Method for monitoring pyridine activation by chloroformate

I am supposed to activate a pyridine using a chloroformate, and then reduce it with hydride to form a dihydropyridine, in a similar way to the paper:


Heusler, A.; Fliege, J.; Wagener, T.; Glorius, F. Substituted Dihydropyridine Synthesis by Dearomatization of Pyridines. *Angew. Chem., Int. Ed.* **2021,** *60* (25), 13793–13797. DOI: [10.1002/anie.202104115](https://doi.org/10.1002/anie.202104115).


I am wondering if there was a convenient way to monitor the activation step as it seems that my substrate is much slower to activate than the ones used in the publication.


