Neuartige spiroverbindungen durch addition von maleinimiden an schiff-basen

Zusammenfassung Mixtures of a Schiff base prepared from an aromatic or heterocyclic aldehyde and an aliphatic amine. and a N-substituted maleimide, on heating in a solvent such as acetic acid. xylene or butanol give 1:2-adducts. Their spectroscopic properties can only be reconciled with the new ring system spiro-pyrrolidin-1,2-(pyrrolidino[3.4- c ]pyrrolidin) and not with a newly formed 6-membered ring as described for adducts of Schiff bases with other dipolarophiles. In some cases isomeric products were isolated. Their stereochemistry is discussed based on NMR data. Reduction of the adducts with LAH in boiling dioxan gives the oxygen-free spiro heterocycles.