ION-CYCLOTRON RESONANCE STUDIES OF ALKYLSILYL IONS .2. REACTIONS OF KETONES, CARBOXYLIC-ACIDS AND ESTERS WITH THE TRIMETHYLSILYL CATION

Nucleophilic attack of a ketone, carboxylic acid or ester at the electrophilic centre of the trimethylsilyl cation (Me3Si+) produces a 1:1 adduct. This adduct does not decompose in the case of ketones. Acid adducts decompose primarily by loss of methane, but a minor pathway exists which involves elimination of a ketene. Ester adducts fragment primarily by this latter process through a four- membered transition state. The transfer of hydrogen was shown to arise solely from the acyl group and was shown to proceed with a small deuterium isotope effect. Further decomposition of the resulting ion by loss of methane provides unequivocal proof that esters react predominantly through the alkyl oxygen with the Lewis acid Me3Si +. © 1979, CSIRO. All rights reserved.