Photochemical Generation of Allenylidenes from Cyclopropanated Phenanthrenes: An Experimental and Computational Study

• DOI: 10.1021/acs.joc.4c00147
• Publication Date: 2024-05-29T09:00:33Z
• Authors: Alexander D. Roth; David R. Ramgren; Yuewei Wen; Megan S. Michie; Dasan M. Thamattoor
• Keywords: Phenanthrenes

To address the scarcity of generally applicable photochemical routes to allenylidenes in solution, phenanthrene-based sources have been investigated. Specifically, syntheses 1-vinylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, 1-(2-phenylvinylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, and 1-(2-methylvinylidene)-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene, precursors propadienylidene, 3-phenylpropadienylidene, 3-methylpropadienylidene carried out. Photolysis these new olefin traps benzene afforded expected cyclopropane adducts corresponding allenylidenes. Quantum chemical calculations show that ground state all three carbenes is a singlet with singlet–triplet gap ∼29, 30, 33 kcal/mol for 3-methylpropadienylidene, respectively.