Guanidine Hydrochloride Catalyzed, Rapid and Efficient One-Pot Synthesis of Naphthoxazinones Under Solvent-Free Conditio
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GUANIDINE HYDROCHLORIDE CATALYZED, RAPID AND EFFICIENT ONE-POT SYNTHESIS OF NAPHTHOXAZINONES UNDER SOLVENT-FREE CONDITIONS A. Olyaei1*, M. Sadeghpour2, and M. Zarnegar1 A novel method for the synthesis of 1-aryl-1,2-dihydro-3H-naphtho[1,2-e][1,3]oxazin-3-one derivatives employing one-pot three-component reaction of β-naphthol, aromatic aldehydes, and urea using a catalytic amount of guanidine hydrochloride under solvent-free thermal conditions is described. This method provides several advantages like clean and environmentally benign reaction, simple work-up procedure, low cost, easy product separation without need of further purification with column chromatography, shorter reaction times, and high yields. Keywords: aldehyde, guanidine hydrochloride, naphthol, naphthoxazinone, solvent-free reaction. Aromatic condensed oxazinone derivatives have received considerable attention due to the attractive pharmacological properties associated with their heterocyclic scaffold, such as herpes virus protease inhibition [1] and antimicrobial activity [2]. Despite their high potential, there are only few reports that describe the synthesis of naphthalene-condensed oxazinone derivatives. Recently, some syntheses of naphthalene-condensed 1,3-oxazin-3-one derivatives have been reported using condensation of aminoalkylnaphthols as precursors with phosgene in the presence of triethylamine [3]. Condensation of naphthol with aldehydes and urea for the synthesis of naphthoxazinones has been explored using different catalysts such as copper nanoparticles in PEG-400 [4], silica-supported perchloric acid [5], phosphomolybdic acid [6], pTSA [7], I2 [8], acetic acid [9], TMSCl/NaI [10], and zinc triflate [11]. However, in these methods, either expensive reagents are required or the reagents used are highly toxic and hazardous. Therefore, the development of new, simple, green one-pot methods for the synthesis of naphthoxazinone derivatives is of prime importance. Organocatalysts have been used widely in many reactions as mono- and bifunctional catalysts due to economic and environmental considerations. Among many organocatalysts, hydrogen-bonding compounds such as guanidine derivatives are becoming powerful tools for activation of the carbonyl functionality in organic transformations. Recently, guanidinium salts have been successfully employed as novel chiral phase-transfer catalyst in the conjugate addition of nitroalkanes with enones [12]. Moreover, these organocatalysts provide an
_______ *To whom correspondence should be addressed, e-mail: [email protected]. 1
Payame Noor University, PO BOX 19395-3697, Tehran. Islamic Azad University, PO BOX 19585-466, Takestan, Iran; е-mail: [email protected]. _________________________________________________________________________________________
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Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1474-1478, September, 2013. Original article submitted August 17, 2012. 1374
0009-3122/13/4909-1374©2013 Springer Science+Business Media New York
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