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Synlett 2005(5): 0761-0764  
DOI: 10.1055/s-2005-863706
LETTER
© Georg Thieme Verlag Stuttgart · New York

Oxidation of Urazoles with 1,3-Dihalo-5,5-dimethylhydantoin, both in Solution and under Solvent-Free Conditions

Mohammad Ali Zolfigol*a, Hossein Nasr-Isfahanib, Shadpour Mallakpourc, Maliheh Safaieea
a Chemistry Department, College of Science, Bu-Ali Sina University, Hamadan, 65174, Iran
e-Mail: zolfi@basu.ac.ir;
b College of Chemistry, Shahrood University of Technology, Shahrood, Iran
c Organic Polymer Chemistry Research Laboratory, College of Chemistry, Isfahan University of Technology, Isfahan, 84156, Iran
Further Information

Publication History

Received 23 August 2004
Publication Date:
09 March 2005 (online)

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Abstract

1,3-dichloro-5,5-dimethylhydantoin (DCH) and 1,3-dibromo-5,5-dimethylhydantoin (DBH) were used as effective oxidizing agents for the oxidation of urazoles and bis-urazoles to their corresponding triazolinediones under mild conditions at room ­temperature with good to excellent yields.

Key words

1,3-dichloro-5,5-dimethylhydantoin (DCH) - 1,3-dibromo-5,5-dimethylhydantoin (DBH) - urazoles - bis-urazoles - ­triazolinediones

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Chemicals were purchased from Fluka, Merck, Riedel-De Haen AG and Aldrich chemical companies. Yields refer to isolated pure products. The oxidation products were characterized by comparison of their spectral (IR, UV, 1H NMR, and 13C NMR) and physical data with authentic samples. Silica sulfuric acid (III) was prepared according to our previously reported procedure. [35] All urazoles and bis-urazoles were also synthesized according to our previously reported procedures. [1] [4] [5]

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Oxidation of 4-Chlorophenyl Urazole ( 1g) to 4-Chloro-phenyl-1,2,4-triazoline-3,5-dione ( 2g) with DBH. A Typical Procedure.
A mixture of compound 1g (0.212 g, 1 mmol) and DBH (0.286 g, 1 mmol) in CH2Cl2 (15 mL) was stirred at r.t. for 2 h. Silica sulfuric acid (0.5 g) was added to the reaction mixture and stirred for 15 min. Then the reaction mixture was filtered and the CH2Cl2 removed to give a red crystalline solid 2g (0.205 g, 92% yield), mp 132-135 °C [lit. [3] mp 130-132 °C]. These compounds are sensitive to the light, heat, alcohols, ethers, transition metals and some nucleophiles. Also they are very volatile so that, if the temperature rises over 50 °C in the course of removing CH2Cl2, some of TADs are lost with solvent.