The Behaviour of a Dialuminoxane and Distannoxanes towards Organic Molecules

Abstract

The concept of the combined acid-base attack is exemplified by the behaviour of organoaluminium amides towards trisubstituted oxiranes, which are converted into allylic alcohols. The coordination of the reagent on the oxirane oxygen occurs in a fast equilibrium, whereas the nitrogen lone pair thus activated abstracts a proton from the ∝-carbon on the same side as the ring hydrogen, and the nucleophilic attack is rate-and product-determining. Furthermore, the above concept is extended to the reaction of neryl diethyl phosphate with (ⁱBu₂Al) ₂O, which involves the intermediary ion-pair containing neryl cation and phosphate-dialuminoxane complex anion. The extensively delocalized negative charge in the anion complex leaves a nearly naked neryl carbocation behind, the cyclization of which is followed by deprotonation. The latter stage of nucleophilic attack is again the real rate and product-determining step. The concept of the combined acid-base attack is exemplified by the behaviour of organoaluminium amides towards trisubstituted oxiranes, which are converted into allylic alcohols. The coordination of the reagent on the oxirane oxygen occurs in a fast equilibrium, whereas the nitrogen lone pair thus activated abstracts a proton from the oc-carbon on the same side as the ring hydrogen, and the nucleophilic attack is rate-and product-determining. Furthermore, the above concept is extended to the reaction of neryl diethyl phosphate with (ⁱBu₂Al)20, which involves the intermediary ion-pair containing neryl cation and phosphate-dialuminoxane complex anion. The extensively delocalized negative charge in the anion complex leaves a nearly naked neryl carbocation behind, the cyclization of which is followed by deprotonation. The latter stage of nucleophilic attack is again the real rate- and product-determining step.