3-Ethoxyacrolein1

(1; R1 = Et, R2 = H)

[19060-08-3]  · C5H8O2  · 3-Ethoxyacrolein  · (MW 100.12) (E)-(1)

[764-63-6] (Z)-(1)

[57155-16-5] (2; R1 = Et, R2 = Me)

[42588-57-8]  · C6H10O2  · 3-Ethoxy-2-methylacrolein  · (MW 114.15) (E)-(2)

[62055-46-3] (3; R1 = Me, R2 = H)

[4652-35-1]  · C4H6O2  · 3-Methoxyacrolein  · (MW 86.09) (E)-(3)

[78923-06-5] (Z)-(3)

[78906-20-4]

(mono- and bifunctional three-carbon electrophile in carbonyl reactions, vinylogous acylations2 and various cyclocondensation reactions1,3)

Alternate Name: 3-ethoxy-2-propenal.

Physical Data: (1) bp 68-72 °C/11 mmHg; d 0.9835 g cm-3; n20D 1.473-1.474. (2) bp 78-81 °C/14 mmHg; d 0.957-0.960 g cm-3; n20D 1.474-1.479. (3) mp 25 °C; bp 36-37 °C/1.5 mmHg; d 1.0306 g cm-3; n20D 1.481-1.482.

Form Supplied in: colorless liquid(s); 3-ethoxy-2-methylacrolein (2) is commercially available.

Preparative Methods: 3-ethoxyacrolein (1) and its 2-alkyl analogs (4) are obtained by mild hydrolysis of malonic dialdehyde bisacetals,4a,b and the former also by decarboxylation of b-acroleinyl carbonate.4c 3-Methoxyacrolein (3) is prepared via the carbonate5a,b or by methylation of malonic dialdehyde sodium salt.5c

Handling, Storage, and Precautions: to avoid polymerization the ethoxyacroleins should be stored in a refrigerator, and the 2-unsubstituted compound kept in a freezer. They are slight lachrymators. Use in a fume hood.

Cyclization with Amino Compounds.

3-Alkoxyacroleins are vinylogous formates. As bifunctional electrophiles they cyclize with amino compounds to give a variety of nitrogen heterocycles. They can replace unstable malonic dialdehydes and the less reactive tetraacetals. Related are 3-aminoacroleins, which can be used for the synthesis of pyridines.6 Amidines cyclocondense with 2-alkyl-3-ethoxyacroleins (2) and (4) to give 2,5-dialkylpyrimidines in better yield than with malonic dialdehyde tetraacetals (eq 1).3 Reaction with Urea, Thiourea, or Guanidine affords 2-hydroxypyrimidines, 2-pyrimidinethiones, or 2-aminopyrimidines, respectively.3

The reaction of (2) or (4) with heterocyclic enamines such as 5-aminopyrazoles, -isoxazoles, or -isothiazoles (eq 2) yields 1H-pyrazolo[3,4-b]-,7a isoxazolo[5,4-b],7b or isothiazolo[5,4-b]pyridines.7c Intermediate heterocyclic aminoacroleins can be isolated. Vinylogous amidation of (2) and (4) with L-proline ester and cyclization of the aminoacroleins give 2,3-dihydro-1H-pyrrolizines.8

The macrocyclic 1,8-dihydro-1,4,8,11-tetraaza[14]annulenes are formed from 3-ethoxyacroleins and enediamines such as diaminomaleodinitrile (eq 3).9a Improvement of yields is achieved by the metal template effect, in which a metal cation coordinates the enediamine.9b

Reaction with Carbon Nucleophiles.

Alkylmagnesium halides add to (2) or (4) regioselectively in a 1,2-addition.10 Hydrolysis of the intermediate g-hydroxyenol ethers affords a,b-unsaturated aldehydes, resulting in the oxopropenylation of the Grignard reagent (eq 4).2 The methoxy analog (3)5b and the reactive 3-trimethylsilyloxyacroleins11 have also been used. Vinylic Grignard reagents afford conjugated polyenes.12

Nitrogen heterocycles with a lithiable a-methylimino group, such as 2-methylpyridine, and (2) or (4) yield labile heterocyclic g-hydroxyenol ethers which cyclize with acids to compounds with a bridgehead nitrogen, such as 3-alkylquinolizinium salts (eq 5).13 Substituted dihydroindolizinium and dihydrothiazolo[3,2-a]-pyridinium are obtained similarly.14

2-Alkyl-1-ethoxy-1,3-butadienes are obtained by Wittig alkenylation of (2) or (4)15 (or (3)5c). Vinylogous transesterification of (2) with chiral 1-arylethanols and methenylation yields 3-aryloxy-1,3-dienes (ee 85-91%).16a These undergo Diels-Alder reactions with electron-deficient dienophiles. Addition to Isoprene (eq 6)16a,b gives an optically active terpene alcohol.

Related Reagents.

(Z)-b-Aminoacrolein; 3-Ethoxyacrylonitrile; Ethyl 3-Ethoxyacrylate; Ethyl Hydroxymethyleneacetate, Sodium Salt; Malondialdehyde; Methyl Diformylacetate; Propargyl Aldehyde.


1. Breitmaier, E.; Ullrich, F.-W.; Potthoff, B.; Böhme, R.; Bastian, H. S 1987, 1.
2. Rustemeier, K.; Breitmaier, E. AG 1980, 92, 841; AG(E) 1980, 19, 816.
3. Kruse, R.; Breitmaier, E. CZ 1977, 101, 305.
4. (a) Rüegg, R.; Lindlar, H.; Montavon, M.; Saucy, G.; Schaeren, S. F.; Schwieter, U.; Isler, O. HCA 1959, 42, 847. (b) Breitmaier, E.; Gassenmann, S. CB 1971, 104, 665. (c) Klimko, V. T.; Protopopova, T. V.; Smirnova, N. V.; Skoldinov, A. P. ZOB 1962, 32, 2961 (CA 1963, 58, 9070b).
5. (a) Kalinina, N. N.; Klimko, V. T.; Protopopova, T. V.; Skoldinov, A. P. ZOB 1962, 32, 2146 (CA 1963, 58, 7826a). (b) Smithers, R. H. JOC 1978, 43, 2833. (c) Maddaluno, J.; d'Angelo, J. TL 1983, 24, 895.
6. (a) Breitmaier, E.; Bayer, E. AG 1969, 81, 785; AG(E) 1969, 8, 765. (b) Breitmaier, E.; Bayer, E. TL 1970, 38, 3291. (c) Breitmaier, E.; Gassenmann, S.; Bayer, E T 1970, 26, 5907.
7. (a) Häufel, J.; Breitmaier, E. AG 1973, 85, 959; AG(E) 1973, 12, 922. (b) Skötsch, C.; Kohlmeyer, I.; Breitmaier, E. S 1979, 449. (c) Skötsch, C.; Breitmaier, E. S 1979, 370.
8. Walizei G. H.; Breitmaier, E. LA 1990, 605.
9. (a) Kohlmeyer, I.; Lorch, E.; Bauer, G.; Breitmaier, E. CB 1978, 111, 2919. (b) Mühmel, G.; Breitmaier, E. AG 1978, 90, 818; AG(E) 1978, 17, 772.
10. Solladié, G.; Berl, V. TL 1991, 32, 6329.
11. Ullrich, F.-W.; Rotscheidt, K.; Breitmaier, E. CB 1986, 119, 1737.
12. Spangler, C. W.; McCoy, R. K.; Karavakis, A. A. JCS(P1) 1986, 1203.
13. Böhme, R.; Breitmaier, E. CB 1986, 119, 2062.
14. Böhme, R.; Rotscheidt, K.; Breitmaier, E. S 1989, 109.
15. Potthoff, B.; Breitmaier, E. CB 1985, 118, 4646.
16. (a) Rieger, R.; Breitmaier, E. S 1990, 697. (b) Zadel, G.; Rieger, R.; Breitmaier, E. LA 1991, 1343.

Roswitha M. Böhme

University of Bonn, Germany



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