142160-11-0Relevant academic research and scientific papers
Novel Syntheses and Reactions of Phosphetanium Salts with a Planar Skeleton
Brauer, David J.,Ciccu, Antonella J.,Hessler, Gisbert,Stelzer, Othmar
, p. 1987 - 1998 (2007/10/02)
Cleavage of the P-Si bond of silylphosphanes R2P-SiMe3 (R = iPr, tBu, 2,4,6-Me3C6H2) with excess 1,3-dihalogenpropanes X-3-X (X = Br, I) affords phosphetanium salts (1+)X(1-) (3) in good yields.These strained four-membered ring systems are also obtained by alkylation of secondary phosphanes R2PH with X-3-X followed by deprotonation of the intermediate phosphonium salts 3-X>(1+)X(1-) (R e.g. tBu; X = Br, 7b).Silylphosphanes and secondary phosphanes with less bulky substituents preferably form open-chain phosphonium salts with 3-X or allyl substituents in these reactions.X-ray structural analysis of (1+)I(1-) (3h) reveals planar geometries for the PC3 skeletons of the cations.The reactivity of 3b towards different types of nucleophiles has been studied.Reaction with CsF or NaNH2, leads to a stable monofluoro or monoamino phosphorane, respectively, with cyclic four-membered PC3 skeletons.In all other cases opening of the phosphetanium ring system occurs leading to derivatives with R2P-3 terminal groups.Bidentate and polydentate ligands, e.g. 19-25, with bulky substituents in terminal position have been synthesized in high yields by cleavage of 3b with mono- and bifunctional lithium phosphides.By deprotonation of 3b with MeLi the cyclic ylide 14 is formed.Treatment with acetone or benzaldehyde leads to the unsaturated open-chain phosphane oxides 15a or 15b in a Wittig-type reaction. Key Words: Phosphetanium salts / Phosphoranes
