Novel reactions of xenon difluoride: a mechanistic and synthetic study

• Main Author: Smith, Rachel G
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-1999
• Subjects: Organic chemistry

Xenon difluoride is a versatile fluorinating agent whose power has led to its effective use in a variety of synthetic problems. However, the confusion surrounding the mechanism by which this reagent work often discourages its use, and has led to it being labelled as unpredictable. The detailed study of xenon difluorides reaction in a variety of environments, manipulating notably the solvent and vessel in which the reaction is conducted led to a greater understanding of the mechanism by which this reagent works.Two distinct modes of reaction of xenon difluoride with organic substrates are now recognised. Under protic conditions (glass vessels, hexafluorobenzene as solvent), ionization occurs and the reacting species is the electrophilic fluoroxenonium cation (FXe+). When reacted with aryltrimethylsilanes this leads to fluorodesilylation, yielding arylflourides with variable success.Under aprotic conditions (in acetontrile as solvent), xenon difluoride remains un-ionized and acts as a one-electron oxidising agent. A single electron transfer mechanism is proposed. When reacted with silyl enol ethers under these conditions -fluoroketones are produced along with ketones, and is some cases solvent derived products. Evidence that product distributions are dependent upon the stability of the radical cation intermediates is discussed.Further investigations reiterate these results and provide more evidence to support our mechanistic conclusions.