PUB - Publikationen an der Universität Bielefeld

Bis(pentamethylcyclopentadienyl) ketone (1) reacts at low temperatures with LiAlH4 to form in good yields (pentamethylcyclopentadienyl)methanol (2) and its corresponding intramolecular Diels-Alder product 3 in a ca. 2:1 ratio. The alcohol 2 is separated from the tetracyclic compound 3 by crystallisation at -70°C from hexane/pyridine as pyridine adduct. The pyridine-free alcohol 2 is available by repeated dissolving of the adduct in hexane and removal of the volatile components in vacuo. The alcohol tends to intramolecular [4 + 2] cycloaddition even at room temperature with formation of 3. A derivatization of 2 is possible by deprotonation with alkyllithium compounds, which leads to the alcoholate 4, and subsequent treatment with phosgen and tosyl chloride, thus affording the chloroformate 6 and the tosylate 7, respectively, in good yields. The thermolabile tosylate 7 decomposes to pentamethylbenzene or, under basic conditions, to the pentacyclic compound 7.