Reactions of Perfluoroalkyl Halides RfX with Ph2P-, Me3Si-, and Me3Sn- Ions

JOSE ALBERTO POSTIGO; A ROSSI, ROBERTO

Toronto

Congreso; Organometallic Chemistry Applied to Organic Synthesis, OMCOS XII.; 2003

The reactions of Me3M- ions (M = Si, Ge, Sn) with perfluoroalkyl halides have not been investigated.  As far as we are concerned, there is no report in the literature on these reactions, or the synthesis of RfGeMe3.  However, RfI (perfluoroalkyl iodides) are able to undergo a variety of nucleophilic substitutions by ET mechanisms with different other nucleophiles, to afford perfluoroalkyl-substituted compounds[i],[ii]. SRN1 substitution is a facile way to obtain them, since RfI are quite unreactive toward classical (polar) nucleophilic substitutions, due to the high electronegativity of fluorine and the resulting destabilization of the carbocation (in SN1 reactions), and the repulsion of the lone electron pairs toward rear attack of the RfI by the nucleophile in an SN2 fashion. We commenced the study by allowing RfI to react with Ph2P- ions in HMPA, as these ions show similar reactivity as Me3Sn- ions toward aromatic electrophiles, and obtanied high yields of the corresponding Ph2PRf  compounds. [iii] These reactions proceed in a facile way by ET mechanism. We then subjected Me3Si- ions to react with RfCl under photostimulation in highly coordinating solvents such as HMPA or DMPU, and obtained the corresponding perfluoroalkylsilane RfSiMe3 compounds in high yields.  This work explores the product and mechanistic studies involving Me3Si- ions, a seies of perfluoroalkyl chlorides, and coordinating solvents, under photostimulation. [i] Chen, Q.Y. Isr.J.Chem. 39, 179-192, 1999. [ii] Postigo, A; Rossi, R.A. Current Organic Chemistry, 7(8),  747-769, 2003. [iii] Vaillard, S.E.; Postigo, A.; Rossi, R.A. Organometallics, 23(12), 3003-3007, 2004