Escape from Flatland: Pericyclic Reactions and Rearrangements of Diazofluorene with Biarylcyclooctynes for the Generation of Helicene‐Like Phenanthro‐Pyrazoles
Year: 2025
Type: article
Abstract: Herein, the voyage of two flat, highly unsaturated systems into the third dimension is reported. Specifically, the 1,3‐dipolar cycloadditions of 9‐diazofluorene with a rapidly growing class of strained dipolarophile—biarylcyclooctynes—are investigated. It is found that the initial spirocyclic 3H‐pyrazole cycloadducts are isolable and can be subjected to controllable [1,5]‐sigmatropic shifts. These van Alphen–Hüttel rearrangements generate either the metastable 4H‐pyrazoles—another spirocyclic fused‐ring system with a highly contorted structure—or the thermodynamically favored 1H‐pyrazoles. The 1H‐pyrazoles display extended conjugation and can be classified as [5]‐helicenes containing a phenanthro‐pyrazole fused to a dihydro‐cyclooctatetraene. Overall, these studies provide a modular framework to control heteroatom placement, ring size, and ring fusion in the syntheses of carbon‐rich materials.
Authors: Atul Ojha, Eshani Das, Xinsong Lin, Brian Gold
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4410195428