ORGANOMETALLIC REACTION MECHANISMS. XVIII. CONCERNING THE NATURE OF THE TRANSITION STATE IN THE REACTION OF TRIALKYLALUMINUM COMPOUNDS WITH KETONES

Article abstract of DOI:10.1016/S0022-328X(00)86812-6

Et2AlCH2AlEt2 (1) has been used as a mechanistic probe to determine the nature of the transition state in the reaction of two equivalents of a trialkylaluminum compound with a ketone in hydrocarbon solvent. 1 was prepared in benzene and the solution composition determined.Low temperature 1H NMR data of 1 as the mono(diethyl etherate) indicate that the ether oxygen is simultaneously coordinated to both aluminum atoms.The reactions of 1 with 4-t-butylcyclohexanone in hydrocarbon solvent were compared to the reactions of triethylaluminium with the same ketone.The results support the importance of a bridging alkyl group described by the formation of a six-centered transition state when two equivalents of a trialkylaluminum compound are allowed to react with a ketone in hydrocarbon solvent.The results also argue against a transition state described by two moles of trialkylaluminum compound complexed to the carbonyl oxygen atom.