A new approach to 3-nitro-2-substituted thiophenes has been developed. Exposure of commercially available 1,4-dithane-2,5-diol to nitroalkenes in the presence of 20% triethylamine results in a tandem Michael-intramolecular Henry reaction to form the corresponding tetrahydrothiophene. Subsequent microwave irradiation on acidic alumina in the presence of chloranil effects the solvent free dehydration and aromatization to form 3-nitro-2-substituted thiophenes cleanly and rapidly. A simple workup procedure removes the requirement for purification by chromatography in most cases.
Facile Synthesis of 3-Nitro-2-substituted Thiophenes -[based on a tandem Michael-intramolecular Henry reaction]. -(O'CONNOR, C. J.; ROYDHOUSE, M. D.; PRZYBYL, A. M.; WALL, M. D.; SOUTHERN*, J. M.; J.
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