Berl Jelena K, Czaschke Christian, Pramor Ann-Kathrin, Stark Christian B W, Thiem Joachim
Department of Chemistry, Institute for Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany.
Molecules. 2024 Oct 15;29(20):4885. doi: 10.3390/molecules29204885.
By treatment of the peracetylated methylester of 4-acetylamino-2,4-dideoxy-d-glycero-d-galacto-octonic acid (ADOA-PAE) with nitrosyl tetrafluoroborate, a serendipitous formation of a highly functionalized carbohydrate-pyrazole conjugate was observed in 95% yield. This observation is remarkable, as it involves a five-step one-pot synthesis that proceeds via an 1,3-acyl shift and a 1,5-electrocyclization, which usually requires thermal conditions; however, the reaction occurred at a temperature of 0 °C. Additionally, the excellent yield of the carbohydrate-decorated pyrazole and the regiospecificity of the cyclization are of particular interest, as regioselectivity is always a challenge in pyrazole synthesis. Subsequently, this novel access to pyrazoles starting from -acetyl-allyl amides via nitrosation and electrocyclization was investigated. In addition, mechanistic studies for the formation of substituted pyrazoles of type were carried out.
通过用四氟硼酸亚硝酰处理4-乙酰氨基-2,4-二脱氧-D-甘油-D-半乳糖辛糖酸的全乙酰化甲酯（ADOA-PAE），意外地以95%的产率得到了一种高度官能化的碳水化合物-吡唑共轭物。这一发现很引人注目，因为它涉及一个五步一锅法合成，该合成通过1,3-酰基迁移和1,5-电环化进行，而这通常需要热条件；然而，该反应在0°C的温度下发生。此外，碳水化合物修饰的吡唑的优异产率和环化的区域特异性特别令人感兴趣，因为区域选择性在吡唑合成中始终是一个挑战。随后，研究了这种从-乙酰基-烯丙基酰胺通过亚硝化和电环化制备吡唑的新方法。此外，还对类型的取代吡唑的形成进行了机理研究。
