Cyclic hydroxamic acids as oxygenating agents - Conversion of imines to anilides

Article abstract of DOI:10.1081/SCC-100106203

Cyclic hydroxamic acid mediated functional group modification of an imine to anilide is reported.

Full text of DOI:10.1081/SCC-100106203

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CYCLIC HYDROXAMIC ACIDS AS OXYGENATING AGENTS
–
CONVERSION OF IMINES TO ANILIDES
a a b
D. Sahadeva Reddy , P. Pratap Reddy & P. S. N. Reddy
a
Department of Chemistry , Osmania University , Hyderabad, 500 007, India
b
Department of Chemistry , Osmania University , Hyderabad, 500007, India
Published online: 22 Aug 2006.
To cite this article: D. Sahadeva Reddy , P. Pratap Reddy & P. S. N. Reddy (2001) CYCLIC HYDROXAMIC ACIDS AS
OXYGENATING AGENTS – CONVERSION OF IMINES TO ANILIDES, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 31:22, 3447-3451, DOI: 10.1081/SCC-100106203
To link to this article: http://dx.doi.org/10.1081/SCC-100106203
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SYNTHETIC COMMUNICATIONS, 31(22), 3447–3451 (2001)
CYCLIC HYDROXAMIC ACIDS
AS OXYGENATING
AGENTS – CONVERSION
OF IMINES TO ANILIDES
D. Sahadeva Reddy, P. Pratap Reddy,
and P. S. N. Reddy*
Department of Chemistry, Osmania University,
Hyderabad – 500 007, India
ABSTRACT
Cyclic hydroxamic acid mediated functional group modifica-
tion of an imine to anilide is reported.
During our search for novel heterocyclics of medicinal importance, we
discovered that cyclic hydroxamic acids can mediate the functional group
modification of an imine to amide. The procedure involves heating an
equimolar mixture of arylideneaniline (1a–f) and 2-phenyl-3-hydroxyquina-
zolin-4(3H )-one (2) under microwave irradiation for 6–8 min, and chromato-
graphing the melt over neutral alumina (ꢀ 150 mesh) using petroleum
ether-benzene (6 : 4) as eluent. The corresponding anilide (3a–f ) was isolated
in 48–67% yield. 2-Phenyl-quinazolin-4(3H )-one (4) was a co-product.
*
Corresponding author. E-mail: sahadeva_reddy@excite.com
447
3
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

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3
448
SAHADEVA REDDY, PRATAP REDDY, AND REDDY
A third product characterised as 3-(a-phenylamino)-benzyloxy-2-phe-
nylquinazolin-4 (3H )-one (5, mp 182 C) was also isolated in the reaction of
1
ꢁ
1a and 2 (4 min). When 5 was independently heated under microwave irra-
diation for 3 min, it readily underwent retro-ene reaction yielding 4 and
benzanilide. The EI mass spectrum (70 eV) of 5 also showed an intense
ion peak at m/z 222 (92%). Isolation of 5 in the reaction of 1a and 2, and
its subsequent conversion to 3a and 4, proved its intermediacy in the for-
mation of 3a from 1a.
The imine–amide conversion described above also occurred
intramolecularly. For example, the Schiff’s base, 2-[2-(4-methoxybenzyl-
2
ideneamino)phenyl]-3-hydroxyquinazolin-4(3H )-one (6a), isomerised to
the amide-2-[2-(4-methoxybenzoylamino)phenyl]quinazolin-4(3H )-one (7a),

ORDER
REPRINTS
CYCLIC HYDROXAMIC ACIDS
3449
on reflux in nitrobenzene (6 h, method a), in diphenyl ether (4 h, method b)
or under microwave irradiation (5 min, method c). The amide 7 was char-
3
acterised by spectral data and comparison with an authentic sample pre-
4
pared by Butler’s method.
The intramolecular imine–amide conversion could be explained in two
ways – (i) compound 6a may first cyclise to an unstable [3, 1, 4]benzoxadia-
zepine 8, and the labile N–O bond cleaves at elevated temperature to form
an oxaziridine derivative 9 which subsequently opens to 7 (Scheme 1); (ii) the
diradical formed initially by N–O bond cleavage in 8 may itself rearrange to
the amide without the intervention of oxaziridine (Scheme 2).
We favour the mechanism in Scheme 1 because thermal cleavage of
N–O bond in O-alkylated cyclic hydroxamic acids and rearrangement of
5
,6
oxaziridines to amides are known in literature.
Scheme 1.
Scheme 2.

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3
450
SAHADEVA REDDY, PRATAP REDDY, AND REDDY
In summary, N-hydroxamic acid mediating the oxygenation of an imine
group can serve as a gainful reagent for >C¼N- to -CONH- functional
group modification.
ACKNOWLEDGMENT
One of the authors (DSR) is thankful to CSIR-UGC for the award of
senior research fellowship.
REFERENCES
þE
1
. a) The mass spectrum did not record M at 70 eV. The highest ion was
recorded at m/z 222.
b) Infrared spectrum showed carbonyl (1684 cm
ꢂ1
)
and NH
ꢂ1
(
c) H NMR spectrum is characteristic by the appearance of a singlet at
3381 cm ).
1
d 8.4 (the methine hydrogen).
. a) Infrared spectrum showed absorptions at 3100–2910 cm (br, OH),
ꢂ1
2
1
689 (C¼O) 1608 (C¼N).
1
b) H NMR (CDCl ) revealed a methoxyl group (d 3.9, s, 3H), para
3
disubstituted benzene (d 6.9, d, J ¼ 11 Hz and d 7.65, d, J ¼ 11 Hz),
quinazolinone peri-proton (d 8.35, d, 1H, J ¼ 10 Hz) and azomethine
proton (d 8.95, s, 1H); Mass spectrum showed the molecular ion peak
at m/z 371.
3
. 7a: IR (KBr): 3283, 3177, 3130, 3060, 1671 (br), 1605, 1575, 1536, 1468,
1
ꢂ1
1
279, 946 cm ; H NMR (DMSO-d ): d 3.9 (s, 3H, OCH ), 7.0–8.2
6
3
(
signals at 12.5 (s, NH) and 12.7 (s, NH). MS m/z 371 (M ), 369, 353,
m, 11H, Ar-H), 8.65 (d, 1H, J ¼ 10 Hz, Peri Ar-H), D O exchangeable
2
þ
1
7
1
35, 107, 92, 77, 64.
b: IR (KBr): 3261, 3180, 3130, 3064, 1683 (br), 1603, 1560, 1525, 1445,
ꢂ1
1
276, 949 cm ; H NMR (DMSO-d ): d 7.3–8.3 (m, 12H, Ar-H), 8.6
6
(
(
d, 1H, J ¼ 10 Hz, peri Ar-H), 12.0 (s, NH), 12.4 (s, NH); MS m/z 341
þ
M ), 323, 294, 264, 162, 105, 77.
7
c: IR (KBr): 3271, 3128, 3060, 1685 (br), 1605, 1540, 1496, 1405, 1276,
ꢂ1
1
949 cm ; H NMR (DMSO-d ): d 7.2–8.2 (m, 11H, Ar-H), 8.5 (d, 1H,
6
þ
J ¼ 10 Hz, peri Ar-H), 12.2 (s, NH) 12.5 (s, NH); MS m/z 375 (M ), 357,
3
7
9
25, 135, 111, 77.
d: IR (KBr): 3254, 3189, 3058, 1686 (br), 1602, 1576, 1519, 1445, 1279,
ꢂ1 1
47 cm ; H NMR (DMSO-d ): d 7.25–8.25 (m, 11H, Ar-H), 8.6 (d, 1H,
6

ORDER
REPRINTS
CYCLIC HYDROXAMIC ACIDS
3451
þ
J ¼ 10 Hz, peri Ar-H), 12.24 (s, NH), 12.45 (s, NH); MS m/z 386 (M ),
368, 264, 150, 123, 119, 77.
4
5
. Butler, K.; Partridge, M.W.; Waite, J.A. J. Chem. Soc. 1960, 4970.
. a) Katrizky, A.R.; Brown, S.B. Synthesis 1978, 619; b) Cook, M.J.;
Katrizky, A.R.; Millet, G.H. Heterocycles 1977, 7, 227; c) Katrizky,
A.R.; Cook, M.J.; Brown, S.B.; Cruz, R.; Millet, G.H. J. Chem. Soc.
Perkin Trans 1 1979, 2493.
6. Emmons, W.D. J. Am. Chem. Soc. 1957, 79, 5739.
Received in the UK February 24, 2000

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