Andersen Joel, Mack James
Department of Chemistry, University of Cincinnati, 404 Crosley Tower, Cincinnati, Ohio, USA.
Angew Chem Int Ed Engl. 2018 Oct 1;57(40):13062-13065. doi: 10.1002/anie.201805263. Epub 2018 Sep 5.
We provide insights into the effects of stable and verifiable, low-temperature conditions on mechanochemical reactions. These are made possible by modifications made to a SPEX 8000 m Mixer/mill allowing reliable fine control of low-temperature mechanochemical reactions. Using the reduction of 4-tert-butylcyclohexanone as a model system we find the diastereomeric product distribution bore a strong dependence on the selected temperature. The same reduction in methanol at room temperature shows similar stereoselectivity trends. In both cases decreasing temperature favors increases in selectivity, although the effect is more pronounced in the solvent-free mechanochemical conditions. These results indicate that the cooled jar provides a heatsink to mitigate the exothermic character of the reaction. Stereoselectivity also showed a dependence on operating frequency, although the nature of this dependence remains unclear. Applications of our reactor extend far beyond what is presented herein.
我们深入研究了稳定且可验证的低温条件对机械化学反应的影响。通过对SPEX 8000 m混合研磨机进行改进，实现了对低温机械化学反应的可靠精细控制，从而使这些研究成为可能。以4-叔丁基环己酮的还原反应作为模型体系，我们发现非对映体产物分布强烈依赖于所选温度。在室温下于甲醇中进行的相同还原反应显示出类似的立体选择性趋势。在这两种情况下，降低温度都有利于选择性的提高，尽管在无溶剂机械化学条件下这种效果更为明显。这些结果表明，冷却罐提供了一个热沉，以减轻反应的放热特性。立体选择性也显示出对操作频率的依赖性，尽管这种依赖性的本质尚不清楚。我们的反应器的应用范围远远超出本文所述内容。
