New type of azacyclization: thermal preparation of 4,6-disubstituted 2-piperidinone from N-sulfonyldienamide and its substituent effect
作者:Yuya Maekawa、Taku Sakaguchi、Hiroshi Tsuchikawa、Shigeo Katsumura
DOI:10.1016/j.tetlet.2011.12.014
日期:2012.2
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 6 pi-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. (C) 2011 Elsevier Ltd. All rights reserved.