SHORT PAPER
Hypervalent Iodine Oxidative Rearrangement of Anthranilamides
543
Benzimidazol-2-ones 5a h and Benzoxazol-2-ones 5i, 5j and 7,
9, 11; General Procedure
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Iodobenzene diacetate (IBD, 5 mmol) was added in portions to a
stirred solution of appropriate carboxamide 4a h, 4i, 4j, 6, 8, 10
(5 mmol) and KOH (560 mg, 10 mmol) in MeOH (20 mL) at
0 5 °C. The stirring was continued for about an hour till the IBD
was consumed (TLC) (a solid separated out in several cases). The
mixture was slowly neutralized with 1 N HCl and stirred with hex-
anes (10 mL) to remove iodobenzene. In most cases solid product
thus separated was filtered and purified by recrystallization from a
suitable solvent. In the other cases, the product was isolated by ex-
traction (5c, 9) or column chromatography (11). The products were
identified by comparing their melting points and spectral data with
those reported in literature (Table).
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Commun. 1997, 27, 2683.
4,6-Dibromo-2-benzimidazolone (15)
To an ice cold solution of anthranilamide (4a; 1g, 7.3 mmol) and
KOH (823 mg, 14.7 mmol) in MeOH (25 mL) was added Br2
(1.16 g, 7.3 mmol) dropwise and with vigorous shaking. The deep
red colored mixture was allowed to stir for 2 h. The mixture was
slowly neutralized with dil HCl to give a solid, which was filtered
and recrystallized from EtOH to give pure 15; mp >300 º C (Lit.35
mp 340 ºC).
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Acta 1960, 43, 1298.
MS: m/z = 288/290 (M+).
6-Bromo-2-benzoxazolone (16)
Following the above procedure, salicylamide (4i) was converted to
16; mp 218 220 ºC (Lit36 mp 220 ºC).
Acknowledgement
We are grateful to Ranbaxy Research Laboratory and CSIR New
Delhi, India and NIH, US under program P01 CA48112 for financi-
al assistance.
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References
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Article Identifier:
1437-210X,E;2001,0,04,0541,0543,ftx,en;M02700SS.pdf
Synthesis 2001, No. 4, 541–543 ISSN 0039-7881 © Thieme Stuttgart · New York