Synthesis and Properties of Four-Membered Phosphorus Heterocycles-2-Fluoro-1,2λ⁵-Oxaphosphetanes

Abstract

The preparation of four-membered phosphorus(V)-heterocycles, 2-fluoro-1, 5 -oxaphosphetanes, by reaction of P-fluoroylides with carbonyl compounds is described. The reaction is stereoselective and leads preferentially to the formation of threo-1,2  -oxaphosphetanes. Oxaphosphetanes were isolated as individual compounds and their structures were confirmed by 1 Н, 13 C, and 31 Р NMR spectra. The fluoro-1, 5 -oxaphosphetanes may be Downloaded by [UQ Library] at 10:36 13 June 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 easily converted to various alkenylphosphonates: allyl-or vinylphosphonates. This reaction represents a good method for the preparation of phosphorylated alkenes

Synthesis, Properties and Stereochemistry of 2-Halo-1,2λ⁵-oxaphosphetanes

“…Dissociation of 2-halo-1,2λ 5 -oxaphosphetanes is enhanced by reducing the electron-accepting properties of substituents and also by increasing priority solvent. The 2-halo-1,2λ 5 -oxaphosphetanes containing electron-accepting groups at C(4) are distinctly stabler than oxaphosphetanes with alkyl groups in this position [25][26][27].…”

“…The 31 Р-NMR spectra of 2-fluoro-oxaphosphetanes 17 present doublets with 800 Hz 1 JРF constants in the high magnetic field of a NMR spectrum at −8− −37ppm. This corresponds to a pentacoordinate state of compounds 17 [24,[26][27][28][29][30][31]. Tetracoordinated forms of 2-fluoro-oxaphosphetanes 17 were not registered by 19 F-and 31 P-NMR spectroscopy (Scheme 11).…”

“…However, the presence of Me3Si at С-3 in G" leads to the elimination of Me3SiF, which has a high energy of formation, that creates a preference for the formation of vinylphosphonates 45 (Scheme 28) [26,40]. [26,40,45].…”

“…These compounds are much distinguished from unstable adducts of carbonyl compounds with triphenylphosphonium ylides. Cycloadducts of P-fluoroylides with carbonyl compounds, 2-fluoro-1,2λ 5 -oxaphosphetanes, are also much more stable than 2-chloro-or 2-bromo-1,2λ 5 -oxaphosphetanes [25][26][27][28][29][30][31]. The stability of 2-fluoro-oxaphosphetanes is explained by the high electronegativity of the fluorine atom, compared to the electronegativities of chlorine and bromine.…”

“…For example, the oxaphosphetanes obtained by reaction of silylated P-chloroylide 5 with terephthalic aldehyde depending on a ratio of initial reactants led to the formation of 1,4-bis-vinylphosphonobenzene or phosphonovinylbenzaldehyde, that represent interest as reactants for organic synthesis (See Table 6, entries 10,11) [13,[18][19][20]. The 2-fluoro-1,2λ 5 -oxaphosphetanes enter readily into a number of interesting organophosphorus compounds proceeding without Р-С bond cleavage [26]. Thus, the treatment of 2-fluorooxaphosphetanes 25 with ether solution of HCl led to the formation of 2-chlorooxaphosphetanes 40, which was isolated in good yield.…”