BF3-induced rearrangement of aziridino cyclopropanes derived from 2-phenylsulfonyl 1,3-dienes.: Application to the total synthesis of (±)-ferruginine

Total synthesis of the alkaloid(+/-)-ferruginine (I) has been developed via the 2-phenylsulfonyl 1,3-diene approach. BF3-induced-rearrangement of the N-protected cyclohexane aziridino cyclopropane 8, derived from its corresponding epoxy cyclopropane, afforded the desired tropane alkaloid skeleton 9 in good yield. Michael addition of nitroethane (as an acyl anion equivalent) and transformation of the nitro group of the adduct 10 to a keto function gave 11. Elimination of benzenesulfinic acid and subsequent replacement of the tosyl group by a methyl group afforded the title compound 1.