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Preparation of N-(2-alkoxyvinyl)sulfonamides from N-tosyl-1,2,3-triazoles and Subsequent Conversion to Substituted Phthalans and Phenethylamines
Published on: January 3, 2018
Synthesis of 2-phenyl-4,5-substituted oxazoles by copper-catalyzed intramolecular cyclization of functionalized
S Vijay Kumar1, B Saraiah, N C Misra
1New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore-560064, Karnataka, India.
Abstract:
An efficient two-step synthesis of 2-phenyl-4,5-substituted oxazoles involving intramolecular copper-catalyzed cyclization of highly functionalized novel β-(methylthio)enamides as the key step has been reported. These enamides are obtained by nucleophilic ring-opening of newly synthesized 4-[(methylthio)hetero(aryl)methylene]-2-phenyl-5-oxazolone precursors by alkoxides, amines, amino acid esters and aryl/alkyl Grignard reagents, thus leading to the introduction of an ester, N-substituted carboxamide or acyl functionalities at 4-position of the product oxazoles. Synthesis of two naturally occurring 2,5-diaryloxazoles, i.e., texamine and uguenenazole, via two-step hydrolysis-decarboxylation of the corresponding 2,5-diaryloxazole-4-carboxylates has also been described. Similarly, three of the serine-derived oxazole-4-carboxamides were elaborated to novel trisubstituted 4,2'-bisoxazoles through DAST/DBU-mediated cyclodehydration-dehydrohalogenation sequence. The present protocol is complementary and an improvement to our previously reported silver carbonate-induced cyclization of β-bis(methylthio)enamides to 2-phenyl-5-(methylthio)-4-substituted oxazoles.
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