title: Methoxy-substituted α,n-didehydrotoluenes. Photochemical generation and polar vs diradical reactivity.
abstract: The photoreactivity of differently substituted (chloromethoxybenzyl)trimethylsilanes in alcohols and alcohol/water mixtures has been investigated by means of a combined computational and experimental approach. Subsequent elimination of the chloride anion and the trimethylsilyl cation gives the corresponding methoxy-substituted α,n-didehydrotoluenes (α,n-MeO-DHTs). The rate of desilylation is evaluated through the competition with arylation via phenyl cation (ca. 10(8) s(-1)). α,2-MeO- and α,4-MeO-DHTs show a purely radical behavior (H abstraction from the solvent, methanol), while α,3-MeO-DHT shows mainly a ionic chemistry, as when the parent α,3-DHT is thermally generated. This is likely due to triplet-singlet surfaces crossing occurring during desilylation.
authors.affiliation: Photogreen Lab, Department of Chemistry, University of Pavia , V. Le Taramelli 12, 27100 Pavia, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Raviola
authors.forename: Davide
authors.initials: D
authors.lastname: Ravelli
authors.forename: Stefano
authors.initials: S
authors.lastname: Protti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Fagnoni
mesh_terms: D005609:Free Radicals / Q000737:chemistry; D015394:Molecular Structure; D055668:Photochemical Processes; D011789:Quantum Theory; D014050:Toluene / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D014050:Toluene