Irradiation of norbornene and silver or thallium trifluoromethanesulfonate in acetonitrile solution results in the efficient formation of exo-2-(cyanomethyl)bicyclo[2.2.1]heptane. Investigation of the scope of this reaction established that (a) copper(I or II) salts are not effective, (b) propionitrile and methanol give analogous norbornene-solvent adducts, and (c) acetonitrile addition is observed for several cyclic and acyclic olefins. Investigation of the mechanism of solvent addition indicates that the reaction is initiated by photoinduced electron transfer to silver(I) from coordinated norbornene. Reaction of the resulting norbornene cation radical with acetonitrile yields norbornyl cation and cyanomethyl radical. Free-radical chain addition of the cyanomethyl radical to norbornene then leads to product formation. In ethereal solvents, metal ion catalyzed photodimerization of norbornene has previously been reported for copper(I) salts. This reaction can also be effected by copper(II) and silver(I) salts, but not by Tl(I) salts.
ASJC Scopus subject areas
- Colloid and Surface Chemistry