Polymer-supported chiral Schrock catalysts immobilized via the arylimido ligand

Article abstract of DOI:10.1002/adsc.200606030

The immobilization of both chiral and non-chiral versions of the Schrock catalyst via the arylimido ligand was accomplished for the first time. For this purpose, four different 4-(6-halogenohexyl)-2,6-R₂-anilines, i.e., {4-[6-X-(CH₂)₆]-2,6-R₂-C₆H ₂-NH₂} (7: R = Me, X = Br; 8: R = Me, X = Cl, 9: R = 2-Pr, X = Cl, 10: R = 2-Pr, X = Br) were prepared and used for the synthesis of the corresponding Mo-bis(imido)dichloro complexes Mo{N-2,6-R₂-4-[6-X- (CH₂)₆]-C₆H₂)₂Cl ₂-DME (11: R = Me, X = Br; 12: R = Me, X = Cl; 13: R = 2-Pr, X = Cl; 14: R = 2-Pr, X = Br). Compounds 11-14 were transformed into the corresponding Mo-bis(imido)dialkyl complexes Mo{N-2,6-R₂-4-[6-X-(CH ₂)₆]-C₆H₂}₂(CH ₂CMe₂Ph)₂ (15: R = Me, X = Br; 16: R = Me, X = Cl, 17: R = 2-Pr, X = Cl; 18: R = 2-Pr, X = Br). These were used for the synthesis of the Mo-imidoalkylidene triflates Mo{N-2,6-R₂-4-[6-X- (CH₂)₆]-C₆H₂}(CHCMe ₂Ph)-(OTf)₂·DME (19: R = Me, X = Br; 20: R = 2-Pr, X = Br, 21: R = 2-Pr, X = Cl). Compounds 19-21 were used in the synthesis of the Schrock type catalysts Mo{N-2,6-Me₂-4-[6-Br-(CH₂) ₆]-C₆H₂} (CHCMe₂Ph)[OC(CH ₃)(CF₃)₂]₂ (22) and Mo{N-2,6-(2-Pr)₂4-[6-Cl-(CH₂)₆]-C ₆H₂}(CHCMe₂Ph)[OC-(CH₃)(CF ₃)₂] (23), Mo{N-2,6-Me₂-4-[6-Br-(CH ₂)₆]-C₆H₂}(CHCMe₂Ph)[(R)- BIPHEN] (24) and Mo{N-2,6-(2-Pr)₂-4-[6-Br-(CH₂) ₆]-C₆H₂}(CHCMe₂Ph)[(R)-BIPHEN] (25). Compounds 22, 24 and 25 were immobilized on Ag-perfluoroalkylsulfonate-modified PS- and PS-DVB materials to yield the corresponding immobilized catalysts Mo{N-2,6-Me₂-4-[PS-CH₂-O-CF₂-CF(CF ₃)-SO₃-(CH₂)₆]-C₆H ₂}(CHCMe₂Ph)-[OCMe(CF₃)₂] ₂ (26), Mo{N-2,6-Me₂-4-[PS-DVB-CH₂-O-CF ₂-CF(CF₃)-SO₃-(CH₂) ₆]-C₆H₂} (CHCMe₂Ph)[(R)-BIPHEN] (27) Mo{N-2,6-(2-Pr)₂-4-[PS-DVB-CH₂-O-CF₂- CF(CF₃)-SO₃-(CH₂)₆]-C ₆H₂) (CHCMe₂Ph)[(R)-BIPHEN] (28). These were used in a series of ring-closing metathesis (RCM), ring-opening cross metathesis, asymmetric RCM and desymmetrization reactions. The use of 27 and 28 resulted in values for enantiomeric excess (ee) virtually identical to those obtained with the corresponding homogeneous chiral catalysts.

Full text of DOI:10.1002/adsc.200606030

FULL PAPERS
DOI: 10.1002/adsc.200606030
Polymer-Supported Chiral Schrock Catalysts Immobilized via the
Arylimido Ligand
Dongren Wang,a Roswitha Krçll,a Monika Mayr,a Klaus Wurst,b
and Michael R. Buchmeisera, c,*
a
Leibniz Institut für Oberflächenmodifizierung e.V. (IOM), Permoserstr. 15, 04318 Leipzig, Germany
Fax : +49-341-235-2584; e-mail: dongren.wang@iom-leipzig.de
Institut für Allgemeine, Anorganische und Theoretische Chemie, Universität Innsbruck, Innrain 52 a, 6020 Innsbruck,
b
Austria
Fax : +43-512-507-2934
Institut für Technische Chemie, Universität Leipzig, LinnØstr. 3, 04103 Leipzig, Germany
c
Fax : +49-341-235-2584; e-mail: buchmeiser@uni-leipzig.de
Received: January 30, 2006; Accepted: April 15, 2006
Dedicated to Prof. Dr. Ing. Oskar Nuyken on the occasion of his retirement.
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: The immobilization of both chiral and
non-chiral versions of the Schrock catalyst via the ar-
R
(CHCMe2Ph)[OC-
ACHTREUNG
ylimido ligand was accomplished for the first time. C6H2}
For this purpose, four different 4-(6-halogenohexyl)- 2,6-
A
ACHTREUNG
A
ACHTREUNG
2,6-R2-anilines, i.e., {4-[6-X-(CH2)6]-2,6-R2-C6H2- BIPHEN] (25). Compounds 22, 24 and 25 were im-
NH2} (7: R=Me, X=Br; 8: R=Me, X=Cl, 9: R= mobilized on Ag-perfluoroalkylsulfonate-modified
2-Pr, X=Cl, 10: R=2-Pr, X=Br) were prepared PS- and PS-DVB materials to yield the correspond-
and used for the synthesis of the corresponding Mo- ing immobilized catalysts Mo{N-2,6-Me2-4-[PS-CH2-
bis
(CH2)6]-C6H2}2Cl2·DME (11: R=Me, X=Br; 12:
R=Me, X=Cl; 13: R=2-Pr, X=Cl; 14: R=2-Pr, CH2-O-CF2-CF
X=Br). Compounds 11–14 were transformed into (CHCMe2Ph)[(R)-BIPHEN] (27) Mo
the corresponding Mo-bis(imido)dialkyl complexes 4-[PS-DVB-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}
Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}2(CH2CMe2Ph)2 (CHCMe2Ph)[(R)-BIPHEN] (28). These were used
A
(CF3)-SO3-(CH2)6]-C6H2}
G
A
ACHTREUNG
AHCTREUNG
A
G
A
A
ACHTREUNG
AHCTREUNG
(15: R=Me, X=Br; 16: R=Me, X=Cl, 17: R=2- in a series of ring-closing metathesis (RCM), ring-
Pr, X=Cl; 18: R=2-Pr, X=Br). These were used opening cross metathesis, asymmetric RCM and de-
for the synthesis of the Mo-imidoalkylidene triflates symmetrization reactions. The use of 27 and 28 re-
Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}
A
sulted in values for enantiomeric excess (ee) virtually
ACHTREUNG
Br, 21: R=2-Pr, X=Cl). Compounds 19--21 were homogeneous chiral catalysts.
used in the synthesis of the Schrock type catalysts
Mo{N-2,6-Me2-4-[6-Br-(CH2)6]-C6H2}
(CHCMe2Ph)[OC(CH3)(CF3)2]2 (22) and Mo
Keywords: asymmetric catalysis; heterogeneous cat-
alysis; immobilization; metathesis; molybdenum
A
G
U
N
G
Introduction
tions.[4–6] Due to the achievements made with cata-
lysts necessary to accomplish these reactions,[7–9] an
Together with palladium-catalyzed reactions such as almost unprecedented progress has been made in this
the Heck, Suzuki and Sonohashira–Hagihara reac- area of research; nevertheless, the demand for new
tions,[1–3] metathesis reactions, particularly those that catalytic systems is a continuous and growing one. In
can be accomplished in an asymmetric way, belong this context, particularly supported versions of meta-
À
nowadays to the most important C C coupling reac- thesis catalysts are now in the center of interest. Ease
Adv. Synth. Catal. 2006, 348, 1567 – 1579
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Dongren Wang et al.
FULL PAPERS
of catalyst removal, access to metal-free products, re- Results and Discussion
cyclability and access to combinatorial processes are
major driving forces. In metathesis reactions, the Synthesis of Ligands
latter is often restricted by the instability of inter-
mediate transition metal methylidenes. While a com- The concept of immobilizing a Schrock catalyst via
parably large number of supported ruthenium-based the arylimido ligand requires the synthesis of a suita-
Grubbs- and Grubbs–Hoveyda-type metathesis cata- ble arylimido ligand. In principle, one might think of
lysts are already available,[10–12] there exists still an many different functional groups that can be attached
only very limited number of supported Schrock-type to the arylimido ligand and that may be used for im-
catalysts.[6] In this context, surface-located transition mobilization purposes later on. However, since both
metal carbenes have been reported to possess meta- strongly nucleophilic and/or basic reagents, i.e., terti-
thesis activity.[13,14] Alternatively, a silica-immobilized ary amines, Grignard reagents, alkoxides, phenoxides,
ꢀ
mimic of the Schrock catalyst, ( SiO)Mo
C
G
CH-t-Bu)
recently, CopØret, Basset, Emsley and Schrock report- with low reactivity towards these reagents could be
ed in a joint paper on the immobilization of Mo[=N- expected to survive catalyst synthesis. At this point it
2,6-(2-Pr)2-C6H3](=CH-t-Bu)
The resulting supported Schrock-type catalyst (
SiO)Mo[=N-2,6-(2-Pr)2-C6H3](=CH-t-Bu)(CH2-t-Bu)
G
AHCTREUNG
A
G
A
Schrock catalyst developed some 15 years ago[26] is,
despite significant efforts,[27] the only broadly applica-
ꢀ
A
G
A
ACHTREUNG
was subject to profound structural and catalytic char- ble one. For the given task, we identified w-halogen-
acterization.[16] Immobilizations on other supports oalkyl groups as suitable. A hexyl spacer was chosen
have been carried out, too,[17–20] however, the actual for two reasons. First it was short enough to prevent
nature of the immobilized catalyst remained un- interaction of the terminal halogen with the molybde-
known. The first supported chiral version of a molyb- num center, second it was expected to be long enough
denum-based Schrock catalyst was reported in to ensure sufficient spacing of the final catalyst from
2002,[21] and consisted of a PS-DVB-bound version of the support. We therefore prepared four different 4-
Mo
A
(2-Pr)2-C6H3]
T
(6-halogenohexyl)-2,6-R2-anilines,
i.e.,
{4-[6-X-
(BIPHEN=3,3’-di-tert-butyl-5,5’,6,6’-tetramethyl-2,2’-
(CH2)6]-2,6-R2-C6H2-NH2} (7: R=Me, X=Br; 8: R=
biphenolate). In course of ongoing projects we report- Me, X=Cl, 9: R=2-Pr, X=Cl; 10: R=2-Pr, X=Br)
ed on a ring-opening metathesis polymerization via the synthetic route shown in Scheme 1. Thus, the
(ROMP)-derived, supported version of the same cata- amino groups in the starting anilines, 2,6-dimethylani-
lyst[22] as well as on its immobilization on norborn-2- line (1) and 2,6-di-2-propylaniline (2), were protected
ene-based monolithic supports.[23] Additional chiral with trimethylsilyl moieties, which allowed replace-
Schrock catalysts immobilized via biphenoxides and ment of the 4-bromo group by lithium. Subsequent re-
binaphthoxides were a short time later jointly report- action with the 1,6-dibromohexane yielded the de-
ed by the Schrock and Hoveyda groups.[24] All sup- sired protected 6-bromohexylanilines 5 and 6.
ported catalysts prepared so far showed excellent re-
sults in terms of activity and enantioselectivity.
Deprotection required the use of concentrated
HBr/methanol. Interestingly, the 6-bromo group
During the past years we were interested in the could be replaced by a chloro group by using concen-
question whether immobilization of a Schrock catalyst trated HCl/methanol. In summary, we obtained the 4
might also be achieved via the arylimido ligand. Such different deprotected 6-halogeno-2,6-R2-alkylanilines
an approach, if successful, would allow for a wider 7–10.
and, in fact, complementary variability in catalyst
structure, the more, since both reactivity and selectivi-
ty of chiral Schrock-type catalysts are strongly gov- Synthesis of Molybdenum Complexes
erned by the nature of the alkoxides, (bi-)phenoxides
and binaphtholates, respectively.[25] Thus, a supported In order to be capable of using the thus modified ani-
version of a Schrock catalyst, where heterogenization lines for catalysts synthesis (Scheme 1), special and
is realized via the arylimido ligand, appeared highly subtle reaction conditions had to be elaborated in
favorable since it would allow for an ultimate variabil- order to prevent the terminal alkyl halide from react-
ity in catalyst tuning. Here, we report on the success- ing with any of the various nucleophilic reagents
ful realization of this task.
used. Thus, triethylamine had to be substituted by a
sterically hindered base, 2,6-lutidine, and reaction
times and temperatures had to be adjusted in order to
reduce salt formation between the base and the
chloroalkyl group. Other bases, e.g., 2,6-di-tert-butyl-
pyridine or dry NaHCO3, K2CO3, Cs2CO3 were found
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Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
Scheme 1. Synthesis of halogenoalkyl-substituted anilines 7–10, Mo-bis(imido) complexes 11–14, Mo-bisimido-dialkyl com-
G
plexes 15–18 and alkyl-substituted Mo-arylimido-neophylidene triflates 19–21.
unsuitable. Following the modified standard protocol
for Schrock catalyst synthesis, a series of Mo-bisami- into the corresponding Mo-bis(imido)dialkyl com-
In a next step, compounds 11–14 were transformed
ACHTREUNG
dodichloro complexes, i.e., Mo{N-2,6-R2-4-[6-X- plexes
Mo{N-2,6-R2-4-[6-X-(CH2)6]-C6H2}2(CH2-
.
(CH2)6]-C6H2}2Cl2 DME (11: R=Me, X=Br; 12: R= CMe2Ph)2 (15: R=Me, X=Br; 16: R=Me, X=Cl;
Me, X=Cl; 13: R=2-Pr, X=Cl; 14: R=2-Pr, X= 17: R=2-Pr, X=Cl; 18: R=2-Pr, X=Br). Crystals
Br), was prepared. Crystals suitable for X-ray analysis suitable for X-ray analysis were obtained for 15. Com-
were obtained for 13. Compound 13 crystallized in pound 15 crystallized in the monoclinic space group
the monoclinic space group C2/c with a=2261.28(7) P21/n with a=1750.6(2) pm, b=845.5(2) pm, c=
pm, b=1970.31(8) pm, c=1556.75(6) pm, a=g=908, 3206.6(2) pm, a=g=908, b=104.720(6)8, Z=4
b=132.566(2)8, Z=4 (Figure 1).
(Figure 2).
À
Figure 1. Mo
G
U
À
À
À
À
174.2(3), Mo(1) N(1)#1 174.2(3), Mo(1) O(1)#1 237.4(3), Mo(1) O(1) 237.4(3), Mo(1) Cl(1) 239.75(12), Mo(1) Cl(1)#1
239.75(12), N(1) Mo(1) N(1)#1 103.6(2), N(1) Mo(1) O(1)#1 162.97(13), N(1)#1 Mo(1) O(1)#1 93.45(13), N(1) Mo(1)
O(1) 93.45(13), N(1)#1 Mo(1) O(1) 162.97(14), O(1)#1 Mo(1) O(1) 69.54(15), N(1) Mo(1) Cl(1) 97.28(12), N(1)#1
Mo(1) Cl(1) 97.11(12), O(1)#1 Mo(1) Cl(1) 79.79(9), O(1) Mo(1) Cl(1) 81.06(9), N(1) Mo(1) Cl(1)#1 97.11(12),
N(1)#1 Mo(1) Cl(1)#1 97.28(12), O(1)#1 Mo(1) Cl(1)#1 81.06(9), O(1) Mo(1) Cl(1)#1 79.79(9), Cl(1) Mo(1) Cl(1)#1
156.63(7).
À
À
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1569

Dongren Wang et al.
FULL PAPERS
extraction of compounds 19–21 from the crude reac-
tion mixture with n-pentane. This finally allowed for
the isolation of pure 19–21 in gram amounts. Having
the Mo-imidoalkylidene triflates as progenitors for
the final catalysts at hand, the advantages of the con-
cept of immobilizing Schrock catalysts via the arylimi-
do ligands become evident. So far, Schrock catalysts
with a very limited number of different imido li-
gands=N-R [R=adamantyl, 2,6-Me2-C6H3, 2,6-(2-
Pr)2-C6H3, 2,6-Cl2-C6H3] yet with a vast number of
(chiral) alkoxides are the “working horses” in meta-
thesis based organic chemistry.[8,28–30] Thus, with a
small set of Mo triflates in hand, one can now ex-
change the triflates by any alkoxide, phenolate, biphe-
nolate, carboxylate, etc., of interest and gain simple
access to almost all relevant Schrock-type catalysts.
Of similar importance is the fact that the final (chiral)
catalysts may be prepared, purified, and analyzed
prior to a last single immobilization step, providing
utmost information about the actual composition of
the corresponding supported catalyst.
Synthesis of Catalysts
Figure 2. Mo
A
(CH3)2-C6H2-4-(CH2)6-Br]
A
ACHTREUNG
Compounds 19–21 were used in the synthesis of the
Schrock-type catalysts. Thus, reaction of 19 and 20, re-
À
À
À
(8): Mo(1) N(2) 172(2), Mo(1) N(1) 175(2), Mo(1) C(11)
203(3), Mo(1) C(1) 219(2), N(2) Mo(1) N(1) 110.6(10),
À
À
À
spectively, with 2 equivs. of Li-OCMe
Mo{N-2,6-Me2-4-[6-Br-(CH2)6]-C6H2}(CHCMe2Ph)-
[OC(CH3)(CF3)2]2 (22) and Mo{N-2,6-(2-Pr)2-4-[6-Cl-
(CH2)6]-C6H2}(CHCMe2Ph)[OC(CH3)(CF3)2] (23).
Similarly, Mo{N-2,6-Me2-4-[6-Br-(CH2)6]-C6H2}(CH-
While 15 and 16 are obtained in crystalline form CMe2Ph)[(R)-BIPHEN] (24) and Mo{N-2,6-(2-Pr)2-4-
quite easily, compound 17 was hard to crystallize, [6-Br-(CH2)6]-C6H2}(CHCMe2Ph)[(R)-BIPHEN] (25)
A
À
À
À
À
N(2) Mo(1) C(11) 104.1(11), N(1) Mo(1) C(11) 107.2(9),
À
À
À
À
N(2) Mo(1) C(1) 102.2(9), N(1) Mo(1) C(1) 110.0(9),
A
G
A
ACHTREUNG
À
À
C(11) Mo(1) C(1) 122.3(9).
A
N
ACHTREUNG
ACHTREUNG
A
ACHTREUNG
AHCTREUNG
which in turn significantly reduces its yield to 60%. were prepared from 19 and 20 and 1 equiv. of the di-
This is, in view of the large amount of non-polar potassium salt of (R)-BIPHEN. An illustration is
groups attached to the molecule, not surprising at all, given in Scheme 2.
however, it does significantly aggravate purification.
At this point, compounds 22, 24 and 25 are perfect
In this context it is worth mentioning that, in contrast mimics of the parent Schrock catalysts. The halogeno-
to “classic” Schrock type catalyst precursors, com- hexyl group might well be expected to have low – if
pounds 15–18 are quite soluble in basically any sol- any – impact on the geometry of the catalyst. Un-
vent including n-pentane, which in turn aggravated fortunately, we were not able to obtain any X-ray
purification. Following the standard Schrock catalyst data on the final catalysts so far to provide experi-
protocol, they were used for the synthesis of the cor- mental evidence for this statement.
responding Mo-imidoalkylidene triflates Mo{N-2,6-
R2-4-[6-X-(CH2)6]-C6H2}
N
N
(19: R=Me, X=Br; 20: R=2-Pr, X=Br, 21: R=2- Immobilization of Catalysts
Pr, X=Cl). A major drawback in the purification of
these compounds was the fact that the corresponding Generally, immobilization of compounds 22–25 had to
anilinium triflates, which form as a by-product in the be accomplished in the absence of any (even weak)
course of the synthesis in stoichiometric amounts, nucleophile, since this would rather lead to the re-
were hard to remove from the target compounds. placement of the alkoxide ligands by the nucleophile
Again, both the anilinium triflates and the Mo-tri- than to any reaction with the 6-halogenoalkyl group.
flates 19--21 were found to be extremely soluble even For this purposes, the reaction of a polymer-bound
in non-polar solvents such as benzene, toluene, xy- silver perfluoroalkanesulfonate with the terminal
lenes and diethyl ether. In due consequence, the only bromo or, respectively, chloro group appeared suita-
applicable purification protocol entailed the extensive ble. The principal applicability of this reaction was
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Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
Scheme 2. Synthesis of catalysts 22–24 and immobilization procedure for the synthesis of the supported catalysts 26–28.
demonstrated by reacting 1-bromooctane with silver ing free perfluoroalkanesulfonic acid was finally con-
trifluoromethanesulfonate in tetrahydrofuran.
1H NMR clearly showed the formation of the corre- support, an immobilized version of 22, Mo{N-2,6-
sponding ester (d=3.50 ppm, OCH2) after 8 h at Me2-4-[PS-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2)}
room temperature. (CHCMe2Ph){[O(CH3)(CF3)2]2} (26, 11.4 mmol
verted into the corresponding silver salt. Using this
AHCTREUNG
A
N
ACHTREUNG
We first investigated the utility of Nafionꢁ, a per- Mo/g), was prepared by reaction of the support (Ag
fluorosulfonated resin for our purposes. These fluoro- form) with 22. To the best of our knowledge this is
sulfonated resins have been used as solid super acid the first time such a reaction of a halogenoalkylgroup
catalysts and in many other variations as catalytic sup- and a polymer-supported silver perfluoroalkanesulfo-
ports,[31–37] nevertheless, in all cases metal immobili- nate has been described. Using 26, standard RCM re-
zation was accomplished by an ion-exchange proce- actions such as the conversion of 1,7-octadiene, di-
dure, i.e., exchange of H+ by the metal of interest. allyldiphenylsilane and diethyldiallyl malonate could
Here, immobilization of compounds 22–25 was at- be accomplished in high yields (Table 1). The same
tempted by formation of an alkanesulfonate according accounts for a ring-opening cross metathesis reaction
to the above-mentioned reaction. Disappointingly, re- between 7-oxanorborn-5-ene-2,3-dicarboxylic anhy-
action with polymer-bound silver trifluoromethanesul- dride and allyltrimethylsilane.
fonate groups as provided by various different
Nafionꢁ resins – whether soluble or insoluble – did
not result in systems with any catalytic activity. We Asymmetric RCM/Desymmetrization Reactions With
tentatively attribute this finding to both the high per- Supported Catalysts 24 and 25
fluorosulfonic acid capacity of these resins as well as
to inappropriate swelling characteristics. Both factors Encouraged by these findings compounds 24 and 25
together are believed to result in a significant number were immobilized on Ag-perfluoroalkanesulfonate-
of free perfluoroalkanesulfonic acid groups, which in modified PS-DVB materials to yield the correspond-
turn destroy the catalytic species. In search of an al- ing immobilized catalysts Mo
ternative we prepared linear poly(styrene) (PS) via DVB-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}
free radical polymerization (Mn =10,000 gmolÀ1
(CHCMe2Ph)[(R)-BIPHEN] (27) Mo{N-2,6-(2-Pr)2-4-
PDI=1.50). This PS was hydroxymethylated and re- [PS-DVB-CH2-O-CF2-CF(CF3)-SO3-(CH2)6]-C6H2}
acted with 1,2,2-trifluoro-2-hydroxy-1-trifluoromethyl- (CHCMe2Ph)[(R)-BIPHEN] (28). Since enhanced re-
ethanesulfonic acid sultone (Scheme 2).[38] The result- activity had to be expected from the 6-bromoalkyl de-
A
G
A
ACHTREUNG
,
N
G
ACHTREUNG
AHCTREUNG
AHCTREUNG
Adv. Synth. Catal. 2006, 348, 1567 – 1579
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
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Dongren Wang et al.
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Table 1. Results for (asymmetric) RCM and ring-opening cross reactions carried out with catalysts 26–28.
Cat [mol%] Substrate
Product
t [h] conversion [%] (conversion [%])[a] ee [%] (ee [%])[a]
26 (0.1)
2
1
64[c]
-
-
26 (1)
100[c]
26 (0.3)
2
2
98[c]
-
-
26 (1)
86[b,e]
26 (1)
27 (5)
27 (5)
4
2
1
77 (95)[d],[41]
91 (93)[d],[41]
99 (-)[d]
95 (99)[41]
79 (93)[41]
86 (-)
27 (5)
28 (5)
1
3
99 (>99)[d]
>98 (97)[d]
6 (4)[39]
87 (89)[20]
28 (5)
28 (5)
2
2
91 (86)[d],[42]
94 (89)[42]
30 (-)41
43 (56)[d],[41]
28 (5)
2
20 (35)[d],[38]
k
rel =2.1 (3)[38]
Reactions were run at room temperature.
[a]
Analogous homogeneous or heterogeneous catalysts.
[b] Polymer formed.
[c]
I n CHCl2.
2
[d] In benzene.
[e]
In CDCl3.
1572
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Adv. Synth. Catal. 2006, 348, 1567 – 1579

Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
rivatives of the Mo-imidoalkylidene triflates, we to cleave the ester must be kept away from the reac-
rather focused on these derivatives than on the corre- tion mixture due to the inherent instability of the cat-
sponding 6-chloroalkyl compounds so far. Both sup- alyst itself.
ported chiral Schrock catalysts 27 and 28 were subject
to various enantioselective ring-closing metathesis
(RCM) reactions. The results obtained were com- Conclusions
pared to those obtained with the parent, unsupported
catalysts, i.e., Mo(N-2,6-Me2-C6H3)
BIPHEN] and Mo[N-2,6-
(CHCMe2Ph)[(R)-BIPHEN], respectively, as well as The concept entails the manufacture of Schrock cata-
with other supported systems. A summary is given in lysts with w-halogenoalkyl groups in the 4-position of
Table 1. the aryl imido ligand. Immobilization is achieved via
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
With one exception, conversions were >90% using reaction with polymer-bound perfluoroalkanesulfo-
5 mol% of supported catalyst. Only 3,5-dimethyl-4-al- nate groups and formation of an ester linkage. This
lyloxy-hepta-2,5-diene gave 77% yield, however, the concept offers a broader variability in catalyst struc-
observed enantiomeric excess (ee, 95%) was basically ture compared to existing immobilization routes that
identical to the reported one (99%). Very similar proceed via polymer-bound alkoxides (biphenolates).
enantioselectivity was also observed with both sup- Future investigations will focus on the identification
ported systems 27 and 28 compared to the parent cat- of more suitable supports, e.g., monolithic ones that
alysts. These data strongly suggest that the supported might well improve recyclability of the catalysts and
systems are perfect mimics of the parent chiral cata- offer access to high-throughput screening techniques.
lysts and any interference of the support with the cat-
alyst, which ever, may be excluded. Compound 28
was further used in a desymmetrization reaction.
Thus, 20% conversion of enantiomeric N-(1-phenyl-4-
buten-1-yl)-N-(2-methyl-2-propen-1-yl)aniline re-
Experimental Section
General Remarks
vealed a value for krel of 2.1, compared to 3 (@ 30%
conversion) with the parent system.[39] This might be
indicative for a non-optimized accessibility of the cat-
alytic sites which may require additional optimization
of the polymeric support. However, the principle at-
tractiveness and competitiveness of the concept is il-
lustrated by the fact that 4 different catalysts precur-
sors, i.e., 22, 23, 24, 25, have been prepared from only
2 progenitor triflates 19 and 20, resulting in three dif-
ferent immobilized catalysts. The supported systems
NMR data were recorded at 300.13 MHz for proton and at
75.74 MHz for carbon in the indicated solvent at 258C on a
Bruker Spectrospin 300 and are listed in parts per million
downfield from tetramethylsilane for proton and carbon.
Coupling constants J are listed in Hz. IR spectra were re-
corded on a Bruker Vector 22 using ATR technology. GC-
MS investigations were carried out on a Shimadzu GCMS-
QP5050, using a SPB-5 fused silica column (30 m”0.25
mm”25 mm film thickness). GC separation of enantiomers
prepared are only exemplary illustrations and the was accomplished on a Supelco, Beta DexTM-120, 30 m”
0.25 mm”0.25 mm film thickness), separation of enantiomer-
ic amines was accomplished by chiral HPLC using a Chiral-
pak AD (4.6 mm”250 mm) in comparison to authentic race-
mic material. Elemental analyses were carried out at the Mi-
croanalytical Laboratory, Anorganisch-Chemisches Institut,
TU München, Lichtenbergstr. 4, 85747 Garching, Germany.
A Jobin Yvon JY 38 plus was used for ICP-OES measure-
ments, a MLS 1200 mega for microwave experiments. Syn-
theses of the ligands and catalysts were performed under an
argon atmosphere by standard Schlenk techniques or in an
range of immobilized catalysts may be well expected
to be easily expanded to other (chiral) versions as
well as to other supports. All supported versions may
easily be removed from the reaction mixture by
simple filtration. The average molybdenum leaching
was 5.5% as measured by ICP-OES, which translates
into an average Mo contamination of the products of
less than 0.14%. This is comparable to or, respective-
ly less, than Mo contaminations observed with sys-
tems immobilized via the biphenolate.[21,40] In view of N2-mediated dry-box (MBraun, Germany) unless stated oth-
erwise. Reagent grade diethyl ether, pentane, tetrahydrofur-
an (THF), dimethoxyethane (DME) and toluene were distil-
led from sodium benzophenone ketyl under argon. Reagent
grade dichloromethane was distilled from calcium hydride
under argon. Other solvents and reagents were used as pur-
chased. Silica G60 (220–440 mesh, Fluka, Germany) was
used for chromatography. Deionized, degassed water was
the inherent instability of intermediate molybdenum
methylidenes, no attempts to recycle any of the sup-
ported catalysts have been undertaken, the more
since these are the final species at conversions>99%.
Finally, it is worth noting that the ester linkage be-
tween the support and the catalyst provides sufficient
stability for immobilization as evidenced by the use of
basic substrates such as N-(1-phenyl-4-buten-1-yl)-N-
(2-methyl-2-propen-1-yl)aniline. This is not surprising
used throughout.
A molybdenum standard containing
1000 ppm of molybdenum was purchased from Alfa Aesar/
Johnson Matthey (Karlsruhe, Germany). Mass spectra were
since even the traces of water that would be necessary recorded on a Finnigan MAT 95S using FAB ionization (Cs-
Adv. Synth. Catal. 2006, 348, 1567 – 1579
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1573

Dongren Wang et al.
FULL PAPERS
gun: 20 kV, 3 mA, matrix: m-nitrobenzylic alcohol). (R)-H2-
pentane and white crystals were isolated; yield: 13.59 g
(33.93 mmol, 80%).
ACHTREUNG
(95%) was purchased from ABCR (Germany). A micro-
wave system (MWS, Germany) was used for dissolving the
samples. Hydroxymethylated polystyrene (55763 Fluka,
~0.6 mmol OH/g, 200–400 mesh, 1% cross-linked with
DVB) was used. 4-Bromo-2,6-dimethylaniline (1) was pur-
chased from Aldrich Chem. Co. IR, 1H NMR, 13C NMR,
and MS data as well data of elemental analyses for com-
pounds 2–25 may be found in the Supporting Information.
4-(6-Bromohexyl)-2,6-dimethyl-N,N-bis-trimethylsilyl-
aniline (5)
To an ethereal solution of 3 (16.78 g, 57.45 mmol) was
added lithium (3 equivs., 1.20 g, 172.3 mmol) and the mix-
ture was refluxed for 4 h. Excess lithium was filtered off and
the light yellow solution was chilled to À408C. 1,6-Dibromo-
hexane (26.26 mL, 172.34 mmol) was added and the mixture
was stirred overnight at room temperature. Next, the solvent
was removed and the product was extracted with n-pentane.
Then, the solution was filtered through a bed of silica G60,
all volatiles were evaporated and the product was extracted
with n-pentane. For further purification the product was
subject to chromatography over silica G60 (column dimen-
sions 2.5”30 cm) using hexane as eluent; Yield: 12.32 g
(28.73 mmol, 50%).
4-Bromo-2,6-di-2-propylaniline (2)
Bromine (16.082 g, 100.64 mmol) was dissolved in small por-
tions in 30 mL of cooled (À108C) pyridine. The red solution
was added drop wise to a cooled (À108C) mixture of 2,6-di-
2-propylaniline (16.99 g, 95.84 mmol) in 20 mL of pyridine.
The reaction mixture was stirred for 30 min at 08C and for a
further 1.5 h at room temperature. Next, it was treated with
an excess of sodium carbonate in water and extracted with
diethyl ether. All volatiles were evaporated. vacuum distilla-
tion afforded of the product (bp 1108C/0.14 Torr), which
was crystallized from n-pentane; yield: 17.01 g (66.40 mmol,
69%).
4-(6-Bromohexyl)-2,6-di-2-propyl-N,N-bis-trimethylsi-
lylaniline (6)
To an ethereal solution of 4 (8.11 g, 57.45 mmol) was added
lithium (3 equivs., 1.20 g, 172.3 mmol) and the mixture was
refluxed for 4 h. Excess lithium was filtered off and the light
yellow solution was chilled to À408C. 1,6-Dibromohexane
(26.26 mL, 172.34 mmol) was added and the mixture was
stirred overnight at room temperature. Next, the solvent
was removed and the product was extracted with n-pentane.
Then, the solution was filtered through a bed of silica G60,
all volatiles were evaporated and the product was extracted
with n-pentane. For further purification the product was
subject to chromatography over silica G60 (column dimen-
sions 2.5”30 cm) using hexane as eluent; yield: 13.88 g
(28.73 mmol, 50%).
4-Bromo-2,6-dimethyl-N,N-bis-trimethylsilylaniline
(3)
Compound 1 (17.47 g, 87.29 mmol) was dissolved in 200 mL
of diethyl ether and chilled to À508C, n-butyllithium (2.2
equivs., 96.02 mL, 192.05 mmol) was added. The mixture
was stirred for 1 h at room temperature. Afterwards, the so-
lution was re-chilled to À508C and trimethylsilyl chloride
(27.60 mL, 218.2 mmol) was added in small portions over a
period of 10 min. After 2 h of further stirring at room tem-
perature the diethyl ether was removed under vacuum, the
resulting solid was extracted with n-pentane and filtered
through a bed of silica G60. The solution was concentrated
and the crude product was collected as a white solid. For
further purification the solid was crystallized from n-pen-
tane; yield: 29.49 g (85.62 mmol, 98%, white crystals).
4-(6-Bromohexyl)-2,6-dimethylaniline (7)
Compound 5 (12.3 g, 28.71 mmol) was mixed with 20 mL of
concentrated hydrobromic acid and stirred at 608C for 5 h.
The resulting precipitate was filtered off and washed with n-
pentane. The solid was stirred with an aqueous sodium hy-
droxide solution (2 N) and finally the product was extracted
with n-pentane; yield: 7.26 g (25.55 mmol, 89%, colorless
oil).
4-Bromo-2,6-di-2-propyl-N,N-bis-trimethylsilylaniline
(4)
Compound 2 (10.94 g, 42.70 mmol) was dissolved in 200 mL
of diethyl ether and chilled to À508C. n-Butyllithium (2.2
equivs., 47.97 mL, 93.94 mmol) was added. The mixture was
stirred for 1 h at room temperature. Afterwards, the solution
was re-chilled to À508C and trimethylsilyl chloride
(12.96 mL, 102.5 mmol) was added in small portions over a
period of 10 min. After 2 h of further stirring at room tem-
perature the diethyl ether was removed under vacuum, the
resulting solid was extracted with n-pentane and filtered
through a bed of silica G60. The solution was concentrated
and the crude product was collected as yellowish crystals.
For further purification the solid was crystallized from n-
4-(6-Chlorohexyl)-2,6-dimethylaniline (8)
Compound 5 was suspended in methanolic hydrochloric acid
(150 mL) and stirred overnight at 1008C. All volatiles were
evaporated and the residue was collected and washed thor-
oughly with n-pentane. The slightly brown salt was treated
with an excess of sodium hydroxide and the product was ex-
tracted with n-pentane. The pentane solution was dried over
1574
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Adv. Synth. Catal. 2006, 348, 1567 – 1579

Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
Na2SO4 and finally all solvent was evaporated to afford a
brownish oil; yield: 6.39 g (26.7 mmol, 90%).
Mo{N
(13)
A
G
N
(NH4)6Mo7O24·4H2O (0.737 g, 0.596 mmol) was suspended
in DME (40 mL) at room temperature. 2,6-Lutidine
(1.94 mL, 16.7 mmol) and trimethylsilyl chloride (5.54 mL,
43.8 mmol) were added and the solution was stirred for
10 min. Next, 9 (2.840 g, 9.598 mmol) was added and the so-
lution was stirred at 658C for 6 h. The solution turned
orange, becoming dark red over time and a white precipitate
formed. The mixture was allowed to cool to room tempera-
ture and was filtered through celite. The solid was rinsed
with DME until the washings ran through colorless. The vol-
atile components were removed under vacuum to yield a
dark red solid. The product was extracted with diethyl ether
and crystallized from diethyl ether with a few drops of n-
pentane (for further purification). Red crystals were isolat-
ed; yield: 2.97 g (3.51 mmol, 84%).
4-(6-Chlorohexyl)-2,6-di-2-propylaniline (9)
Compound 6 was suspended in methanolic hydrochloric acid
(150 mL) and stirred overnight at 1008C. All volatile sol-
vents were evaporated and the precipitate was collected and
washed thoroughly with n-pentane. The slightly brown col-
ored salt was treated with an excess of NaOH and the prod-
uct was extracted with n-pentane. The organic layer was
dried over Na2SO4 and finally the solvent was evaporated;
yield of pure product: 4.58 g (15.5 mmol, 73%).
4-(6-Bromohexyl)-2,6-di-2-propylaniline (10)
Compound 6 (12.3 g, 25.4 mmol) was mixed with 20 mL of
hydrobromic acid and stirred at 608C for 5 h. The resulting
precipitate was filtered off and washed with n-pentane. The
solid was stirred with an aqueous sodium hydroxide solution
(2 N) and finally the product was extracted with n-pentane;
yield: 6.82 g (20.10 mmol, 79%, colorless oil).
Mo{N
(14)
A
G
R
A
in DME (40 mL) at room temperature. 2,6-Lutidine
(1.94 mL, 16.7 mmol) and trimethylsilyl chloride (5.54 mL,
43.8 mmol) were added and the solution was stirred for
10 min. Next, 10 (2.829 g, 8.344 mmol) was added and the
solution was stirred at 658C for 6 h. The solution turned
orange, becoming dark red over time and a white precipitate
formed. The mixture was allowed to cool to room tempera-
ture and was filtered through celite. The solid was rinsed
with DME until the washings ran through colorless. The vol-
atile components were removed under vacuum to yield a
dark red solid. The product was extracted with diethyl ether
and crystallized from diethyl ether with a few drops of n-
pentane (for further purification). Red crystals were isolat-
ed; yield: 1.91 g (2.01 mmol, 50%).
Mo{N[2,6-Me2-4(6-BrC6H12)]C6H2}2Cl2(DME) (11)
A
A
DME (200 mL). 2,6-Lutidine (6.53 g, 60.9 mmol) and trime-
thylsilyl chloride (14.06 g, 129.5 mmol) were added and the
solution was stirred for 5 min at room temperature. Next, 7
(8.66 g, 30.6 mmol) was added and the solution was stirred
at 508C oil-bath temperature for 3 h. During this time the
solution turned deep red. The reaction mixture was cooled
to room temperature, filtered through celite and all volatile
compounds were evaporated. Finally, the product was ex-
tracted with ether/n-pentane and stored at À388C for crys-
tallization. A red solid was obtained; yield: 5.6 g (4.0 mmol,
45%).
Mo{N[2,6-Me2-4(6-BrC6H12)]C6H2}2(CH2CMe2C6H5)2
(15)
Compound 11 (0.50 g, 0.61 mmol) was dissolved in 50 mL of
diethyl ether. The solution was cooled to À408C and 2
equivs. of neophylmagnesium chloride (2.42 mL, 1.22 mmol,
0.503M in diethyl ether) were added dropwise. The solution
turned orange and a precipitate formed. After 3 h of stirring
at room temperature the solvent was removed under
vacuum. The resulting solid was extracted with n-pentane,
filtered through celite and concentrated for crystallization;
yield: 0.449 g (0.485 mmol, 80%, orange crystals).
Mo{N[2,6-Me2-4(6-ClC6H12)]C6H2}2Cl2(DME) (12)
A
(NH4)6Mo7O24·4H2O (0.713 g, 0.577 mmol) was suspended
in DME (60 mL) at room temperature. 2,6-Lutidine
(1.88 mL, 16.2 mmol) and trimethylsilyl chloride (5.37 mL,
42.4 mmol) were added and the solution was stirred for
10 min. Next, 8 (2.297 g, 9.580 mmol) was added and the so-
lution was stirred at 658C for 3.5 h. The solution turned
orange, becoming dark red over time and a white precipitate
formed. The mixture was allowed to cool to room tempera-
ture and was filtered through celite. The solid was rinsed
with DME until the washings ran through colorless. The vol-
atiles were removed under vacuum to yield a dark red solid.
The product was extracted with diethyl ether and crystal-
lized from diethyl ether with a few drops of n-pentane. Red
crystals were obtained; yield:1.054 g (1.439 mmol, 36%).
Mo{N[2,6-Me2-4(6-ClC6H12)]C6H2}2(CH2CMe2C6H5)2
(16)
Compound 12 (0.740 g, 1.01 mmol) was dissolved in 100 mL
of diethyl ether. The solution was cooled to À388C and 2
Adv. Synth. Catal. 2006, 348, 1567 – 1579
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1575

Dongren Wang et al.
FULL PAPERS
equivs. of neophylmagnesium chloride (2.84 mL, 2.02 mmol,
0.71M in diethyl ether) were added over a period of 10 min.
The solution turned orange and a precipitate formed. After
14 h of stirring at room temperature the solvent was re-
moved under vacuum. The resulting solid was extracted
with n-pentane. Next, the solution was filtered through
celite and concentrated for crystallization. Yellow-orange
crystals were obtained; yield: 0.679 g (0.810 mmol, 80%).
Mo{N[2,6-
(CHCMe2C6H5)(OTf)2
ACHTREUNG
AHCTREUNG
Compound 18 (511.8 mg, 0.49 mmol) was dissolved in 30 mL
of DME and cooled to À408C. Triflic acid (221.8 mg,
1.47 mmol) diluted in 5 mL of DME and chilled to À408C
was added. The mixture was stirred 4 h at room tempera-
ture; the solvent was removed under vacuum. The solid was
re-dissolved in cooled diethyl ether and filtered. Finally, all
volatiles were removed under vacuum to afford a yellow-
brownish oil; yield: 374 mg (0.392 mmol, 80%). For further
purification, the oil was extracted with n-pentane.
Mo{N
N
N
(CH2CMe2C6H5)2 (17)
Compound 13 (1.377 g, 1.630 mmol) was dissolved in 50 mL
of diethyl ether. The solution was cooled to À408C and 2
equivs. of neophylmagnesium chloride (4.59 mL, 3.26 mmol;
0.71M in diethyl ether) was added dropwise. The solution
turned orange and a precipitate formed. After 16 h stirring
at room temperature the solvent was removed under
vacuum. The resulting solid was extracted with n-pentane,
filtered through celite and then concentrated for crystalliza-
tion; yield: 0.945 g (0.994 mmol, 61%).
Mo{N
A
G
U
ACHTREUNG
Compound 17 (0.380 g, 0.399 mmol) was dissolved in 30 mL
of DME and the solution was cooled to À388C. Triflic acid
(0.168 g, 1.12 mmol) diluted in 10 mL of DME and chilled
to À388C was added and the mixture was stirred for 2 h.
The volatiles were removed under vacuum and the solid was
extracted with n-pentane. The brownish solution was filtered
through celite and dried under vacuum, affording a yellow-
brownish oil; yield: 0.218 g (0.239 mmol, 60%).
Mo{N
N
E
(CH2CMe2C6H5)2 (18)
Compound 14 (1.52 g, 1.63 mmol) was dissolved in 50 mL of
diethyl ether. The solution was cooled to À388C and 2
equivs. of neophylmagnesium chloride (4.59 mL, 3.26 mmol,
0.71M in diethyl ether) were added over a period of 10 min.
The solution turned orange and a precipitate formed. After
16 h of stirring at room temperature the solvent was re-
moved under vacuum. The resulting solid was extracted
with n-pentane. Next, the solution was filtered through
celite and concentrated for crystallization. An orange oil
was isolated; yield: 1.354 g (1.3 mmol, 80%).
Mo{N[2,6-Me2-4(6-BrC6H12)]C6H2}(CHCMe2C6H5)-
[OC(CF3)2Me]2 (22)
A
Compound 19 (246 mg, 0.185 mmol) was dissolved in diethyl
(CF3)2CH3 (108 mg,
ether and cooled to À388C. LiOC
ACHTREUNG
0.572 mmol) was added and the solution was stirred for
30 min at room temperature. The solvents were removed
under vacuum and the resulting solid was extracted with n-
pentane. The brown organic layer was filtered through
celite. Finally, all volatile compounds were removed under
vacuum. A yellow-brownish oil was obtained; yield: 121 mg
(0.139 mmol, 75%).
Mo{N[2,6-Me2-4(6-BrC6H12)]C6H2}(CHCMe2C6H5)-
A
N
Mo{N
(CHCMe2C6H5)[OC
[2,6-
ACHTREUNG
Compound 15 (0.972 g, 1.049 mmol) was dissolved in
100 mL of dimethoxyethane (DME) and the solution was
cooled to À388C. Triflic acid (0.472 g, 3.15 mmol) diluted in
10 mL of DME and chilled to À388C was added and the
mixture was stirred for 12 h. The volatile components were
removed under vacuum and the solid was re-dissolved in di-
ethyl ether and filtered. All volatiles were removed; the res-
idue was extracted with n-pentane. The solution was filtered
through celite and all volatile compounds were evaporated;
yield: 0.802 g (0.891 mmol, 85%, yellow-brownish oil).
AHCTREUNG
Compound 21 (57.0 mg, 0.063 mmol) was dissolved in dieth-
(CF3)2CH3 (24.0 mg,
yl ether and cooled to À388C. LiOC
ACHTREUNG
0.126 mmol) was added and the solution was stirred for
30 min at room temperature. The solvents were removed
under vacuum and the resulting solid was extracted with n-
pentane. The organic layer was filtered through celite. Final-
ly, all volatile compounds were removed under vacuum, af-
fording a brown oil; yield: 41 mg (0.047 mmol, 74%).
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Adv. Synth. Catal. 2006, 348, 1567 – 1579

Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
were neutral, and dried at 1008C overnight. (~0.2 mmol
OH/g).
Mo{N[2,6-Me2-4-(6-Br-C6H12)]C6H2}2-
(CHCMe2C6H5)[(R)-BIPHEN] (24)
Potassium hydride (3 equivs., 68.73 mg, 1.71 mmol) was
added in portions to a stirred THF (20 mL) solution of (R)-
Reaction of Hydroxymethylpoly(styrene) with
A
H2[Biphen] (202.5 mg, 0.57 mmol). After 18 h, a THF solu-
A
1,2,2-Trifluoro-2-hydroxy-1-trifluoromethylethanesul-
fonic Acid Sultone,[38] Conversion into the Ag Salt
tion of 19 (513.3 mg, 0.57 mmol) was added. The red solu-
tion was stirred for 3 h at room temperature and then con-
centrated under vacuum. The residue was extracted with
benzene. The suspension was filtered through Celite and
washed with benzene until the washings were colorless. The
benzene was removed under vacuum to furnish a red solid
product; yield: 160 mg (0.185 mmol, 33%).
Hydroxymethylpoly(styrene-co-divinylbenzene)
(1.0 g,
0.60 mmol OH) was added to a solution of 1,2,2-trifluoro-2-
hydroxy-1-trifluoromethylethanesulfonic acid sultone (2.5
equivs., 345 mg, 1.50 mmol) in 50 mL of dry toluene. The
mixture was refluxed for 8 h, the solid was filtered and
washed thoroughly with toluene and finally dried at8C over-
night. It was then suspended in an aqueous solution of KOH
(25 mL, 0.1 N), mixed with 10 mL of THF and the mixture
was stirred for 12 h. The solid was filtered off and washed
with water until the washings were neutral. Finally, the solid
was suspended in an aqueous solution of AgNO3 (25 mL,
0.1m) with 10 mL THF and stirred for 4 h at room tempera-
ture. The solid was filtered and washed with water until the
washings were free of silver, as checked with aqueous
sodium iodide solution, Finally, the solid was washed with
dry THF. The brown solid was dried at 1008C overnight.
Mo{N
N
N
(CHCMe2C6H5)[(R)-BIPHEN] (25)
Potassium hydride (3 equivs. 19.0 mg, 0.48 mmol) was added
in portions to a stirred THF (10 mL) solution of (R)-H2-
A
of 20 (153 mg, 0.16 mmol) was added. The red solution was
stirred for 3 h at room temperature, and then concentrated
under vacuum. The residue was extracted with benzene. The
suspension was filtered through celite and washed with ben-
zene until the washings were colorless. The benzene was re-
moved under vacuum to furnish the red solid product; yield:
105 mg (71%).
Reaction of Ag Trifluoromethanesulfonate with
1-Bromooctane
1-Bromooctane (19.1 mg, 0.099 mmol) and silver trifluoro-
methanesulfonate (22.7 mg, 0.089 mmol) were dissolved in
dimethyl sulfoxide-d6. The mixture was stirred for 8 h and
then subject to 1H NMR [d=3.50 (m, 2H, OCH2)]. Circa
30% conversion of the parent 1-bromooctane into the ester
was observed. No vinyl compounds (1-octene), resulting
from elimination reactions, were observed.
Synthesis of Poly(styrene)
A
Styrene (5.20 g, 50.0 mmol) and perbenzoic anhydride
(0.120 g, 0.5 mmol) were dissolved in 10 mL of absolute tol-
uene. The solution was stirred at 608C for 4 h. After addi-
tion of acidic methanol with HCl, a white solid precipitated,
it was filtered off, washed with methanol and finally dried
under vacuum; yield: 3.00 g (60%) (Mn: 10,000 gmolÀ1
,
Synthesis of Poly
Complex (26)
A
PDI: 1.5).
A suspension of the silver salt of trifuoromethansulfonated
PS (200 mg, 0.04 mmol) and the molybdenum complex 22
(36 mg, 0.04 mmolgÀ1) in C6H6 (50 mL) was stirred at room
temperature for 24 h. The resulting product was filtered,
washed with C6H6 (3”15 mL, only slightly yellow washings)
and pentane (4”5 mL) and dried under vacuum to afford
180 mg of a grey powder. Catalyst-loadings as determined
by measurement of Mo by means of ICP-OES: 26:
0.01 mmolg.À1
Chloromethylation of Poly
Hydrolysis[41]
A
Trioxane (0.90 g, 10.0 mmol) and chlorotrimethylsilane
(3.8 mL, 30.0 mmol) were dissolved in 10 mL of absolute
chloroform. Poly(styrene) (1.00 g) and SnCl4 (0.5 mL,
A
4.30 mmol) were added at 08C. The mixture was stirred at
08C for 30 min and for another 2 h at room temperature.
After addition of methanolic water, the polymer was filtered
and washed with methanol and water and finally dried
under vacuum overnight; anal. found: C 81.35, H 7.13, Cl
9.43.
The polymer was then suspended in an aqueous solution
of NaOH (100 mL, 0.01 N) and 10 mL of THF, and then the
mixture was stirred for 12 h at room temperature. The poly-
mer was filtered and washed with water until the washings
Synthesis of Poly(styrene-co-divinylbenzene)-
Supported (Chiral) Mo Complexes 27 and 28
(Representative Example)
A suspension of the silver salt of trifuoromethansulfonated
poly(styrene-co-DVB) (200 mg, 0.120 mmol) and the corre-
Adv. Synth. Catal. 2006, 348, 1567 – 1579
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1577

Dongren Wang et al.
FULL PAPERS
sponding
molybdenum
complexes
24
(100 mg,
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supplemen-
tary publications no. CCDC 602508 and 602509. Copies of
the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: int.
0.12 mmolgÀ1) and 25 (112 mg, 0.12 mmolgÀ1) in C6H6
(50 mL) was stirred at room temperature for 24 h. The re-
sulting product was filtered, washed with C6H6 (3”15 mL,
only slightly yellow washings) and pentane (4”5 mL) and
dried under vacuum to afford 180 mg of a dark-grey
powder. Catalyst-loadings as determined by measurement of
code + 44(1223)336–033; E-mail: deposit@ccdc.cam.ac.uk].
A
Mo by means of ICP-OES: 27: 0.08 mmolgÀ1
0.13 mmolgÀ1
; 28:
.
Acknowledgements
This work was supported by the Austrian Science Fund
(START Y-158) and the Freistaat Sachsen.
Representative RCM with Supported (Chiral)
Complexes
A vial was charged with monomer (8”10À3 mmol) and the
supported catalyst (4”10À4 mmol Mo) in the indicated sol-
vent. The reaction mixture was stirred at room temperature
for the time indicated in Table 1 and conversion was
checked by GC-MS. The mixture was filtered and washed
with pentane. The crude material was concentrated under
vacuum and analyzed by chiral GC-MS for ee. Desymmetri-
zation reactions were checked for ee by means of chiral
HPLC. Separation conditions were identical to those report-
ed in the literature.[39,42,43] Finally, the sample was dissolved
in aqua regia (5 mL) and analyzed by means of ICP-OES
for the residual metal content (5.5% average leaching).
References
[1] W. Cabri, I. Candiani, Acc. Chem. Res. 1995, 28, 2.
[2] A. de Meijere, F. E. Meyer, Angew. Chem. 1994, 106,
2473; Angew. Chem. Int. Ed. 1994, 33, 2379–2411.
[3] J. G. de Vries, Can. J. Chem. 2001, 79, 1086.
[4] R. H. Grubbs, S. J. Miller, G. C. Fu, Acc. Chem. Res.
1995, 28, 446.
[5] A. Fürstner, Angew. Chem. 2000, 112, 3140; Angew.
Chem. Int. Ed. 2000, 39, 3012–3043.
[6] R. H. Grubbs (Ed.), Handbook ofMetathesis, Vols. 1–3 ,
1 st edn., Wiley-VCH, Weinheim, 2003.
[7] R. R. Schrock, Chem. Rev. 2002, 102, 14.
[8] R. R. Schrock, A. H. Hoveyda, Angew. Chem. 2003,
115, 4740; Angew. Chem. Int. Ed. 2003, 42, 4592–4633.
[9] T. M. Trnka, R. H. Grubbs, Acc. Chem. Res. 2001, 34,
18.
[10] J. S. Kingsbury, A. H. Hoveyda, in: Polymeric Materials
in Organic Synthesis and Catalysis, (Ed.: M. R. Buch-
meiser), Wiley-VCH, Weinheim, 2003, p. 467.
[11] M. R. Buchmeiser, New. J. Chem. 2004, 28, 549.
[12] F. Michalek, D. Mädge, J. Rühe, W. Bannwarth, Eur. J.
Org. Chem. 2006, 577.
X-Ray Measurement and Structure Determination of
13 and 15
Single crystals of 13 and 15 suitable for X-ray analysis were
obtained by slow crystallization from dichloromethane/pen-
tane. Data collection was performed on a Nonius Kappa
CCD equipped with graphite-monochromatized Mo-Ka-ra-
diation (l=0.71073 Š) and a nominal crystal to area detec-
tor distance of 36 mm. Compound 13: monoclinic space
group C2/c (No.15), a=2261.28(7) pm, b=1970.31(8) pm,
c=1556.75(6) pm, b=132.566(2)8, V=5.1083(3) nm3, Z=4,
[13] E. M. Zahidi, H. Oudghiri-Hassani, P. H. McBreen,
Nature 2001, 409, 1023.
&
calcd. =1.209 gcmÀ3, T=233.2 K, m=0.708 mmÀ1, red prism,
[14] M. Siaj, P. H. McBreen, Science 2005, 309, 588.
[15] F. Blanc, M. Chabanas, C. CopØret, B. Fenet, E. Herd-
weck, J. Organomet. Chem. 2005, 690, 5014.
[16] F. Blanc, C. CopØret, J. Thivolle-Cazat, J.-M. Basset, A.
Lesage, L. Emsley, A. Sinha, R. R. Schrock, Angew.
Chem. 2006, 118, 1238; Angew. Chem. Int. Ed. 2006,
2513 reflections>2s(I). The structure was solved and re-
fined using SHELXS83 and SHELXL97 to R1 =0.0477 and
wR2 =0.11738. Compound 15: monoclinic space group C21/n
(No.14), a=1750.6(2) pm, b=845.5(2) pm, c=3206.6(2) pm,
b=104.720(6)8,
V=4.5904(12)
nm3,
Z=4,
, yellow plates,
&
=
calcd.
1.341 gcmÀ3 T=233.2 K, m=2.050 mmÀ1
,
45, 1216–1220.
ˇ
2673 reflections>2s(I). The structure was solved and re-
fined using SHELXS83 and SHELXL97 to R1 =0.1604 and
wR2 =1.136.
ˇ
[17] H. Balcar, N. Zilkovꢂ, J. Sedlꢂcek, J. Zednꢃ, J. Mol.
Catal. A: Chem. 2005, 232, 53.
[18] S. I. Wolke, R. Buffon, J. Mol. Catal. A: Chem. 2000,
160, 181.
[19] P. Preishuber-Pflügl, E. Eder, F. Stelzer, e-Polymers
2002, 045.
[20] P. Preishuber-Pflügl, P. Buchacher, E. Eder, R. M.
Schitter, F. Stelzer, J. Mol. Catal. A: Chem. 1998, 133,
151.
Intensities were integrated using DENZO and scaled with
SCALEPACK.[44] Several scans infand w direction were
made to increase the number of redundant reflections,
which were averaged in the refinement cycles. This proce-
dure replaces in a good approximation an empirical absorp-
tion correction. The structures were solved with direct meth-
ods SHELXS86 and refined against F2 SHELX97.[45] The
[21] K. C. Hultzsch, J. A. Jernelius, A. H. Hoveyda, R. R.
Schrock, Angew. Chem. 2002, 114, 609; Angew. Chem.
Int. Ed. 2002, 41, 589–593.
2
2 2
function minimized was S[w
N
fined as wÀ1 =[s2(Fo )+(xP)2+P] and P=(Fo +2Fc )/3. All
A
2
non-hydrogen atoms were refined with anisotropic displace-
ment parameters.
[22] R. M. Krçll, N. Schuler, S. Lubbad, M. R. Buchmeiser,
Chem. Commun. 2003, 2742.
1578
www.asc.wiley-vch.de
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2006, 348, 1567 – 1579

Polymer-Supported Chiral Schrock Catalysts
FULL PAPERS
[23] M. Mayr, D. Wang, R. Krçll, N. Schuler, S. Prühs, A.
Fürstner, M. R. Buchmeiser, Adv. Synth. Catal. 2005,
347, 484.
[24] S. J. Dolman, K. C. Hultzsch, F. Pezet, X. Teng, A. H.
Hoveyda, R. R. Schrock, J. Am. Chem. Soc. 2004, 126,
10945.
[25] A. H. Hoveyda, R. R. Schrock, Chem. Eur. J. 2001, 7,
945.
[26] J. H. Oskam, H. H. Fox, K. B. Yap, D. H. McConville,
R. OꢄDell, B. J. Lichtenstein, R. R. Schrock, J. Organo-
met. Chem. 1993, 459, 185.
[34] G. A. Olah, P. S. Iyer, G. K. S. Prakash, Synthesis 1986,
513.
[35] A. J. Seen, J. Mol. Catal. A: Chemical 2001, 177, 105.
[36] B. Tçrçk, I. Kiricsi, A. Molnꢂr, G. A. Olah, J. Catal.
2000, 193, 132.
[37] I. Tꢅth, B. E. Hanson, M. E. Davis, J. Organomet.
Chem. 1990, 397, 109.
[38] M. Alvaro, A. Corma, D. Das, V. FornØs, H. Garcꢃa,
Chem. Commun. 2004, 956.
[39] S. J. Dolman, E. S. Sattely, A. H. Hoveyda, R. R.
Schrock, J. Am. Chem. Soc. 2002, 124, 6991.
[40] M. Mayr, M. R. Buchmeiser, Macromol. Rapid.
Commun. 2004, 25, 231.
[27] G. Schoettel, J. Kress, J. A. Osborn, J. Chem. Soc.,
Chem. Commun. 1989, 1062.
[28] R. R. Schrock, Chem. Commun. 2005, 2773.
[29] M. R. Buchmeiser, Chem. Rev. 2000, 100, 1565.
[30] R. R. Schrock, The Discovery and Development of
High-Oxidation State Mo and W Imido Alkylidene
Complexes for Alkene Metathesis, in: Handbook of
Metathesis, (Ed.: R. H. Grubbs), Vol. 1, Wiley-VCH,
Weinheim, 2004.
[41] S. Itsuno, K. Uchikoshi, K. Ito, J. Am. Chem. Soc. 1990,
112, 8187.
[42] D. S. La, J. B. Alexander, D. R. Cefalo, D. D. Graf,
A. H. Hoveyda, R. R. Schrock, J. Am. Chem. Soc.
1998, 120, 9720.
[43] A. F. Kiely, J. A. Jernelius, R. R. Schrock, A. H. Hovey-
da, J. Am. Chem. Soc. 2002, 124, 2868.
[31] D. E. Bryant, M. Kilner, J. Mol. Catal. A: Chemical
[44] Z. Otwinowski, W. Minor, in: Methods in Enzymology,
Vol. 276, Academic Press, New York, 1997.
[45] G. M. Sheldrick, Program package SHELXTL V.5.1,
Bruker Analytical X-Ray Instruments Inc, Madison,
USA, 1997.
2002, 178, 1.
[32] D. E. Bryant, M. Kilner, J. Mol. Catal. A: Chemical
2003, 193, 83.
[33] L. El Aakel, F. Launay, J.-M. BrØgeault, A. Atlamsani,
J. Mol. Catal. A: Chemical 2004, 212, 172.
Adv. Synth. Catal. 2006, 348, 1567 – 1579
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
1579