Prevention of undesirable isomerization during olefin metathesis

Article abstract of DOI:10.1021/ja052939w

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. Electron-deficient benzoquinones are the most effective additives for the prevention of olefin migration. This mild, inexpensive, and effective method to block olefin isomerization increases the synthetic utility of olefin metathesis via improvement of overall product yield and purity. Copyright

Full text of DOI:10.1021/ja052939w

Supporting Information for:
Prevention of Undesirable Isomerization During Olefin
Metathesis Reactions
Soon Hyeok Hong,† Daniel P. Sanders,† Choon Woo Lee,‡ and Robert H. Grubbs†*
†Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 9112, and ‡Materia, Inc.,
Pasadena, California 91107
General Considerations.
Manipulation of organometallic compounds was performed using
standard Schlenk techniques under an atmosphere of dry argon or in a nitrogen-filled Vacuum
Atmospheres drybox (O2 < 2.5 ppm). NMR spectra were recorded on a Varian Mercury 300 (299.817
1
MHz for H). GC analysis were performed on Rtx-5 column (Restek, 5% diphenyl - 95% dimethyl
polysiloxane) with HP 6890 GC.
Materials and Methods. CD2Cl2 was dried by distillation from CaH2 and degassed by three
freeze-pump-thaw cycles . The catalysts 1, 2, and 3 were obtained from Materia, Inc. and further
purified by column chromatography using silica gel obtained from TSI.1 1,4-Benzoquinones, allyl ether
1 We purified commercial ruthenium catalysts to eliminate the possibility that catalyst impurities caused
the isomerization. However, purified catalysts behaved almost identical with unpurified commercial
ones. For detailed catalyst purification procedure, see: Sutton, A. E.; Seigal, B. A.; Finnegan D. F.;
Snapper, M. L. J. Am. Chem. Soc. 2002, 124, 13390-13391.
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and other additives were obtained from Aldrich and used as received. N,N-diallylaniline 19 was
purchased from Pfaltz & Bauer and used as received. The complex 4,2 (Z)-5-tert-butyldimethylsilyloxy-
2-pentenoate 5,3 (Z)-1,4-Bis(tert-butyldimethylsilyloxy)-2-butene 11,4 11-eicosenyl acetate 165 were
prepared according to literature procedures. Meadowfoam oil methyl esters were produced by
transesterification of Meadowfoam oil purchased from Natural Plant Products LLC, Oregon, USA.
O
MeC20:1 63%
MeC22:1 16%
MeC22:2 17%
CH3O
12
O
O
CH3O
CH3O
14
4
Meadow Foam Oil Methyl Esters
General experimental procedure for Table 1, 2, and 3, and Scheme 2. Catalyst 2 (2 mol% or 5
mol%) and additive (0.1 ~ 1.0 equiv. of substrate) were dissolved in CD2Cl2 (0.7mL) in a 5mL vial in a
nitrogen-filled Vacuum Atmospheres drybox. Substrate (0.16 mmol) was added to the solution, and the
reaction mixture was transferred to an NMR tube fitted with a screw cap. The NMR tube was taken out
2 Hong, S. H.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc. 2004, 126, 7414-7415.
3 Herold, P.; Mohr, P.; Tamm, C. Helv. Chim. Acta. 1983, 66, 744-754.
4 Jones, K.; Storey, J. M. D. Tetrahedron 1993, 49, 4901-4906.
5 Pederson, R. L.; Fellows, I. M.; Ung, T. A.; Ishihara, H.; Hajela, S. Adv. Synth. Catal. 2002, 344, 728-
735.
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o
1
of the drybox, and heated to 40 C in an oil bath. The reaction was monitored by H NMR. The
conversion was measured by 1H NMR using 20 mol% of anthracene as an internal standard.6
(E)-5-tert-butyldimethylsilyloxy-2-pentenoate (6).3 1H NMR (CD2Cl2): δ6.96 (td, 1H, J=7.2,
15.6 Hz), 5.88 (td, 1H, J=1.5, 15.6 Hz), 3.74 (t, 2H, J=6.5 Hz), 3.70 (s, 3H), 2.41 (td, 2H, J=6.5, 7.2 Hz),
0.90 (s, 9H), 0.06 (s, 6H)
(Z) & (E) mixture of 5-tert-butyldimethylsilyloxy-4-pentenoate (E/Z ~ 1:1) (7).7 1H NMR
(CD2Cl2): δ6.30 (td, 1H, J=1.5, 12.3 Hz, E), 6.22 (dd, 1H, J=2.4, 6.0 Hz, Z), 4.95 (td, 1H, J=7.4, 12.0
Hz, E), 4.47 (dt, 1H, J=6.0, 7.0 Hz, Z), 2.40~2.15 (m, 8H, E & Z), 3.65 (s, 6H, E & Z), 0.94 (s, 9H, Z),
0.92 (s, 9H, E), 0.15 (s, 6H, Z), 0.13 (s, 6H, E)
2,5 Dihydrofuran (9). 1H NMR (CD2Cl2): δ5.91 (t, 2H, J=0.9Hz), 4.60 (d, 4H, J=0.9Hz)
2,3-Dihydrofuran (10). 1H NMR (CD2Cl2): δ6.32 (m, 1H), 4.95(m, 1H), 4.28 (t, 2H, J=9.6Hz),
2.59 (m, 2H)
(E)-1,4-Bis(tert-butyldimethylsilyloxy)-2-butene (12).4
J=3.0Hz), 4.18 (d, 4H, J=3.0Hz), 0.92 (s, 9H), 0.08 (s, 6H)
1H NMR (CD2Cl2): δ5.77 (t, 2H,
(Z) & (E) mixture of 1,4-Bis(tert-butyldimethylsilyloxy)-1-butene (E/Z ~ 1:1.4) (13).8 1H NMR
(CD2Cl2): δ6.29 (td, 1H, J=1.2, 12.1 Hz, E), 6.22 (td, 1H, J=1.5, 5.7 Hz, Z), 4.95 (td, 1H, J=7.2, 12.1 Hz,
6 Conversions measured by 1H NMR were identical between with and without an internal standard.
7 Ohba, T.; Ikeda, E.; Tsuchiya, N.; Nishimura, K.; Takei, H. Bioorg. Med. Chem. Lett. 1996, 6, 2629-
2634.
8 Kang, K. ; Weber, W. P. Tetrahedron Lett. 1985, 26, 5753-5754.
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E), 4.49 (dt, 1H, J=5.7, 7.2 Hz, Z), 3.60 (t, 2H, J=6.9 Hz, Z), 3.57 (t, 2H, J=6.6 Hz, E), 2.30 (td, 2H,
J=6.9, 7.2 Hz, Z), 2.09 (td, 2H, J=6.6, 7.2 Hz, E), 0.94 (s, 9H, Z), 0.91 (s, 9H, E), 0.15 (s, 6H, E), 0.07 (s,
6H, Z)
N-Phenyl-3-pyrroline (20).9 1H NMR (CD2Cl2): δ7.24 (m, 2H), 6.67 (m, 1H), 6.54 (m, 2H), 5.99
(s, 2H), 4.12 (s, 4H)
N-Phenyl-2-pyrroline (21).10 1H NMR (CD2Cl2): δ7.47, 7.30, and 6.56 (m, 5H aromatic), 7.13 (m,
1H), 6.35 (m, 1H), 3.30 (m, 2H), 2.02 (m, 2H)
Ethenolysis of Meadowfoam oil methyl ester 14.11
Meadowfoam oil methyl ester 14 was
degassed with anhydrous argon for 10 minutes. 10 g (31.3 mmol) of 14 was added to two Fisher-Porter
bottles. To one bottle was added 1,4-benzoquinone (20 mg, 0.19 mmol) followed by ruthenium catalyst
1 (77 mg, 0.094 mmol) at room temperature. To the other bottle was added only catalyst 1 (77 mg), as
the control reaction. Both bottles were pressurized with ethylene (130 psi), and stirred for 66.5 hrs at 40
oC. The reaction mixture was collected during the reaction, and then quenched with an excess amount
o
of 1 M THMP solution (trishydroxymethyl phosphine in IPA), stirred at ~ 50 C for 1h and then
analyzed by GC and GC-MS. GC and GC/MS results: tR 1.67 min (Methyl 5-hexenoate 15, M+=128),
tR 1.73 and 1.77 min (isomerized products of 15, M+=128), tR 2.04 min (cyclooctene12, M+=110), tR 2.09
min (1-Decene, M+=140), tR 8.88 min (1-Hexadecene, M+=224), tR 16.39 min (Methyl 5-Eicosenoate,
M+=324), tR 18.34 min (Methyl 5,13-Docosadienoate, M+=350), tR 18.65 min (Methyl 5-Docosenoate,
M+=352).
9 Martinez, V.; Blais, J.-C.; Bravic, G.; Astruc, D. Organometallics 2004, 23, 861-874.
10 Seto, Y.; Guengerich, F. P. J. Biol. Chem. 1993, 268, 9986-9997.
11 Acetic acid was not as effective as 1,4-benzoquinone in ethenolysis.
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Figure S1. GC Traces of Ethnolysis of Meadowfoam Oil Methyl Ester 14 Without 1,4-
Benzoquinone (Control)
Figure S2. GC Traces of Ethnolysis of Meadowfoam Oil Methyl Ester 14 With 1,4-
Benzoquinone
12 Cyclooctene is formed from intramolecular ring-closing metathesis of MeC22:2.
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Table S1. Ethnolysis of Meadowfoam Oil Methyl Ester (reported as percent GC Area)
Time (hr)
Reaction
Methyl
1-Decene
Methyl 5-hexenoate
%Isomerized
15
5-Eicosenoate
15
Benzoquinone
Control
63
63
31
39
30
33
28
31
29
31
0
0
7
6
8
7
7
7
7
4
0
0
0
0
0
Benzoquinone
Control
10
8
0
1
0
Benzoquinone
Control
11
9
0
3
1
Benzoquinone
Control
11
9
1
21.3
66.5
3
Benzoquinone
Control
10
5
1
49
Ethenolysis of 11-Eicosenyl Acetate 16. 11-Eicosenyl acetate 16 was degassed with anhydrous
Argon for 10 minutes. 8 g (23.7 mmol) of 16 was added to two Fisher-Porter bottles. To one bottle was
added 1,4-benzoquinone (15 mg, 0.14 mmol) followed by ruthenium catalyst 1 (59 mg, 0.071 mmol) at
room temperature. To the other bottle was added only catalyst 1 (59 mg), as the control reaction. Both
o
bottles were pressurized with ethylene (130 psi) and stirred for 41.5 hrs at 40 C or room temperature.
During the reaction, samples were collected and analyzed. The reactions were quenched with an excess
o
amount of 1 M THMP solution (trishydroxymethyl phosphine in IPA) at ~ 50 C for 1h, then analyzed
by GC and GC-MS. GC and GC/MS results: tR 2.10 min (1-Decene 17, M+=140), tR 2.19 and 2.25 min
(isomerized products of 17, M+=140), tR 9.05 min (11-Dodecenyl acetate 18, M+=226), tR 9.18 and 9.30
min (isomerized products of 18, M+=226), tR 10.96 and tR 11.03 min (9-Octadecene, M+=252), tR 17.27
min (11-Eicosenyl acetate, M+=338), tR 30.36 and tR 31.33 min (11-Docosenyl 1,22-Diacetate,
M+=424).
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Figure S3. GC Traces of Ethnolysis of 11-Eicosenyl Acetate 16 Without 1,4-Benzoquinone
(Control)
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Figure S4. GC Traces of Ethnolysis of 11-Eicosenyl Acetate 16 With 1,4-Benzoquinone
Table S2. Ethenolysis of 11-Eicosenyl Acetate 16 (reported as percent GC Area)
Time
(min)
Reaction
11-
Eicosenyl
acetate
1-Decene
11-Dodecenyl
acetate, 18
9-Octadecene
11-Docosenyl
1,22-Diacetate
%Isomerized 17,
%Isomerized 18
17
Benzoquinone
Control
98
98
42
27
41
23
41
23
0
0
0
0
1
2
2
3
2
3
0
0
2
3
2
4
2
4
0, 0
0, 0
0
0
0
Benzoquinone
Control
23
28
22
22
22
20
32
39
32
32
32
28
0, 0
100
1110
2490
1, 1
Benzoquinone
Control
0, 1
22, 23
1, 2
Benzoquinone
Control
30, 32
Effect of benzoquinone structure on prevention of olefin isomerization. Catalyst 2 (69 mg, 5
mol%) and additive (10 mol%) were dissolved in CD2Cl2 (4 mL) in a 50mL schlenk tube in a nitrogen-
filled Vacuum Atmospheres drybox. The flask was removed from the drybox. Diallyl ether 8 (0.2 ml,
1.6 mmol) was added to the solution, and the reaction mixture was heated to 40 oC in an oil bath. After
24 hrs, conversions were determined by 1H NMR.
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