Chiral phosphino- and (phosphinooxy)-substituted N-heterocyclic carbene ligands and their application in indium-catalyzed asymmetric hydrogenation

Article abstract of DOI:10.1002/hlca.200690157

Enantiomerically pure iridium complexes with phosphino- and (phosphinooxy)-substituted N-heterocyclic carbene (NHC) ligands were synthesized. Investigation of their electronic properties showed a similar trans influence of the phosphino (or phosphinooxy) and the NHC units. The complexes were tested in iridium-catalyzed hydrogenation. While low conversions were observed with unfunctionalized olefins, the catalysts proved to be suitable for hydrogenation of the α,β-unsaturated ester 20, allylic alcohol 21, and imine 22. The enantioselectivities were, however, moderate.

Full text of DOI:10.1002/hlca.200690157

Helvetica Chimica Acta – Vol. 89 (2006)
1559
Chiral Phosphino- and (Phosphinooxy)-Substituted N-Heterocyclic Carbene
Ligands and Their Application in Iridium-Catalyzed Asymmetric
Hydrogenation
by Steve Nanchen and Andreas Pfaltz*
Department of Chemistry, University of Basel, St-Johanns Ring 19, CH-4056 Basel
(fax: +41612671103; e-mail: andreas.pfaltz@unibas.ch)
Dedicated to Professor Giambattista Consiglio on the occasion of his 65th birthday
Enantiomerically pure iridium complexes with phosphino- and (phosphinooxy)-substituted N-heter-
ocyclic carbene (NHC) ligands were synthesized. Investigation of their electronic properties showed a
similar trans influence of the phosphino (or phosphinooxy) and the NHC units. The complexes were
tested in iridium-catalyzed hydrogenation. While low conversions were observed with unfunctionalized
olefins, the catalysts proved to be suitable for hydrogenation of the a,b-unsaturated ester 20, allylic alco-
hol 21, and imine 22. The enantioselectivities were, however, moderate.
Introduction. – In recent years, N-heterocyclic carbenes (NHC) have generated
growing interest in organometallic chemistry [1]. Their efficiency as ligands in homoge-
neous catalysis was demonstrated by the development of catalytic systems with unpre-
cedented activities as, for example, in Ru-catalyzed metathesis [2] and Pd-catalyzed
coupling reactions [3].
Chiral NHC ligands have also been successfully applied in asymmetric catalysis [4].
Monodentate NHC ligands were investigated first because they were readily accessible
from simple chiral building blocks. Subsequently, chiral chelating ligands were intro-
duced, in which the NHC moiety is linked to other coordinating units such as alkoxy
[
5], phosphine [6], dihydrooxazole [7], or imino [8] groups. Successful applications of
these ligands include Ru-catalyzed ring-opening cross-metathesis, Rh-catalyzed hydro-
silylation of ketones, Rh- and Ir-catalyzed hydrogenation.
[(Dihydrooxazolyl)NHC] iridium complexes were shown to be efficient catalysts
for Ir-catalyzed hydrogenation of unfunctionalized olefins [7b]. In contrast, only very
few phosphinoNHC bidentate chiral ligands have been studied. Bolm and co-workers
reported that iridium complexes of ligand A catalyze the hydrogenation of olefins, but
require long reaction times and give only moderate enantiomeric excess (ee) [6c]. The
chiral phosphinoNHC ligands B and C were used in rhodium-catalyzed hydrogenation
of dimethyl itaconate and a,b-unsaturated esters. While ligand B induced only 12% ee
[
6b], ligand C induced almost perfect enantioselectivity [6a]. In view of these results,
we decided to evaluate other types of chiral phosphinoNHC bidentate ligands for Ir-
catalyzed hydrogenation.
Herein, we report two classes of chiral ligands D and E and the evaluation of the
corresponding Ir complexes as hydrogenation catalysts. Ligands D are structurally
©
2006 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 89 (2006)
related to the efficient pyridylalkyl phosphinite ligands recently developed in our lab-
oratory [9]. Ligands E, we thought, would be of interest, because they should be readily
accessible from optically active epoxides.
Results and Discussion. – Synthesis of (PhosphinoNHC)iridium Complexes. The
synthesis of the phosphinoNHC precursors, i.e., of the imidazolium salts 6, is closely
related to a route developed by Hoveyda and co-workers to access chiral (hydroxyal-
kyl)imidazolium salts [5a]. The key step is the reductive amination of aldehyde 3
with chiral phosphinoalkanamine 4, prepared in four steps from (S)-valinol according
to a literature procedure (Scheme 1) [10].
Boc-protected amines 1 (Boc=(tert-butoxy)carbonyl) were deprotonated with KH
in DMF and then subjected to nucleophilic substitution with g,g-dimethylallyl bromide
to give protected unsaturated amines 2. Since the latter were not stable on silica gel, the
crude products were directly converted into aldehydes 3 by ozonolysis. Reductive ami-
nation of aldehydes 3 with phosphinoalkanamines 4 in the presence of NaHB(OAc)3
gave compound 5 in good yield. Removal of the Boc group, followed by imidazo-
lium-salt formation with NH BF and HC(OEt) , yielded the desired tetrafluoroborate
4
4
3
ꢀ
salts, which were converted to the BArF (=tetrakis[3,5-bis(trifluoromethyl)phenyl]bo-
rate) salts 6 upon treatment with NaBAr . The weakly coordinating BAr counterion
ꢀ
F
F
was used since it is known to improve the performance of iridium complexes as hydro-
genation catalysts compared to other weakly coordinating anions such as hexafluoro-
phosphate, tetrafluoroborate, or triflate [11].
The Ir complexes 7a–c were obtained by deprotonation of the corresponding imi-
t
dazolium salts with freshly sublimed NaO Bu in the presence of the metal precursor
t
[
Ir Cl (cod) ] (cod=cycloocta-1,5-diene). Upon addition of NaO Bu, a fast color
2
2
2
change from yellow to dark red was observed.
Synthesis of [(Phosphinooxy)NHC]iridium Complexes. In the synthesis of the phos-
phinoimidazolium salt 6, the heterocyclic ring was formed in the last step, because
introduction of a phosphino group in general requires strongly basic conditions that
are incompatible with an imidazolium group. In the synthesis of (phosphinooxy)imida-

Helvetica Chimica Acta – Vol. 89 (2006)
1561
Scheme 1. Synthesis of Iridium Complexes 7a–c
a) 1. KH, DMF, 0 ! 258; 2. Me C=CHCH Br, DMF, r.t. b) 1. O /O , MeOH/CH Cl 1:3, ꢀ788; 2.
A
H
R
U
G
2
2
3
2
2
2
Me S, r.t.; 30–48% over two steps. c) NaHB(OAc) , CH ClCH Cl, r.t.; 74–82%. d) CF COOH,
A
H
R
N
2
3
2
2
3
CH Cl , r.t.; 82–99%. e) 1. HC(OEt) , NH BF , 1008; 2. NaBAr , CH Cl , r.t.; 48–80%. f)
2
2
3
4
4
F
2
2
t
[
Ir Cl (cod) ], NaO Bu, THF, r.t.; 69–75%.
2
2
2
zolium salt 12, the phosphinooxy group could be introduced in the last step under only
mildly basic conditions. This has the advantage that the structure of the PR unit can be
2
easily varied (Scheme 2). Thus, (hydroxyalkyl)imidazolium salt 10 was prepared by con-
densation of the (R)-configurated epoxide 9 with 1H-imidazole (8), followed by al-
A
C
H
T
R
E
U
N
G
kylation with isopropyl iodide. The corresponding iodide salt was converted into imida-
ꢀ
F
zolium salt 10 by anion exchange with NaBAr . The BAr counterion enhanced the
F
solubility of the imidazolium salt 10 in CH Cl , which was then submitted to phospho-
2
2
A
C
H
T
R
E
U
N
G
rylation with diphenylphosphinic amide 11 in the presence of Et N and 4,5-dichloro-
A
T
E
N
3
1
H-imidazole as catalyst. Purification of the (phosphinooxy)imidazolium salt 12 proved
to be crucial to obtain pure complex 13. A test experiment with a crude sample of 12
yielded complex 13 with impurities that could not be removed. After extensive exper-
imentation, we established that chromatography with aluminium oxide under inert
atmosphere gave pure (phosphinooxy)imidazolium salt 12 without oxidation or hydro-
A
C
H
T
R
E
U
N
G
lysis of the phosphinooxy moiety. The Ir complex 13 was obtained under the same con-
ditions as those used for the preparation of phosphinoNHC complexes 7a–c.
Structural Analysis of Iridium Complexes 7 and 13. Iridium complexes 7a–c were
characterized by standard 2D-NMR techniques, which showed two sets of signals at
1
room temperature. Clearly, two species were present in solution. In addition, the H-
NMR signals of complex 7c were broad, indicating that the two species could be at
the origin of the dynamic behavior. This assumption was confirmed by further analyses
of complex 7c at low temperature. At ꢀ278, the two sets of signals (3 :1 ratio) were
sharp, and full NMR analyses allowed the assignment of structure 7c to both species.
Particular care was taken to establish the coordination mode of the NHC at the
NCN position of the ring for both species. A NOESY experiment of complex 7c at

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562
Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 2. Synthesis of Iridium Complexes 13
i
a) 1. Neat, 508; 2. PrI, MeCN, 808; 3. NaBAr , CH Cl , r.t.; 25%. b) 4,5-Dichloro-1H-imidazole, Et N,
A
H
R
U
G
F
2
2
3
t
CH Cl , r.t.; 60%. c) [Ir Cl (cod) ], NaO Bu, THF, r.t.; 69%.
2
2
2
2
2
ꢀ
278 indicated that the two species interconvert, but no cross-peak was observed for
the two ortho-methyl groups of the mesityl (=2,4,6-trimethylphenyl) moiety. Rotation
of the NHC substituent was, therefore, ruled out.
Further structural information about complex 7c was obtained from X-ray analysis
ꢀ
ꢀ
1
of complex 7c’, the analogue of 7c with BF4 instead of BArF as counterion ).
As depicted in Fig. 1, the Ir-atom lies in an almost square-planar arrangement, with
the cod C=C bonds perpendicular to the coordination plane. A boat-like conformation
of the chelate ring is expected with this type of ligand, since the planarity of the NHC
moiety forces the C(4), N(1), C(1), and Ir(1) atoms to lie in the same plane (measured
torsion angle=3.98). With these geometric constraints, complex 7c can adopt two con-
formations, in which the isopropyl substituent is either bent over the Ir-atom (confor-
mation observed for 7c’) or pointing away from the metal (Fig. 2).
The assumption that the two conformers of complex 7c arise from a flip of the che-
late ring is consistent with the NOESY plot, which showed an NOE contact between
the isopropyl group and the cod for one of the two conformers. Similar observations
for the complexes 7a,b led to the same conclusion, although no interconversion
between the two conformers was observed on the NMR time scale.
NMR Analyses of complex 13 also indicated the presence of two species in solution.
Assignment of the two structures confirmed that they were conformers, but no inter-
conversion was observed in the NOESY experiment. In analogy to the phosphinoNHC
complexes 7a–c, the NOESY data suggest that the two conformers arise from a ring
flip of the chelate ring.
13
The electronic properties of complexes 7b and 7c are reflected by the C-NMR
chemical shifts of the cod olefinic C-atoms and the distances from the cod C=C
1)
Complexes 7b’ and 7c’, analogues of complexes 7b and 7c bearing a BF4 counter ion, were synthe-
sized from the corresponding tetrafluoroborate imidazolium salts and characterized by X-ray struc-
ture analysis.
ꢀ

Helvetica Chimica Acta – Vol. 89 (2006)
1563
Fig. 1. Structure of the cation of 7c’
Fig. 2. Two Conformations of the cation of 7c’
bonds to the Ir-atom, i.e., Irꢀ(C=C) trans to the carbene and trans to the phosphino
units (Fig. 3).
The data of complexes 7b–c were compared with those of the [(dihydrooxazo-
lyl)NHC]iridium complexes 14 and 15 [7g] and (dihydrophosphinooxazole)iridium 16
[
12]. The data summarized in Fig. 3 imply that the phosphino group has the strongest
trans influence, followed by the NHC and the dihydrooxazole units. This is illustrated
by the longest Irꢀ(C=C)] distance and the largest chemical shift of the cod olefinic C-
atoms trans to the P-atom in complex 16. In complexes 7b and 7c, the difference
between the phosphino and the NHC moiety is less pronounced, as shown by the
Irꢀ(C=C) distances, which all lie in the same range (207–209 pm). Accordingly, in con-
trast to the [(dihydrooxazolyl)NHC]- and (dihydrophosphinooxazole)iridium com-
plexes 14–16, the (phosphinoNHC)iridium complexes 7b–c have two coordinating
units with similar trans influence.
Asymmetric Hydrogenation. The (phosphinoNHC)iridium complexes 7a–c and
[
(phosphinooxy)NHC]iridium complexes 13 were tested in the iridium-catalyzed
hydrogenation of three unfunctionalized olefins, 17–19, a,b-unsaturated ester 20,
allylic alcohol 21, and imine 22.

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564
Helvetica Chimica Acta – Vol. 89 (2006)
Fig. 3. Measured Irꢀ(C=C) Distances in 7b’, 7c’, and 14–16, and d(C) of the corresponding C=C
moieties of 7b, 7c, and 14–16
Initial studies were undertaken with unfunctionalized trisubstituted olefins 17–19
(Table 1). It quickly became apparent that our catalysts were not very active in compar-
ison to [Ir(P,N-ligand)] complexes of type 16, for which turnover frequency (TOF) val-
ꢀ
1
ues up to 5000 h were measured during the hydrogenation of 17 [11b]. Twelve hours
at room temperature and 50 bar H were not sufficient to fully hydrogenate substrates
2
17–19. Complexes 7a–c were also less reactive and less enantioselective than [(dihy-
drooxazole)NHC]iridium complexes. In the hydrogenation of 17, the choice of the
NHC substituent is crucial for enantioselectivity. An increase from 5% to 63% was
observed when the N-isopropyl group was replaced by a mesityl group. However,
this effect was not observed for the hydrogenation of alkenes 18 and 19.
In contrast to the results obtained with unfunctionalized olefins 17–19, catalysts
7a–c showed higher activities with functionalized alkenes 20–22 (Table 2). After 12
h at room temperature and 50 bar H , full conversion was obtained with the a,b-unsa-
2
turated ester 20. Furthermore, the reaction time for allylic alcohol 21 and imine 22 was

Helvetica Chimica Acta – Vol. 89 (2006)
1565
Table 1. Asymmetric Hydrogenation of Alkenes 17–19a)
Substrate
Catalyst
Time [h]
Yield [%]b)
ee [%]c)
7a
7b
7c
3
4
5
12
12
12
12
2
10
21
38
12
>99
>99
rac
5 (R)
63 (R)
6 (R)
87 (R)
90 (R)
1
1
1
2
7a
7b
7c
3
4
5
12
12
12
12
2
68
80
77
>99
>99
>99
rac
rac
36 (R)
rac
69 (R)
87 (R)
1
1
1
2
7a
7b
7c
3
4
5
12
12
12
12
2
52
68
61
95
>99
>99
5 (S)
rac
10 (S)
15 (S)
41 (S)
66 (S)
1
1
1
2
a) 1 mol-% of catalyst and 0.1 mmol of substrate in CH Cl (0.5 ml) at r.t. and 50 bar H . ) Determined by
GC. ) Determined by HPLC.
b
2
2
2
c
reduced to 1 h without loss of conversion (except for catalyst 7c). The remarkable activ-
ity of (phosphinoNHC)iridium complexes 7a–c with imine 22 is emphasized by the
comparison with [(dihydrooxazolyl)NHC]iridium complexes 14 and 15, which did
not hydrogenate imine 22 even after 12 h at room temperature and 50 bar H2.
The enantioselectivities of catalysts 7a–c were moderate. For each substrate, the
highest enantioselectivity was obtained with catalyst 7b bearing an isopropyl substitu-
ent at the NHC unit, followed by catalyst 7a and catalyst 7c. For imine 22, catalyst 7b
gave 49% ee. By reducing the pressure to 10 bar, an increase of the enantioselectivity to
6
0% was observed. Further experiments at 100 and 20 bar H confirmed the inverse-
2
pressure dependence of the enantioselectivity in the hydrogenation of imine 22.
The catalytic activity of [(phosphinooxy)NHC]iridium complex 13 is similar to that
of the (phosphinoNHC)iridium complexes 7a–c. However, the enantioselectivities of
complex 13 were inferior to those of the best (phosphinoNHC)iridium catalysts.
Conclusions. – Three (phosphinoNHC)iridium complexes, 7a–c, were synthesized
starting from the chiral phosphinoalkanamine 4. In addition, a simple synthesis of
the [(phosphinooxy)NHC]iridium complex 13 starting from the chiral epoxide 9 was
developed.
In contrast to the [(dihydrooxazolyl)NHC]- and (dihydrophosphinooxazole)iridium
complexes 14–16, complexes 7a–c and 13 showed a similar trans influence for both
coordinating units. They also behaved differently as hydrogenation catalysts. Contrary
to the [(dihydrooxazolyl)NHC]iridium complexes, catalysts 7a–c and 13 was not suit-

1
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Helvetica Chimica Acta – Vol. 89 (2006)
Table 2. Asymmetric Hydrogenation of Functionalized Alkenes 20 and 21 and Imine 22a)
Substrate
Catalyst
Time [h]
Yield [%]b)
ee [%]c)
7a
7b
7c
3
12
12
12
12
>99
>99
>99
>99
20 (S)
43 (S)
6 (S)
1
11 (S)
7a
7b
7c
3
1
1
1
1
>99
>99
>99
71
35 (ꢀ)
42 (ꢀ)
26 (ꢀ)
20 (+)
1
7
7
7
3
7
7
7
a
b
c
1
1
1
1
>99
>99
18
>99
>99
>99
98
6 (S)
49 (R)
rac
46 (S)
34 (R)
57 (R)
60 (R)
1
d
b
b
b
1 )
e
3 )
f
3 )
a) 1 mol-% of catalyst and 0.1 mmol of substrate in CH Cl (0.5 ml) at r.t. and 50 bar H , unless otherwise
2
2
2
b
c
d
e
f
stated. ) Determined by GC. ) Determined by HPLC. ) 100 bar H at r.t. ) 20 bar H at r.t. ) 10 bar H
2
2
2
at r.t.
able for hydrogenation of unfunctionalized olefins but showed good catalytic activity
with a,b-unsaturated ester 20, allylic alcohol 21, and imine 22.
NMR Analyses of the Ir complexes 7a–c and 13 showed fluxional behavior of the
chelate ring. Such lack of rigidity is likely to affect the chirality transfer from the cata-
lyst to the substrate during hydrogenation, thus making the asymmetric induction dif-
ficult to control. A possible way to improve these ligands would be to rigidify their
structure by introduction of an additional ring.
Financial support by the Swiss National Science Foundation is gratefully acknowledged. We thank
Dr. Sylvia Schaffner and Markus Neuburger for the crystal structure analyses and Dr. Klaus Kulicke
for NMR measurements. We also thank Novartis (Basel) and OMG AG & Co (Germany) for samples
of valuable starting materials.
Experimental Part
General. Reactions with air- or moisture-sensitive compounds were performed under Ar by using
standard Schlenk techniques or under purified N in a MBraun glovebox. Glassware was oven-dried
2
and flame-dried prior to use. All chemicals were purchased from Fluka Chemie GmbH (Buchs, Switzer-
land), with the exception of 3,5-bis(trifluoromethyl)bromobenzene (Fluorochem Ltd., Derbyshire, UK).
Et2
A
H
R
U
G
under a stream of N prior to use. Aldehyde 3c and precursors were already reported in the literature
2
[
5a]. CC=Column chromatography. HPLC: Shimadzu systems, SCL-10A system controller, CTO-

Helvetica Chimica Acta – Vol. 89 (2006)
1567
1
0AC column oven, LC10-AD pump system, DGU-14A degasser, SPD-M10A diode-array detector or
UV/VIS detector (220 and 254 nm). M.p.: Büchi-535 melting-point apparatus; not corrected. Optical
ꢀ1
rotations: sodium lamp, 1-dm cuvette, c in g/100 ml. IR Spectra: in cm . NMR Spectra: d in ppm, J in
Hz. MS: in m/z (rel. %).
1
,1-Dimethylethyl Methylcarbamate (1a). A soln. of Boc (O) (24.00 g, 110 mmol) in THF (50 ml) was
A
H
R
U
G
2
added to a soln. of 2M MeNH (50 ml, 100 mmol) in THF at 08 over 10 min. N,N-Dimethylpyridin-4-
2
amine (DMAP; 122 mg, 1 mmol) was added to the mixture, which was then stirred at r.t. for 19 h. The
solvent was evaporated and the residue dissolved in Et2
A
H
R
U
G
H O and a sat. aq. NaHCO soln., dried (MgSO ), and evaporated, and the colorless oil purified by chro-
2
3
4
matography (silica gel, 7×20-cm column, R 0.33, AcOEt/hexane 1:9): 1a (7.15 g, 55%). Colorless oil. IR
f
(
1
Me
(
NaCl): 3357m (br.), 2976m, 2933m, 1696s (br.), 1531m, 1456w, 1419w, 1391w, 1366m, 1277m, 1250m,
1
175s, 954w, 868w, 782w. H-NMR (400.1 MHz, CDCl , 300 K): 4.41 (br., NH); 2.69 (s, MeN); 1.41 (s,
3
13
1
A
H
R
N
C). C{ H}-NMR (100.6 MHz, CDCl , 300 K): 157.0 (OCON); 79.5 (Me
MeN). FAB-MS: 132 (10, M+H] ), 76 (63), 57 (100), 41 (44). Anal. calc. for C H NO (131.17): C
A
H
R
N
A
H
R
U
G
3
3
3
+
6 13 2
5
4.94, H 9.99, N 10.68; found: C 54.92, H 9.79, N 10.51.
,1-Dimethylethyl (1-Methylethyl)carbamate (1b). As described for 1a, with PrNH (1.00 g, 16.92
i
1
2
mmol), Boc (O) (4.06 g, 18.61 mmol), and DMAP (20 mg, 0.17 mmol): 1b (2.21 g, 74%). White solid.
A
T
E
N
2
R (AcOEt/hexane 1:9) 0.48. M.p. 69–718. IR (KBr): 3346m, 2978m, 2935m, 1683s, 1539m, 1459m,
f
1
1
367m, 1256s, 1174s, 1078s, 938w, 886w, 841w, 778w, 753w, 643m, 461w, 424w. H-NMR (400.1 MHz,
CDCl , 300 K): 4.31 (br., NH); 3.71 (m, Me
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
3
2
3
13
1
Me2
A
H
R
U
G
A
H
R
U
G
3
3
(Me
A
H
R
U
G
A
H
R
U
G
3
1
0.76, N 8.80, O 20.10; found: C 60.41, H 10.56, N 8.64, O 20.28.
,1-Dimethylethyl Methyl(2-oxoethyl)carbamate (3a). A soln. of 1a (10.05 g, 76.6 mmol) in DMF (100
1
ml) at 08 was added to a suspension of KH (3.38 g, 84.3 mmol; free of mineral oil) in DMFat 08 over 0.5 h.
The mixture was stirred at r.t. until the gas evolution had ceased (typically 2 h). Then 1-bromo-3-
methylbut-2-ene (13.7 g, 91.9 mmol) was added and the resultant mixture stirred at r.t. for an additional
hour. The soln. was quenched with sat. aq. NaHCO soln. (100 ml) and H O (100 ml) and extracted with
3
2
Et2O (3×100 ml), and the combined org. layer was dried (MgSO ) and evaporated: 2a (11.56 g) as a col-
A
H
R
U
G
4
orless oil, which was not stable on silica gel and used for the next step without purification.
A soln. of crude 2a in CH Cl /MeOH 3 :1 (500 ml) was cooled to ꢀ788, and ozone was bubbled into
2
2
the mixture for ca. 0.5 h (TLC monitoring). Then the mixture was warmed to r.t. and reduced with Me S
A
H
R
U
G
2
(7.21 g, 116 mmol). The solvent and excess Me2
A
H
R
U
G
(
silica gel, 7×20 cm column, R 0.40, AcOEt/hexane 3 :7): 3a (6.38 g, 48% over two steps). Colorless oil.
f
IR (NaCl): 2976m, 2933m, 1734m, 1695s, 1481m, 1456m, 1392m, 1297w, 1242m, 1158s, 1056w, 929w, 878w,
1
7
1
1
75w. H-NMR (400.1 MHz, CDCl , 300 K): 9.56 (s, CHO); 3.99–3.87 (m, CH N); 2.93–2.88 (m, MeN);
3
2
13
1
.44–1.38 (m, 9 H, Me3
55.8 (NCOO); 81.1 (Me C); 80.9 (Me C); 59.6 (CH N); 59.1 (CH N); 36.2 (MeN); 28.6 (br., Me C);
3
two sets of signals due to amide conformers. FAB-MS: 174 (37, [M+H] ), 118 (100), 57 (88). Anal.
A
H
R
U
G
A
H
R
U
G
3
3
2
2
+
calc. for C H NO (173.21): C 55.47, H 8.73, N 8.09; found: C 54.73, H 8.44, N 8.09.
8
15
3
1
,1-Dimethylethyl (1-Methylethyl)(2-oxoethyl)carbamate (3b). As described for 3a, with 1b (4.83 g,
0.4 mmol), KH (1.34 g, 33.4 mmol), 1-bromo-3-methylbut-2-ene (5.97 g, 40.1 mmol), and Me2S (2.52
g, 40.6 mmol): 3b (1.790 g, 30% over two steps). White solid. R (AcOEt/hexane 3 :7) 0.54. M.p.
3
ACHTREUNG
f
3
1
6–378. IR (KBr): 2978m, 2805w, 2709w, 1739m, 1696s, 1437m, 1398m, 1366m, 1295m, 1253m, 1219m,
1
169s, 1108m, 1019m, 900m, 857w, 823w, 773m, 680w, 456w. H-NMR (500.1 MHz, CDCl , 295 K): 9.48
3
(
(
(
(
(
5
br., 1 H, CHO), 4.50 (br., 0.64 H, Me
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
2
2
13
1
m, 6 H, Me2CH). C{ H}-NMR (125.7 MHz, CDCl , 295 K): 200.2 (CHO); 155.8 (NCOO); 154.8
A
H
R
U
G
NCOO); 80.8 (Me C); 80.6 (Me C); 51.4 (CH N); 51.1 (CH N); 47.4 (Me CH); 46.0 (Me CH); 28.4
3
3
2
2
br., Me3
A
H
R
U
G
A
H
R
N
A
H
R
U
G
2
+
10, [M+H] ), 172 (39), 146 (21), 116 (34), 72 (60), 57 (100). Anal. calc. for C H NO (201.26): C
10
19
3
9.68, H 9.51, N 6.96, O 23.85; found: C 59.61, H 9.37, N 7.05, O 23.96.
,1-Dimethylethyl {2-{{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}amino}ethyl}methyl-
carbamate (5a). A soln. of 3a (421 mg, 2.43 mmol) in 1,2-dichloroethane (5 ml) was added to a soln. of
1

1
568
Helvetica Chimica Acta – Vol. 89 (2006)
(
2S)-1-(diphenylphosphino)-3-methylbutan-2-amine (4; 600 mg, 2.21 mmol) and NaHB(OAc) (933 mg,
3
4
.42 mmol) in 1,2-dichloroethane (3 ml). The mixture was stirred at r.t. for 4 h and quenched with sat. aq.
NaHCO soln. (10 ml). The aq. layer was extracted with CH Cl (3×10 ml), the combined org. phase
3
2
2
dried (MgSO ) and evaporated, and the yellow oil purified by CC (silica gel, 3×18-cm column, R
4
f
20
0
.56, AcOEt/hexane 4 :6): 5a (700 mg, 74%). Colorless oil. [a] =+52.2 (c=1.00, CHCl ). IR (NaCl):
D
3
1
3
056w, 2961m, 1694s, 1478m, 1433w, 1392m, 1368w, 1247w, 1155m, 879w, 741w, 696w. H-NMR (500.1
MHz, CDCl , 295 K): 7.49–7.43 (m, 2 arom. H); 7.43–7.38 (m, 2 arom. H); 7.37–7.27 (m, 6 arom. H);
3
3
2
.19 (br., CH N); 2.82 (s, Me); 2.71–2.58 (br., CH N); 2.36 (m, PCH
A
H
R
U
G
2
2
2
2
3
3
.25–1.85 (br., 2 H, CH P, Me
A
H
R
U
G
A
H
R
U
G
2
2
3
13
1
H, Me CH); 1 NH not detected. C{ H}-NMR (125.7 MHz, CDCl , 295 K): 155.9 (br., NCO); 139.6
A
H
R
U
2
3
(
(
(
br., arom. C); 138.4 (br., arom. C); 133.4 (arom. CH); 133.2 (arom. CH); 132.7 (br., arom. CH); 132.6
br., arom. CH); 129.0 (arom. CH); 128.7–128.4 (5 arom. CH); 70.4 (Me C); 60.6 (br., PCH CH); 49.2
3
2
CH N); 45.9 (CH N), 35.2 (MeN); 30.8 (br., Me CH); 30.6 (br., CH P); 28.6 (Me C); 18.4 (br., 1 C, Me -
A
H
R
U
G
2
2
2
2
3
2
31
1
A
C
H
T
R
E
U
N
G
CH); 17.5 (1 C, Me
A
H
R
U
G
2
3
+
[
M+H] ), 445 (18); oxidation during measurement. Anal. calc. for C H N O P (428.55): C 70.07, H
25 37 2 2
8
.70, N 6.54, O 7.47; found: C 69.83, H 8.52, N 6.60, O 7.55.
,1-Dimethylethyl {2-{{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}amino}ethyl}(1-meth-
1
ylethyl)carbamate (5b). As described for 5a, with 3b (250 mg, 1.24 mmol), 4 (306 mg, 1.13 mmol), and
NaHB(OAc) (526 mg, 2.48 mmol): 5b (413 mg, 80%). Colorless oil that crystallized on standing. R
3
f
2
D
0
(
AcOEt/hexane 1:1) 0.69. M.p. 51–528. [a] =+60.4 (c=1.00, CHCl ). IR (KBr): 3068w, 2967m,
3
2
8
872m, 2815m, 1593s, 1472m, 1412m, 1367m, 1343m, 1299m, 1250w, 1169m, 1122m, 1089w, 998w, 905w,
1
36w, 744m, 695m, 508w. H-NMR (500.1 MHz, CDCl , 295 K): 7.46 (m, 2 arom. H); 7.40 (m, 2 arom.
3
H); 7.36–7.27 (br., 6 arom. H); 4.40–3.80 (br., Me
2
A
H
R
U
G
2
N); 2.65 (br., CH
2
N); 2.40
C); 1.07
3
(
(
(
br., PCH2
br., Me2CHN); 0.89 (br., 3 H, Me
125.7 MHz, CDCl
A
T
E
N
A
H
R
U
G
ACHTREUNG
2
2
2
13
1
A
H
R
U
G
A
H
R
U
G
A
H
R
N
2
1
2
3
, 295 K): 138.3 (d, J(P,C)=12.6, arom. C); 133.4 (d, J(P,C)=19.3, 2 arom. CH);
32.6 (d, J(P,C)=17.5, 2 arom. CH); 128.8–128.3 (5 arom. CH); 60.5 (br., PCH CH); 47.9 (CH N);
2
1
4
2
2
2
1
6.5 (br., Me CHC); 42.8 br., (CH N); 30.8 (d, J(P,C)=7.0, CH P); 30.5 (br., Me CHC); 28.6 (Me C);
A
H
R
U
G
2
2
2
2
3
0.9 (Me
A
H
R
U
G
A
H
R
U
G
A
H
R
N
2
2
31
1
P{ H}-NMR (202.5 MHz, CDCl , 295 K): ꢀ21.1 (br.). FAB-MS: 457 (100, [M+H] ), 473 (17); oxida-
3
tion during measurement. Anal. calc. for C H N O P (456.60): C 71.02, H 9.05, N 6.14, O 7.01;
27
41
2
2
found: C 70.91, H 8.97, N 6.22, O 7.03.
,1-Dimethylethyl {2-{{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}amino}ethyl}(2,4,6-tri-
1
methylphenyl)carbamate (5c). As described for 5a, with 3c (675 mg, 2.43 mmol), 4 (600 mg, 2.21
mmol), and NaHB(OAc) (937 mg, 4.42 mmol): 5c (961 mg, 82%). Colorless oil. R (AcOEt/hexane
3
f
2
D
0
2
1
7
:8) 0.43. [a] =+30.5 (c=1.00, CHCl ). IR (KBr): 3054m, 2959m, 2927m, 2867m, 1695s, 1479m,
370m, 1310m, 1254m, 1150m, 1030w, 994w, 855w, 741m, 696m. H-NMR (500.1 MHz, CDCl , 295 K):
3
1
3
.47–7.24 (m, 10 arom. H (Ph)); 6.88–6.83 (m, 2 arom. H (Mes)); 3.55–3.25 (m, CH2
A
H
R
U
G
(
m, CH N); 2.35 (m, PCH
ACHTREUNG
CH); 2.28–2.24 (m, Me (Mes)); 2.24–2.17 (m, 1 H, CH P); 2.16–2.09 (m, 2
2
2
2
Me (Mes)); 2.02–1.87 (m, 2 H, CH P, Me
A
H
R
U
G
A
H
R
U
G
A
H
E
N
2
2
3
13
1
A
C
H
T
R
E
U
N
G
CHC); 1 NH not detected. C{ H}-NMR (125.7 MHz, CDCl , 295 K): 139.7 (arom. C); 139.6 (arom. C);
1
1
38.3 (arom. C); 138.2 (arom. C); 138.0 (arom. C); 136.8 (arom. C); 136.5 (br., arom. C); 135.9 (arom. C);
35.8 (arom. C); 135.3 (br., arom. C); 133.4 (arom. C); 133.29 (arom. C); 133.28 (arom. C); 133.1 (arom.
C); 132.8 (arom. C); 132.7 (arom. C); 132.6 (arom. C); 132.4 (arom. C); 129.4 (arom. C); 129.3 (arom. C);
2
1
29.2–128.3 (m, arom. C); 60.8 (br., PCH CH); 60.5 (d, J(P,C)=12.6, PCH CH); 51.0 (CH N); 49.9 (br.,
2
2
2
1
1
CH N); 46.6 (br., CH N); 30.8 (d, J(P,C)=7.0, CH P); 30.7 (d, J(P,C)=7.3, CH P); 30.6 (br., Me CHC);
A
H
R
U
G
2
2
2
2
2
3
0.5 (br., Me CHC); 28.6 (Me
A
H
R
U
G
A
H
R
U
G
2
3
(
Me); 17.8 (Me); 17.3 (Me); two sets of signals due to amide rotamers; 2 quat. Me C not detected.
3
+
3
1
1
P{ H}-NMR (202.5 MHz, CDCl , 295 K): ꢀ21.2 (br.), ꢀ21.3 (s). FAB-MS: 533 (100, [M+H] ), 549
3
(
38); oxidation during measurement. Anal. calc. for C H N O P (532.70): C 74.41, H 8.51, N 5.26, O
33
45
2
2
6
.01; found: C 74.43, H 8.49, N 5.29, O 6.12.
-{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}-4,5-dihydro-1-methyl-1H-imidazolium
3
Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (1ꢀ) (6a). CF COOH (6.00 g, 53.0 mmol) was added to a
3

Helvetica Chimica Acta – Vol. 89 (2006)
1569
soln. of 5a (450 mg, 1.05 mmol) in CH Cl (15 ml) at 08. The mixture was stirred at r.t. for 20 h and then
2
2
quenched with H O (15 ml) and 5M NaOH until the pH was 10. The aq. layer was extracted with CH Cl
2
2
2
(
9
2×15 ml). The combined org. extract was dried (MgSO ) and evaporated to yield a yellow oil (327 mg,
4
1
5%) of >95% purity (by H-NMR). A soln. of this oil (217 mg, 0.661 mmol) and NH BF (77 mg, 0.726
4
4
mmol) in triethyl orthoformate (4.0 ml, 26.0 mmol) was heated at 1108 for 1 h. The precipitate was de-
canted and dissolved in CH Cl (10 ml). Sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate(1ꢀ)
ACHTREUNG
2
2
(
NaBAr ; 586 mg, 0.661 mmol) was added to the mixture, which was then stirred for 15 min. The soln.
F
was filtered, the filtrate evaporated, and the crude product purified by CC (silica gel, 5×8-cm column,
2
D
0
inert atmosphere, CH Cl (500 ml)): 6a (409 mg, 51%). White solid. M.p. 97–988. [a] =+26.5
2
2
(
9
c=1.00, CHCl ). IR (KBr): 3076w, 2975w, 1659m, 1612w, 1526w, 1467w, 1435w, 1358s, 1280s, 1123s,
3
1
30w, 889m, 838w, 748w, 711w, 674m, 501w, 450w. H-NMR (400.1 MHz, CDCl , 300 K): 7.69 (m, 8 H
3
o
(
Ar )); 7.53 (m, 4 H (Ar )); 7.45–7.25 (m, 10 arom. H); 7.05 (s, NCHN), 3.65–3.43 (m, 3 H, CH N);
F
p
F
2
3
.43–3.15 (m, 2 H, CH N, PCH
A
H
R
U
G
2
2
2
2
3
3
13
1
(m, Me
A
H
R
U
G
2
1
CDCl , 300 K): 162.0 (q, J(B,C)=49.9, 4 C (ArF)); 156.0 (NCHN); 136.2 (d, J(P,C)=10.2, 1 arom.
C); 135.2 (br., 8 Co (Ar )); 134.4 (d, J(P,C)=9.8, 1 arom. C); 133.3 (d, J(P,C)=20.2, 2 arom. CH);
3
F
1
32.8 (d, J(P,C)=19.5, 2 arom. CH); 130.59 (arom. CH); 130.57 (arom. CH); 129.7 (d, J(P,C)=7.4, 2
2
3
arom. CH); 129.6 (d, J(P,C)=7.7, 2 arom. CH); 129.3 (qq, J(F,C)=31.1, J(B,C)=2.9, 8 C (Ar ));
1
PCH CH); 50.0 (CH N); 46.0 (d, J(P,C)=3.5, 1 C, CH N); 35.2 (MeN); 32.2 (d, J(P,C)=6.7,
Me CH); 29.3 (d, J(P,C)=15.2, CH P); 19.6 (1 C, Me CH); 19.4 (1 C, Me CH). P{ H}-NMR (202.5
m
F
1
3
2
24.9 (q, J(F,C)=272.5, 8 CF ); 117.9 (sept., J(F,C)=3.8, 4 Cp (Ar )); 65.8 (d, J(P,C)=14.8,
3
F
4
3
2
2
2
1
31
1
A
H
R
U
G
2
2
2
2
+
MHz, CDCl , 295 K): ꢀ25.4 (s). FAB-MS: 339 (100, [MꢀBAr ] ), 355 (29); oxidation during measure-
3
F
ment. Anal. calc. for C53
H40BF24
N
2
P (1202.64): C 52.93, H 3.35, N 2.33; found: C 53.14, H 3.34, N 2.36.
3
-{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}-4,5-dihydro-1-(1-methylethyl)-1H-imidaz-
olium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (1ꢀ) (6b). As described for 6a, with 5b (167 mg,
.472 mmol), CF COOH (4.47 g, 39.2 mmol), NH BF (49 mg, 0.468 mmol): triethyl orthoformate (2.0
ml, 13.0 mmol), and NaBAr (414 mg, 0.468 mmol): 6b (460 mg, 79% over two steps). White solid.
ACHTREUNG
0
3
4
4
F
20
M.p. 98–998. [a] =+25.1 (c=1.00, CHCl ). IR (KBr): 3072w, 2978w, 1643m,1470w, 1434w, 1358s,
D
3
1
1
7
3
279s, 1128s, 930w, 890w, 838w, 744w, 708m, 674m, 506w, 450w. H-NMR (500.1 MHz, CDCl , 295 K):
3
.70 (m, 8 H (Ar )); 7.53 (m, 4 H (ArF)); 7.44–7.35 (m, 10 arom. H); 7.13 (s, NCHN); 3.70–3.55 (m,
o
F
p
H of NCH , Me
A
H
R
U
G
A
H
E
N
2
2
2
3
H, CH P); 1.79 (m, Me
A
H
R
U
G
A
H
R
U
G
A
H
R
N
2
2
3
13
1
1
J(H,H)=6.4, 3 H, Me2CHC). C{ H}-NMR (125.7 MHz, CDCl , 295 K): 161.8 (q, J(B,C)=49.9, 4
A
H
R
U
3
1
1
Cipso (Ar )); 153.8 (NCHN); 135.9 (d, J(P,C)=9.8, 1 arom. C); 134.9 (br., 8 C (Ar )); 135.0 (d, J(P,
F
o
F
C)=9.3, 1 arom. C); 132.8 (d, J(P,C)=11.4, 2 arom. CH); 132.7 (d, J(P,C)=11.2, 2 arom. CH); 130.5
arom. CH); 130.2 (arom. CH); 129.6 (d, J(P,C)=7.4, 2 arom. CH); 129.4 (d, J(P,C)=7.5, 2 arom.
(
2
3
1
CH); 129.0 (qq, J(F,C)=31.1, J(B,C)=2.9, 8 C (Ar )); 124.7 (q, J(F,C)=272.5, 8 CF ); 117.5 (sept.,
m
F
3
3
2
J(F,C)=3.8, 4 Cp (Ar )); 65.3 (d, J(P,C)=11.9, PCH CH); 51.4 (Me CHN); 45.8 (CH N); 44.8 (d,
J(P,C)=4.1, 1 C, CH N), 31.8 (d, J(P,C)=6.1, Me CHN); 28.9 (d, J(P,C)=13.9, CH P); 20.57 (Me -
F
2
2
2
4
3
1
2
2
2
2
31
1
A
C
H
T
R
E
U
N
G
CHN); 20.47 (Me
A
H
R
U
G
A
T
E
N
A
H
R
U
G
2
2
+
ꢀ
22.6 (s). FAB-MS: 367 (100, [MꢀBAr ] ), 383 (37); oxidation during measurement. Anal. calc. for
F
C H BF N P (1230.70): C 53.68, H 3.60, N 2.28; found: C 53.49, H 3.64, N 2.36.
55
44
24
2
3-{(1S)-1-[(Diphenylphosphino)methyl]-2-methylpropyl}-4,5-dihydro-1-(2,4,6-trimethylphenyl)-1H-
imidazolium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate(1ꢀ) (6c). As described for 6a, with 5c (225
mg, 0.423 mmol), CF COOH (4.53 g, 39.8 mmol), NH BF (36 mg, 0.347 mmol), triethyl orthoformate
3
4
4
(
4.0 ml, 26.0 mmol), and NaBAr (307 mg, 0.347 mmol): 6c (218 mg, 39% over two steps). Colorless
F
20
oil. [a] =+63.2 (c=1.00, CHCl ). IR (NaCl): 3067w, 2970w, 2939w, 1639m, 1357m, 1279s, 1126s (br.),
9
D
3
1
98w, 934w, 889m, 839m, 744w, 710m, 675m, 577w, 504w. H-NMR (500.1 MHz, CDCl , 295 K): 7.70
3
(
m, 8 H (Ar )); 7.50 (m, 4 H (Ar )); 7.48–7.39 (m, 3 arom. H (Ph), 2 arom. H (Mes)); 7.38–7.30 (m,
o F p F
NCHN, 5 arom. H (Ph)); 6.98 (br., 2 arom. H (Ph)); 4.25–4.06 (m, 3 H, CH N); 3.96 (m, 1 H, CH N);
2
2
3
.18 (m, PCH2CH); 2.78 (m, 1H, CH P); 2.40–2.25 (br., 2 Me); 2.15 (m, 4 H, 1 Me, CH P); 1.93 (m, Me -
A
T
E
N
2
2
2
3
3
13
1
A
C
H
T
R
E
U
N
G
CH); 1.00 (d, J=6.6, 3 H, Me
A
H
R
U
G
A
T
E
N
2
1
1
2
95 K): 161.8 (q, J(B,C)=49.9, 4 C (Ar )); 156.9 (NCHN); 142.1 (arom. C (Mes)); 135.7 (d, J(P,
ipso F

1
570
Helvetica Chimica Acta – Vol. 89 (2006)
1
C)=7.9, 1 arom. C (Ph)); 134.9 (br., C (ArF)); 133.6 (d, J(P,C)=10.6, 1 arom. C (Ph)); 133.3 (d, J(P,
o
C)=10.5, 2 arom. C (Ph)); 131.9 (d, J(P,C)=18.7, 2 arom. CH (Ph)); 131.0 (2 arom. CH (Mes)); 130.6
(
arom. CH (Ph)); 129.8 (arom. CH (Ph)); 129.8 (d, J(P,C)=7.4, 2 arom. CH (Ph)); 129.2 (d, J(P,
2
3
C)=7.2, 2 arom. CH (Ph)); 129.1 (arom. C (Mes)); 129.0 (qq, J(F,C)=31.1, J(B,C)=2.9, 8 C
m
1
3
2
(Ar )); 124.7 (q, J(F,C)=272.5, 8 CF ); 117.5 (sept., J(F,C)=3.8, 4 C (Ar )); 64.7 (d, J(P,C)=11.1,
F
3
p
F
4
3
PCH CH); 50.6 (CH N); 45.9 (d, J(P,C)=5.8, 1 C, CH N); 31.9 (d, J(P,C)=5.1, Me CH); 28.8 (d,
2
2
2
2
1
J(P,C)=13.9, CH P); 21.1 (Me (Mes)); 19.5 (Me
A
H
R
U
G
A
H
E
N
2
2
31
1
arom. C (Mes) not observed. P{ H}-NMR (202.5 MHz, CDCl , 295 K): ꢀ26.0 (s). FAB-MS: 443
3
+
(
100, [MꢀBAr ] ), 459 (32); oxidation during measurement. Anal. calc. for C H BF N P (1306.80):
F
61 48
24
2
C 56.07, H 3.70, N 2.14; found: C 55.95, H 3.70, N 2.12.
(1,2,5,6-h)-Cycloocta-1,5-diene]{1-{(1S)-1-[(diphenylphosphino-kP)methyl]-2-methylpropyl}-4,5-
dihydro-3-methyl-2H-imidazol-2-ylidene-kC}iridium(1+) Tetrakis[3,5-bis(trifluoromethyl)phenyl]bo-
[
t
rate(1ꢀ) (7a). Freshly sublimed NaO Bu (18 mg, 0.192 mmol) was added to a soln. of 6a (231 mg,
0
2
7
1
4
5
.192 mmol) and [Ir Cl (cod) ] (64 mg, 0.096 mmol) in THF (10 ml). The mixture was stirred at r.t. for
2 2 2
hand then evaporated. The crude product was purified by CC (silica gel, 15×3-cm column, CH Cl ):
2
2
2
D
0
a (210 mg, 73%). Red solid. [a] =ꢀ17 (c=0.15, CHCl ). IR (KBr): 3076w, 2968w, 2887w, 2840w,
3
612w, 1526m, 1440m, 1357s, 1279s, 1127s, 998w, 934w, 889m, 838w, 744w, 711m, 674m, 579w, 518w,
1
79w, 448w. H-NMR (500.1 MHz, CD Cl , 295 K): 7.75 (m); 7.67 (m); 7.42 (m); 7.10 (m); 5.14 (m);
2
2
.08 (m); 4.63 (m); 4.59 (m); 4.46 (m); 4.35 (m); 3.64–3.48 (m); 3.44 (m); 3.40–3.32 (m); 3.27–3.16
m); 3.15–3.04 (m); 3.02–2.67 (m); 2.66–2.31 (m); 2.25–2.05 (m); 1.93–1.74 (m); 1.71–1.56 (m); 1.54
(
(
3
3
13
1
s); 1.27 (d, J(H,H)=6.1); 1.18 (d, J(H,H)=6.6); 1.12–0.72 (m); 1.36 :1 major/minor ratio. C{ H}-
NMR (125.7 MHz, CD Cl , 295 K): 204.0 (d, J(P,C)=12.0, NCN min.); 200.0 (d, J(P,C)=13.4, NCN
2
2
1
maj.); 161.8 (q, J(B,C)=49.9, 4 Cipso (Ar
F o F
)); 134.9 (br., 8 C (Ar )); 134.0; 133.6; 133.4; 133.0;
1
32.2–132.1 (overlapping signals); 131.2; 131.1; 130.9 (br.); 130.7; 130.6; 129.5–128.5 (overlapping sig-
1
3
nals); 124.7 (q, J(F,C)=272.5, 8 CF ); 117.6 (sept., J(F,C)=3.8, 4 C (Ar )); 89.8 (d, J(P,C)=8.6, CH
3
p
F
(
(
(
(
2
cod), maj.); 88.7 (d, J(P,C)=7.7, CH (cod), min.); 86.8 (d, J(P,C)=13.9, CH (cod), min.); 82.4 CH
cod), min.); 81.65 (d, J(P,C), CH (cod), min.); 81.6 (CH (cod), min.); 79.8 (CH (cod), maj.); 78.4 (CH
cod), maj.); 67.7 (d, J(P,C)=6.7); 66.0; 53.2; 51.9; 51.7; 44.3; 39.6; 38.0; 37.5 (d, J(P,C)=3.8); 35.6
br.); 35.3 (d, J(P,C)=3.8); 35.0; 30.7; 30.6; 29.8; 28.5; 28.2; 27.3 (br.); 26.8; 26.7; 26.6 (br.); 26.5; 20.9;
31
1
0.8; 19.9; 19.6. P{ H}-NMR (202.5 MHz, CD Cl , 295 K): 17.0 (s, 0.75 P, min.); 16.4 (s, 1.00 P, maj.).
2
2
+
FAB-MS: 639 (100, [MꢀBAr ] ). Anal. calc. for C H BF IrN P (1502.02): C 48.78, H 3.42, N 1.87;
F
61 51
24
2
found: C 48.81, H 3.45, N 1.84.
[(1,2,5,6-h)-Cycloocta-1,5-diene]{1-{(1S)-1-[(diphenylphosphino-kP)methyl]-2-methylpropyl}-4,5-
dihydro-3-(1-methylethyl)-2H-imidazol-2-ylidene-kC}iridium(1+) Tetrakis[3,5-bis(trifluoromethyl)phe-
nyl]borate(1ꢀ) (7b). As described for 7a, with 6b (291 mg, 0.237 mmol), [Ir Cl (cod) ] (79 mg, 0.118
2
2
2
t
20
mmol), and NaO Bu (23 mg, 0.237 mmol): 7b (250 mg, 69%). Red solid. [a] =ꢀ5 (c=0.10, CHCl ).
D
3
IR (KBr): 3065w, 2977w, 2886w, 2839w, 1611w, 1491m, 1453m, 1357s, 1279s, 1127s, 999w, 933w, 889m,
1
8
7
3
2
39w, 743w, 711m, 675m, 585w, 535w, 524w, 447w. H-NMR (500.1 MHz, CD Cl , 295 K): 7.72 (m);
2 2
.70–7.14 (m); 7.03 (m); 5.16 (m); 5.12 (m); 4.67–4.23 (m); 4.37 (m); 4.23 (m); 3.70–3.20 (m);
.19–3.14 (m); 3.14–2.96 (m); 2.93–2.79 (m); 2.76–2.63 (m); 2.60–2.48 (m); 2.40–2.31 (m);
.28–2.05 (m); 1.93–1.76 (m); 1.75–1.67 (m); 1.63–1.43 (m); 1.31–0.40 (m); 1.45 :1 major/minor
ratio. C{ H}-NMR (125.7 MHz, CD Cl , 295 K): 203.5 (d, J(P,C)=12.5, NCN, maj.); 198.8 (d, J(P,
C)=12.5, NCN, min.); 162.3 (q, J(B,C)=49.9, 4 C (Ar )); 135.6, 135.4 (br., 8 C (Ar )); 132.8 (d,
13
1
2
2
1
ipso
F
o
F
J(P,C)=2.4); 132.7 (d, J(P,C)=2.5); 131.8 (d, J(P,C)=9.6); 131.3 (br.); 131.0 (d, J(P,C)=9.1);
1
3
1
30.2–128.8 (overlapping signals); 125.1 (q, J(F,C)=272.5, 8 CF ); 118.1 (sept., J(F,C)=3.8, 4 Cp
3
(
Ar )); 90.1 (d, J(P,C)=8.6, CH (cod), min.); 88.8 (d, J(P,C)=7.7, CH (cod), maj.); 87.2 (d, J(P,
F
C)=14.4, CH (cod), min.); 84.0 (CH (cod), maj.); 81.9 (d, J(P,C)=16.3, CH (cod), maj.); 81.5 (CH
cod), maj.); 79.4 (CH (cod), min.); 79.2 (CH (cod), min.); 68.7 (d, J(P,C)=6.7); 67.0; 53.2 (br.); 52.5;
4.1; 43.5; 43.0; 37.0 (d, J(P,C)=4.8); 36.6 (br.); 36.2 (d, J(P,C)=4.3); 35.7 (br.); 31.1; 31.0; 27.7; 27.5
(
4
31
1
(br.); 27.4; 27.3; 27.0; 26.7 (br.); 22.1; 22.0; 21.5; 21.4; 20.9; 20.7; 20.6; 20.3. P{ H}-NMR (202.5 MHz,
+
CD Cl , 295 K): 15.1 (s, 1.00 P, maj.); 14.3 (s, 0.72 P, min.). FAB-MS: 667 (100, [MꢀBAr ] ). Anal.
2
2
F
calc. for C H BF IrN P (1530.08): C 49.45, H 3.62, N 1.83; found: C 49.45, H 3.76, N 1.94.
63
55
24
2

Helvetica Chimica Acta – Vol. 89 (2006)
1571
[(1,2,5,6-h)-Cycloocta-1,5-diene]{1-{(1S)-1-[(diphenylphosphino-kP)methyl]-2-methylpropyl}-4,5-
dihydro-3-(2,4,6-trimethylphenyl)-2H-imidazol-2-ylidene-kC}iridium(1+) Tetrakis[3,5-bis(trifluorome-
thyl)phenyl]borate(1ꢀ) (7c). As described for 7a, with 6c (150 mg, 0.115 mmol), [IrCl (cod) ] (39 mg,
2
2
t
20
0
.057 mmol), and NaO Bu (11 mg, 0.115 mmol): 7c (138 mg, 75%). Red solid. [a] =ꢀ6 (c=0.1,
D
CHCl ). IR (KBr): 2971w, 2928w, 2888w, 2840w, 1611w, 1486w, 1435w, 1356s, 1278s, 1127s, 1000w,
3
1
9
68w, 935w, 889w, 839w, 744w, 711w, 676m, 580w, 513w, 448w. H-NMR (500.1 MHz, CD Cl , 246 K):
2
2
7
.78 (m, 8 Co (Ar )); 7.64–7.51 (m, arom. CH); 7.47 (m, 2 arom. CH, min.); 7.40–7.33 (m, arom.
F
CH); 7.18 (m, 2 arom. CH, min.); 7.05 (m, 2 arom. CH, maj.); 6.88–6.84 (m, 4 arom. CH (Mes)); 6.84
s); 5.36 (m, 1 CH (cod), min.); 5.11 (m, 1 CH (cod), maj.); 4.53 (m, 1 CH (cod), min.); 4.33 (m, CHN,
min.); 4.13 (m, 1 CH (cod), maj.); 4.01 (m, 1 H, CH N); 3.94–3.70 (m, 4 H, CH N); 3.63–3.47 (m, 3
(
2
2
H, CH N); 3.44–3.38 (m, 1 CH (cod), maj., and 1 CH (cod), min.); 3.37 (m, CHN, maj.); 3.27 (m, Me -
2
2
A
C
H
T
R
E
U
N
G
CH, maj.); 3.18 (m, 1 CH (cod), min.); 3.09 (m, 1 CH, maj.); 2.91 (m, 1 H of CH P, maj.); 2.73 (m, 1 H of
2
CH P, maj.); 2.64 (m, 1 H of CH P, min.); 2.49 (CH (cod), maj.); 2.49 (m, 1 H of CH (cod), maj.);
2
2
2
2
13
1
2
2
4
1
.40–0.70 (complex overlapping signals); 3.4 :1 major/minor ratio. C{ H}-NMR (125.7 MHz, CD Cl ,
46 K): 202.0 (d, J(P,C)=9.6, NCN, min.); 194.3 (d, J(P,C)=10.5, NCN, maj.); 161.7 (q, J(B,C)=49.9,
Cipso (Ar )); 138.9; 136.2; 135.9; 135.5; 135.4; 135.0; 134.7 (br., 8 C (Ar )); 133.9 (d, J(P,C)=11.1);
2 2
1
F
o
F
33.4 (d, J(P,C)=11.0); 132.0 (d, J(P,C)=9.9); 131.8 (br.); 131.6; 131.2 (br.); 131.1; 130.9 (br.); 130.6
1
(
br.); 130.3; 129.0; 129.5–128.4 (overlapping signals); 125.5 (q, J(F,C)=272.5, 8 CF ); 117.5 (sept.,
3
3
J(F,C)=3.8, 4 C (Ar )); 88.8 (d, J(P,C)=13.2, CH (cod), maj.); 87.2 (d, J(P,C)=8.7, OH (cod), maj.);
p
F
8
8
6.5 (d, J(P,C)=7.5, CH (cod), min.); 83.6 (d, J(P,C)=14.4, CH (cod), min.); 82.5 (CH (cod), min.);
1.5 (CH (cod), min.); 78.9 (CH (cod), maj.); 77.8 (CH (cod), maj.); 66.4 (d, J(P,C)=7.5 Hz, CHN,
min.); 65.5 (br., CHN, maj.); 53.6 (CH N, maj.); 52.3 (CH N, min.); 52.0 (CH N, maj.); 43.2 (CH N,
2
2
2
2
min.); 37.1 (d, J(P,C)=6.4, Me
2
A
H
R
U
G
2
2 2
(cod), min.); 35.74 (CH (cod), maj.); 35.71 (CH
(
cod), min.); 35.5 (br., CH (cod), maj.); 30.2 (d, J(P,C)=11.9, Me C, min.); 26.9 (CH (cod), maj.);
2
2
2
2
6.3 (CH (cod), min.); 25.7 (CH (cod), min.); 25.6 (m, CH P, maj.); 25.5 (CH (cod), maj.); 21.0 (p-
2 2 2 2
Me (Mes), min.); 20.9 (1 C, Me
2
A
H
R
U
G
2
A
H
R
U
G
2
CH, min, and Me -
ACHTREUNG
CH, maj.); 19.5 (o-Me (Mes), min.); 19.3 (o-Me (Mes), maj.); 18.0 (o-Me (Mes), min.); 17.9 (o-Me (Mes),
31
1
maj.). P{ H}-NMR (202.5 MHz, CD Cl , 246 K): 9.9 (s, 0.44 P, min.); 6.6 (s, 1.00 P, maj.). FAB-MS: 743
(
3
2
2
+
100, [MꢀBAr ] ). Anal. calc. for C H BF IrN P (1606.18): C 51.60, H 3.70, N 1.74; found: C 51.57, H
F
69 59
24
2
.60, N 1.81.
-[(2-R)-2-Hydroxy-2-phenylethyl]-1-(1-methylethyl)-1H-imidazolium Tetrakis[3,5-bis(trifluorome-
3
thyl)phenyl]borate(1ꢀ) (10). A mixture of 1H-imidazole (8; 960 mg, 14.1 mmol) and commercially avail-
able (2R)-2-phenyloxirane (9; 1.693 mg, 14.1 mmol) was heated at 508 for 12 h. Degassed MeCN (5 ml)
i
and PrI (2.39 g, 14.1 mmol) were added to the mixture at r.t. The soln. was heated at 808 for 3 h. Upon
cooling, a solid precipitated from the mixture, which was filtered and carefully washed once with MeCN
(
5 ml). NaBAr (3.75 g, 4.23 mmol) was added to a soln. of the collected imidazolium iodide salt (1.51 g)
F
in CH Cl (120 ml). The mixture was filtered, the filtrate evaporated, and the crude product purified by
2
2
2
D
0
CC (silica gel, 15×7-cm column, 5% MeOH in CH Cl ): 10 (3.84g, 25%). Colorless oil. [a] =+23.7
2
2
(
9
c=1.00, CHCl ). IR (NaCl): 3645w, 3171w, 3083w, 2992w, 1611w, 1555w, 1461m, 1359s, 1280s, 1120s,
3
1
27w, 889m, 834w, 762w, 738w, 710m, 673m, 579w, 528w, 446w. H-NMR (400.1 MHz, CDCl , 300 K):
3
7
.89 (m, 1 arom. CH); 7.72 (m, 8 H (Ar )); 7.54 (m, 4 H (Ar )); 7.32 (m, 2 arom. CH) ; 7.11 (m, 2
o
F
p
F
arom. CH); 7.03 (m, CHN); 7.01 (m, CHN); 5.05 (m, CHOH); 4.31 (m, 2 H, CH N, Me CH); 4.15 (m,
A
H
R
U
G
2
2
1
3
1
1
H, CH N); 2.32 (br., OH); 1.39 (m, Me
A
H
R
U
G
2
1
CDCl , 300 K): 162.0 (q, J(B,C)=49.9, 4 C (Ar )); 138.1 (arom. C), 135.2 (br., 8 C (Ar )); 133.1
NCHN); 130.5 (arom. CH); 130.1 (2 arom. CH); 129.4 (qq, J(F,C)=31.1, J(B,C)=2.9, 8 C (Ar ));
25.4 (2 arom. CH); 124.9 (q, J(F,C)=272.5, 8 CF ); 124.4 (CHN); 120.1 (CHN); 117.9 (sept., J(F,
3
3
ipso
F
o
F
2
3
(
1
m F
1
3
C)=3.8, 4 Cp (Ar )); 72.0 (CHOH); 57.3 (CH N); 54.5 (Me CH); 22.82 (Me
A
H
R
U
G
A
H
R
U
G
F
2
2
2
+
FAB-MS: 231 (100, [MꢀBAr ] . Anal. calc. for C H BF N O (1094.52): C 50.48, H 2.85, N 2.56, O
F
46 31
24
2
1
.46; found: C 50.56, H 2.89, N 2.63, O 1.64.
[(1,2,5,6-h)-Cycloocta-1,5-diene]{1-{(2R)-2-[(diphenylphosphino-kP)oxy]ethyl}-3-(1-methylethyl)-
2
H-imidazol-2-ylidene-kC}iridium(1+) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate(1ꢀ) (13). Phos-
phinic amide 11 (80 mg, 0.312 mmol) was added to a homogeneous soln. of 10 (228 mg, 0.208 mmol),
,5-dichloro-1H-imidazole (43 mg, 0.312 mmol), and Et3N (32 mg, 0.312 mmol) in CH Cl (3 ml) at 08.
4
ACHTREUNG
2
2

1
572
Helvetica Chimica Acta – Vol. 89 (2006)
31
1
The mixture was stirred at r.t. for 48 h. The reaction was monitored by P{ H}-NMR (101.2 MHz,
CD Cl , 300 K): d 115.8 ((phosphinooxy)imidazolinate 12); 58.2 (phosphinic amide 11); 17.9 (oxidized
2
2
phosphinooxy derivative). The soln. was evaporated and the residue purified by CC (aluminum oxide
Fluka, adjusted to grade III), inert atmosphere, CH Cl ): 12 (160 mg, 0.124 mmol, 60%). Highly air-sen-
(
2
2
t
sitive oil. NaO Bu (12 mg, 0.124 mmol) and [Ir Cl (cod) ] (41.6 mg, 0.062 mmol) were added to a soln. of
2
2
2
1
2 (160 mg, 0.124 mmol) in THF (5 ml). The mixture was stirred at r.t. for 2 h and then evaporated to
yield a red solid. The crude product was purified by CC (silica gel, 15×3-cm column, CH Cl ): 13 (135
2
2
2
D
0
mg, 69%). Red solid. [a] =+33 (c=0.10, CHCl ). IR (KBr): 2955w, 2924w, 2894w, 2848w, 1611w,
453m, 1358s, 1280s, 1114s, 933w, 887m, 837w, 756w, 709m, 675m, 581w, 491w, 447w. H-NMR (500.1
3
1
1
MHz, CD Cl , 295 K): 7.70–7.35 (m); 7.34–7.27 (m); 7.21–7.11 (m); 6.98 (m, CHN, min.); 6.96 (m,
2
2
3
3
CHN, min.); 6.81 (d, J=2.0, CHN, maj.); 6.39 (d, J=2.1, CHN, maj.); 6.25 (m, NCH CH, maj.); 5.76
dd, J=14.0, J=6.1, 1 H, CH N, maj.); 5.67 (dd, J=15.2, J=7.3, 1 H, CH N, min.); 5.35 (m, 1 CH
A
H
R
U
2
2
3
2
3
(
2
2
(
cod), maj.); 5.23 (m, CH (cod), min., and NCH2
A
H
R
U
A
H
R
U
G
3
J=6.6, Me2
4
A
H
R
U
G
2
3
.25 (m, 1 H of CH N, min.); 4.23 (dd, J=14.0, J=4.3, 1 H of CH N, maj.); 4.14 (m, 1 CH (cod),
2
2
min.); 3.54 (m, 1 CH (cod), maj.); 3.47 (m, 1 CH (cod), min.); 2.53 (m, 1 CH (cod), maj.); 2.42 (m, 1
2
CH (cod), maj.); 2.21 (m, 1 H of CH (cod), maj.); 2.11 (m, 1 CH (cod), maj.); 1.87 (m, 1 H of CH
2
2
2
2
3
3
(
cod), maj.); 1.48 (d, J=6.6, 3 H of Me
A
H
R
U
G
A
H
R
U
G
2
3
3
J=6.6, 3 H of Me2
A
H
R
U
G
A
H
R
N
13
1
observed; 5.0 :1 major/minor ratio. C{ H}-NMR (125.7 MHz, CD Cl , 295 K): 171.1 (d, J(P,C)=13.4;
2
2
1
NCN, maj.); 170.1 (d, J(P,C)=10.2, NCN, min.); 162.2 (q, J(B,C)=49.9, 4 Cipso (Ar )); 138.4 (d,
F
J(P,C)=7.5); 135.1 (br., 8 Co (Ar )); 134.7; 133.7; 133.3; 133.0 (br.); 132.7 (d, J(P,C)=2.3); 132.2 (d,
F
J(P,C)=2.0); 132.0; 131.7; 131.6; 131.2 (br.); 130.6; 130.5; 130.1–128.7 (overlapping signals); 128.6;
1
1
28.5; 128.1; 126.6; 126.0; 124.9 (q, J(F,C)=272.5, 8 CF ); 124.0 (CHN, maj.); 123.1 (CHN, min.);
3
1
19.4 (CHN, min); 117.8 (m, 5 C, C (Ar ), 1 CHN, maj.); 97.4 (d, J(P,C)=11.7, CH (cod), min.); 95.7
p
F
(d, J(P,C)=10.7, CH (cod), maj.); 89.9 (d, J(P,C)=11.7, CH (cod), min.); 89.0 (d, J(P,C)=14.5, CH
(
cod), maj.); 82.1 (NCH CH, min.); 81.1 (CH (cod), maj.); 80.7 (CH (cod), min.); 79.5 (CH (cod),
2
maj.); 79.2 (CH (cod), min.); 77.0 (NCH CH, maj.); 57.5 (br., CH N, min.); 55.8 (br., CH N, maj.);
2
2
2
5
3.8 (Me CH, maj.); 53.2 (Me CH, min.); 35.3 (br., CH (cod), maj.); 35.1 (br., CH (cod), maj.); 34.9
2
2
2
2
(
br., CH (cod), min.); 34.6 (br., CH (cod), min.); 28.7 (br., CH (cod), min.); 27.7 (br., CH (cod),
2
2
2
2
maj.); 25.2 (Me
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
2
2
2
31
1
(
0
cod), min., not observed. P{ H}-NMR (162.0 MHz, CD Cl , 295 K): 96.5 (s, 1.00 P; maj.); 86.8 (s,
2 2
+
.19 P; min.). FAB-MS: 715 (100, [MꢀBAr ] ). Anal. calc. for C H BF IrN PO (1578.08): C 50.23,
61 51
24
2
H 3.26, N 1.78; found: C 50.22, H 3.45, N 1.82.
Catalytic Hydrogenation at Elevated Pressure: General Procedure. In a glove box, 0.1 mmol of sub-
strate, 1 mol-% of Ir complex, and 0.5 ml of CH Cl were subsequently added to a 60-ml autoclave
2
2
(Premex AG, Lengnau, Switzerland) with four glas inserts (1.5 ml) and magnetic stirring bars. The auto-
clave was pressurized at 50 bar H (99.995%; Carbagas, Switzerland) and the mixture was stirred at r.t. for
2
2
h. After pressure release, the solvent was evaporated, and heptane (3 ml) was added. The resulting sus-
pension was filtered through a short plug of silica gel (0.5×6 cm) eluting with hexane/Et O 1:1, and the
AHCTREUNG
2
filtrate was analyzed by GC and chiral HPLC to determine conversion and enantioselectivity [13].
2
Crystal Structure Analysis ). Crystal Data for 7b’. Formula C H BF IrN P, M 753.69, F(000)=752;
31
43
4
2
orange block, size 0.20×0.22×0.24 mm; monoclinic, space group P21, Z=2, a=9.6146(1) Å,
3
b=15.1396(1) Å, c=11.0797(1) Å, a=908, b=110.3712(5)8, g=908, V=1511.91(2) Å , D =1.655
calc.
ꢀ
3
Mg·m . The crystal was measured on a Nonius-Kappa-CCD diffractometer at 173 K with graphite-
monochromated MoK radiation with l 0.71073 Å, Vmax 32.6008. Minimal/maximal transmission 0.37/
.41, m=4.517 mm . The COLLECT suite was used for data collection and integration. From a total
of 21652 reflections, 10991 were independent (merging r=0.026). From these, 10142 were considered
AHCTREUNG
a
ꢀ1
0
2)
CCDC-293590 (7b’) and CCDC-293591 (7c’) contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via http://www.ccdc.cam.ac.uk/data_request/cif.

Helvetica Chimica Acta – Vol. 89 (2006)
1573
as observed (I>3.00s(I)) and were used to refine 362 parameters. The structure was solved by direct
methods with the program SIR92. Least-squares refinement against F was carried out on all non-H
atoms with the program CRYSTALS. R=0.0202 (observed data), wR=0.0238 (all data),
ꢀ
3
g.o.f.=1.0632. Minimal/maximal residual electron density=ꢀ2.85/2.24 e Å . Chebychev polynomial
weights were used to complete the refinement. Plots were produced with CAMERON.
Crystal data for 7c’. Formula C H BF IrN P, M 829.79, F(000)=832; orange block, size
37
47
4
2
0
.16×0.20×0.22 mm, monoclinic, space group P2 , Z=2, a=10.20430(10) Å, b=11.02200(10) Å,
1
3
ꢀ3
c=15.4744(2) Å, a=908, b=91.4777(4)8, g=908, V=1739.85(3) Å , D =1.584 Mg·m . The crystal
calc.
was measured on a Nonius-Kappa-CCD diffractometer at 173 K with graphite-monochromated MoK
a
ꢀ
1
radiation with l 0.71073 Å, Vmax 32.6348. Minimal/maximal transmission 0.46/0.53, m=3.933 mm . The
COLLECT suite was used for data collection and integration. From a total of 24740 reflections, 12640
were independent (merging r=0.040). From these, 11832 were considered as observed (I>3.00s(I))
and were used to refine 417 parameters. The structure was solved by direct methods with the program
SIR97. Least-squares refinement against F was carried out on all non-H atoms with the program CRYS-
TALS. R=0.0200 (observed data), wR=0.0238 (all data), g.o.f.=1.0669. Minimal/maximal residual elec-
ꢀ
3
tron density=ꢀ2.02/2.20 e Å . Chebychev polynomial weights were used to complete the refinement.
Plots were produced with CAMERON.
REFERENCES
[
1] A. J. Arduengo III, R. L. Harlow, M. Kline, J. Am. Chem. Soc. 1991, 113, 361; H. W. Wanzlick, H. J.
Schoenherr, Angew. Chem., Int. Ed. 1968, 7, 141; K. Oefele, J. Organomet. Chem. 1968, 12, 42.
2] J. Huang, E. D. Stevens, S. P. Nolan, J. L. Petersen, J. Am. Chem. Soc. 1999, 121, 2674; M. Scholl, T.
M. Trnka, J. P. Morgan, R. H. Grubbs, Tetrahedron Lett. 1999, 40, 2247; T. Weskamp, F. J. Kohl, W.
Hieringer, D. Gleich, W. A. Herrmann, Angew. Chem., Int. Ed. 1999, 38, 2416.
[
[
[
[
3] G. Altenhoff, R. Goddard, C. W. Lehmann, F. Glorius, J. Am. Chem. Soc. 2004, 126, 15195.
4] V. Cesar, S. Bellemin-Laponnaz, L. H. Gade, Chem. Soc. Rev. 2004, 33, 619.
5] a) J. J. Van Veldhuizen, S. B. Garber, J. S. Kingsbury, A. H. Hoveyda, J. Am. Chem. Soc. 2002, 124,
4954; b) P. L. Arnold, M. Rodden, K. M. Davis, A. C. Scarisbrick, A. J. Blake, C. Wilson, Chem.
Commun. 2004, 1612.
[
6] a) E. Bappert, G. Helmchen, Synlett 2004, 1789; b) H. Seo, H.-j. Park, B. Y. Kim, J. H. Lee, S. U. Son,
Y. K. Chung, Organometallics 2003, 22, 618; c) T. Focken, G. Raabe, C. Bolm, Tetrahedron: Asym-
metry 2004, 15, 1693.
[
7] a) M. T. Powell, D.-R. Hou, M. C. Perry, X. Cui, K. Burgess, J. Am. Chem. Soc. 2001, 123, 8878; b)
M. C. Perry, X. Cui, M. T. Powell, D.-R. Hou, J. H. Reibenspies, K. Burgess, J. Am. Chem. Soc. 2003,
125, 113; c) V. Cesar, S. Bellemin-Laponnaz, L. H. Gade, Organometallics 2002, 21, 5204; d) L. H.
Gade, V. Cesar, S. Bellemin-Laponnaz, Angew. Chem., Int. Ed. 2004, 43, 1014; e) V. Cesar, S. Bel-
lemin-Laponnaz, L. H. Gade, Eur. J. Inorg. Chem. 2004, 3436; f) W. A. Herrmann, L. J. Goossen, M.
Spiegler, Organometallics 1998, 17, 2162; g) S. Nanchen, A. Pfaltz, Chem.–Eur. J. 2006, 12, 4550.
8] a) L. G. Bonnet, R. E. Douthwaite, B. M. Kariuki, Organometallics 2003, 22, 4187; b) L. G. Bonnet,
R. E. Douthwaite, R. Hodgson, J. Houghton, B. M. Kariuki, S. Simonovic, Dalton Trans. 2004, 3528.
9] W. J. Drury III, N. Zimmermann, M. Keenan, M. Hayashi, S. Kaiser, R. Goddard, A. Pfaltz, Angew.
Chem., Int. Ed. 2004, 43, 70.
[
[
[
10] A. Saitoh, T. Morimoto, K. Achiwa, Tetrahedron: Asymmetry 1997, 8, 3567.
[
11] a) D. G. Blackmond, A. Lightfoot, A. Pfaltz, T. Rosner, P. Schnider, N. Zimmermann, Chirality
2000, 12, 442; b) S. P. Smidt, N. Zimmermann, M. Studer, A. Pfaltz, Chem.–Eur. J. 2004, 10, 4685.
[
[
12] S. P. Smidt, Ph.D. Thesis, University of Basel, Basel, 2003.
13] J. Blankenstein, A. Pfaltz, Angew. Chem., Int. Ed. 2001, 40, 4445.
Received January 31, 2006