132.7 (Cquart), 131.6 (CHar), 131.3
(CHar), 129.5 (CHar), 129.3 (CHar), 129.0 (CHar), 128.7 (CHar), 126.5
4202
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 4198 4205

Homogeneously Catalyzed Hydrogenations
4198 4205
(CHar), 126.0 (CHar), 107.7 (CHtropp), 77.4 (OCHmenthyl), 48.2 (CHmenthyl),
39.6 (CH2menthyl), 34.5 (CH2menthyl), 31.4 (CHmenthyl), 26.1 (CHmenthyl), 23.4
(CH2menthyl), 22.1 (CH3menthyl), 20.9 (CH3menthyl), 16.5 (CH3menthyl) ppm;IR:
n˜ = 3064(w), 2955(m), 2923(m), 2869(m), 1707(s), 1648(m), 1620(s),
1594(s), 1558(m), 1447(m), 1386(m), 1369(m), 1301(m), 1251(s),
1200(s), 1130(s), 1085(s), 1040(m), 933(m), 905(m), 826(w), 768(s),
753(s), 700(s);MS (70 eV, m/z,%): 361 (65), 360 (74) [M]+, 223 (65), 222
(100), 194 (80), 176 (39), 165 (76), 139 (18), 83 (66), 69 (45), 55 (56).
The borane adduct (S,R)-14 (1383 mg, 2.54 mmol) was dissolved in mor-
pholine (3 mL), and the solution was stirred for 1 h. The excess of mor-
pholine was then evaporated under vacuum, and the free phosphane was
separated from the aminoborane (BH3¥morpholine) by filtration over alu-
minium oxide N (toluene, Rf >0.9). Concentration to dryness and recrys-
tallization of the residue from CH3CN yielded (S,R)-13 (1280 mg,
2.41 mmol, 95%) as colorless crystals. The other diastereomer (R,R)-13
was obtained analogously from (R,R)-14 (966 mg, 1.77 mmol) in 96%
yield (904 mg, 1.70 mmol).
(5R/S)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-ol ((R,R)-
[(5S)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-yl]diphenyl-
phosphane ((S,R)-13): M.p: 1308C; 1H NMR (300.1 MHz, CDCl3): d =
7.75 (dd, J = 7.5 Hz, J = 1.7 Hz, 1H;C Har), 7.37 7.09 (m, 14H;C Har),
7.02 (ddd, J = 7.3 Hz, J = 7.3 Hz, J = 1.1 Hz, 1H;C Har), 6.97 (d(br), J
10 and (S,R)-10):
A solution of sodium borohydride (577 mg,
15.25 mmol, 55%) and sodium hydroxide (55 mg, 1.38 mmol, 5%) in
water (10 mL) was added to a solution of 10-[(1R)-menthyloxy]-5H-di-
benzo[a,d]cyclohepten-5-one (9) (10.00 g, 27.7 mmol) in MeOH
(500 mL). The reaction mixture was stirred for 3 h at room temperature,
and was then concentrated under vacuum. The resulting yellow oil was
dissolved in Et2O, and this solution was washed with saturated aqueous
NaCl. The organic phase was separated, dried over Na2SO4, and subse-
quently concentrated to dryness. The resulting yellow oil was purified by
medium-pressure chromatography (MPLC) (silica;EE/hexane 1:9),
which resulted in a pure, colorless oil containing both diastereoisomers
(R,R)-10 and (S,R)-10 . Yield: 9.42 g (94%);TC (silica, EE/hexane: 1/9):
Rf = 0.36; 1H NMR (300.1 MHz, CDCl3): d = 7.76 7.63 (brm, 3H;
CHar), 7.48 7.40 (m, 1H;C Har), 7.35 7.16 (m, 4H;C Har), 6.52 (s, 0.5H;
CHtropp), 6.42 (s, 0.5H;C Htropp), 5.26 (brs, 1H;C HP), 4.28 (m, 0.5H;
OCHmenthy), 4.04 (m, 0.5H;OC Hmenthyl), 2.58 (brs, 1H;O H), 2.45 2.31
(m, 2H;C Hmenthyl, CH2menthyl), 1.84 0.82 (m, 16H;C Hmenthyl, CH2menthyl).
The product consists of a 50/50 mixture of both diastereomers. The 13C
resonances are additionally broadened by dynamic exchange between
two isomers, which differ in the position of the hydroxy group in a 5-
endo or 5-exo orientation in the central seven-membered ring. A mere
listing of the signals without any assignments is given here. 13C NMR
(75.5 MHz, CDCl3): d = 153.8, 153.7, 141.4, 139.4, 131.8, 131.7, 129.4,
127.5, 126.7, 126.4, 126.0, 120.8, 108.0, 103.6, 76.6, 70.6, 48.2, 39.9, 39.6,
34.5, 31.4, 31.4, 26.1, 25.9, 23.4, 23.3, 22.2, 22.2, 21.1, 21.0, 16.5 ppm;IR:
n˜ = 3419(m), br, 3065(w), 2953(s), 2923(s), 2867(s), 1615(m), 1564(m),
1484(m), 1455(m), 1370(m), 1283(w), 1241(m), 1188(s), 1131(s),
1086(m), 1039(s), 985(m), 970(m), 904(w), 819(w), 767(s), 750(m),
723(s), 650(m) cmꢀ1;MS (70 eV, m/z, %): 362 (12) [M]+, 224 (96), 207
(30), 195 (51), 179 (100), 178 (73), 165 (48), 152 (15), 83 (35), 69 (16), 55
(41).
2
= 7.0 Hz, 2H;C Har), 6.47 (s, 1H;C Htropp), 4.84 (d, JP,H = 5.6 Hz, 1H;
CHP), 4.28 (ddd, J = 10.4 Hz, J = 10.4 Hz, J = 4.0 Hz, 1H;OC Hmenthyl),
2.73 (d(br), J = 12.3 Hz, 1H;C H2menthyl), 2.50 (m, 1H;C Hmenthyl), 1.89
1.79 (m, 2H;C H2menthyl), 1.75 1.53 (m, 2H;C Hmenthyl, CH2menthyl), 1.33
3
1.09 (m, 3H;C Hmenthyl, CH2menthyl), 1.07 (d, JH,H = 6.5 Hz, 3H;C H3menthyl),
3
3
1.05 (d, JH,H
CH3menthyl) ppm; 13C NMR (75.5 MHz, CDCl3): d
4.9 Hz, COquart), 139.3 (d, JC,P 9.4 Hz; Cquart), 138.4 (d, JC,P
=
7.1 Hz, 3H;C H3menthyl), 1.00 (d, JH,H
= 6.9 Hz, 3H;
=
154.3 (d, JC,P
=
=
=
=
7.9 Hz; Cquart), 137.1 (d, JC,P = 7.6 Hz; Cquart), 136.8 (d, JC,P = 8.5 Hz;
Cquart), 134.5 (d, JC,P = 4.3 Hz; Cquart), 133.8 (CHar), 133.7 (CHar), 133.6
(Cquart), 133.5 (CHar), 133.4 (CHar), 129.7 (d, JC,P = 2.7 Hz; CHar), 129.4 (d,
JC,P
= 3.3; CHar), 129.1 (d, JC,P = 1.5 Hz; CHar), 129.0 (CHar), 128.3
(CHar), 127.8 (2C; CHar), 127.7 (CHar), 127.7 (CHar), 127.6 (CHar), 127.4
(d, JC,P = 1.4 Hz; CHar), 126.2 (CHar), 126.2 (CHar), 126.1 (CHar), 108.0 (d,
1
JC,P = 5.5 Hz; CHtropp), 76.4 (CHOmenthyl), 56.8 (d, JC,P = 20.7 Hz; CHP),
48.4 (CHmenthyl), 40.2 (CH2menthyl), 34.7 (CH2menthyl), 31.5 (CHmenthyl), 26.0
(CHmenthyl), 23.8 (CH2menthyl), 22.4 (CH3menthyl), 21.0 (CH3menthyl), 17.0
(CH3menthyl) ppm; 31P NMR (121.5 MHz, CDCl3): d = ꢀ14.1 (s) ppm;IR:
n˜
= 3053(w), 2953(m), 2915(m), 2865(w), 1952(w), 1810(w), 1621(s),
1564(w), 1490(m), 1453(m), 1432(m), 1383(m), 1246(m), 1204(m),
1130(w), 1087(s), 1041(w), 987(w), 915(m), 809(m), 764(m), 741(s),
694(s), 661(m), 642(m), 615(m) cmꢀ1;MS (70 V, m/z,%): 530 (19) [M]+,
391 (100) [Mꢀmenthyl]+, 345 (6), 207 (74), 183 (14), 178 (28), 108 (6), 83
(25), 69 (15), 55 (46).
[(5R)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-yl]diphenyl-
phosphane ((R,R)-13): M.p. 1478C; 1H NMR (300.1 MHz, CDCl3): d =
7.81 (dd, J = 7.6 Hz, J = 1.7 Hz, 1H;C Har), 7.32 7.08 (m, 14H;C Har),
2
7.02 6.95 (m, 3H;C Har), 6.40 (s, 1H;C Htropp), 4.82 (d, JP, H = 5.8 Hz,
[(5S)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-yl]diphenyl-
phosphane ((S,R)-13) and [(5R)-10-[(1R)-menthyloxy]-5H-dibenzo[a,d]-
cyclohepten-5-yl]diphenylphosphane ((R,R)-13): A mixture of (R,R)-10
and (S,R)-10 (3.25 g, 8.97 mmol) was dissolved in toluene (50 mL) and
cooled to ꢀ158C. At this temperature, thionyl chloride (1.96 mL,
26.9 mmol, 3 equiv) was added dropwise. The solution was allowed to
warm to room temperature and stirred overnight. Subsequently, the
excess of thionyl chloride and all solvents were evaporated under
vacuum. The residue was dissolved in toluene (10 mL) and subsequently
concentrated under vacuum (P = 10ꢀ2 Torr). This procedure was per-
formed twice. Finally, a mixture of the diastereomeric chlorides (R,R)-12
and (S,R)-12 was obtained as a sticky yellow oil. This was dissolved in
toluene (30 mL), and diphenylphosphane (1.754 g, 9.42 mmol, 1.05 equiv)
was added at room temp. The reaction solution was heated for 10 min at
1208C. Subsequently, a saturated aqueous solution of Na2CO3 (20 mL)
was added. The organic layer was separated, and the aqueous phase was
extracted twice with toluene (10 mL). The combined organic phases were
dried over Na2SO4, filtered, and concentrated. The raw material was puri-
fied by column chromatography (under an argon atmosphere, aluminium
oxide N, THF/hexane 1:6, Rf = 0.4). This procedure gave a mixture of
the two diastereomers (R,R)-13 and (S,R)-13 as a colorless oil (3.86 g,
7.27 mmol, 81%).
1H;C HP), 4.40 (ddd, J = 10.3 Hz, J = 10.3 Hz, J = 3.8 Hz, 1H;OC H-
menthyl), 2.84 (brd, J = 12.8 Hz, 1H;C H2menthyl), 2.56 (m, 1H;C Hmenthyl),
1.92 1.73 (m, 3H;C H2menthyl), 1.72 1.56 (m, 1H;C Hmenthyl), 1.34 1.11 (m,
3
3H;C Hmenthyl, CH2menthyl), 1.10 (d, JH,H = 7.0 Hz, 3H;C H3menthyl), 1.04 (d,
3
3JH,H = 6.6 Hz, 3H;C H3menthyl), 0.99 (d, JH,H = 7.0 Hz, 3H;C H3menthyl
)
ppm; 13C NMR (75.5 MHz, CDCl3): d = 154.6 (d, JC,P = 5.2 Hz, =CO-
quart), 139.6 (d, JC,P = 9.4 Hz; Cquart), 138.5 (d, JC,P = 8.2 Hz; Cquart), 138.2
(d, JC,P = 8.2 Hz; Cquart), 137.1 (d, JC,P = 8.5 Hz; Cquart), 134.4 (d, JC,P
4.6 Hz; Cquart), 134.0 (d, JC,P = 4.9 Hz; Cquart), 133.8 (CHar), 133.7 (CHar),
133.5 (CHar), 133.5 (CHar), 129.5 (d, JC,P = 2.7 Hz; CHar), 129.2 (d, JC,P
=
=
3.3, CHar), 129.1 (CHar), 128.8 (d, JC,P = 1.5 Hz; CHar), 128.2 (CHar),
128.2 (CHar), 127.8 (CHar), 127.8 (CHar), 127.7 (CHar), 127.6 (CHar), 127.0
(d, JC,P = 1.4 Hz; CHar), 126.2 (CHar), 126.1 (CHar), 125.9 (CHar), 105.5
(d, JC,P = 5.5 Hz; CHtropp), 76.3 (CHOmenthyl), 56.9 (d, JC,P = 20.7 Hz;
CHP), 48.1 (CHmenthyl), 39.9 (CH2menthyl), 34.7 (CH2menthyl), 31.6 (CHmenthyl),
26.2 (CHmenthyl), 23.3 (CH2menthyl), 22.3 (CH3menthyl), 21.1 (CH3menthyl), 16.2
(CH3menthyl) ppm; 31P NMR (121.5 MHz, CDCl3): d = ꢀ12.8 (s) ppm;IR:
n˜ = 3058(w), 3016(w), 2956(m), 2920(m), 2867(w), 1965(w), 1618(s),
1566(m), 1490(m), 1450(w), 1435(m), 1386(m), 1245(s), 1208(s),
1160(w), 1132(m), 1089(s), 1043(m), 914(m), 811(m), 772(m), 745(s),
717(m), 696(s), 661(m), 641(m), 615(w) cmꢀ1
.
[(5S)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-yl]diphenyl-
1
A borane-dimethylsulfide solution (3.40 mL, 2.0m in toluene, 6.80 mmol)
was added dropwise at ꢀ158C to a mixture of (R,R)-13 and (S,R)-13
(3.61 g, 6.80 mmol) in toluene (20 mL). The solution was allowed to
warm to room temperature and was stirred for one hour. Afterwards the
solvent was evaporated under vacuum and both diastereomeric borane-
phosphane adducts were separated by FC (silica toluene/hexane 1:1).
(S,R)-14: Yield 1520 mg (41%), TC (silica, toluene Rf = 0.71). (R,R)-14:
Yield: 940 mg (25%), TC (silica, toluene, Rf = 0.66).
phosphane¥BH3 ((S,R)-14): H NMR (300.1 MHz, CDCl3): d = 7.74 7.68
(m, 1H;C Har), 7.58 7.06 (m, 17H;C Har), 5.71 (s, 1H;C Htropp), 5.14 (d,
2JP, H = 14.6 Hz, 1H;C HP), 4.05 (ddd, J = 10.3 Hz, J = 10.3 Hz, J =
3.9 Hz, 1H;OC Hmenthyl), 2.47 2.31 (m, 2H;C Hmenthyl), 1.80 1.71 (m, 2H;
CH2menthyl), 1.64 1.52 (m, 1H;C H2menthyl), 1.51 1.36 (m, 1H;C Hmenthyl),
3
1.28 0.96 (m, 3H;C H2menthyl), 1.00 (d, JH,H = 7.0 Hz, 3H;C H3menthyl),
3
3
0.94 (d, JH,H = 6.9 Hz, 3H;C H3menthyl), 0.93 (d, JH,H = 6.6 Hz, 3H;
CH3menthyl), 1.4 0.2 (br, 3H;B H3) ppm; 13C NMR (75.5 MHz, CDCl3): d
Chem. Eur. J. 2004, 10, 4198 4205
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4203

H. Gr¸tzmacher et al.
FULL PAPER
= 152.8 (=COquart), 135.6 (d, JC,P = 3.9 Hz; Cquart), 135.1 (Cquart), 134.8
(d, JC,P = 3.0 Hz; Cquart), 133.7 (Car), 133.6 (CHar), 132.8 (CHar), 132.7
(CH2mentyl), 22.1 (CH3menthyl), 22.0 (CH3menthyl), 16.6 (CH3menthyl) ppm; 19F
NMR (282.4 MHz, CDCl3): d
=
ꢀ78.4 ppm; 31P NMR (121.5 MHz,
(Cquart), 132.5 (d, JC,P = 2.1 Hz; Cquart), 131.0 (Cquart), 130.6 (d, JC,P
2.5 Hz; CHar), 130.4 (d, JC,P = 2.4, CHar), 130.2 (d, JC,P = 6.4, CHar),
129.9 (d, JC,P = 5.2 Hz; CHar), 129.7 (Cquart), 129.5 (CHar), 129.3 (d, JC,P
=
CDCl3): d = 69.1 ppm;IR: n˜ = 3053(w), 2928(m), 2870(m), 2031(w),
1991(w), 1595(w), 1483(m), 1451(w), 1436(m), 1368(w), 1259(s),
1222(m), 1146(s), 1098(m), 1029(s), 940(w), 900(w), 746(m), 694(m),
=
1.8 Hz; CHar), 129.0 (CHar), 128.2 (CHar), 128.0 (CHar), 127.9 (CHar),
127.7 (CHar), 127.6 (d, JC,P = 2.0 Hz; CHar), 127.3 (CHar), 127.2 (CHar),
668(w), 652(w), 635(s) cmꢀ1;UV/Vis (CH Cl2): lmax = 497 nm.
2
[Ir(cod)(5R)-10-(1R)-menthyloxytroppph]CF3SO3 ((R,R)-15): Compound (R,R)-13
(106 mg, 0.20 mmol) and [Ir(cod)2]CF3SO3 2 (111 mg, 0.20 mmol) were
dissolved in CH2Cl2 (3 mL) to give a red violet solution. This was layered
with n-hexane (5 mL), whereupon the complex (R,R)-15 was obtained as
a red microcrystalline powder. Yield: 176 mg (90%). M.p.: >1958C
1
126.6 (CHar), 108.3 (CHtropp), 75.9 (CHOmenthyl), 56.4 (d, JC,P = 25.0 Hz;
CHbenzyl), 48.1 (CHmenthyl), 38.8 (CH2menthyl), 34.6 (CH2menthyl), 31.4 (CHmenthyl),
25.2 (CHmenthyl), 23.2 (CH2menthyl), 22.3 (CH3menthyl), 21.3 (CH3menthyl), 16.6
(CH3menthyl) ppm; 31P NMR (101.3 MHz, CDCl3): d
= 25.9 (br) ppm;
11B NMR (96.3 MHz, CDCl3): d = ꢀ36.5 (br) ppm;IR: n˜ = 3056(w),
2952(m), 2923(m), 2867(m), 2367 m P-BH3, 2343 m P-BH3, 1960(w),
1623(s), 1567(w), 1494(m), 1436(m), 1384(w), 1246(m), 1207(m),
1133(m), 1100(m), 1085(m), 1056(s), 984(w), 971(w), 917(w), 821(w),
1
(decomp); H NMR (300.1 MHz, CDCl3): d = 8.00 (dd, J = 8.1 Hz, J =
1.3 Hz, 1H;C Har), 7.49 7.11 (m, 15H;C Har), 7.00 (d, J = 7.6 Hz, 1H;
CHar), 6.97 (dd, J = 9.0 Hz, J = 1.4 Hz, 1H;C Har), 6.78 (d, J = 2.4 Hz,
2
1H;C Htropp), 6.02 (brm, 1H;C Hcod), 5.90 (d, JP, H = 13.8 Hz, 1H;C HP),
746(m), 732(s), 694(s), 608(m) cmꢀ1
.
5.41 (brm, 1H;C Hcod), 4.91 (ddd, J = 10.2 Hz, J = 10.2 Hz, J = 4.2 Hz,
1H;OC Hmenthyl), 3.86 (brm, 1H;C Hcod), 3.05 (brm, 1H;C Hcod), 2.52
1.11 (m, 16H;8C H2cod and 3CHmenthyl and 5CH2menthyl), 1.05 0.99 (m, 1H;
[(5R)-10-[(1R)-Menthyloxy]-5H-dibenzo[a,d]cyclohepten-5-yl]diphenyl-
phosphane¥BH3 ((R,R)-14): 1H NMR (300.1 MHz, CDCl3): d = 7.84
7.80 (m, 1H;C Har), 7.53 7.06 (m, 17H;C Har), 5.73 (s, 1H;C Htropp), 5.12
3
3
CH2menthyl), 1.01 (d, JH,H
=
6.3 Hz, 3H;C H3menthyl), 0.85 (d, JH,H
=
2
3
(d, JP, H = 14.7 Hz, 1H;C HP), 4.02 (m, 1H;OC Hmenthyl), 2.45 2.29 (m,
7.0 Hz, 3H;C H3menthyl), 0.79 (d, JH,H = 6.9 Hz, 3H;C H3menthyl) ppm; 13C
1H;C Hmenthyl), 2.16 (brd, J = 12.6 Hz, 1H;C Hmenthyl] 1.80 1.60 (m, 3H;
CH2menthyl), 1.56 1.41 (m, 1H;C Hmenthyl), 1.19 0.89 (m, 3H;C H2menthyl),
NMR (75.5 MHz, CDCl3): d = 152.7 (d, JP,C = 4.6 Hz; =COquart), 135.9
(d, JP, C
=
1.2 Hz; Cquart), 134.5 (CHar), 134.4 (CHar), 133.4 (d, JP, C
=
=
3
3
1.03 (d, JH,H = 6.5 Hz, 3H;C H3menthyl), 0.99 (d, JH,H = 7.0 Hz, 3H;
5.8 Hz; Cquart), 132.9 (CHar), 132.7 (CHar), 132.5 (CHar), 132.3 (d, JP, C
3
CH3menthyl), 0.76 (d, JH,H
=
6.9 Hz, 3H;C H3menthyl), 1.3 0.2 (br, 3H;
3.7 Hz; Cquart), 131.8 (d, JP, C = 2.4 Hz; CHar), 131.6 (d, JP, C = 2.4 Hz;
CHar), 131.3 (d, JP, C = 5.8 Hz; CHar), 130.5 (d, JP, C = 7.6 Hz; Cquart),
BH3) ppm; 13C NMR (75.5 MHz, CDCl3): d = 154.2 (=COquart), 135.8 (d,
JC,P = 4.0 Hz; Cquart), 135.4 (Cquart), 134.4 (d, JC,P = 3.3 Hz; Cquart), 133.6
(Cquart), 133.4 (CHar), 132.9 (CHar), 132.8 (d, JC,P = 2.4 Hz; Cquart), 132.7
129.5 (d, JP,C
= 7.0 Hz; CHar), 129.3 (d, JP, C = 1.8 Hz; CHar), 129.1
(CHar), 129.1 (CHar), 129.0 (CHar), 129.0 (CHar), 128.7 (CHar), 128.7
(CHar), 128.4 (d, JP, C = 2.1 Hz; CHar), 128.4 (d, JP, C = 2.1 Hz; CHar),
128.1 (d, JP, C = 6.7 Hz; CipsoPh), 126.8 (d, JP,C = 51.7 Hz; CipsoPh), 105.7 (d,
JP, C = 10.0 Hz; CHcod), 97.7 (d, JP, C = 12.5 Hz; CHcod), 83.8 (OCHmenthyl),
(CHar), 130.9 (CHquart), 130.7 (d, JC,P = 2.5 Hz; CHar), 130.5 (d, JC,P
2.3, CHar), 130.3 (d, JC,P = 6.1, CHar), 130.3 (CHar), 129.9 (d, JC,P
=
=
5.2 Hz; CHar), 129.6 (CHar), 129.1 (d, JC,P = 2.1 Hz; CHar), 128.3 (CHar),
128.2 (CHar), 128.0 (CHar), 127.8 (CHar), 127.4 (d, JC,P = 2.3 Hz; CHar),
1
74.7 (CHtropp), 69.4 (CHcod), 67.9 (CHcod), 56.8 (d, JP,C = 25.3 Hz; CHP),
127.3 (d, JC,P
=
2.4 Hz; CHar), 127.2 (d, JC,P
=
2.4 Hz; CHar), 126.3
49.9 (CHmenthyl), 40.9 (CH2menthyl), 35.7 (d, JP, C = 3.0 Hz; CH2cod), 33.8
1
(CHar), 104.7 (CHtropp), 76.5 (CHOmenthyl), 56.9 (d, JC,P = 25.0 Hz; CHP),
48.2 (CHmenthyl), 40.4 (CH2menthyl), 34.4 (CH2menthyl), 31.6 (CHmenthyl), 25.9
(CHmenthyl), 23.0 (CH2menthyl), 22.3 (CH3menthyl), 21.2 (CH3menthyl), 15.9
(CH3menthyl) ppm; 31P NMR (121.5 MHz, CDCl3): d = 25.6 (br) ppm; 11B
(CH2menthyl), 32.9 (CH2cod), 31.2 (CHmenthyl), 29.7 (d, JP, C = 3.4 Hz; CH2cod),
27.6 (CH2cod), 25.7 (CHmenthyl), 22.7 (CH2menthyl), 22.3 (CH3menthyl), 21.1
(CH3menthyl), 16.5 (CH3menthyl) ppm; 19F NMR (282.4 MHz, CDCl3): d =
ꢀ78.4 ppm; 31P NMR (121.5 MHz, CDCl3): d
= 64.8 ppm;IR: n˜ =
NMR (96.3 MHz, CDCl3): d
=
ꢀ33.7 (br) ppm;IR: n˜
=
3058(w),
3063(w), 2933(m), 2871(m), 1982(w), 1594(w), 1485(m), 1438(m),
1261(s), 1222(w), 1147(m), 1099(w), 1031(s), 642(w), 904(m), 841(w),
765(w), 730(m), 697(m), 635(s) cmꢀ1;UV/Vis (CH 2Cl2): lmax = 497 nm,
453 nm.
2954(m), 2925(m), 2868(m), 2388 m P-BH3, 1981(w), 1621(m), 1568(w),
1494(w), 1436(m), 1385(w), 1248(m), 1209(m), 1135(m), 1086(s),
1056(s), 970(w), 917(w), 820(w), 746(m), 732(s), 694(s), 608(m) cmꢀ1
;
MS (70 eV, m/z,%): 544 (53) [M]+, 530 (17) [MꢀBH3]+, 391 (100)
[MꢀmenthylꢀBH3]+, 345 (10), 207 (40), 192 (5), 178 (12), 108 (6), 83
(10), 69 (12), 55 (22).
[Rh(cod)(5S)-10-(1R)-menthyloxytroppph]CF3SO3 ((S,R)-17): Compound (S,R)-13
(106 mg, 0.20 mmol) and [Rh(cod)2]CF3SO3 16 (94 mg, 0.20 mmol) were
dissolved in CH2Cl2 (3 mL). The deep red solution was stirred for 1 h at
[Ir(cod)(5S)-10-(1R)-menthyloxytroppph]CF3SO3 ((S,R)-15): Compound (S,R)-13
(106 mg, 0.20 mmol) and [Ir(cod)2]CF3SO3 2 (111 mg, 0.20 mmol) were
dissolved in CH2Cl2 (3 mL). The resulting red violet solution was layered
with n-hexane (5 mL), whereupon the complex (S,R)-15 precipitated as a
red microcrystalline powder. Yield: 180 mg (92%). M.p.: 1888C
room temperature and was then concentrated under vacuum (P =
10ꢀ2 Torr). The residue was suspended in n-hexane (5 mL) with stirring
until an orange powder was obtained;this was filtered and dried in
vacuum. Yield 145 mg (82%). Crystals suitable for a X-ray analysis were
obtained by slow diffusion of hexane into a concentrated solution of
(S,R)-17 in CH2Cl2. M.p.: 1358C (decomp); 1H NMR (300.1 MHz,
CDCl3): d = 8.17 (dd, J = 7.3 Hz, J = 2.2 Hz, 1H;C Har), 7.72 (dd, J =
7.9 Hz, J = 1.0 Hz, 1H;C Har), 7.50 7.13 (m, 13H;C Har), 7.02 6.92 (m,
3H;C Har), 6.66 (d, J = 2.7 Hz, 1H;C Htropp), 6.38 (brm, 1H;C Hcod),
5.64 (brm, 1H;C Hcod), 5.35 (d, J = 14.8 Hz, 1H;C HP), 4.82 (ddd, J =
1
(decomp); H NMR (300.1 MHz, CDCl3): d = 8.34 (dd, J = 7.8 Hz, J =
1.7 Hz, 1H;C Har), 7.61 7.15 (m, 13H;C Har), 7.02 (dd, J = 7.7 Hz, J =
7.7 Hz, 1H;C Har), 6.89 (d, J = 7.6 Hz, 1H;C Har), 6.78 (d, J = 2.1 Hz,
1H;C Htropp), 6.69 (d, J = 7.2 Hz, 1H;C Har), 6.66 (dd, J = 8.6 Hz, J =
2
1.2 Hz, 1H;C Har), 6.35 (brm, 1H;C Hcod), 5.84 (d, JP, H = 14.3 Hz, 1H;
CHP), 5.24 (brm, 1H;C Hcod), 4.92 (ddd, J = 10.3 Hz, J = 10.3 Hz, J =
4.0 Hz, 1H;OC Hmenthyl), 3.77 (brm, 1H;C Hcod), 3.40 (brm, 1H;C Hcod),
2.52 2.38 (m, 2H;1îC Hmenthyl and 1îCH2cod), 2.24 1.47 (m, 12H;7î
CH2cod and 2îCHmenthyl and 3îCH2menthyl), 1.37 1.24 (m, 1H;C H2menthyl),
10.5 Hz, J
= 10.5 Hz, J = 4.0 Hz, 1H;OC Hmenthyl), 3.96 (brm, 1H;
CHcod), 3.45 (brm, 1H;C Hcod), 2.68 1.24 (m, 15H;8îC H2cod, 3îCHmenthyl
,
4îCH2menthyl), 1.17 (d, J = 6.9 Hz, 3H;C H3menthyl), 1.04 (d, J = 6.9 Hz,
3H;C H3menthyl), 0.95 0.78 (m, 2H;C H2menthyl), 0.74 (d, J = 6.4 Hz, 3H;
3
3
1.13 (d, JH,H = 6.9 Hz, 3H;C H3menthyl), 1.02 (d, JH,H = 6.8 Hz, 3H;
CH3menthyl) ppm; 13C NMR (75.5 MHz, CDCl3): d
= 155.5 (dd, J =
3
CH3menthyl), 0.89 0.71 (m, 2H;C H2menthyl), 0.66 (d, JH,H = 6.3 Hz, 3H;
3.4 Hz, J = 1.8 Hz; Cquart), 135.2 (dd, J = 3.1 Hz, J = 0.9 Hz; Cquart),
134.9 (dd, J = 5.6 Hz, J = 1.3 Hz; Cquart), 133.7 (CHar), 133.6 (CHar),
133.4 (CHar), 133.2 (CHar), 132.5 (CHar), 131.8 (d, J = 2.4 Hz; CHar),
131.7 (d, J = 2.6 Hz; CHar), 131.6 (dd, J = 4.7 Hz, J = 1.0 Hz; Cquart),
131.4 (d, J = 8.1 Hz; Cquart), 131.3 (d, J = 5.3 Hz; CHar), 129.9 (dd, J =
45.1 Hz, J = 1.1 Hz; CipsoPh), 129.4 129.2 (7C; CHar), 128.9 (CHar), 128.8
(CHar), 128.7 (d, J = 1.5 Hz; CHar), 127.6 (dd, J = 41.3 Hz, J = 1.8 Hz;
CipsoPh), 114.4 (dd, J = 9.3 Hz, J = 5.5 Hz; CHcod), 108.7 (dd, J = 9.5 Hz,
J = 6.1 Hz; CHcod), 86.2 (d, J = 12.5 Hz; CHcod), 85.4 (OCHmenthyl), 84.1
(dd, J = 4.9 Hz, J = 2.3 Hz; CHtropp), 80.6 (d, J = 11.9 Hz; CHcod), 57.6
(d, J = 18.6 Hz; CHP), 49.7 (CHmenthyl), 39.1 (CH2menthyl), 34.3 (CH2cod),
34.3 (CH2menthyl), 31.2 (CH2cod), 31.1 (CH2cod), 29.8 (CHmenthyl), 27.2
(CH2cod), 25.9 (CHmenthyl), 23.4 (CH2menthyl), 22.3 (CH3menthyl), 22.2
CH3menthyl) ppm; 13C NMR (75.5 MHz, CDCl3): d
= 146.4 (=COquart),
136.6 (Cquart), 134.3 (CHar), 134.2 (CHar), 134.0 (d, JP, C = 2.1 Hz; Cquart),
133.2 (CHar), 133.0 (CHar), 132.1 (CHar), 131.9 (d, JP, C = 5.8 Hz; CHar),
131.8 (d, JP, C = 8.5 Hz; CHar), 131.7 (CHar), 131.7 (Cquart), 130.7 (d, JP, C
=
2.7 Hz; Cquart), 129.3 (CHar), 129.3 (CHar), 129.3 (CHar), 129.2 (CHar),
129.1 (CHar), 129.1 (CHar), 129.0 (CHar), 128.9 (d, JP, C = 2.1 Hz; CHar),
128.7 (CHar), 128.5 (CHar), 128.2 (d, JP, C = 55.7 Hz; CipsoPh), 125.9 (d, JP, C
=
48.4 Hz; CipsoPh), 106.6 (d, JP, C = 10.4 Hz; CHcod), 98.7 (d, JP, C = 11.9 Hz;
CHcod), 86.3 (OCHmenthyl), 80.4 (CHtropp), 76.8 (CHcod), 65.6 (CHcod), 57.0
1
(d, JP, C = 24.7 Hz; CHbenzyl), 49.6 (CHmenthyl), 39.5 (CH2menthyl), 35.4 (d,
JP, C = 3.4 Hz; CH2cod), 34.1 (CH2menthyl), 32.9 (CH2cod), 31.1 (CHmenthyl),
29.9 (d, JP, C
=
3.1 Hz; CH2cod), 27.4 (CH2cod), 25.6 (CHmenthyl), 23.0
4204
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2004, 10, 4198 4205

Homogeneously Catalyzed Hydrogenations
4198 4205
(CH3menthyl), 17.0 (CH3menthyl) ppm; 19F NMR (282.4 MHz, CDCl3): d =
drien, J. A. F. Boogers, J. G. de Vries, Org. Lett. 2003, 5, 1503;d) F.
Menges, A. Pfaltz, Adv. Synth. Catal. 2002, 344, 40;e) H.-U. Blaser,
B. Pugin, F. Spindler, A. Togni, C. R. Chim. 2002, 5, 379;f) D. Xiao,
X. Zhang, Angew. Chem. 2001, 113, 3533; Angew. Chem. Int. Ed.
2001, 40, 3425;g) T. Ohkuma, M. Kitamura, R. Noyori, in Catalytic
Asymmetric Synthesis (2nd Edition), Wiley-VCH, New York, 2000,
1;h) S. Kainz, A. Brinkmann, W. Leitner, A. Pfaltz, J. Am. Chem.
Soc. 1999, 121, 6421;i) H.-U. Blaser, B. Pugin, F. Spindler, in Com-
prehensive Asymmetric Catalysis I III, Vol. 1, (Eds.: E. N. Jacobsen,
A. Pfaltz, H. Yamamoto), Springer, Berlin, 1999, 247;j) Hydrogena-
tion of enamides: M. J. Burk, Y. M. Wang, J. R. Lee, J. Am. Chem.
Soc. 1996, 118, 5142.
ꢀ78.4 ppm; 31P NMR (121.5 MHz, CDCl3):
d = 85.9 (d, JRh,P =
163 Hz) ppm;IR: n˜ = 2925(m), 1486(w), 1435(m), 1259(vs), 1147(s),
1029(s), 745(m), 693(m) cmꢀ1;UV/Vis(CHCl ): lmax = 469 nm.
3
Catalyses: The catalytic experiments were performed in a 60 mL high-
pressure steel-vessel (Medimex). For the pressure control, a pressflow
control unit (bpc 6002, B¸chi) was used. The products in the catalytic ex-
periments were analyzed with a HP 6890 gas chromatograph equipped
with a flame-ionization detector (Hewlett Packard). For the separation
of the product mixtures, H2 was used as carrier gas and the following col-
umns were employed: HP-5 crosslinked 5% PH ME SILOXANE
(30 mî320 mmî0.25 mm). Lipodex E (25 mî0.25 mm ID) Machery
&
[9] Data collection was on Bruker SMART (CCD) ((R,R)-13, (S,R)-13,
(S,R)-17) and STOE IPDS I [(R,R)-15] diffractometers. The struc-
tures were solved by Patterson ((R,R)-15) or direct methods ((R,R)-
13, (S,R)-13, (S,R)-17), all atoms except hydrogen being refined ani-
sotropically (SHELXTL). In the cases of (R,R)-13, (S,R)-13, and
(S,R)-17 the data were corrected for absorption by use of the pro-
gram SADABS. (R,R)-13: C37H39OP;crystal size 1.00î0.36î
Nagel.
Phenyl(1-phenylethyl)amine 7 from phenyl(1-phenylethyliden)amine 5:
The conversion rate was determined on the HP-5 (1508C isotherm;flow
rate: 1.9 mL H2 minꢀ1). Retention times: 9.2 min.: phenyl(1-phenylethyl)-
amine (7);10.5 min.: phenyl(1-phenylethyliden)amine ( 5). The enantio-
meric excess (ee) was determined on Lipodex E (1108C for 1 min., then
heating to 1508C with a rate of 0.68Cminꢀ1;flow rate: 0.9 mL H 2 minꢀ1.).
Retention times: 65.7 min.: (S)-7;66.4 min.: ( R)-7.
0.14 mm;orthorhombic, space group P212121, a
= 9.155(2), b =
9.382(2), c = 36.290(9) ä, V = 3117(1) ä3, Z = 4, m = 0.12 mmꢀ1
;
N-(1-Phenylethyl)acetamide (19) from N-(1-phenylvinyl)acetamide (18):
The conversion rate was determined on the HP-5 (1508C isotherm;flow
rate: 1.9 mL H2 minꢀ1). Retention times: 3.6 min: N-acetyl-1-phenylethyl-
amine;4.5 min: N-acetyl-1-phenylethenamine. The enantiomeric excess
(ee) was determined on Lipodex E (1408C for 1 min, then heating to
1508C with a rate of 0.68Cminꢀ1;flow rate: 0.7 mL H 2 minꢀ1). Retention
times: 16.4 min: (R)-19;16.9 min: ( S)-19.
l(MoKa) = 0.71073 ä, T = 233 K, 2qmax/2qmin = 53.088/2.248, col-
lected (independent) reflections = 18148 (6387), Rint = 0.0758;332
refined parameters, R1 = 0.0532 for 3345 reflections with I>2s,
wR2 = 0.1384 for all data, GooF on F2 = 0.924, Flack x parameter
=
0.1(1), max./min. residual electron density
=
0.28/ꢀ0.22 eäꢀ3
.
(S,R)-13: C37H39OP;crystal size 0.48î0.44î0.40 mm;monoclinic,
space group P21, a = 9.63(1), b = 29.57(3), c = 10.69(1) ä, b =
98.95(2)8, V 4, m ) =
=
3005(6) ä3, Z 0.12 mmꢀ1; l(MoKa
=
=
0.71073 ä, T = 293 K, 2qmax/2qmin = 52.748/2.768, collected (inde-
pendent) reflections = 19295 (11987), Rint = 0.0545;703 refined
Acknowledgement
parameters, R1 = 0.0424 for 7133 reflections with I>2s, wR2
=
0.0937 for all data, GooF on F2
0.00(7), max./min. residual electron density
= 0.814, Flack x parameter
=
0.14/ꢀ0.18 eäꢀ3
.
This work was supported by BAYER AG and the Swiss National Science
Foundation.
=
(R,R)-15: C46H51Cl3F6IrOP2;crystal size 0.30î0.27î0.21 mm;mono-
clinic, space group P21,
a
=
9.998(2),
=
b
=
22.088(4),
2,
c
m
=
10.313(2) ä, 97.23(3)8,
b
=
V
2259.4(8) ä3,
Z
=
=
3.26 mmꢀ1; l(MoKa) = 0.71073 ä, T = 293 K, 2qmax/2qmin = 46.508/
[1] M. T. Benson, T. R. Cundari, Inorg. Chim. Acta 1997, 259, 91.
[2] This concept has been patented with 5-phosphanyl-[a,d]dibenzocy-
cloheptenes as ligands: H. Gr¸tzmacher, S. Deblon, P. Maire, H.
Schˆnberg, 2002, DE 101 59 015.6.
4.508, collected (independent) reflections = 12186 (6166), Rint
=
0.0447;536 refined parameters, R1 = 0.0441 for 5641 reflections
with I>2s, wR2 = 0.1093 for all data, GooF on F2 = 1.071, Flack
x parameter = 0.01(2), max./min. residual electron density = 1.87/
ꢀ1.97 eäꢀ3. (S,R)-17: C47H53Cl2F3O4PRhS;crystal size 0.54î0.50î
[3] For a very recent application of C2-symmetric norbornadiene as
ligand to rhodium in catalyzed asymmetric 1,4-additions see: T.
Hayashi, K. Ueyama, N. Tokunaga, K. Yoshida, J. Am. Chem. Soc.
2003, 125, 11508.
0.46 mm;monoclinic, space group P2
, a = 10.181(1), b =
1
19.492(1), c = 11.926(4) ä, b = 106.304(1)8, V = 2271.4(1) ä3, Z
= 2, m = 0.63 mmꢀ1; l(MoKa) = 0.71073 ä, T = 298 K, 2qmax/2qmin
= 56.568/3.568, collected (independent) reflections = 13430 (9234),
Rint = 0.0181;532 refined parameters, R1 = 0.0303 for 8345 reflec-
tions with I>2s, wR2 = 0.0729 for all data, GooF on F2 = 1.023,
Flack x parameter = 0.02(2), max./min. residual electron density =
0.28/ꢀ0.49 eäꢀ3. CCDC-242539 CCDC-242542 contain the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB21EZ, UK;fax: ( +44)1223-336-033;or deposit
@ccdc.cam.ac.uk).
[4] For a very recent report on the use of a chiral olefin as ligand in IrI
complexes for the kinetic resolution of allyl carbonates, see: C.
Fischer, C. Defieber, T. Suzuki, E. M. Carreira, J. Am. Chem. Soc.
2004, 126, 1628.
[5] Olefin hydride complexes are indeed quite stable when the olefin is
incorporated within a chelating ligand framework;see for examples:
a) C. Bˆhler, N. Avarvari, H. Schˆnberg, M. Wˆrle, H. R¸egger, H.
Gr¸tzmacher, Helv. Chim. Acta 2001, 84, 3127;b) S. Hua Liu, X.
Huang, Z. Lin, C. Po Lau, G. Jia, Eur. J. Inorg. Chem. 2002, 1697.
[6] For recent examples of enantiomerically pure tripods see: a) G.
Brinkmann, R.-M. Pfeifer, C. Rummey, K. Hartner, M. Breuning, J.
Org. Chem. 2003, 68, 6859;b) I. Hegelmann, N. Burzlaff, Eur. J.
Inorg. Chem. 2003, 409;c) L. Gade, Acc. Chem. Res. 2002, 35, 575.
[7] a) J. Thomaier, S. Boulma‚z, H. Schˆnberg, H. R¸egger, A. Currao,
H. Gr¸tzmacher, H. Hillebrecht, H. Pritzkow, New J. Chem. 1998,
22, 947;b) S. Deblon, L. Liesum, J. Harmer, H. Schˆnberg, A.
Schweiger, H. Gr¸tzmacher, Chem. Eur. J. 2002, 8, 601.
[10] a) Ru0 vinylether (vinyl sulfide) complexes: J. G. Pinas, T. Marumo,
Y. Ichikawa, M. Hirano, S. Komiya, J. Chem. Soc. Dalton Trans.
2000, 2613, and lit. cited therein;b) for a dinuclear Rh complex with
a special vinyl ether moiety see: R. S. Dickson, G. D. Fallon, F. I.
McLure, R. J. Nesbit, Organometallics 1987, 6, 215.
[11] G. Walker, A. R. Engle, J. Org. Chem. 1972, 37, 4294.
[8] For selected recent publications see: a) C. J. Cobley, J. P. Henschke,
Adv. Synth. Catal. 2003, 345, 195;b) E. Guiu, B. MuÊoz, S. Castil-
liÛn, C. Claver, Adv. Synth. Catal. 2003, 345, 169;c) X.-b. Jiang, A. J.
Minnaard, B. Hessen, B. L. Feringa, A. L. L. Duchateau, J. G. O. An-
Received: February 6, 2004
Published online: July 5, 2004
Chem. Eur. J. 2004, 10, 4198 4205
www.chemeurj.org
¹ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4205