A novel two-step access to polysubstituted pyrroles from nitroalkenes was developed. It involves [4+2]-cycloaddition with enol ethers to give six-membered cyclic nitronates followed by reductive ring contraction with Ra-Ni/AcOH or Ra-Ni/EtOH systems. The process is applicable to a variety of nitroalkenes and enol ethers bearing electron-rich and electron-poor substituents and functional groups. The anti-inflammatory drug Bimetopyrol and its structural modifications were successfully synthesized by the strategy developed. The key side products were identified that provided an insight into the mechanism of the developed reductive ring contraction to pyrroles.

中文翻译：

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通过[4+2]-环加成/还原环收缩策略从硝基烯烃中获得多取代的NH吡咯


开发了一种从硝基烯烃制备多取代吡咯的新型两步法。它涉及与烯醇醚的[4+2]-环加成反应生成六元环状硝基化合物，然后与 Ra-Ni/AcOH 或 Ra-Ni/EtOH 系统进行还原环收缩。该方法适用于多种带有富电子和贫电子取代基和官能团的硝基烯烃和烯醇醚。通过所开发的策略成功合成了抗炎药物Bimetopyrol及其结构修饰。确定了关键的副产物，从而深入了解所开发的还原环收缩为吡咯的机制。