Diene-titanium complexes as synthetic intermediates for the construction of three- or five-membered carbocycles

It has been shown that diene-titanium complexes exhibit substrate-dependent 1,2- or 1,4-dicarbanion reactivity. On this basis, 3-cyclopentenylamines and spiro-vinylcyclopropane lactams were easily prepared by using homoallylic Grignard reagents, Ti(O-i-Pr)(4), and nitriles or cyanoesters, respectively.