Intermolecular and Intramolecular Diels−Alder Cycloadditions of 3-Ylidenepiperazine-2,5-diones and 5-Acyloxy-2(1<i>H</i>)-pyrazinones
作者:Shangde Jin、Pablo Wessig、Jürgen Liebscher
DOI:10.1021/jo0100897
日期:2001.6.1
Diels-Alder reactions of alkenes and alkynes to the piperazine ring, under acidic conditions or in the presence of acetyl chloride, to afford tricyclic piperazine-2,5-diones 19, 20, 23-25, 27, 44, and 45. Intramolecular cycloadditions occur if 3-ylidenepiperazine-2,5-diones 30 and 32 are used as the starting materials. This procedure is a convenient path to bridged bicyclo[2.2.2]diazaoctane ring systems such
Treatment of 3-alkylidene or 3-benzylidene-2,5-piperazinediones 6 with catalytic amounts of acid gives rise to the formation of isomers 7 by migration of the CC bond into the alkyl substituent at position 6, or results in mixtures of racemic 7 and E isomers 8. The existence of tautomeric equilibria is discussed.
用催化量的酸处理 3-亚烷基或 3-亚苄基-2,5-哌嗪二酮 6,通过 CC 键迁移到 6 位的烷基取代基中形成异构体 7,或导致外消旋体 7 的混合物和 E 异构体 8. 讨论了互变异构平衡的存在。