Photochemical reactions of an αβ-unsaturated nitro compound

Abstract

(E)-2-Nitro-1-(9-phenanthryl)prop-1-ene on irradiation in solution undergoes geometric isomerisation to the Z-isomer (ϕ_E→Z 0.50), and also yields small amounts of phenanthrene-9-carbaldehyde. No other products are detected at low conversions to the Z-isomer. The Z-isomer behaves differently and yields 2-methylphenanthro-[9,10-b]furan and phenanthrene-9-carbaldehyde, the former being formed from an excited singlet state of the Z-isomer and the latter from an excited triplet state. Flash photolysis and low temperature n.m.r. studies demonstate the presence of a photochromic transient formed from the Z-isomer and the probable structure of this transient is suggested.