Studies toward terminal (fluoroalkyl)silanes. Investigation of diethylaminosulfur trifluoride (DAST) in exchange reactions with some terminal (hydroxyalkyl)silanes

• The reaction of DAST with 2-((2-hydroxyethyl)diphenylsilyl)ethyl acetate led to the formation of the substitution product 2-((2-fluoroethyl)diphenylsilyl)ethyl acetate in considerable amount.
• Various reaction conditions were tested for reaction optimization.
• Substitution of the two phenyl groups with 2,4,6-trimethoxyphenyl groups favored exclusively the elimination route.
• Reaction of DAST with ((hydroxymethyl)diphenylsilyl)methyl acetate does not yield the corresponding fluoromethyldiphenyl silane.

Aiming at a convenient way toward the synthesis of terminal (fluoroalkyl)silanes, the effect of (diethylamino)sulfur trifluoride (DAST) on some terminal hydroxyalkylsilanes was investigated. Reaction of DAST with a substituted (hydroxyethyl)diphenylsilane led to the formation of the desired (2-fluoroethyl)diphenylsilane in considerable amounts although the competing elimination route was still the favored mechanism. This new reaction was studied under various parameters with the best conditions yielding the substitution product in a ratio of 1:4 over the undesired elimination product. In a different approach trying to optimize the outcome of the reaction, the presence of two bulky 2,4,6-trimethoxyphenyl (TMOP) groups on the silicon atom favored the elimination route.

Effect of DAST on some terminal (hydroxyalkyl)silanes.Figure optionsDownload as PowerPoint slide