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.