Sh. Koo et Ls. Liebeskind, GENERAL SYNTHETIC ENTRY TO HIGHLY-OXYGENATED, ANGULARLY-FUSED POLYCYCLIC AROMATIC-COMPOUNDS, Journal of the American Chemical Society, 117(12), 1995, pp. 3389-3404
A convergent and efficient synthesis of highly-oxygenated, angularly-f
used polycyclic aromatic compounds has been developed. Nucleophilic ad
dition of [4-(tri-n-butylstannyl)phenyl]lithium to a 3,4-disubstituted
-cyclobutene-1,2-dione followed by appropriate protection of the hydro
xyl group and thermal rearrangement of the O-protected addition produc
t generated a xygenated-2,3-disubstituted-6-(tri-n-butylstannyl) napht
halene. Stille coupling of the 6-(tri-n-butylstannyl)naphthalene with
a 4-chloro-2,3-disubstituted-2-cyclobutenone and thermolysis of the co
upled product gave highly-oxygenated phenanthrenes. An isomeric series
of compounds was generated from [3-(tri-n-butylstannyl)phenyl]lithium
. Substituted phenanthrenes at higher overall levels of oxygenation we
re prepared by (1) thermolysis of the adduct obtained by addition of a
lithiated naphthalene, generated by Sn --> Li exchange from a 1,4-dio
xygenated-2,3-disubstituted-6-(tri to a cyclobutenedione or (2) thermo
lysis of the double adducts generated by reaction of 2 equiv of a cycl
obutenedione with either 1,4-dilithiobenzene or 1,3 dilithiobenzene. P
henanthrenes at lower levels of oxygenation were prepared by the palla
dium-catalyzed cross-coupling/thermolysis of 2 equivalents of a 4-chlo
rocyclobutenone with either 1,4-bis(tri-n-butylstannyl)benzene or 1,3-
bis(tri-n-butylstannyl)benzene.