Ethyl Crotonate1

(E)

[623-70-1]  · C6H10O2  · Ethyl Crotonate  · (MW 114.16) (Z)

[6776-19-8] (Me ester)

[623-43-8]  · C5H8O2  · Methyl Crotonate  · (MW 100.13)

(alkylating and annulating reagent commonly used in cycloadditions,2 conjugate additions,3 tandem vicinal dialkylation reactions,4 and Heck reactions5)

Physical Data: bp 142-143 °C; d204 0.916 g cm-3; n20D 1.425.

Solubility: insol H2O; sol EtOH, ether, most other polar solvents.

Form Supplied in: typically furnished predominantly as the (E)-isomer; purity &egt;96%; widely available.

Preparative Method: the (Z)-isomer can be prepared by semihydrogenation of ethyl tetrolate in excellent chemical yield.6

Purification: commercial material can be washed with 5% aq Na2CO3, followed by aq saturated CaCl2. Drying with CaCl2 and distillation at atmospheric or reduced pressure provides the pure ester.7

Handling, Storage, and Precautions: should be stored tightly capped in an amber container and preferably refrigerated. Crotonates are flammable and corrosive, usually with a lachrymatory odor. This toxic reagent should be handled in a fume hood.

The chemistry of alkyl crotonates parallels that of the alkyl acrylates (see Ethyl Acrylate), particularly in their use as dienophiles in cycloadditions8 and in their conjugate addition reactions.9


1. Sutherland, I. O. In Comprehensive Organic Chemistry; Barton, D. H. R.; Ollis, W. D., Eds.; Pergamon: New York, 1979; Vol. 2, p 869.
2. Carruthers, W. Cycloaddition Reactions in Organic Synthesis; Pergamon: New York, 1990.
3. (a) Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis; Pergamon: New York, 1992; p 199. (b) Bergmann, E. D.; Ginsburg, D.; Pappo, R. OR 1959, 10, 179.
4. (a) Hulce, M.; Chapdelaine, M. J. COS 1991, 4, 237. (b) Chapdelaine, M. J.; Hulce, M. OR 1990, 38, 225.
5. (a) Heck, R. F. Palladium Reagents in Organic Syntheses; Academic: San Diego, 1985. (b) Heck, R. F. OR 1982, 27, 345.
6. Taschner, M. J.; Rosen, T.; Heathcock, C. H. OSC 1990, 7, 226.
7. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory Chemicals, 3rd ed; Pergamon: New York, 1988; p 177.
8. Krohn, K. In Organic Synthesis Highlights; Mulzer, J.; Altenbach, H.-J.; Braun, M.; Krhn, K.; Reissig, H.-U., eds.; VCH: New York, 1991; p 54.
9. (a) Fukuzawa, S.; Nakanishi, A.; Fujinami, T.; Sakai, S. JCS(P1) 1988, 1669. (b) Spitzner, D.; Engler, A. OS 1987, 66, 37. (c) Franck, R. W.; Bhat, V.; Subramaniam, C. S. JACS 1986, 108, 2455.

Martin Hulce

Creighton University, Omaha, NE, USA



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