The curious case of a sterically crowded Stenhouse salt

We report a peculiar Stenhouse salt. It does not evolve into cyclopentenones upon basification, due to the steric hindrance of its bulky stable carbene patterns. This allowed for the observation and characterization of the transient open-chain neutral derivative, which was isolated as its cyclized form. The latter features an unusually long reactive C-O bond (150 pm) and a rich electrochemistry, including oxidation into an air-persistent radical cation.

Automated summary

In this study, we report a peculiar Stenhouse salt that does not undergo cyclopentenones formation upon basification due to the steric hindrance of its bulky stable carbene patterns. This unique feature allowed us to observe and characterize the transient open-chain neutral derivative, which was isolated in its cyclized form. The cyclized form exhibits an unusually long reactive C-O bond (150 pm) and demonstrates rich electrochemistry, including oxidation into an air-persistent radical cation.