ALUMINUM ETHOXIDE 1
Esters from Aldehydes. When Tishchenko treated a variety
Aluminum Ethoxide1
of aldehydes with a catalytic amount of aluminum ethoxide in the
absence of solvents, he obtained primarily esters derived from ox-
Al(OEt)2
idation of one half of the aldehyde and reduction of the other half.
Extensive studies later verified this early work.6 Although alkali
[555-75-9] C6H15AlO3 (MW 162.16) metal alkoxides have been used successfully in the Tishchenko
reaction for aldehydes lacking Ä…-hydrogens,3b aluminum ethox-
InChI = 1/3C2H5O.Al/c3*1-2-3;/h3*2H2,1H3;/q3*-1;+3/
ide is almost invariably the catalyst of choice in those cases where
rC6H15AlO3/c1-4-8-7(9-5-2)10-6-3/h4-6H2,1-3H3
aldol condensations would otherwise predominate. For example,
InChIKey = JPUHCPXFQIXLMW-MHHMYNCNAZ
treatment of butanal, 2-ethylbutanal, or octanal with aluminum
(reagent for reduction of aldehydes to alcohols;2 catalyst for
ethoxide (5% by weight relative to the aldehyde) gave the corre-
conversion of aldehydes to esters3)
sponding esters in good yield (eq 2).6b Crossed Tishchenko reac-
ć% ć% tions generally give mixtures of products.
Physical Data: mp 157 160 C; liq bp 200 C/6 8 mmHg; mix-
ture of oligomers in solution; physical properties drastically
affected by traces of moisture.
O
O
Al(OEt)3
Solubility: sol hot xylene, cholorobenzene, other high boiling
2
(2)
R OCH2R
R H
solvents.
Form Supplied in: available as white powder.
R = n-Pr 81%
R = Et2CH 70%
Preparative Method: react Aluminum filings with absolute
R = Me(CH2)6 69%
ethanol using small amounts of Mercury(II) Chloride or
Iodine as catalysts.4
Handling, Storage, and Precautions: use in a fume hood; air
Aluminum ethoxide in xylene has also been used to polymer-
and moisture sensitive; extremely destructive to tissue of the
ize terephthalaldehyde into high molecular weight chains in a
mucous membranes and upper respiratory tract, eyes and skin,
Tishchenko-like process.7
and should be handled with appropriate caution. Contact via
inhalation route is particularly hazardous.
1. (a) Mehrotra, R. C., J. Indian Chem. Soc. 1953, 30, 585. (b) Beuhler,
C. A.; Pearson, D. E. Survey of Organic Syntheses; Wiley: New York,
Reductions. The reagent, while commercially available, may
1970; Vol. 1, p 853. (c) Bersin, T. Newer Methods of Preparative Organic
be conveniently prepared prior to use.4 It has been used in
Chemistry; Interscience: New York, 1948; p 125. (d) Wagner, R. B.;
Meerwein Ponndorf Verley reductions for the selective conver- Zook, H. D. Synthetic Organic Chemistry; Wiley: New York, 1953;
p. 494.
sion of Ä…-halo aldehydes and Ä…,²-unsaturated aldehydes to the
corresponding alcohols. For example, reaction of chloral with alu- 2. Meerwein, H.; Schmidt, R., Justus Liebigs Ann. Chem. 1925, 444,
233.
minum ethoxide in ethanol as solvent gives acetaldehyde and the
3. (a) Cichon, L., Wiad. Chem. 1966, 20, 641, 783. (b) Kamm, O.; Kamm,
aluminum salt of trichloroethanol. Subsequent treatment of the
W. F., Org. Synth., Coll. Vol. 1941, 1, 104.
salt with sulfuric acid liberates trichloroethanol in excellent yield
4. Chalmers, W., Org. Synth., Coll. Vol. 1943, 2, 598.
(eq 1).4 Similar high-yield reductions have been carried out on
5. Dworzak, R., Monatsh. Chem. 1926, 47, 11.
bromal, cinnamaldehyde, and various halogenated cinnamyl and
6. (a) Child, W. C.; Adkins, H., J. Am. Chem. Soc. 1923, 45, 3013. (b) Villani,
crotyl aldehydes.2,5
F. J.; Nord, F. F., J. Am. Chem. Soc. 1947, 69, 2605.
O O
7. Sweeney, W., J. Appl. Polym. Sci., 1963, 7, 1983.
3 Cl3C + Al(OEt)3 3 + Al(OCH2CCl3)3
H H
Gary W. Morrow
2 Al(OCH2CCl3)3 + 3 H2SO4 84% 6 CCl3CH2OH + Al2(SO4)3 (1)
The University of Dayton, Dayton, OH, USA
Avoid Skin Contact with All Reagents