到4- nitrothiochroman容易访问小号,小号经由环放大-dioxides从3-硝基苯并[ b ]噻吩
摘要:
(E)-2-芳基-1- [2-(甲硫基)苯基] -1-硝基乙烯5可以很容易地氧化成相关的砜6并在用双(三甲基甲硅烷基)锂金属化后通过分子内迈克尔加成反应有效地进行环化酰胺在THF中的溶液。用氯化铵淬灭后,以非对映异构体混合物的形式获得3-芳基-4-硝基硫代苯并二氢吡喃S 2,S-二氧化物2,收率良好至优异。闭环步骤的产率和立体化学似乎都受到3-芳基部分的空间效应的影响。由于硫化物5源自3-硝基苯并[ b ]噻吩(1),整个1到2的过程可以被认为是硫杂环的5到6个环的有效扩环。还完成了对分离的非对映异构体2的构象1 H NMR和分子力学研究。
Ring opening of 2-substituted 4-nitrothiophenes with pyrrolidine. Access to new functionalized nitro-unsaturated building blocks
摘要:
The reaction conditions of the ring-opening processes of 3-nitrothiophene 7a and of 3-nitrobenzo[b]thiophene 7b with pyrrolidine and silver nitrate were optimized as well as those of the subsequent S-methylation of the ensuing silver enethiolates 8a and 8b to 4-methylthio-2-nitro-1-pyrrolidino-1,3-butadiene 9a and 1-(2-methylthiophenyl)-1-nitro-2-pyrrolidinoethylene 9b. Under such conditions 2-X-substituted 4-nitrothiophenes 7c-i consistently gave good yields of the corresponding 4-methylthio-2-nitro-1-pyrrolidino-4-X-1,3-butadienes 9c-i. The nitroenamine derivatives 9a-i were then reacted with p-tolylmagnesium bromide to furnish moderate to good yields of 4-methylthio-2-nitro-1-(p-tolyl)-4-X-1,3-butadienes 10a,c-i and 1-(2-methylthiophenyl)-1-nitro-2-(p-tolyl)ethylene 10b. Stereochemistry of the interesting building blocks 9a-i and 10a-i was assigned on the grounds of H-1 NMR data and NOE experiments. (C) 2001 Elsevier Science Ltd. All rights reserved.