1,3-DIPOLAR CYCLOADDITION TO ETA)-2-METHOXY-5-METHYLENECYCLOHEXA-1,3-DIENE]IRON - RAPID CONSTRUCTION OF A SPIRO[4.5]DECANE SYSTEM

ta)-2-methoxy-5-methyl-enecyclohexa-1,3-diene]iron (1) undergoes 1,3-d ipolar cycloaddition reaction regio-, stereo-, and chemoselectively at its exocyclic double bond, yielding a spiro[4.5]-decane system. React ive 1,3-dipoles with low-lying LUMO's such as nitrile oxides, ozone, d iazoacetate, and oxoallyl cation participate well in cycloaddition to give isoxazole, ketone, pyrazoline, and cyclopentanone adducts, respec tively. The complex 1 can be viewed as the synthetic equivalent of syn thon 2 and has been illustrated for the first time as a versatile synt hetic intermediate.