K. Takahashi et al., SYNTHESIS AND STRUCTURE OF A BIFURAN-CONTAINING P-QUATERPHENOQUINONE - AN UNUSUAL O-CIS 2,2'-BIFURAN CONFORMATION IN THE CRYSTALLINE STATE, Tetrahedron letters, 36(44), 1995, pp. 8055-8058
cyclohexadien-1-ylidene)-5,5'-dihydro-2,2'-bifuran has been synthesize
d. This heteroquaterphenoquinone has been proved to exist in an unusua
l O-cis bifuran conformation in the solid state by X-ray crystallograp
hy.