Highly selective cross-metathesis with phenyl vinyl sulphone using the 'second generation' Grubbs' catalyst

Article abstract of DOI:10.1016/S0040-4039(01)01269-2

A cross-metathesis reaction was achieved between functionalised terminal olefins and phenyl vinyl sulfone by using the commercially available ruthenium catalyst 1c. The cross-metathesis products were isolated in moderate to good yield with excellent (E)-stereoselectivity.

Full text of DOI:10.1016/S0040-4039(01)01269-2

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 6425–6428
Highly selective cross-metathesis with phenyl vinyl sulphone
using the ‘second generation’ Grubbs’ catalyst
Karol Grela* and Michał Bieniek
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
Received 30 May 2001; revised 5 July 2001; accepted 13 July 2001
Abstract—A cross-metathesis reaction was achieved between functionalised terminal olefins and phenyl vinyl sulfone by using the
commercially available ruthenium catalyst 1c. The cross-metathesis products were isolated in moderate to good yield with
excellent (E)-stereoselectivity. © 2001 Elsevier Science Ltd. All rights reserved.
During recent years, olefin metathesis has gained a
position of increasing significance.1 The ruthenium car-
bene 1a developed by Grubbs et al. constitutes a highly
efficient metathesis pre-catalyst tolerating most func-
tional groups. In spite of the generally superb applica-
tion profile of the ruthenium carbene 1a, its limited
thermal stability and the low activity towards substi-
tuted double bonds are major drawbacks. Specifically,
the preparation of substituted olefins with electron-
withdrawing functionality, such as a,b-unsaturated car-
bonyl compounds, nitriles, etc., via cross metathesis
with terminal alkenes (Scheme 1) remains a difficult task.1
unreactive towards Grubbs’ catalyst 1a, readily partici-
pates in cross-metathesis reactions catalysed by the
more active Schrock alkylidene 1b.1c Other olefins, such
as acrylic acid esters and enones also fail to react with
1a and are not functional group compatible with the
very sensitive catalyst 1b.
The newly-introduced highly active ruthenium alkyli-
dene complexes with sterically demanding N-hetero-
cyclic carbene (NHC)3 ligands have dramatically
alleviated this limitation.4 Complexes of type 1c–f were
found to catalyse efficiently reactions of previously
metathesis-inactive substrates, including a,b-unsatu-
rated carbonyl compounds.5
Crowe and Goldberg2 demonstrated that acrylonitrile,
Scheme 1. Cross-metathesis with electron deficient olefins.
Keywords: carbene complex; olefin metathesis; sulfone; ruthenium; homogenous catalysis.
* Corresponding author. Tel.: +48-22-6323221 ext. 2108; fax: +48-22-6326681; e-mail: grela@technologist.com
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01269-2

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K. Grela, M. Bieniek / Tetrahedron Letters 42 (2001) 6425–6428
Grubbs et al. have shown recently that the ‘second
generation’ catalyst 1d, which contains a 1,3-dime-
sityl-4,5-dihydroimidazol-2-ylidene ligand, readily pro-
motes the cross-metathesis reaction of terminal olefins
with a,b-unsaturated aldehydes, ketones and esters
(Scheme 1).5b The authors have noted, however, that
other electron deficient substrates, such as vinyl sul-
fones and acrylonitriles6 are not reactive in cross-
metathesis using 1d.5b The compatibility of remote
sulfone and sulfoxide functions in the standard
metathesis reactions is well established,7 but according
to our best knowledge the successful metathesis of
vinyl sulfones has not yet been reported.8 Substituted
a,b-unsaturated sulfones are generally well accepted
as useful intermediates in organic synthesis. Thus,
vinyl sulfones serve efficiently, e.g. as Michael accep-
tors and as 2p partners in cycloaddition reactions. In
addition, the stability and ease of further transforma-
tion of the sulfonyl group via elimination or either
reductive or alkylative desulfonylation renders further
advantages to vinyl sulfones as synthetic interme-
diates.9
Therefore, we decided to investigate the cross-
metathesis of readily available phenyl vinyl sulfone
with terminal olefins. In this communication, we
report the single-step synthesis of functionalised a,b-
unsaturated sulfones catalysed by the commercially
available10 Grubbs’ alkylidene 1c.
Test reactions between olefin 2a (1 equiv.), phenyl
vinyl sulfone 3 (2 equiv.) and complexes 1a and 1c
(0.10 equiv.) were performed under argon, at 45°C in
dichloromethane. The ‘classical’ Grubbs’ alkylidene 1a
did not react under these conditions. However, in the
case of the NHC–ruthenium complex 1c; the corre-
sponding product 4a was formed after 15 h in quanti-
tative yield (>99%) and with excellent stereoselectivity
as the (E)-isomer was the only product detected by
GC and NMR. Under such conditions, we observed
the initial formation of a small amount of the
homodimer 5 which decreased during prolongation of
the reaction time (Scheme 2). However, in the
absence of vinyl sulfone 3, the dimerisation product 5
was formed almost quantitatively instead.
Table 1. Cross-metathesis between olefins 2a–g and phenyl vinyl sulfone 3

K. Grela, M. Bieniek / Tetrahedron Letters 42 (2001) 6425–6428
6427
References
1. For recent reviews, see the following for leading refer-
ences: (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res.
2001, 34, 18–29; (b) Fu¨rstner, A. Angew. Chem., Int. Ed.
2000, 39, 3012–3043; (c) Schrock, R. S. Tetrahedron 1999,
55, 8141–8153; (d) Grubbs, R. H.; Chang, S. Tetrahedron
1998, 54, 4413–4450; (e) Schuster, M.; Blechert, S.
Angew. Chem., Int. Ed. Engl. 1997, 36, 2036–2055; (f)
Fu¨rstner, A. Top. Catal. 1997, 4, 285–299; (g) Ivin, K. J.;
Mol, J. C. Olefin Metathesis and Metathesis Polymeriza-
tion, 2nd ed.; Academic Press: New York, 1997.
2. Crowe, W. E.; Goldberg, D. R. J. Am. Chem. Soc. 1995,
117, 5162–5163.
3. For a comprehensive survey of N-heterocyclic carbenes,
see: (a) Bourissou, D.; Guerret, O.; Gabba¨ı, F. P.;
Bertrand, G. Chem. Rev. 2000, 100, 39–91; (b) Arduengo,
A. J. A. Acc. Chem. Res. 1999, 32, 913–921; (c) Her-
rmann, W. A.; Ko¨cher, C. Angew. Chem., Int. Ed. Engl.
1997, 36, 2163–2187.
Scheme 2. Selected results of the cross-metathesis of 2a.
4. (a) Weskamp, T.; Kohl, F. J.; Herrmann, W. A. J.
Organomet. Chem. 1999, 582, 362–365; (b) Weskamp, T.;
Kohl, F. J.; Hieringer, W.; Gleich, D.; Herrmann, W. A.
Angew. Chem., Int. Ed. 1999, 38, 2416–2419; (c) Acker-
mann, L.; Fu¨rstner, A.; Weskamp, T.; Kohl, F. J.; Her-
rmann, W. A. Tetrahedron Lett. 1999, 40, 4787–4790; (d)
Huang, J.; Stevens, E. D.; Nolan, S. P.; Petersen, J. L. J.
Am. Chem. Soc. 1999, 121, 2674–2678; (e) Scholl, M.;
Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999, 1,
953–956; (f) Chatterjee, A. K.; Grubbs, R. H. Org. Lett.
1999, 1, 1751–1753.
5. For some recent examples, see: (a) Fu¨rstner, A.; Thiel, O.
R.; Ackermann, L.; Schanz, H.-J.; Nolan, S. P. J. Org.
Chem. 2000, 65, 2204–2207; (b) Chatterjee, A. K.; Mor-
gan, J. P.; Scholl, M.; Grubbs, R. H. J. Am. Chem. Soc.
2000, 122, 3783–3784. (c) Gessler, S.; Randl, S.; Blechert,
S. Tetrahedron Lett. 2000, 41, 9973–9976; (d) Randl, S.;
Gessler, S.; Wakamatsu, H.; Blechert, S. Synlett 2001,
430–432; (e) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.;
Hoveyda, A. H. J. Am. Chem. Soc. 2000, 122, 8168–8179;
(f) BouzBouz, S.; Cossy, J. Org. Lett. 2001, 3, 1451–1454;
(g) Cossy, J.; BouzBouz, S.; Hoveyda, A. H. J.
Organomet. Chem. 2001, 601, 327–332.
6. For a few examples of successful RCM of dienes contain-
ing an a-substituted a,b-unsaturated nitrile function
catalysed by 1c, see: Ref. 5c. However, according to the
authors, the acrylonitrile itself does not react with termi-
nal olefins in the presence of 1c. The latter transforma-
tion is only possible when phosphine free complex 1f is
used instead. See: Refs. 5c,d.
7. For example, see: (a) Paquette, L. A.; Fabris, F.; Tae, J.;
Gallucci, J. C.; Hofferberth, J. E. J. Am. Chem. Soc.
2000, 122, 3391–3398; (b) Fu¨rstner, A.; Gastner, T.;
Weintritt, H. J. Org. Chem. 1999, 64, 2361–2366.
8. For the only example of the RCM of vinyl sulfoxide with
a stoichiometric amount of 1a, see: Liras, S.; Davoren, J.
E.; Bordner, J. Org. Lett. 2001, 3, 703–706.
Using the model reaction of olefin 2a we have further
studied the effect of ratio of the reagents and conditions
on this transformation (Scheme 2). We have found that
the optimal conditions for the sulfone cross-metathesis
are: ratio of the reagents 2:3:1c as 1:2:0.05 in refluxing
dichloromethane as the solvent.
Under such conditions the reaction of terminal alkenes
2a–e with commercially available10 sulfone 3 proceeds
smoothly to give the corresponding products 4a–e in
moderate to good yields.11,12 In all reported cases the
(E)-alkene was the only isomer detected by GC/MS
and NMR. Dimerisation products of the terminal olefin
were observed in only trace amounts. Unprotected
alcohol 2b and highly CꢀH acidic malonic ester 2c were
converted in good yields. Somewhat lower yields were
obtained from sterically crowded substrates such as 2e
and g (Table 1). The geminal disubstituted olefin (entry
f) did not react, as ester 2f was recovered after the
reaction almost quantitatively (87%), suggesting that
the cross-metathesis of phenyl vinyl sulfone is very
sensitive to steric hindrance.
In conclusion, the use of the robust catalyst 1c and
readily available sulfone 310 demonstrates the appli-
cability of cross-metathesis for the preparation of syn-
thetically
useful,
functionalised
a,b-unsaturated
sulfones with excellent stereoselectivity under mild con-
ditions. Further studies in the field of cross-metathesis
of substituted vinyl sulfones and sulfoxides are in pro-
gress in our laboratory.
Acknowledgements
9. For reviews, see: (a) Procter, D. J. J. Chem. Soc., Perkin
Trans. 1 1999, 641–667; (b) Simpkins, N. S. Tetrahedron
1990, 46, 6951–6984; (c) The Chemistry of Sulphones and
Sulphoxides; Patai, S.; Rappaport, Z.; Stirling, C., Eds.;
John Wiley and Sons Ltd.: New York, 1988.
M.B. thanks the Institute of Organic Chemistry for a
scholarship. We thank Mr. Igor Prowotorow for the
providing the sample of ester 2f and Dr. Jacek
Stalewski for the preparation of 2g.13
.

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K. Grela, M. Bieniek / Tetrahedron Letters 42 (2001) 6425–6428
10. Catalyst 1c is available from Strem Chemicals. Cf. also:
The Strem Chemiker 2000, 1, 30; Sulfone 3 is available
from Aldrich Chemical Co.
NMR (200 MHz, CDCl3): l 0.03 (s, 6H, (CH3)2Si),
0.88 (s, 9H, (CH3)3C), 1.46–1.60 (m, 4H, (CH2)2), 2.20–
2.35 (m, 2H, CH2), 3.53–3.62 (m, 2H, CH2O), 6.32 (tt,
J=15.1, 1.5 Hz, 1H, CH=CHSO2Ph), 7.00 (tt, J=
15.1, 6.8 Hz, 1H, CH=CHSO2Ph), 7.47–7.67 and 7.83–
7.93 (2m, 5H, Ph); 13C NMR (50 MHz, CDCl3): l
−5.37, 18.26, 24.02, 25.89, 31.22, 32.01, 62.49, 127.50,
129.18, 130.43, 133.16, 140.72, 147.00; MS (EI): m/z
339 (4, [M−15]+), 297 (100), 217 (1), 199 (10), 135 (49),
125 (5), 81 (5), 79 (5), 75 (12), 61 (2), 55 (1); HRMS
(LSIMS) calcd for [M+H]+ (C18H31O3SSi): 355.1763.
Found: 355.1768.
11. All described new compounds were characterised by 1H
and 13C NMR, IR, MS and combustion or HRMS
analysis.
12. General procedure for cross-metathesis reactions with
phenyl vinyl sulfone: To a mixture of 2a (53.6 mg, 0.25
mmol) and vinyl sulfone 3 (84.1 mg, 0.50 mmol) in
dichloromethane (15 mL) was added a solution 1c (10.6
mg, 5 mol%) in dichloromethane (5 mL). The resulting
mixture was stirred at 45°C for 15 h. The solvent was
removed under reduced pressure. Flash chromatography
(c-hexane/EtOAc 8:2 v/v) of the crude brown residue
gave 75.1 mg of 4a (85%). Colourless oil: IR (film):
13. (a) Prowotorow, I.; Wicha, J.; Mikami, K. Synthesis
2001, 145–149; (b) Makosza, M.; Stalewski, J.; Woj-
ciechowski, K.; Danikiewicz, W. Tetrahedron 1997, 53,
193–214.
2952, 2931, 2858, 1447, 1321, 1148, 1088, 835 cm−1 1H
;
.