B. List et al. / Tetrahedron 62 (2006) 476–482
481
(l) From ethyl(benzothiazol-2-ylsulfonyl)acetate: Blakemore,
P. R.; Ho, D. K. H.; Nap, W. M. Org. Biomol. Chem. 2005, 3,
1365–1368.
2.2.24. Ethyl-(E)-4,4-diphenyl-2-butenoate (1h). Colour-
less oil (483.1 mg, 1.81 mmol, 91%, E:ZO99:1). NMR data
is in accordance with the lit.22
3. For comparably efficient atom economic approaches to
a,b-unsaturated esters that do not rely on aldehydes, see for
example: (a) Heck-reaction,Beletskaya, I. P.; Cheprakov,
A. V. Chem. Rev. 2000, 100, 3009–3066. (b) Cross metathesis,
Chatterjee, A. K.; Toste, F. D.; Choi, T.-L.; Grubbs, R. H. Adv.
Synth. Catal. 2002, 6–7, 634–637.
2.2.25. Ethyl-(E)-4,4-dimethyl-2-pentenoate (1i). Colour-
less oil (286.5 mg, 1.83 mmol, 92%, E:ZO99:1). NMR data
is in accordance with the lit.28
2.2.26. Ethyl-(E)-6,6-dimethoxy-2-hexenoate (1j). Colour-
1
4. For a two step methodology for the recycling of triphenylphos-
phine oxide (via Ph3PCl2), see: Process for the manufacture of
triphenyl phosphine. Hermeling, D.; Bassler, P.; Hammes, P.;
Hugo, R.; Lechtken, P.; Siegel, H., (BASF AG, Germany).
Eur. Pat. Appl. EP 6385807, 1995, p 7, CAN 123:9689.
5. (a) For aromatic aldehydes, see: Galat, A. J. Am. Chem. Soc.
1946, 68, 376–377. (b) For linear aldehydes, see: Martin, C. J.;
Schepartz, A. I.; Daubert, B. F. J. Am. Chem. Soc. 1948, 70,
2601–2602. (c) Klein, J.; Bergmann, E. D. J. Am. Chem. Soc.
1957, 79, 3452–3454. (d) Shabtai, J.; Ney-Igner, E.; Pines, H.
J. Org. Chem. 1981, 46, 3795–3802.
less oil (373.1 mg, 1.85 mmol, 92%, E:ZZ94:6). H NMR
(400 MHz, CDCl3) d 1.22 (t, 3H, JZ7.1 Hz), 1.66–1.71
(m, 2H), 2.17–2.22 (m, 2H), 3.25 (s, 6H), 4.12 (q, 2H, JZ
7.1 Hz), 4.30 (t, 1H, JZ5.6 Hz), 5.78 (d, 1H, JZ15.6 Hz),
6.89 (dt, 1H, JZ15.6 Hz). 13C NMR d 13.9, 26.9, 30.5, 52.5,
59.8, 103.3, 121.3, 147.7, 166.2.
Acknowledgements
Generous gifts of chemicals by Degussa and general support
of our work by Lanxess is most gratefully acknowledged.
We thank Kathrin Wobser, Hendrik van Thienen, and Pedro
Llamas Galilea for technical assistance.
6. Aldrich cataloge: (carbethoxymethylene)triphenylphosphorane
(3, R2ZEt), 10 mmol ca. 17 V; triethylphosphono acetate
(4, R2ZEt), 10 mmol ca. 2 V; mono-ethyl malonate (7a, R2Z
Et) 10 mmol ca. 5 V; mono-ethyl malonate, potassium salt
(7d), 10 mmol ca. 2 V.
7. (a) Carmona, A. T.; Fuentes, J.; Robina, I.; Rodriguez Garcia,
E.; Demange, R.; Vogel, P.; Winters, A. L. J. Org. Chem.
2003, 68, 3874–3883. (b) Ragoussis, N.; Ragoussis, V.
J. Chem. Soc., Perkin Trans. 1 1998, 3529–3533. (c) Influence
of heteroaromatic amines on Knoevenagel condensation:
Yamanaka, H.; Yokoyama, M.; Sakamoto, T.; Shiraishi, T.;
Sagi, M.; Mizugaki, M. Heterocycles 1983, 20, 1541–1544.
8. For a preliminray communication of our results, see: List, B.;
Doehring, A.; Hechavarria Fonseca, M. T.; Wobser, K.; van
Thienen, H.; Rios Torres, R.; Llamas Galilea, P., Adv. Synth.
Catal. 2005, in press.
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10. In one report DMAP has been used as a catalyst for the
reaction of malonic acid half esters with a,b-unsaturated
aldehydes at elevated temperature in pyridine to give the
corresponding a,b,g,d-unsaturated esters. See: Rodriguez, J.;
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transformed into the a,b-unsaturated ester under the slightly
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14. ‘Process for the production of olefins from carbonyl com-
pounds‘ (Studiengesellschaft Kohle mbH), Patent pending.
15. For recent studies on the use of malonic acid half thioesters in
asymmetric catalysis, see: Magdziak, D.; Lalic, G.; Lee,
H. M.; Fortner, K. C.; Aloise, A. D.; Shair, M. D. J. Am. Chem.
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16. In selected cases (see Tables), piperidine (10 mol%) was
added as co-catalyst (at 10 8C) to reduce the reaction times.