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13
NMR, C NMR and GC/MS data of compounds 1, 2, 4, 5, 7, 8, 9,
to the reaction medium precipitated the catalyst allowing
10 and 12 were in full agreement with those reported previously.[10d]
its simple recovery by filtration; the catalyst could therefore
be recycled and used several times without appreciable loss
(E)-1-phenyl-1-pentene (1): Yield: 130 mg (89%) (entry 1, Table 1).
of activity. The reaction to give alkene 1 was in fact re- Yield: 120 mg (82%) (entry 13).
peated three times, washing the catalyst with CH2Cl2 and
(E)-1-(4-methylphenyl)-1-pentene (2): Yield: 145 mg (91%) (entry 2).
drying it at 70 °C for two hours after each run, with the
Yield: 130 mg (81%) (entry 2).
following yields: 83%, 81% and 81%. Therefore the con-
(E)-1-(4-fluorophenyl)-1-pentene (3): Yield: 140 mg (85%) (entry 3).
comitant formation of a carboxylic acid as a reaction prod-
1
Yield: 135 mg (81%) (entry 18). Colourless oil. H NMR: ´ 0.98
uct, capable of rendering Yb(OTf)3 ineffective as an aldol-
(t, J 7.1 Hz, 3 H), 1.52 1.74 (m, 2 H), 2.15 2.27 (m, 2 H),
Grob catalyst (by chelation), does not significantly affect its
6.11 6.23 (m, 1 H), 6.48 (d, J 12.0 Hz, 1 H), 7.08 7.48 (m, 4
catalytic activity.
13
H) ppm. C NMR: ´ 13.7, 22.5, 36.1, 115.0, 127.2, 127.3, 128.7,
The absence of solvents seems to be crucial in driving the
130.6, 134.1, 152.5 ppm. MS (EI): m/z (%) 164 (33), 135 (100),
process to yield the aldol-Grob adduct, while the presence
122 (27), 115 (25), 109 (27). C11H13F (164.2): calcd. C 80.45, H
of solvents like THF, alcohols or water leads to the forma-
7.98; found C 80.47, H 7.96.
tion of only aldol condensation products (±,²-unsaturated
(E)-1-(4-chlorophenyl)-1-pentene (4): Yield: 150 mg (83%) (entry 4).
ketones) and the use of dichloromethane, n-hexane or tolu-
Yield: 140 mg (83%) (entry 19).
ene greatly decreases the catalytic activity of Yb(OTf)3;
starting materials were recovered in almost quantitative
(E)-1-(4-bromophenyl)-1-pentene (5): Yield: 160 mg (71%).
yield.
(E)-1-(4-phenylphenyl)-1-pentene (6): Yield: 170 mg (77%). colour-
1
less oil. H NMR: ´ 1.02 (t, J 7.0 Hz, 3 H), 1.51 1.82 (m, 2
H), 2.22 2.34 (m, 2 H), 6.27 6.35 (m, 1 H), 6.49 (d, J 12.5 Hz,
13
1 H), 7.32 7.74 (m, 9 H) ppm. C NMR: ´ 13.8, 22.6, 35.2,
Conclusions
126.3, 126.9, 127.1, 127.2, 128.8, 129.3, 131.2, 137.0, 139.5,
140.9 ppm. MS (EI): m/z (%) 222 (84), 193 (100), 178 (93), 165
In this paper we have shown that Yb(OTf)3 hydrate is an
(36), 152 (16), 115 (16). C17H18 (222.3): calcd. C 91.84, H 8.16;
effective catalyst in promoting the reaction between ketones found C 91.85, H 8.15.
and aromatic aldehydes, affording only (E)-alkenes. The
(E)-1-(4-nitrophenyl)-1-pentene (7): Yield: 30 mg (15%).
main difference in our methodology compared to BF3-cata-
lysed reactions is the Lewis acid/substrate ratio, the optimal (E)-1-(4-methoxyphenyl)-1-pentene (8): Yield: 20 mg (11%).
value of which was found to be 0.1:1; in the other cases a
(E)-1-(3-chlorophenyl)-1-pentene (9): Yield: 125 mg (70%).
1:1 ratio or even an excess of Lewis acid is needed to effec-
tively promote the coupling reaction. Furthermore, product (E)-1-(3-nitrophenyl)-1-pentene (10): Yield: 10 mg (5%).
yields, easy workup procedure, absence of solvent, simple
(E)-1-(2-methylphenyl)-1-pentene (11): Yield: 130 mg (81%).
recovery, very high recyclability and easy handling of the
1
Colourless oil. H NMR: ´ 1.08 (t, J 7.0 Hz, 3 H), 1.51 1.68
catalyst are other important features of our methodology.
(m, 2 H), 2.17 2.32 (m, 2 H), 2.42 (s, 3 H), 6.07 6.19 (m, 1 H),
Finally, the different reactivity of methylene- and methyl-
6.68 (d, J 12.3 Hz, 1 H), 7.25 (m, 3 H), 7.12 7.54 (m, 1 H) ppm.
13
derived enolates could allow the use of readily available
C NMR: ´ 13.8, 19.8, 22.6, 35.4, 125.5, 126.0, 126.8, 127.8,
methyl ketones. 130.2, 132.4, 134.9, 137.1 ppm. MS (EI): m/z (%) 160 (46), 131
Eur. J. Org. Chem. 2003, 1631 1634 www.eurjoc.org © 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1633
M. Curini, F. Epifano, F. Maltese, M. C. Marcotullio
SHORT COMMUNICATION
[5b]
Suemune, K. Sakai, Chem. Commun. 1990, 1538. H. Yama-
(100), 115 (16), 91 (16). C12H16 (160.2): calcd. C 89.94, H 10.06;
moto, H. Suemune, K. Sakai, Tetrahedron 1991, 47, 8523.
found C 89.92, H 10.08.
[6] [6a]
C. M. Amann, P. V. Fisher, M. L. Pugh, F. G. West, J. Org.
[6b]
(E)-1-(2-chlorophenyl)-1-pentene (12): Yield: 140 mg (78%). Chem. 1998, 63, 2806. G. A. Molander, Y. Le Huerou, G.
A. Brown, J. Org. Chem. 2001, 66, 4511.
[7] [7a]
(E)-7-Phenyl-6-heptenoic acid (13): Yield: 140 mg (68%). White
A. Waldemar, L. Blancafort, J. Org. Chem. 1997, 62, 1623.
1
[7b]
solid. m.p. 93 94 °C. H NMR: ´ 1.44 1.61 (m, 4 H),
T. Koch, K. Bandemer, W. Boland, Helv. Chim. Acta 1997,
[7c]
2.12 2.25 (m, 2 H), 2.32 (t, J 6.9 Hz, 2 H), 6.12 6.19 (m, 1 H), 80, 838. D. Renneberg, H. Pfander, C. J. Leumann, J. Org.
13
Chem. 2000, 65, 9069.
6.32 (d, J 12.5 Hz, 1 H), 7.25 7.37 (m, 5 H) ppm. C NMR:
[8]
J. J. Grove, C. W. Holzhapfel, D. B. G. Williams, Tetrahedron
´ 23.4, 26.6, 32.7, 33.4, 126.2, 128.4, 128.5, 129.0, 131.9, 135.4,
Lett. 1996, 37, 5817.
177.2 ppm. MS (EI) (as methyl ester): m/z (%) 218 (34), 186 (65),
[9]
S. Nagumo, A. Matsukuma, H. Suemune, K. Sakai, Tetra-
169 (11), 158 (12), 143 (12), 130 (40), 117 (100), 104 (36), 91 (36).
hedron 1993, 49, 10501.
C13H16O2 (204.2): calcd. C 76.44, H 7.90; found C 76.46, H 7.89.
[10] [10a]
G. W. Kabalka, D. Tejedor, N. S. Li, R. R. Malladi, S.
[10b]
Trotman, J. Org. Chem. 1998, 63, 6438. G. W. Kabalka, D.
Tejedor, N. S. Li, R. R. Malladi, S. Trotman, Tetrahedron 1998,
Acknowledgments [10c]
54, 15525. G. W. Kabalka, N. S. Li, D. Tejedor, R. R.
Malladi, X. Gao, S. Trotman, Synth. Commun. 1999, 29, 2783.
The authors wish to thank the Università degli Studi di Perugia,
[10d]
G. W. Kabalka, D. Tejedor, N. S. Li, R. R. Malladi, S.
Italy, for financial support.
Trotman, J. Org. Chem. 1999, 64, 3157.
[11]
G. M. Strunz, H. Finlay, Phytochemistry 1995, 39, 731.
[1] [1a] [12]
R. Kane, Ann. Physik Chem. 1838, 44, 475; J. Prakt. Chem. G. M. Strunz, H. Finlay, Tetrahedron 1994, 50, 11113.
[1b] [13]
1838, 15, 129. A. Wurtz, Bull. Soc. Chim. Fr. 1872, 17, 436; S. Kobayshi, M. Sugiura, H. Kitagawa, W. W. L. Lam, Chem.
[1c]
Ber. 1872, 5, 326. A. T. Nielsen, W. J. Houlihan, Org. React. Rev. 2002, 102, 2227.
[14] [14a]
1968, 16. M. Curini, F. Epifano, M. C. Marcotullio, O. Rosati, Tetra-
[2] [14b]
C. A. Grob, Angew. Chem. Int. Ed. Engl. 1969, 8, 535. hedron Lett. 2001, 42, 3193. M. Curini, F. Epifano, M. C.
[3] [14c]
X. L. Armesto, M. Canle, M. Losada, J. Santaballa, J. Org. Marcotullio, O. Rosati, Heterocycles 2001, 55, 1599. M.
Chem. 1994, 59, 4659. Curini, F. Epifano, M. C. Marcotullio, O. Rosati, Eur. J. Org.
[4] [14d]
M. De Giacomo, R. M. Bettolo, R. Scarpelli, Tetrahedron Lett. Chem. 2002, 1562. M. Curini, F. Epifano, F. Maltese, O.
1997, 38, 3469. Rosati, Tetrahedron Lett. 2002, 43, 4895.
[5] [5a]
A. Nagumo, A. Matsukuma, F. Inoue, T. Yamamoto, H. Received February 2, 2003
1634 © 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org Eur. J. Org. Chem. 2003, 1631 1634 [ Pobierz caÅ‚ość w formacie PDF ]