M. Stratakis, M. Sta6roulakis / Tetrahedron Letters 42 (2001) 6409–6411
6411
the progress of the reaction, since minor amounts of
ascaridole are formed compared to p-cymene. A similar
observation has been reported by Garcia, Miranda and
coworkers3 for an intrazeolite photoinduced electron
transfer reaction.
4. (a) Forne´s, V.; Garcia, H.; Miranda, M. A.; Mojarrad,
F.; Sabater, M.-J.; Suliman, N. E. Tetrahedron 1996, 52,
7755–7760; (b) Scaiano, J. C.; Garcia, H. Acc. Chem. Res.
1999, 32, 783–793.
5. Park, Y. S.; Um, S. Y.; Yoon, K. B. J. Am. Chem. Soc.
1999, 121, 3193–3200.
Spontaneous intrazeolite electron transfer reactions are
so far known to occur within ZSM-513 and Ca-Y.14 To
the best of our knowledge, this paper describes the first
example of the spontaneous formation of radical
cations within Na-Y. The advantages of the MV2+/Na-
Y compared to the ZSM-5 is that for zeolite Y, the void
space of the supercages is significantly larger, and they
can host organic molecules even the size of a steroid.
Also Ca-Y is acidic, while Na-Y is almost neutral.
6. The doped zeolite used in this study was prepared by
stirring 10 g of zeolite Na-Y (Degussa) in 1 L of deion-
ized water containing 35 mg of methyl viologen dichlo-
ride for 24 h. The supported-zeolite was filtered, dried in
the air and then washed with water in a Soxhlet appara-
tus for 2 days. Finally, it was dried under vacuum for
several hours at 120°C, until the white powder turned to
light blue, indicative of the formation of the radical
cation of methyl viologen. We estimate that the doped
zeolite contains approximately less than one MV2+
molecule per 10 supercages.
7. Ascaridole was prepared by reaction of singlet oxygen
with a-terpinene (CH2Cl2/methylene blue), and was
purified by flash column chromatography using chloro-
form/hexane=1/1 as eluent. The relative amounts of
ascaridole formed if the intrazeolite reactions are carried
out in the open air depend on the substrate, and are as
follows: for 1, 15%, for 2, 5%, for 3, 6%, and for 4, 3%.
8. Jayathirma Rao, V.; Perlstein, D. L.; Robbins, R. J.;
Lakshminarasimhan, P. H.; Kao, H.-M.; Grey, C. P.;
Ramamurthy, V. J. Chem. Soc., Chem. Commun. 1998,
269–270.
In summary, we have presented a simple and effective
system for performing spontaneous electron transfer
reactions under very mild conditions, in the absence of
irradiation. Further uses of MV2+/Na-Y are currently
under investigation.
Acknowledgements
This work was supported in part by the Greek Secretar-
iat of Research and Technology (Program 1476), and
by the EPEAEK program ‘Isolation and synthesis of
natural products with biological activity’. We thank
Professor G. J. Karabatsos for valuable comments.
9. Pitchumani, K.; Ramamurthy, V. Tetrahedron Lett. 1996,
37, 5297–5300.
10. (a) Weng, H.; Sheik, Q.; Roth, H. D. J. Am. Chem. Soc.
1995, 117, 10655–10661; (b) Climent, M.-J.; Miranda, M.
A.; Roth, H. D. Eur. J. Org. Chem. 2000, 1563–67.
11. Electron transfer from MV+ to molecular oxygen within
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