Pyruvaldehyde Diethyl Acetal

(R = Et)

[16330-13-5]  · C7H14O3  · Pyruvaldehyde Diethyl Acetal  · (MW 146.21) (R = Me)

[18218-94-5]  · C5H10O3  · Pyruvaldehyde Dimethyl Acetal  · (MW 118.15) (R,R = -CH2CH2-)

[39050-39-0]  · C5H8O3  · Pyruvaldehyde Ethylene Acetal  · (MW 116.12)

(reagents for preparation of a-ethylenic1 and a-allenic2 carbonyl compounds)

Alternate Names: 2,2-diethoxypropanal; methylglyoxal diethyl acetal.

Physical Data: R = Et: bp 27-29 °C/3 mmHg. R = Me: bp 27.5-28 °C/6 mmHg. R,R = -CH2CH2-: bp 32-35 °C/5 mmHg.

Preparative Methods: preparations involve either reductive ozonolysis of methyl vinyl ketone dioxolane3 or reduction of Ethyl Pyruvate Diethyl Acetal followed by oxidation of the resulting alcohol.2,4 2,2-Dialkoxypropionaldehydes can also be obtained by alcohol addition to a-alkoxyacroleins.5

Handling, Storage, and Precautions: these liquid compounds should be stored under inert gas and at low temperature.

Wittig Reactions.

Reaction with Cyclopropylidenetriphenylphosphorane gives the expected a,b-ethylenic acetal, which leads to the corresponding a,b-ethylenic carbonyl compound by deacetalization with moist silica gel (eq 1).1

Reactions with Organometallic Compounds.

Reaction between methylglyoxal ethylene acetal and Ethynylmagnesium Bromide followed by oxidation of the intermediate alcohol leads to 1-pentyne-3,4-dione 4-ethylene acetal (eq 2).3 Other propargylic alcohols can also be prepared by reaction with organomagnesium compounds. Their corresponding mesylates react with organocopper species prepared from a Grignard reagent and Copper(I) Bromide to give a,b-allenic acetals. These acetals are hydrolyzed to a,b-allenic ketones by column chromatography on silica gel. Overall yields are fair to moderate (eq 3).2 The same reactions may be carried out with phenylglyoxal diethyl acetal.2

Related Reagents.

(2-Dimethylaminoethyl)triphenylphosphonium Bromide; Ethyl 3,3-Diethoxypropanoate; Pyruvaldehyde 2-Phenylhydrazone.

1. Lechevallier, A.; Huet, F.; Conia, J. M. T 1983, 39, 3307 (CA 1984, 100, 120 544k).
2. Bernard, D.; Doutheau, A.; Gore, J. T 1987, 43, 2721 (CA 1988, 108, 130 669j).
3. Hahn, E. F. JOC 1973, 38, 2092.
4. Huet, F.; Pellet, M.; Lechevallier, A.; Conia, J. M. JCR(S) 1982, 246; Huet, F.; Pellet, M.; Lechevallier, A.; Conia, J. M. JCR(M) 1982, 2528.
5. (a) Shostakovskii, M. F.; Keiko, N. A.; Filippova, A. Kh. IZV 1967, 392 (CA 1967, 67, 21 241c). (b) Shostakovskii, M. F.; Keiko, N. A.; Chichkarev, A. P.; Filippova, A. Kh. IZV 1967, 2351 (CA 1968, 68, 39 005j).

François Huet

University of Le Mans, France

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