[141-43-5]  · C2H7NO  · Ethanolamine  · (MW 61.08)

(synthesis of oxazolidines,1 oxazolidinones,2 2-oxazolines;3 hydroboration workup4)

Alternate Names: 2-aminoethanol; monoethanolamine; MEA.

Physical Data: viscous liquid; bp 170 °C; 58 °C/5 mmHg; mp 10.3 °C; d 1.018 g cm-3; pH = 12.1 (25 w/w % aqueous solution); pKa = 9.4 (25 °C).

Solubility: sol H2O, alcohol, CHCl3; slightly sol ether, benzene; insol hydrocarbons.

Preparative Methods: large-scale preparation by ammonolysis of Ethylene Oxide.5

Purification: azeotrope with benzene followed by fractional distillation under reduced pressure.

Handling, Storage, and Precautions: hygroscopic; absorbs CO2 from atmosphere; corrosive.

N-Arylation and Alkylation.

MEA can be used to introduce b-hydroxyethylamino functionality onto aromatics containing electron-withdrawing groups (eq 1)6 or heterocycles (eq 2)7 by nucleophilic substitution. N-Alkyl or N,N-dialkylated derivatives of MEA can be obtained in good yields under mild conditions by alkylation (e.g. Benzyl Chloride, Sodium Hydroxide; mono, 68%; di, 72%)8 or reductive amination (e.g. Acetone, Platinum(IV) Oxide, 95%;9 Acetaldehyde, Sodium Borohydride, 76%1c). MEA derives its versatility by conversion to derivatives that serve in other transformations. Substituted ethanolamines are used in many asymmetric reactions.

Reactions with Carbonyls.

MEA condenses with aldehydes and ketones to give oxazolidines (1),1 carbonates to give oxazolidinones (2),2 acids to give oxazolines (3),3 and standard acylating agents (eq 3). These heterocycles are used as intermediates in natural product and polymer synthesis. It selectively deacylates acyl glycosides10 and replaces hydrazine for cleavage of Gabriel synthesis intermediates.11


MEA aids hydroboration reaction workup by transesterifying the borate ester to give the product alcohol and a borinate precipitate (eq 4).4 MEA has also been used to increase optical purities by crystallization of the resulting MEA esters.12

Heterocycle Synthesis.

Besides the heterocyclic systems shown in eq 3, different ring systems are obtained on reaction of MEA with CO2, CS2, isocyanates, nitriles, a-diketones [(4) and (5) depending on the reaction conditions],13 and with 1,4-butenediol to give (6).14

MEA is converted into a dienophile that has been used to prepare vicinal cis-amino alcohols (eq 5).15

Quaternary Amine Dealkylation.

MEA dealkylates quaternary ammonium salts (methyl groups) prepared during exhaustive methylation of amines (eq 6).15

1. (a) Bergmann, E. CRV 1953, 53, 309. (b) Saavedra, J. E. JOC 1985, 50, 2379. (c) Saavedra, J. E. JOC 1985, 50, 2271.
2. (a) Dyen, M. E.; Swern, D. CRV 1967, 67, 197. (b) Scholz, K.-H.; Heine, H.-G.; Hartmann, W. OS 1990, 7, 4. (c) Matsunaga, H.; Kimura, K.; Ishizuka, T.; Haratake, M.; Kunieda, T. TL 1991, 32, 7715.
3. (a) Wiley, R. H.; Bennett, L. L. CRV 1949, 44, 447. (b) Meyers, A. I.; Mihelich, E. D. AG(E) 1976, 15, 270.
4. Kramer, G. W.; Brown, H. C. JOC 1977, 42, 2292.
5. For an excellent source of information about industrial applications, see: Ethanolamine; In Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M., Ed.; Wiley: New York, 1984.
6. Knipe, A. C.; Sridhar, N. S 1976, 606.
7. Pan, H. L.; Fletcher, T. L. S 1971, 592.
8. Rumpf, P.; Kwass, R. BSF 1943, 10, 347.
9. Hancock, E. M.; Cope, A. C. OS 1955, 3, 501.
10. Grynkiewwicz, G.; Fokt, I.; Szeja, W.; Fitak, H. JCR(S) 1989, 152.
11. BASF AG, Eur. Patent 127 114, 1984.
12. Brown, H. C.; Prasad, J. V. N. V. JOC 1986, 51, 4526.
13. Alcaide, B.; Plumet, J.; Rodriguez-Campos, I. M.; García-Blanco, S.; Martínez-Carrera, S. JOC 1992, 57, 2446.
14. Murahashi, S.-I; Shimamura, T.; Moritani, I. JCS(C) 1974, 931.
15. Hünig, S.; Quast, H.; Brenninger, W.; Frankenfeld, E. OS 1973, 5, 1018.

Kenneth C. Caster

Union Carbide Corporation, South Charleston, WV, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.