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SET mechanism as described for debenzylation in the presence of
DDQ.9a,14 The 3,4DMB ether is expected to be more reactive to the
PIFA oxidation because it has a lower oxidation potential which
makes it more electron-donating than the PMB group.9a,15 Hence,
benzylic oxidation with PIFA has been applied to the oxidative re-
moval of the 3,4DMB group, which proceeds by initial formation of
the CT-complex between the electron-donative dimethoxybenzene
ring and the electron-attractive PIFA, followed by dehydration and
hydrolysis.
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In conclusion, we have established that 3,4DMB ethers can effi-
ciently be deprotected by treatment with excess PIFA (2.0 equiv)
in CH2Cl2 at room temperature. This reaction produces the corre-
sponding alcohols in excellent yields and selectivities, thus provid-
ing a mild and efficient method for the chemoselective deprotection
of 3,4DMB ethers that does not require the use of generate toxic
waste products. The use of the PIFA reagent system for organic
synthetic transformations is in progress.
Acknowledgments
This work was supported in part by a grant for private univer-
sities and a Grant-in-Aid for Scientific Research from the Ministry
of Education, Culture, Sports, Science, and Technology (MEXT) of
Japan(Grant Nos. 20790016 and 23790018), a Grant-in-Aid for Sci-
entific Research on Priority Area‘Creation of Biologically Functional
molecules’ (Grant Nos. 17035073 and 18032065) and the Promo-
tion and Mutual Aid Corporation for Private Schools of Japan.
13. (a) Dohi, T.; Maruyama, A.; Takenaga, N.; Senami, K.; Minamitsuji, Y.; Fujioka,
H.; Caemmerer, S. B.; Kita, Y. Angew. Chem., Int. Ed. 2008, 47, 3787; (b) Dohi, T.;
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Arisawa, M.; Ramesh, N. G.; Nakajima, M.; Tohma, H.; Kita, Y. J. Org. Chem.
2001, 66, 59.
Supplementary data
Supplementary data associated with this article can be found, in
References and notes
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