New library of aminosulfonyl-tagged Hoveyda-Grubbs type complexes: Synthesis, kinetic studies and activity in olefin metathesis transformations

Article abstract of DOI:10.3762/bjoc.6.132

Seven novel Hoveyda-Grabbs precatalysts bearing an aminosulfonyl function are reported. Kinetic studies indicate an activity enhancement compared to Hoveyda's precatalyst. A selection of these catalysts was investigated with various substrates in ring-clo

Full text of DOI:10.3762/bjoc.6.132

New library of aminosulfonyl-tagged Hoveyda–
Grubbs type complexes: Synthesis, kinetic studies
and activity in olefin metathesis transformations
Etienne Borré1,2, Frederic Caijo1,3, Christophe Crévisy*1,2
and Marc Mauduit*1,2
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2010, 6, 1159–1166.
1École Nationale Supérieure de Chimie de Rennes, CNRS, UMR
6226, Av. du Général Leclerc, CS 50837 35708 Rennes cedex 7,
France, 2Université Européenne de Bretagne, 35000 Rennes, France
and 3Omega cat system Sàrl - École Nationale Supérieure de Chimie
de Rennes, Av. du Général Leclerc, CS 50837 35708 Rennes cedex
7, France
doi:10.3762/bjoc.6.132
Received: 13 September 2010
Accepted: 09 November 2010
Published: 06 December 2010
Guest Editor: K. Grela
Email:
Etienne Borré - etienne.borre@ensc-rennes.fr; Frederic Caijo -
f.caijo@omcat-system.com; Christophe Crévisy* -
christophe.crevisy@ensc-rennes.fr; Marc Mauduit* -
marc.mauduit@ensc-rennes.fr
© 2010 Borré et al; licensee Beilstein-Institut.
License and terms: see end of document.
* Corresponding author
Keywords:
cross-metathesis; kinetic studies; olefin metathesis; RCM; ruthenium
Abstract
Seven novel Hoveyda–Grubbs precatalysts bearing an aminosulfonyl function are reported. Kinetic studies indicate an activity
enhancement compared to Hoveyda’s precatalyst. A selection of these catalysts was investigated with various substrates in ring-
closing metathesis of dienes or enynes and cross metathesis. The results demonstrate that these catalysts show a good tolerance to
various chemical functions.
Introduction
In the last decades, olefin metathesis has become a powerful rocyclic carbene (NHC) moiety. Despite the stability enhance-
tool in organic chemistry. Since the discovery of the well- ment of the active species (due to NHC), these catalysts still
defined ruthenium precatalyst (Cl2(PPh3)2Ru=CHPh) [1], required a high catalytic loading (up to 20 mol % in some cases
which is tolerant to many functional groups, several synthetic [7]). Later, Hoveyda synthesized a recyclable phosphine-free
routes (from petrochemical to fine chemical products) have precatalyst (2a) [8] based on a release/return concept of the
been facilitated [2-4]. However, many research groups have benzylidene ether fragment. Electronic or steric modifications
focused their research on the development of more efficient made by Blechert (2b) [9,10], Grela (2c) [11,12] or Zhan (2d)
precatalysts (Figure 1). In 1999, Grubbs (1a) [5] and [13] have allowed a decrease of precatalyst loading (down to
Nolan (1b) [6] reported ruthenium species bearing one N-hete- 1 mol %).
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
Figure 2: Structure of precatalyst 3 and 4.
obtained with these catalysts enabled us not only to combine the
enhancement of activity with a better stability (1 month in
dichloromethane solution) but also to combine it with excellent
recyclability (up to 60% at 0.3 mol %). Extremely low levels of
Ru-contamination in the final products were determined by
ICP-MS analyses (below 6 ppm) after silica gel chromatog-
Figure 1: Ruthenium precatalysts for olefin metathesis.
Nevertheless, despite all these recent developments, the raphy. Additionally, a recent study in the synthesis of natural
problem of the ruthenium contamination in products has still products involving a library of precatalysts 3 [7] shows that the
not yet been resolved. Indeed, high concetrations of metal structure of the catalyst must be carefully designed and adapted
impurities are often present in the final products, limiting indus- for a specific transformation.
trial applications. Several attempts have been made to reduce
the Ru-contamination to <10 ppm, as required by regulatory Owing to this substrate dependency, we focused our attention
bodies, for example, by the use of Ru-scavengers, biphasic on the development of a new library of catalysts bearing an
extraction, silica gel chromatography etc. [14]. Nevertheless, aminosulfonyl function 4 (Figure 2).
some difficulties remain, for instance: Lower yields are
observed when successive silica gel chromatography is Results and Discussion
performed and some scavengers are very toxic (PbOAc2, To synthesize the catalysts, the required aminosulfonyl func-
DMSO…) [15]. Another strategy aims to control the catalyst tion had to be introduced into the styrenylether fragment. The
activity in order to improve recyclability. Recently, various ligands (6a–f) were synthesized in one step from the previously
aminocarbonyl-containing “boomerang” precatalysts 3 were reported aniline 5 [19,20] and either trifluoromethanesulfonic
synthesized in our laboratory (Figure 2) [16-18]. The results anhydride or various chlorosulfonyl derivatives (Scheme 1).
Scheme 1: Synthesis of catalysts 4a–g.
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
Figure 3: Kinetic studies of RCM of 8 (0.1 M) with precatalysts 4a–g (1 mol %) in CD2Cl2 at 30 °C.
Ligands 6a–f were isolated in moderate to good yields In order to investigate potential substrate dependency, the
(60–80%). Their reaction with Ru-indenylidene complex 7a activity of the five SIMes-catalysts 4a–e was evaluated in three
[21] or 7b [22] in the presence of CuCl afforded the expected different cross-metathesis (CM) reactions involving methyl
precatalysts 4a–g in good yields.
acrylate, methyl vinyl ketone (MVK) and acrylonitrile as
electro-deficient alkenes and the two electron-rich olefins S1
Then, the reactivity profile of each catalyst was investigated and S2 (Table 1).
using 1H NMR monitored kinetic studies. Comparison between
catalysts was done at the initiation step. Moreover, conversions In the reaction of methyl acrylate and S1, complexes 4c and 4d
were compared over a reaction time of one hour. The 2-allyl-2- proved to be the most efficient catalysts (entries 1–5) while no
methallylmalonate 8 is usually used as benchmark substrate for clear-cut difference in reactivity was observed when MVK and
ring-closing metathesis, inasmuch it shows significant differ- S2 were used (entries 6–10). The CM of S1 and acrylonitrile,
ences between an activated or a non-activated precatalyst. The which is known to be a demanding substrate, was more prob-
reactions were performed at low loading of precatalyst lematic since low conversions were observed after 24 h of reac-
(1 mol %) and 30 °C (Figure 3).
tion at 2 mol % catalyst loading (entries 11–15). Unexpectedly,
complex 4c was half as efficient as the other analogues (entry
The graphs presented in Figure 3 show three different types of 13). So, the nature of the electron-withdrawing group (EWG)
behavior. The catalysts 4c, 4d and 4e are not activated appears to have a rather weak influence on the behaviour of the
compared to Hoveyda’s complex 2a. They can be classified as catalysts in these cases.
Hoveyda-like complexes. Complexes 4a, 4b and 4f can be
considered to be activated catalysts, while catalyst 4g bearing a Finally, the reactivity profiles of 4a and 4g were compared in
more sterically demanding NHC (SIPr) ligand shows a faster various metathesis reactions in order to evaluate the influence
initiation compared to its SIMes analogue catalyst 4b. Add- of the NHC ligand. The last point of our study was the compari-
itionally, 4g gave the best conversion over a reaction time of son between catalysts in RCM of dienes or enynes and in one
one hour.
CM reaction (Table 2).
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
Table 1: Scope of 4a–e for CM transformationsa.
Entry
Substrates
Product
Time
0.5 h
Catalyst
Conversion (%)b,c
1
2
3
4
5
4a
4b
4c
4d
4e
69
50
71
73
62
6
7
8
9
10
4a
4b
4c
4d
4e
81
88
86
83
80
0.5 h
24 h
11
12
13
14
15
4ad
4bd
4cd
4dd
4ed
39 (E/Z 1/4)
42 (E/Z 1/4)
24 (E/Z 1/4)
47 (E/Z 1/4)
49 (E/Z 1/4)
aReaction conditions: 1 mol % of catalyst, CH2Cl2, 0.1 M, rt. bDetermined by 1H NMR, cE/Z ratio 20/1, d2 mol % of catalyst, CH2Cl2, 0.1 M, 40 °C.
Both catalysts 4b and 4g proved to be efficient in all reactions, tion between the SIPr unit and the electronic activation of the
except in the formation of tetrasubstituted olefin P6 (entries benzylidene fragment.
7–8). Nevertheless, in almost all cases, either the conversion
was higher and/or the reaction duration shorter when SIPr-based Conclusion
complex 4g was used showing its highest efficiency. This A new library of Hoveyda type catalysts bearing aminosulfonyl
confirms the reactivity profile found in the kinetic study. The functions has been synthesized. Their activity profiles have
outstanding reactivity of 4g in the CM of S1 and acrylonitrile been investigated through kinetic studies and through evalua-
must be highlighted since a very good conversion was obtained tion of a group of substrates. Most of these have shown high
(entry 14, 84%) [23]. This demonstrates the beneficial combina- activities, nevertheless the SIPr-based complex 4g proved to be
Table 2: Comparison of 4b and 4g in metathesis reactionsa.
Entry
Substrate
Product
Catalyst
Time
Conversion (%)b
1
2
4b
4g
5 h
2 h
62
100
3
4
4b
4g
1.75 h
1 h
100
100
5
6
4b
4g
4.5 h
2 h
96
100
7
8
4b
4g
24 h
24 h
18c
3c
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
Table 2: Comparison of 4b and 4g in metathesis reactionsa. (continued)
9
10
4b
4g
0.75 h
0.5 h
100
100
11
12
4b
4g
0.5 h
0.5 h
100
100
13
14
4b
4g
24 h
24 h
48c (E/Z 1/4)
84c (E/Z 1/4)
aReaction conditions: 1 mol % of catalyst, CH2Cl2, 0.1 M, rt. bDetermined by 1H NMR, c2 mol % of catalyst, CH2Cl2, 0.1 M, 40 °C.
the most efficient, notably in the case where acrylonitrile was MHz, CDCl3, δ): 1.25 (d, J = 6.0 Hz, 6H, 2 CH3), 4.4 (sept, J =
involved in the CM.
6.0 Hz, 1H, CH), 5.15 (dd, J = 11.2 Hz and 1.3 Hz, 1H, CH),
5.52 (dd, J = 17.8 Hz and 1.3 Hz, 1H, CH), 6.67 (d, J = 8.7 Hz,
1H, CH), 6.83 (dd, J = 8.7 Hz and 2.8 Hz, 1H, CH), 6.84 (dd, J
Experimental
Synthesis of 1,1,1-trifluoro-N-(4-isopropoxy-3-vinylphenyl)- = 17.8 Hz and 11.2 Hz, 1H, CH), 7.07 (d, J = 2,8 Hz, 1H, CH),
methanesulfonamide (6a):To a solution of aniline 5 (40 mg, 7.82 (d, J = 9.0 Hz, 2H, CH), 8.19 (d, J = 9,0 Hz, 2H, CH). 13C
0.23 mmol) in dry DCM (3 mL), 2,6-lutidine (54 μL, 0.46 NMR (100 MHz, CDCl3, δ): 22.0 (2C), 71.1, 114.5, 115.3,
mmol, 2 equiv) was added at 0 °C. Then, trifluoromethanesul- 122.6, 124.1 (2C), 124.5, 127.5, 128.6 (2C), 128.8, 130.9,
fonic anhydride (41 μL, 0.25 mmol, 1.1 equiv) was added drop- 144.7, 150.1, 154.0.
wise and the mixture was allowed to warm to rt during 12 h.
After removal of the solvent under vacuum, the crude product Synthesis of N-(4-isopropoxy-3-vinylphenyl)-2-nitrobenzene-
was purified by flash chromatography on silica gel (DCM) to sulfonamide (6c): Following the procedure described for 6b
give the expected product as a brown oil (42 mg, 72%). using o-nitrobenzenesulfonyl chloride, 6c was obtained as a
1H NMR (400 MHz, CDCl3, δ): 1.35 (d, J = 6.1 Hz, 6H, 2 pale yellow amorphous solid (46 mg, 57%). 1H NMR (400
CH3), 4.54 (sept, J = 6.1 Hz, 1H, CH), 5.30 (dd, J = 11.2 Hz MHz, CDCl3, δ): 1.31 (d, J = 6.1 Hz, 6H, 2 CH3), 4.47 (sept., J
and 1.2 Hz, 1H, CH), 5.73 (dd, J = 17.7 Hz and 1.2 Hz, 1H, = 6.1 Hz, 1H, CH), 5.21 (dd, J = 11.2 Hz and 1.3 Hz, 1H, CH),
CH), 6.85 (d, J = 8.9 Hz, 1H, CH), 6.97 (dd, J = 17.7 Hz and 5.59 (dd, J = 17.8 Hz and 1.3 Hz, 1H, CH), 6.75 (d, J = 8.8 Hz,
11.2 Hz, 1H, CH), 7.13 (dd, J = 8.9 Hz and 2.8 Hz, 1H, CH), 1H, CH), 6.91 (dd, J = 17.8 Hz and 11.2 Hz, 1H, CH), 7.01 (dd,
7.36 (d, J = 2.8 Hz, 1H, CH). 13C NMR (100 MHz, CDCl3, δ): J = 8.8 Hz and 2.7 Hz, 1H, CH), 7.11 (s, 1H, NH), 7.22 (d, J =
22.0 (2C), 71.2, 114.4, 115.6, 119.8 (q, J = 322.8 Hz), 121.4, 2.7 Hz, 1H, CH), 7.56 (td, J = 7.7 Hz and 1.3 Hz, 1H, CH),
125.6, 125.8, 128.9, 130.8, 154.8. 19F NMR (376 MHz, CDCl3, 7.69 (td, J = 7.5 Hz and 1.4 Hz, 1H, CH), 7.77 (dd, J = 7.8 Hz
δ): −74,1 (s, 3F).
and 1.4 Hz, 1H, CH), 7.85 (dd, J = 7.9 Hz and 1.3 Hz, 1H, CH).
13C NMR (100 MHz, CDCl3, δ): 22.0 (2C), 71.1, 114.4, 115.2,
Synthesis of N-(4-isopropoxy-3-vinylphenyl)-4-nitrobenzene- 122.8, 124.9, 125.1, 127.8, 128.6, 130.9, 131.9, 132.2, 134.4,
sulfonamide (6b): To a solution of aniline 5 (40 mg, 0.23 133.8, 148.2, 154.0.
mmol) in dry toluene (4 mL), were added successively pyridine
(37 μL, 0.46 mmol, 2 equiv) and a solution of p-nitrobenzene- N-(4-isopropoxy-3-vinylphenyl)-2,4-dinitrobenzenesulfon-
sulfonyl chloride (50 mg, 0.23 mmol, 1 equiv) in 1 mL of amide (6d): Following the procedure described for 6b using
toluene. The mixture was stirred at rt overnight. After removal 2,4-dinitrobenzenesulfonyl chloride, 6d was obtained as a
of the solvent under vacuum, the crude product was purified by yellow oil (57 mg, 62%). 1H NMR (400 MHz, CDCl3, δ): 1.31
chromatography (cyclohexane/ethyl acetate, 8:2) to give 6b as a (d, J = 6.1 Hz, 6H, 2 CH3), 4.48 (sept., J = 6.1 Hz, 1H, CH),
pale yellow amorphous solid (49 mg, 60%). 1H NMR (400 5.24 (dd, J = 11.2 Hz and 1.3 Hz, 1H, CH), 5.63 (dd, J = 17.8
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
Hz and 1.3 Hz, 1H, CH), 6.75 (d, J = 8.9 Hz, 1H, CH), 6.91 CDCl3, δ): 1.13 (d, J = 6.1 Hz, 6H, 2 CH3), 2.34 (s, 18H, 6
(dd, J = 17.8 Hz and 11.2 Hz, 1H, CH), 6.99 (dd, J = 8.9 Hz CH), 4.08 (s, 4H, 2 CH2), 4.72 (sept, J = 6.1 Hz, 1H, CH), 6.54
and 2.7 Hz, 1H, CH), 7.24 (d, J = 2.7 Hz, 1H, CH), 8.00 (d, J = (d, J = 8.7 Hz, 1H, CH), 6.61 (d, J = 2.2 Hz, 1H, CH), 6.98 (s,
8.6 Hz, 1H, CH), 8.37 (dd, J = 8.6 Hz and 2.2 Hz, 1H, CH), 4H, CH), 7.08 (dd, J = 8.7 and 2.2 Hz, 1H, CH), 16.21 (s, 1H,
8.65 (d, J = 2.2 Hz, 1H, CH). 13C NMR (100 MHz, CDCl3, δ): CH). 19F (376 MHz, CDCl3, δ): -75.72 (s, 3F)
22.0 (2C), 71.2, 114.2, 115.6, 116.4, 119.0, 122.5, 127.7, 129.2,
129.9, 131.3, 134.7, 140.5, 144.0, 146.3, 152.1.
(1,3-dimesitylimidazolidin-2-ylidene)(2-isopropoxy-5-(4-nitro-
phenylsulfonamido)benzylidene)ruthenium(II) chloride (4b):
N-(4-isopropoxy-3-vinylphenyl)-2,3,4,5,6-pentafluorobenzene- Following the general procedure using the ligand 6b, complex
sulfonamide (6e): Following the procedure described for 6b 4b was isolated as a green powder (55 mg, 71%). 1H NMR (400
using 2,3,4,5,6-pentafluorobenzenesulfonyl chloride, 6e was MHz, CDCl3, δ): 1.21 (d, J = 6.1 Hz, 6H, 2 CH3), 2.42 (s, 18H,
obtained as a red oil (65 mg, 71%). 1H NMR (400 MHz, 6 CH), 4.19 (s, 4H, 2CH2), 4.84 (sept, J = 6.1 Hz, 1H, CH),
CDCl3, δ): 1.32 (d, J = 6.1 Hz, 6H, 2 CH3), 4.49 (sept, J = 6.1 6.57 (d, J = 7.3 Hz, 1H, CH), 6.71 (bs, 1H, NH), 6.95 (d, J =
Hz, 1H, CH), 5.27 (dd, J = 11.2 Hz and 1.1 Hz, 1H, CH), 5.67 7.1 Hz, 1H, CH), 7.08 (s, 4H, 4 CH), 7.33 (s, 1H, CH), 7.91 (d,
(dd, J = 17.8 Hz and 1.1 Hz, 1H, CH), 6.79 (d, J = 8.8 Hz, 1H, J = 7.1 Hz, 2H, 2 CH), 8.27 (d, J = 7.3 Hz, 2H, 2 CH), 16.34 (s,
CH), 6.93 (dd, J = 17.8 Hz and 11.2 Hz, 1H, CH), 7.04 (dd, J = 1H, CH).
8.8 Hz and 2.7 Hz, 1H, CH), 7.19 (s, 1H, NH), 7.25 (d, J = 2.7
Hz, 1H, CH). 13C NMR (100 MHz, CDCl3, δ): 22.0 (2C), 71.2, (1,3-dimesitylimidazolidin-2-ylidene)(2-isopropoxy-5-(2-nitro-
114.7, 115.5, 121.1, 123.1, 126.9, 127.5–131.2 (dm, J = 245 phenylsulfonamido)benzylidene)ruthenium(II) chloride (4c):
Hz), 129.0, 130.8,135.3-138.3 (dm, J = 256 Hz), 142.2–145.1 Following the general procedure using the ligand 6c, complex
(dm, J = 259 Hz), 154.1. 19F NMR (376 MHz, CDCl3, δ): −158 4c was isolated as a green powder (78 mg, 74%). 1H NMR
(2F), −144.7 (1F), −136 (2F).
(400 MHz, CDCl3, δ): 1.09 (d, J = 6.1 Hz, 6H, 2 CH3), 2.30 (s,
18H, 6 CH3), 4.07 (s, 4H, 2 CH2), 4.71 (sept., J = 6.1 Hz, 1H,
N-(4-isopropoxy-3-vinylphenyl)-3,5-bis(trifluoromethyl)- CH), 6.64 (d, J = 8.8 Hz, 1H, CH), 6.66 (d, J = 2.6 Hz, 1H,
benzenesulfonamide (6f): Following the procedure described CH), 6.95 (s, 4H, 4 CH), 7.15 (s, 1H, CH), 7.33 (dd, J = 8.8 and
for 6b using 3,5-bis(trifluoromethyl)benzenesulfonyl chloride, 2.6 Hz, 1H, CH), 7.51 (dt, J = 7.7 and 1.2 Hz, 1H, CH), 7.64
6f was obtained as a brown solid (81 mg, 79%). 1H NMR (400 (dt, J = 7.8 and 1.4 Hz, 1H, CH), 7.70 (dd, J = 7.8 and 1.3 Hz,
MHz, CDCl3, δ): 1.32 (d, J = 6.1 Hz, 6H), 4.48 ( sept., J = 6.1 1H, CH), 7.79 (dd, J = 8.0 and 1.1 Hz, 1H, CH), 16.14 (s, 1H,
Hz, 1H), 5.22 (dd, J = 1.2 and 11.2 Hz, 1H), 5.57 (dd, J = 1.2 CH).
and 17.8 Hz, 1H), 6.78 (d, J = 8.84 Hz, 1H), 6.92 (m, 2H), 7.02
(s, 1H), 7.12 (d, J = 2.7 Hz, 1H), 8.03 (s, 1H), 8.14 (s, 2H). 13C (1,3-dimesitylimidazolidin-2-ylidene)(5-(2,4-dinitrophenylsul-
NMR (100 MHz, CDCl3, δ): 21.9 (2C), 71.3, 114.8, 115.2, fonamido)-2-isopropoxybenzylidene)ruthenium(II) chloride
122.4 (q, 270 Hz, 2C), 123.0, 124.9, 126.3 (q, J = 3.7 Hz, 2C), (4d): Following the general procedure using the ligand 6d, com-
127.2, 127.6 (2C), 129.1, 130.7, 132.7 (q, 34.0 Hz, 2C), 141.5, plex 4d was isolated as a green powder (55 mg, 65%). 1H NMR
154.3. 19F NMR (376 MHz, CDCl3, δ): −63.1.
(400 MHz, CDCl3, δ): 1.09 (d, J = 6.1 Hz, 6H, 2 CH3), 2.31 (s,
18H, 6 CH3), 4.07 (s, 4H, 2 CH2), 4.70 (sept., J = 6.1 Hz, 1H,
General procedure for catalyst formation: To a solution of cata- CH), 6.64 (d, J = 8.7 Hz, 1H, CH), 6.73 (d, J = 2.4 Hz, 1H,
lyst 7 and copper chloride (1.1 equiv) in dry DCM (1 mL for CH), 6.96 (s, 4H, 4 CH), 7.33 (dd, J = 8.6 and 2.4 Hz, 1H, CH),
0.02 mmol of Ru-indenylidene complex) was added a solution 7.98 (d, J = 8.6 Hz, 1H, CH), 8.28 (dd, J = 8.6 and 2.2 Hz, 1H,
of 6a–f (1 equiv) in DCM (1 mL for 0.05 mmol of ligand). The CH), 8.56 (d, J = 2.2 Hz, 1H, CH), 16.17 (s, 1H, CH).
resulting mixture was stirred at 35 °C for 5 h. Volatiles were
removed under reduced pressure, acetone was added to the (1,3-dimesitylimidazolidin-2-ylidene)(2-isopropoxy-5-(perfluo-
residue, and the solution was filtered trough a pad of Celite. The rophenylsulfonamido)benzylidene)ruthenium(II) chloride (4e):
filtrate was concentrated and purified by chromatography on Following the general procedure using the ligand 6e, complex
silica gel (pentane/acetone, 75/25) to yield the expected 4e was isolated as a green powder (69 mg, 78%). 1H NMR (400
complexes 4a–i.
MHz, CDCl3, δ): 1.09 (d, J = 6.1 Hz, 6H, 2 CH3), 2.33 (s, 18H,
6 CH3), 4.08 (s, 4H, 2 CH2), 4.72 (sept., J = 6.1 Hz, 1H, CH),
(1,3-dimesitylimidazolidin-2-ylidene)(2-isopropoxy-5-(trifluo- 6.61 (d, J = 8.8 Hz, 1H, CH), 6.67 (d, J = 2.5 Hz, 1H, CH),
romethylsulfonamido)benzylidene)ruthenium(II) chloride (4a): 6.98 (s, 4H, 4 CH), 7.24 (dd, J = 8.8 and 2.5 Hz, 1H, CH),
Following the general procedure using the ligand 6a, complex 16.20 (s, 1H, CH). 19F NMR (376 MHz, CDCl3, δ): −159.1
4a was isolated as a green powder (62 mg, 73%). 1H (400 MHz, (2F), −145.6 (1F), −137.2 (2F).
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Beilstein J. Org. Chem. 2010, 6, 1159–1166.
(5-(3,5-bis(trifluoromethyl)phenylsulfonamido)-2-isopropoxy-
benzylidene)(1,3-dimesitylimidazolidin-2-ylidene)ruthenium(II)
chloride (4f): Following the general procedure using the ligand
6f, complex 4f was isolated as a green powder (96 mg, 87%).
1H NMR (400 MHz, CDCl3, δ): 1.08 (d, J = 6.1 Hz, 6H, 2
CH3), 2.31 (s, 18H, 6 CH3), 4.06 (s, 4H, 2 CH2), 4.69 (sept., J
= 6.1 Hz, 1H, CH), 6.48 (d, J = 2.6 Hz, 1H, CH), 6.61 (d, J =
8.7 Hz, 2H, CH), 6.95 (s, 4H, 4 CH), 7.26 (dd, J = 8.7 and 2.6
Hz, 1H, CH), 7.47 (t, J = 7.8 Hz, 1H, CH), 7.60 (t, J = 7.7 Hz,
1H, CH), 7.82 (dd, J = 13.2 and 7.8 Hz, 2H, 2 CH), 16.13 (s,
1H, CH). 19F NMR (376 MHz, CDCl3, δ): −58.1 (3F).
Supporting Information
Supporting Information File 1
The Supporting Information contains the 1H NMR
spectrum of P8, the calculation of the substrate/dimer ratio
(Table 2, entry 1) and the calculation of
product/substrate/dimer ratio (Table 2, entry 14).
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-6-132-S1.pdf]
Acknowledgements
(1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene)(2-
isopropoxy-5-(4-nitrophenylsulfonamido)benzylidene)ruthe-
nium(II) chloride (4g): Following the general procedure using
the ligand 6g, complex 4g was isolated as a green powder (88
mg, 65%). 1H NMR (400 MHz, CDCl3, δ): 1.11 (bd, J = 5.3
Hz, 12H, 4 CH3), 1.17 (d, J = 6.9 Hz, 12H, 4 CH3), 1.19 (d, J =
6.1 Hz, 6H, 2 CH3), 3.45 (sept., J = 6.7 Hz, 4H, CH), 4.11 (s,
4H, CH2), 4.78 (sept., J = 6.1 Hz, 1H, CH), 6.27 (d, J = 8.6 Hz,
1H, CH), 6.50 (m, 2H, 2 CH), 7.15 (bs, 1H, NH), 7.29 (d, J =
7.8 Hz,4H, CH), 7.46 (m, 2H, CH), 7.73 (m, 2H, 2 CH), 8.13
(m, 2H, 2 CH), 16.16 (s, 1H, CH).
We thank the European Community for its financial support
(CP-FP 211468-2 EUMET). Financial support by the CNRS,
the ENSCR, the region-Bretagne (Feder Program) and OSEO
are also gratefully acknowledged.
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