Paper
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suggested mechanism involves an oxygen transfer from the
solvent water to the carbonyl products. Further applications of
this protocol are ongoing in our laboratory.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
This work was nancially supported by the National Natural
Science Foundation of China (No. 21202031 and 21372231) and
the Hangzhou Normal University. We acknowledge the excellent
support from the analysis and test center of the key laboratory
in HZNU. We thank Prof. Z. Li in our key laboratory for GC-MS
analysis.
Notes and references
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Scheme 2 Mechanistic considerations.
a,b-unsaturated ketone 2a in the presence of electrophilic
iodine species via intermediates such as A.15 The proposed
reaction mechanism was further convinced by following
experiments.14 First, to gain a better understanding of the
possible reaction intermediates, we monitored the oxidation of
1a under optimal conditions by GC-MS. Surprisingly, full
conversion of 1a was observed only aer 30 min under the
standard reaction conditions, yielding allylic alcohol 3 (65% GC
yield), desired ketone 2a (30% GC yield) and a large amount of
benzyl alcohol. Aer 24 h, the allylic alcohol 3 was completely
disappeared. These results clearly proved the possibility of
above proposed deprotection/oxidation sequence, and also
indicated that the deprotection step is faster than the following
alcohol oxidation step under current reaction conditions.
Moreover, the oxidation of 3 to 2a (84% yield) could be effec-
tively achieved under standard conditions. Finally, 18O-labeling
experiment revealed that the oxygen atom of ketone group in
the formed a,b-unsaturated ketone originated from the 18O-
labeled water instead of the starting ether 1a, thus giving
a very facile method for the preparation of 18O-labeled a,b-
unsaturated ketones and aldehydes.
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Conclusions
In summary, we have disclosed a protocol for the direct
protective oxidation of a variety of allylic ethers to their corre-
sponding aldehydes or ketones promoted by molecular iodine
in the presence of water. Our protocol is practically simple and
proceeds under ligand- and metal-free conditions. In addition,
allylic esters can also undergo this oxidative process. The
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