Preparation and electron transfer-induced cis-trans isomerization reactions of 1-(5-nitro-2-furyl)-, 1-(5-nitro-2-thienyl)-, and 1-(4-nitrophenyl)-2-R ethylenes

Abstract

Mixtures of E- and Z-isomers of 1,2-bis(5-nitro-2-furyl)ethylene (I), 1-(5-nitro-2-furyl)-2-(4-nitrophenyl)ethylene (II), 1,2-bis(4-nitrophenyl)ethylene (III), 1-(5-methoxycarbonyl-2-furyl)-2-(4-nitrophenyl)ethylene (IV), 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-furyl)ethylene (V) and 1-(5-methoxycarbonyl-2-furyl)-2-(5-nitro-2-thienyl)ethylene (VI) were prepared by the Wittig reaction. These derivatives were isomerized by electron transfer-induced reactions via the radical anion in the CT-complex using aniline as electron donor at 25 °C in the light or at 80 °C in the dark. The starting as well as the final E:Z ratio was determined by 1H NMR spectroscopy. In all cases only the cis → trans isomerization was observed.