New type of azacyclization: thermal preparation of 4,6-disubstituted 2-piperidinone from N-sulfonyldienamide and its substituent effect |
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Authors: | Yuya Maekawa Taku Sakaguchi Hiroshi Tsuchikawa Shigeo Katsumura |
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Affiliation: | Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337, Japan |
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Abstract: | The thermal 6-endo cyclization of N-sulfonyl-2,4-dienamide compounds to produce 4,6-disubstituted 2-piperidinone is described. The observed remarkable substituent effect due to the N-sulfonyl and C3 ethoxycarbonyl groups for acceleration of this 6-endo cyclization strongly suggests that the reaction would proceed via the 6π-azaelectrocyclization of the intermediary imidic acid. On the contrary, the corresponding 5-formyl and 5-acetyl derivatives rapidly cyclized at room temperature to produce the 5-exo cyclized products. |
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