New Approaches to the Preparation of Phosphanes Containing P-Rfn Bonds. Reactivity of RfnI

MARIO N. LANTERI; SANDRA E. MARTÍN

Los Cocos, Córdoba. Argentina.

Congreso; 9th Latin American Conference on Physical Organic Chemistry (CLAFQO9); 2007

NEW APPROACHES TO THE PREPARATION OF PHOSPHANES CONTAINING P-Rfn BONDS. REACTIVITY OF RfnI   Mario N. Lanteri and Sandra E. Martín   Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba. Ciudad Universitaria. 5000 Córdoba-Argentina. E-mail: mlanteri@mail.fcq.unc.edu.ar          Organofluorine compounds are well-known for displaying unique reactivities and selectivities. Both, the high electronegativities and the apolarity of prefluoroorganyl groups give special properties of solubility and a strong electron withdrawing effect to phosphane ligands. Our work focused on the development of strategies to obtain phosphanes with perfluoroalkyl groups (Rfn). Herein, we report our results of two methods. One approach is based on the Pd-catalyzed cross-coupling reaction with RfnI as electrophiles, and the other is the photochemical reaction of the “P3-” ion with RfnI.      Recently, we have described the Pd-catalyzed cross-coupling reaction of the stannane n-Bu3SnSePh with perfluoroalkyl iodides.1 To extend the applications of this methodology; we have studied the cross-coupling reaction of the phosphorus stannane n-Bu3SnPPh2 (1). The stannane 1 was synthesized by the reaction of the Ph2P- anion with n-Bu3SnCl. Afterwards, the Pd-catalyzed cross-coupling reaction of 1 with RfnI was carried out, all in a one-pot procedure. After oxidation, the reaction afforded the bisphenylperfluoroalkyl phosphane oxide Ph2P(O)Rfn (5-48%)(eq. 1).            We evaluated the effect of different additives (CsF and CuI), ligands (Ph3P, Ph3As, (o-tol)3P, (o-furyl)3P), solvents and catalysts to establish the optimal conditions for the coupling reaction and to explain the reactivity in the catalyzed reaction of these particularly electrophiles, RfnI.      On the other hand, it is known that elemental phosphorus reacts with sodium in liquid ammonia to produce “P3-” ion which could act as nucleophile. With aryl halides under irradiation the corresponding symmetrical triarylphosphanes were obtained.2 Similarly, this ion could be used to react with RfnI to obtain triperfluoroalkylphosphanes P(Rfn)3, compounds of interest as a tunable alternative  to the carbon monoxide ligand. We have studied the overtaking of the formation of “P3-” and the photochemical reaction of this anion with RfnI to obtain the phosphanes P(Rfn)3. After oxidation, we have found only 10-20% of the product P(O)(Rfn)3. Different aspects of the reaction were explored to account for the reactivity of the “P3-” ion and the RfnI. [1] Bonaterra, M.; Martín, S. E. and Rossi, R. A. Tetrahedron Lett. 2006, 47, 3511-3515. 2 Bornancini, E. R.; Alonso, R. A. and Rossi, R. A. J. Organomet. Chem. 1984, 270, 177-183.