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DOI: 10.1055/s-0028-1087886
Synthesis of Imidazoles and Oxazoles by Aldimine Cross-Coupling
Contributor(s):Victor Snieckus, Josefine KarlssonJohannes Gutenberg-Universität Mainz and Universität Hamburg, Germany
Modular Synthesis of Tetrasubstituted Imidazoles and Trisubstituted Oxazoles by Aldimine Cross-Coupling
Chem. Eur. J. 2009, 15: 843-845
Publication History
Publication Date:
23 March 2009 (online)
Key words
imidazoles - oxazoles - aldimines - cross-coupling
Significance
Reported here are the syntheses of tetrasubstituted imidazoles and trisubstituted oxazoles in one or two steps from α-acylamino-imines 5 which are readily obtained by 1,2-addition of N-monosubstituted α-aminonitriles 1 to N-acylimines 2. The intermediates 3 are subjected to the next DBU-catalyzed step without purification to give imidazoles 4 and intermediates 5; the cyclization directly to 4 is promoted by bulky substituents in the 5-position. The intermediates 5 are converted into oxazoles 6 in simple steps and purification is then achieved by column chromatography.
Comment
Imidazoles are an important class of heterocycles due to their extensive use in chemistry and technology, and their presence as partial structures in many natural products (L. De Luca Curr. Med. Chem. 2006, 13, 1). In the present report, imidazoles and oxazoles are prepared in modest to good yields from easily synthesized starting materials. In comparison to known methodologies for these rings systems (S. Kamijo, Y. Yamamoto Chem. Asian J. 2007, 2, 568), the described procedures are fairly easy and provide a comparable method. A limitation is the need to use 1 with R² = aromatic substituent to avoid the retro-Strecker reaction. Only three examples of oxazole 6 are described.