title: Photochemical generation, intramolecular reactions, and spectroscopic detection of oxonium ylide and carbene intermediates in a crystalline ortho-(1,3-dioxolan-2-yl)-diaryldiazomethane.
abstract: Photochemical excitation of a diaryldiazomethane with an ortho-acetal both in solution and in crystals led to products that originate from the expected diarylcarbene and form an intramolecular oxonium ylide. While crystals strongly favored the formation of a benzocyclobutane by intramolecular hydrogen abstraction in the triplet carbene, reactions in benzene led exclusively to products that derive from the oxonium ylide. Studies in methyl cyclohexane glasses and in mixed crystals at 77 K led to the spectroscopic detection of triplet carbene (3)C, which partially transformed into a new species that we assign as the sought-after oxonium ylide Y. The formation of a formally ionic intermediate suggests that the scope of reactions by reactive intermediates in crystalline solids may be broader than it is generally assumed.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 405 Hilgard Ave, Los Angeles, CA, USA. mgg@chem.ucla.edu
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Garcia-Garibay
authors.forename: Hung
authors.initials: H
authors.lastname: Dang
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects*; D018360:Crystallography, X-Ray; D004148:Dioxolanes / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D008958:Models, Molecular; D015394:Molecular Structure; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; D004148:Dioxolanes; C030011:carbene; D008697:Methane