Efficient heterogeneous catalytic intramolecular Tishchenko reaction
of o-phthalaldehyde to phthalide with alkaline earth oxides
Tsunetake Seki and Hideshi Hattori*
Center for Advanced Research of Energy Technology, Hokkaido University, Kita-13, Nishi-8, Kita-ku,
Sapporo 060-8628, Japan. E-mail: hattori@carbon.caret.hokudai.ac.jp
Received (in Cambridge, UK) 10th October 2001, Accepted 30th October 2001
First published as an Advance Article on the web
The heterogeneous catalytic systems realized by alkaline
earth oxides are successfully applicable to the highly
efficient intramolecular Tishchenko lactonization of o-
phthalaldehyde to phthalide.
or 50 mg) was added a benzene (1 mL) solution of o-
phthalaldehyde (1 mmol) under N2 at room temperature. Then
the reaction mixture was warmed to 313 K and stirred for a
prescribed reaction time. The resulting solution, after alkaline
earth oxide was separated, was analyzed by GC equipped with
a DB-1 column (total length: 60 m; diameter: 0.25 mm) to
determine the yield (%) of phthalide. The product was identified
by 1H NMR and GC–MS analysis.
The heterogeneous catalytic Tishchenko reaction using solid
bases involves the dimerizarion of aldehydes yielding the
corresponding esters initiated by the interactions of polarized
carbonyl groups of aldehydes with surface acidic and basic sites
of solid bases. The adaptability of solid base catalysts to the
Tishchenko reaction has been demonstrated in several in-
vestigations.1 Most of previous development of efficient
catalysis for Tishchenko reaction, however, has been confined
to homogeneous catalytic systems. Recent articles dealing with
homogeneous catalyses have reported considerable improve-
ments in activities for the dimerization of aldehydes in
comparison with traditional aluminium alkoxides catalysts.2,3
Solid base catalysts, unlike these homogeneous catalysts, can be
easily separated from the reaction mixture after carrying out the
reaction, and are inexpensive and environmentally benign.
These excellent properties emphasize the importance of the
replacement of homogeneous catalyses with heterogeneous
ones both in the laboratory and in industrial processes utilizing
Tishchenko esterification.
Although several studies have been conducted on the
intermolecular Tishchenko reaction over solid base catalysts as
mentioned above, there have been no reports of the intra-
molecular Tishchenko reaction which results in cyclization.2,4
In addition, to our knowledge, in the field of heterogeneous
basic catalysis, there has been only one report dealing with
intramolecular cyclization (dehydration of monoethanolamine
to ethylenimine).5 Here we report the intramolecular Ti-
shchenko reaction of o-phthalaldehyde to phthalide using
alkaline earth oxides as powerful and highly selective heteroge-
neous catalysts. The general reaction equation is shown in
Scheme 1.
The catalytic activities of alkaline earth oxides for the
intramolecular Tishchenko reaction of o-phthalaldehyde to
phthalide are given in Table 1. To compare the activities of
alkaline earth oxides, o-phthalaldehyde was treated with 10 mg
of each alkaline earth oxide at 313 K for 60 min (entries 1, 3, 5
and 7). Barium oxide did not furnish the corresponding lactone
at all (entry 7). Magnesium oxide and SrO showed almost equal
moderate activities (entries 1 and 5). In contrast, however, CaO
exhibited an excellent activity (entry 3). It should be empha-
sized that MgO, CaO and SrO yielded phthalide selectively
(intermolecular Tishchenko dimerization products were not
observed by GC–MS analysis). In an attempt to attain a
synthetically satisfactory level of yield, the amount of MgO,
CaO, and SrO was increased without changing the reaction
temperature. Thus, when the reaction was carried out at 313 K
with 50 mg of CaO, the reaction proceeded instantaneously, and
phthalide was obtained quantitatively in a short time of 15 min
(entry 4). Under the same conditions, MgO and SrO also
furnished pthalide in excellent yields of 91 and 86%, re-
spectively (entries 2 and 6).
In summary we have shown that efficient heterogeneous
catalytic lactonization of dialdehydes can be realized by using
alkaline earth oxides through the intramolecular Tishchenko
reaction of o-phthalaldehyde to phthalide.
Experimental procedures are as follows: MgO, CaO, SrO and
BaO were prepared from Mg(OH)2, Ca(OH)2, SrCO3 and
BaCO3, respectively, by thermal decomposition at elevated
temperatures in vacuo. The pretreatment temperatures and
surface areas of the catalysts examined are listed in Table 1. To
a Schlenk tube containing the alkaline earth oxide pretreated (10
Scheme 1 Heterogeneous catalytic intramolecular Tishchenko reaction of
o-phthalaldehyde to phthalide with alkaline earth oxides.
Table 1 Activities of alkaline earth oxides for the intramolecular Tishchenko reaction of o-phthalaldehyde to phthalidea
Catalyst
weight/mg
Pretreatment
temperature/K
Surface
areab/m2 g21
Reaction
time/min
Reaction
temp./K
Entry
Catalyst
Yieldc (%)
1
2
3
4
5
6
7
MgO
MgO
CaO
CaO
SrO
10
50
10
50
10
50
10
873
873
873
267
267
48
48
12
12
2
60
15
60
15
60
15
60
313
313
313
313
313
313
313
15
91
59
873
Quantitative
1273
1273
1273
15
86
0
SrO
BaO
a Reactant: 1 mmol of o-phthalaldehyde; solvent, 1 mL of benzene. All reactions were carried out under N2. b Surface areas were determined by the BET
method. c Yield was determined by the GC analysis of the resulting solution and was calculated by the equation: yield (%) = {(mol% of phthaide)/[(mol%
of o-phthalaldehyde) + (mol% of phthalide)]} 3 100.
2510
Chem. Commun., 2001, 2510–2511
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b109249a
Seki
