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Organic & Biomolecular Chemistry
Page 4 of 5
DOI: 10.1039/C5OB01569C
COMMUNICATION
Journal Name
Scheme 3. Control experiments.
This work was supported by CSIR-ORIGIN (CSC0108), New Delhi. We
are thankful to NMR, Mass divisions of CSIR-IICT, for providing the
analytical facilities. P.S.N, O.R and P.R.M. thank UGC and CSIR for
the Ph.D. fellowships.
standard conditions
(A)
(B)
3a, 92%
3a, 0%
2a
2a
[Cu] (30 mol%)
solvent, O2 (balloon)
Notes and references
standard conditions
(4-OMe)-Ph-(CO)-(CHO)
(C)
(D)
3a, 87%
3a, 0%
9
1
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standard conditions
(4-OMe)-Ph-CN
10
standard conditions
standard conditions
Ph(CNOH)Ph
Ph-(CO)-Ph
(E)
(F)
11
12, 20%
(4-OMe)-Ph-CHO
(4-OMe)-Ph-CN
13
10, 93%
Vol.
Chem. Eur. J., 2014, 20, 11776 – 11782.
3 pp. 97-129. (i) Y. Yang, F. Ni, W-M. Shu and A-X. Wu,
Based on these results, we propose a mechanistic possibility of this
Cu-catalyzed reaction under an O2 atmosphere as shown in scheme
3. Reaction starts with the oxime (a) formation and its subsequent
Cu(I)-mediated oxidation provides corresponding α-oxo oxime b8.
This intermediate reacts further with hydroxylamine to produce di-
oxime c. Subsequent dehydration of aldoxime (c) generates benzoyl
cyanide oxime d. This further produce intermediate oxazirene e
along with the release of hydrogen cyanide (HCN) via C-C bond
cleavage. Next, It reacts with water to generate oxaziridine f.
Finally, oxaziridine undergo hydrolysis14 to deliver the desired acid.
In case of higher alkyl groups the entire chain has decomposes to
HCN.
2
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Scheme 3. Proposed mechanism
4
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In conclusion,
a novel and efficient copper-catalyzed aerobic
oxidative C-C bond cleavage of ketones to corresponding acids via
unprecedented cleavage of alkyl groups adjacent to oxime has been
developed. Readily available and inexpensive copper catalyst, and
use of molecular oxygen as oxidant make this transformation green
and practical. Wide array of ketones having aryl/aralkyl/vinyl at one
end and methyl to any higher alkyl at the other end can be
efficiently cleaved and converted in to their corresponding acids in
fair to excellent yields. Preliminary mechanistic experiments have
disclosed the formation of oxime intermediate. Further
investigations to clearly understand the reaction mechanism and
the synthetic applications are currently underway.
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4 | J. Name., 2012, 00, 1-3
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