T. Seki et al. / Journal of Catalysis 217 (2003) 117–126
125
arise from the intramolecular alkoxide ion transfer in IV
occurring rapidly and thus predominantly.
We also became interested in the reaction mechanism of
the intramolecular Tishchenko reaction of 1 to 2 over γ -
alumina and measured the infrared spectra of the adsorbed
of 1 to 2 can be realized over γ -alumina at 313 K as listed
in entries 9–15 in Table 1. The facility of the intramolecu-
lar alkoxide ion transfer in IV to yield V can be explained
by the similar consideration described for the same reaction
over MgO.
1
on γ -alumina. The change in the infrared spectra of 1 ad-
sorbed on γ -alumina (JRC-ALO-4) with evacuation temper-
ature is shown in Fig. 4. The absorption bands at 1554 and
4. Conclusion
−1
1
431 cm whose intensities increased remarkably when
evacuation was conducted above 473 K can be assigned to
the asymmetric and symmetric stretching vibrations of the
carbonate group of III, respectively. The absorption bands
We have developed a new synthetic method for the syn-
thesis of phthalide–skeleton under mild conditions using
heterogeneous catalytic intramolecular Tishchenko reaction
with environmentally benign, economical, and highly effec-
tive solid bases such as MgO, CaO, SrO, and γ -alumina. It
should be noted that the intramolecular Tishchenko reactions
of o-phthalaldehyde and 2,3-naphthalenedicarbaldehyde to
the corresponding lactones over these metal oxides pro-
ceeded quite smoothly and selectively without producing
any byproducts including the intermolecular Tishchenko
products. The present approach is certainly one of the po-
tential answers toward an increasing demand for the se-
lective, nontoxic, and effective organic reactions providing
phthalide–skeletons that are contained in a number of phar-
maceuticals and naturally occurring compounds exhibiting
significant biological activities and are employed in the syn-
thetic precursors of more complex compounds.
−1
at 2962 and 2904 cm can be assigned to the stretching of
the CH2 group of IV. Kuiper et al. pointed out the possi-
−1
bility that the band at 1370 cm which appears when ben-
zyl alcohol is adsorbed on alumina is due to the vibration
of the –CH2–O– group of aluminum benzylate [11]. Thus,
−1
the absorption band at 1378 cm , which continued to di-
minish as the evacuation temperature was raised, may be
due to the vibration of the –CH2–O– group of IV. In the
case of benzaldehyde adsorbed on alumina, Kuiper et al. re-
ported that the absorption band due to the vibration of the
C=O bond of the aldehyde group is reduced to a consider-
ably small shoulder by evacuation at room temperature and
disappears almost completely by evacuation at 503 K [11].
In the case of 1 adsorbed on γ -alumina, however, the strong
absorption bands due to the vibrations of the carbonyl group
−1
were confirmed at 1739 and 1694 cm when evacuation
was performed at room temperature. In addition, even at
higher evacuation temperatures of 473, 573, and 673 K, the
bands due to the carbonyl group did not disappear, implying
that chemically adsorbed species with an aldehyde group,
namely III and IV, exist on the surface of γ -alumina. As
for the stretching of the C–H bond of the aldehyde group,
Acknowledgment
This work is supported by a grant-in-aid for scientific
research from the Ministry of Education, Culture, Sports,
Science, and Technology, Japan.
−1
a very weak absorption band was confirmed at 2732 cm
.
References
Since the formations of III and IV on γ -alumina were con-
firmed, it can be deduced that the lactonization of 1 to 2 over
γ -alumina occurs by the same mechanism as that over MgO
shown in Scheme 2.
[
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