(E)-(Carboxyvinyl)trimethylammonium Betaine

[54299-83-1]  · C6H11NO2  · (E)-(Carboxyvinyl)trimethylammonium Betaine  · (MW 129.16)

(reaction of allylic alcohols with (E)-(carboxyvinyl)trimethylammonium betaine affords (E)-3-(allyloxy)acrylic acids, which on heating are transformed to g,d-unsaturated aldehydes via Claisen rearrangement/decarboxylation8,9)

Physical Data: mp 176-177 °C (dec);9 240-245 °C (dec).7

Analysis of Reagent Purity: IR (KBr) cm-1: 1665, 1600, 1360; 1H NMR (D2O, DSS ref) d: 3.3 (br s, 9 H, Me3N), 6.3 (br d, 1 H, J = 13, vinyl CH), 6.8 (br d, 1 H, J = 13, vinyl CH); elemental analysis.

Preparative Methods: A mixture of 25.0 g of ethyl propiolate, 14 mL of dichloromethane, and 440 mL of water is cooled to 5 °C and 90 mL of an aqueous 25% solution of trimethylamine is added with vigorous stirring over a period of 30 min. The mixture is then warmed to 25 °C for 3 h. The aqueous layer is separated and washed three times with 100 mL of dichloromethane. The aqueous solution is concentrated in vacuo at 45 °C. When the residue gives the appearance of a wet solid, it is treated with 150 mL of dioxane and concentrated as described above. The dioxane treatment-concentration procedure is repeated three times. The resulting yellow solid is triturated with acetonitrile until a white solid is obtained (25 g, 76% yield).

Purification: yellow impurities can be removed by trituration with acetonitrile to obtain a white solid. This is dried at 25 °C in vacuo (0.1 mmHg) for 14 h.

Handling, Storage, and Precautions: the reagent will slowly decompose at room temperature over a period of several months. Storage in a closed container at low temperatures is recommended. This reagent should be handled in a fume hood.

Synthesis of g,d-Unsaturated Aldehydes.

The Claisen rearrangement of allyl vinyl ethers1 is a useful synthetic transformation. However, this synthetic method is limited due to the lack of efficient general methods for the preparation of allyl vinyl ethers. These intermediates are normally prepared by vinyl ether exchange with simple alkyl vinyl ethers and an allylic alcohol in the presence of a Lewis acid (usually mercury(II) acetate) or mineral acid.2 Often yields in these reactions are low, and the use of mercury is becoming unacceptable environmentally.

Useful modifications of the Claisen rearrangement have been reported (e.g. those of Johnson,3 Ireland,4 and Eschenmoser5); however, these methods give products at the carboxylic acid oxidation level, and additional steps are required if an aldehyde is the desired product.

The betaine (1)6,7 can be used to convert primary and secondary allylic alcohols (2) to the corresponding g,d-unsaturated aldehydes (3) via allyloxyacrylic acids (4a).8,9 The g,d-unsaturated aldehydes (3) obtained from the Claisen rearrangement-decarboxylation of (4a) are the same products that would be obtained from Claisen rearrangement of the corresponding allyl vinyl ethers. The basic conditions required for the addition of allyic alcohols to the betaine (1) complement the previous methods of allyl vinyl ether formation.

Thus heating the sodium alkoxides of allylic alcohols with betaine (1) affords moderate to good yields of the corresponding trans-3-(allyloxy)acrylic acid sodium salts (4b). Aqueous solutions of the adducts (4b) are first washed with ether and then acidified to give the corresponding carboxylic acids (4a). These crude products are heated with a trace of hydroquinone at temperatures of 150-200 °C to give products (3) from Claisen rearrangement-decarboxylation of (4a).10 Sealed tubes or other high-pressure vessels are not necessary since the acrylic acids (4a) have a much higher boiling point than the aldehydes (3). The acids are heated under the appropriate reduced pressure such that the product is removed rapidly from the reaction mixture. The aldehydes (3) are isolated in good to excellent yields often in analytically pure form (Table 1).

For a similar reaction useful for the preparation of ketones via Claisen rearrangement-decarboxylation, see Büchi and Vogel.11

1. (a) Ziegler, F. E. CRV 1988, 88, 1423. (b) Ziegler, F. E. ACR 1977, 10, 227. (c) Bennett, G. B. S 1977, 589. (d) Rhoads, S. J.; Raulins, N. R. OR 1975, 22, 1.
2. (a) Koft, E. R.; Broadbent, T. A. OPP 1988, 20, 199. (b) Miyashita, M.; Suzuki, T.; Yoshikoshi, A. JACS 1989, 111, 3728. (c) Saucy, G.; Marbet, R. HCA 1967, 50, 2091 (CA 1968, 68, 2991b). (d) Watanabe, W. H.; Conlon, L. E. JACS 1957, 79, 2828. (e) Church, R. F.; Ireland, R. E.; Marshall, J. A. JOC 1966, 31, 2526. (f) Thomas, A. F. JACS 1969, 91, 3281. (g) Dauben, W. G.; Dietsche, T. J. JOC 1972, 37, 1212.
3. Johnson, W. S.; Werthemann, L.; Bartlett, W. R.; Brocksom, T. J.; Li, T.; Faulkner, D. J.; Petersen, M. R. JACS 1970, 92, 741.
4. (a) Ireland, R. E.; Mueller, R. H. JACS 1972, 94, 5897. (b) Ireland, R. E.; Mueller, R. H.; Willard, A. K. JACS 1976, 98, 2868.
5. Felix, D.; Gschwend-Steen, K.; Wick, A. E.; Eschenmoser, A. HCA 1969, 52, 1030.
6. Herkes, F. E.; Simmons, H. E. JOC 1973, 38, 2845.
7. McCulloch, A. W.; McInnes, A. G. CJC 1974, 52, 3569.
8. Büchi, G. H.; Vogel, D. E. JOC 1983, 48, 5406.
9. Vogel, D. E.; Büchi, G. H. OS 1988, 66, 29.
10. For substituent effects in the Claisen rearrangement, see: Burrows, C. J.; Carpenter, B. K. JACS 1981, 103, 6983 and 6984.
11. Büchi, G. H.; Vogel, D. E. JOC 1985, 50, 4664.

Dennis E. Vogel

3M Company, St Paul, MN, USA

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