Chemo-, Regio- and Stereoselective Tricyclohexylphosphine-Catalyzed [3+2] Cycloaddition of Enynes with [60]Fullerene Initiated by 1,4-Michael Addition: Synthesis of Cyclopenteno[60]fullerenes and their Electrochemical Properties

Abstract

Herein we demonstrate a tricyclohexylphosphine-catalyzed cycloaddition of (E)- or (Z)-alkyl 5-substituted phenylpent-2-en-4-ynoates with [60]fullerene to give cyclopentenofullerenes in good to excellent yields, through initial chemo- and regioselective 1,4-addition of phosphines at the -carbon of the enyne substrates. The nucleophilic addition pattern of P(cHx)(3) is found to be different from that of Gilman or Grignard reagents toward the studied enynes. The resulting cyclopentenofullerenes, characterized with spectrometric methods and single crystal X-ray diffraction analysis, exhibit comparable or higher LUMO energy levels than a typical n-type material, [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM).