Reactivity of [60]Fullerene with Primary Nitro Compounds: Addition or Catalysed Condensation to Isoxazolo[60]fullerenes

The catalysed condensation of [60]fullerene with ethyl nitroacetate (1b) or analogous activated nitro derivatives to afford isoxazolino[60]fullerenes has been achieved in both homogeneous and heterogeneous conditions. This direct synthetic approach is more convenient than previous methods. Model reactions with electron-poor dipolarophiles led to either condensation to isoxazolines or to conjugate addition products, depending on the nitro compound and catalyst. The former product was favoured by the use of CuII in the catalytic system. Conversely, [60]fullerene underwent catalytic condensation, even in the absence of copper(II) salts, only with activated nitro compounds and addition only with nitroalkanes in excess base. Note, the formal conjugated fullerene addition product was obtained in isomeric form, as previously reported. A possible explanation is presented for this contrasting behaviour.