Synthesis of tricarbonylcyclobuta[I]phenanthreneiron

Abstract

1,2-Dichloro-1,2,2a,10b-tetrahydrocyclobuta[I]phenanthrene (II) was prepared both by photocycloaddition of phenanthrene to trans-dichloroethylene and by dichlorobisdecarboxylation of the 1,2-dicarboxylic acid (III) derived by hydrolysis of the photoadduct of phenanthrene with dimethyl maleate. Reaction of the dichloride (II) with N-bromosuccinimide, followed by chromatography on alumina, gave 1,2-dichloro-1,2-dihydrocyclobuta-[I]phenanthrene (IV). Treatment of the product (IV) with enneacarbonyldi-iron afforded tricarbonylcyclobuta-[I]phenanthreneiron (V). Oxidative decomposition of compound (V) with cerium(IV) ion in the presence of cyclopentadiene gave the endo-adduct (VI).