Synthesis of Tri‑, Tetra‑, and Pentacarbonyl Derivatives via Ozonolysis of 1,4-Dienes and Cyclization to Polyaromatic Systems

The aim of this work was the synthesis
of polyaromatic systems
by cyclization of β-polycarbonyls. Useful synthons for β-polycarbonyl
derivatives are branched 1,4-dienes generated by cobalt-catalyzed
hydrovinylation of terminal alkenes and 2,3-dimethyl-1,3-butadiene.
Thus, a series of tri-, tetra-, and pentacarbonyl synthons was successfully
synthesized. Subsequently, these synthons were examined in an ozonolysis/cyclization
reaction sequence. Polyaromatic derivatives were obtained in good
yields and the method was applied in the synthesis of the natural
product Kwanzoquinone A.