Kinetics and Mechanism of Pyrrolidine Buffer-Catalyzed Fulvene Formation

Rapid
synthesis of fulvenes is achieved using pyrrolidinium/pyrrolidine
buffers in anhydrous acetonitrile. Time-dependent UV–vis absorption
and NMR spectroscopy reveal that the rate and yield of fulvene formation
depend strongly on both the presence of acid in the medium and the
choice of solvent, and they are negatively affected by water. Kinetic
data have been collected for various substrates, and the synthetic
benefits of the adjusted reaction conditions are showcased. Enhancements
of reaction rates are found in comparison to literature procedures.
α-Unsaturated fulvenes that were previously difficult to access
can now be obtained in good yields.

本研究采用吡咯烷鎓/吡咯烷缓冲液（pyrrolidinium/pyrrolidine buffers）于无水乙腈（anhydrous acetonitrile）体系中，实现了富烯（fulvenes）的快速合成。通过时间依赖性紫外-可见吸收光谱（Time-dependent UV–vis absorption）与核磁共振波谱（NMR spectroscopy）表征分析，研究发现富烯的生成速率与产率显著依赖于体系内酸的存在情况及溶剂选择，且水会对反应速率与产率产生不利影响。本研究采集了多种底物的动力学数据，并展示了优化后反应条件的合成优势。相较于已有文献报道的合成方法，本方法可显著提升反应速率。此前难以获取的α-不饱和富烯（α-Unsaturated fulvenes），如今可通过本方法以优异产率制备得到。