Photochemical reactions of nitrile compounds. Part 2. Photochemistry of an α,β-unsaturated γ,δ-epoxy nitrile and an γ,δ-cyclopropyl nitrile
Direct irradiation (λ 254 nm) of the α,β-unsaturated γ,δ-epoxy nitrile(1) led selectively to the products (13)–(19) arising from a carbonyl ylide or a carbene intermediate. However, products of an (E/Z)isomerization and a transformation via C(γ)–O bond cleavage of the oxirane, which are triplet processes, were not observed. On singlet excitation (λ 254 nm), the α,β-unsaturated γ,δ-cyclopropyl nitrile (4) afforded (38) as the main product along with (39) whereas, on triplet excitation of (4)(E/Z)-isomerization was the main process observed. Acid-catalysed rearrangements of compounds (1) and (8) were also studied.