Novel Cyclization Reactions for η2-Furan Complexes

A series of complexes has been prepared of the form [Os(NH3)(5)(4,5-eta(2)-L)](2+) where L=furan and various 2-alkylated furans. Electrophilic addition to C(3) results in an unstable reaction intermediate, a 4,5-eta(2)-3H-furanium species, that leads to several novel cyclization reactions with tethered nucleophiles to form new heterocycles. (C) 2000 Elsevier Science Ltd. All rights reserved.