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

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.