Long-range coupling in the proton nuclear magnetic resonance spectra of some benzothiophen and benzofuran analogues

Abstract

The ¹H n.m.r. spectra of benzo[1,2-b:4,3-b′]difuran, benzo[1,2-b:4,3-b′]dithiophens, and thieno[3,2-e]benzofuran are discussed in the light of a possible five bond long-range coupling. The photocyclisations of 1-(5-bromo-2-thienyl)-2-(2-thienyl)ethylene and 1-(5-chloro-2-thienyl)-2-(2-thienyl)ethylene gave benzo[1,2-b:4,3-b′]dithiophen and 7-chlorobenzo[1,2-b:4,3-b′]dithiophen respectively.