A variety of activated unsaturated compounds, including acrylonitrile, react with Fp(ƞ1-C5H5), where Fp = (ƞ5-C5H5)Fe(CO)2, to give cycloadducts in good yield. Diethylchloroalane facilitates these cycloadditions and even methyl acrylate cycloadds ingood yield in the presence of this Lewis acid. These reactions all occur regioandstereoselectively to afford syn-7-Fp cycloadducts exclusively. The stereochemistry at(2)and C(3) is selective in some cases but not in others. Stereospecific replacement of the Fp moiety in these cycloadducts by a CO2Me group with retention of configuration occurs in good yield by oxidation with ammonium cerium(IV) nitrate in carbonmonoxide saturated methanol. This two-step sequence, cycloaddition followed by oxidation, renders Fp(ƞ1-C5H5) a synthetic equivalent of methyl 1,3-cyclopentadiene-5-carboxylate in cycloaddition reactions.
ASJC Scopus subject areas
- Organic Chemistry