Spirophosphoranes

Bismuth heterocycles, 1, 539-561 Bismuthiol I metal complexes, 6, 565 IR spectra, 6, 552 ring structure, 6, 561 structure, 6, 557 Bismuthiol II metal complexes, 6, 565 IR spectra, 6, 552 Bisnorisopenicillin, 7, 332, 333 Bisnorpenicillin V, 7, 331 Bis( l,3,4-oxathiazol-2-ones) applications, 6, 945 Bisoxiranes synthesis, 7, 42 Bi(spiroisoxazolines) synthesis, 6, 108 Bi(spirophosphoranes) polytopal rearrangements, 1, 529 reactions, 1, 535 Bispyranones synthesis, 3, 793 a,oj-Bispyranones, alkylene-irradiation, 3, 678... 

To overcome this problem and obtain desired [P(aa)2(bb)] or [P(aa)(bb)(cc)] type products in high yields and to the exclusion of all others, it is necessary to consider a synthetic route that allows the sequential introduction of each of the three ligands in three different and orthogonal chemical steps. This is done by treating PX3 derivatives (X=halogens, NR2, ORf) with diols to form mono-cyclic adducts, which are in turn oxidized to bicyclic spirophosphoranes using... 

C. 1,3,2-Oxazaphospholans.—The diastereoisomeric spirophosphoranes (25) and (26) obtained from ( - )-ephedrine and trisdimethylaminophosphine are in equilibrium in benzene solution, their relative proportions varying with temperature. That this equilibration, which requires epimerization at... 

The secondary products formed in the synthesis of spirophosphoranes from trisdimethylaminophosphine and j3-amino-alcohoIs have been identified as the betaines (29), formed from the spirophosphoranes as shown. 

D. Miscellaneous.—Low yields of the spirophosphoranes (34) were obtained on heating the phosphorane (32) with the aziridines (33). Stable phosphoranes have been obtained from phenanthraquinone mono-imine (35) and trialkyl phosphites, and from 2-chlorotropone (36) and ylides. In the latter reaction cyanomethylenetriphenylphosphorane gave instead the betaine (37). 

Further investigations for the radical isomerisation of hydro-spirophosphoranes have shown that, on heating with di-t-butyl peroxide in benzene, phosphoranes (66) and (67) are transformed into (68) and (69) respectively93. The proposed mechanism, as written for (67), proceeds through the phosphoranyl radical (70) which rearranges to (71) which in turn reacts with (67) to form (69) and (70) in the propagation step. 

Several new spirophosphoranes (e.g. 82) have been derived from a further study of the reactions of phosphites (e,g. 80) with isatin (SI)46. The compounds were characterised by analysis, i.r. and 31P n.m.r. spectra and the course and rates of reaction depend substantially on the steric and electronic effects of the substituents on phosphorus. 

The spirophosphorane (115) has been found to react with triphenylphosphine by a conventional Staudinger reaction to produce (116) with the novel X5 P-N-X4P grouping 2L ray data are available for the latter51. ... 

In a related study, the reaction of (117) with (118) failed to give the expected bis-spirophosphorane (119) but instead gave an isomer (120) with two N,N1-dimethylurea bridges across a X5 P-O-X5P bond system. The product was characterised by m.s., i.r. and n.m.r. and its structure was determined by a single crystal -ray diffraction study35. 

Investigations of hypervalent phosphorus compounds have tended to concentrate on the more stable bicyclic systems. Elegant studies of spirophosphoranes and a thorough investigation of permutational isomerisations within amidinium fluorphosphates are worth noting. 

Table 4 Spirophosphoranes with carbon-bonded phosphorus...

The equilibrium interconversion between an ethylene phosphite and a bicyclic spirophosphorane is shown to proceed by the insertion of the phosphite into the labile O-H bond of the hydroxyethyl ester. The mechanism is similar to the insertion of carbenes or nitrenes. Energy relationships of reaction intermediates were studied by MO RHF, MP2(full), MP4SDTQ, and DFT calculations. In most cases, they predicted that hydroxyethyl ethylene phosphates were more stable than the strained spirophosphoranes, which is not supported by the experimental evidence. The best correspondence to experimental data was obtained by DFT calculations with Perdew-Wang correlation functions <2003JST35>. 

P nuclear magnetic resonance (NMR) spectroscopy has been of great use in determining the coordination state and stereochemistry of the phosphorus atom at the spiro position in spirophosphonia compounds, spirophosphoranes and spiroperphosporanides. The 31P chemical shift is also sensitive to the nature of the atoms directly bonded to the spiro phosphorus center and the size of rings of the spirocyclic system. 

Fragmentation of amino acid-derived spirophosphorane 128 has been analyzed using field desorption (FD), El, and Cl mass spectrometry <1997RCM1825, 1997CCL629>. In spiro-crypta cyclophosphazene derivatives 129, the major decomposition pathway involved the initial cleavage of a P-Cl bond rather than cleavage of an exocyclic P-N bond as is normally seen for cyclophosphazenes <2004JST139>. 

In the hydrolysis of neutral tricyclic hexacoordinate spirophosphorane 143 with internal N—>P dative bonds, the six-membered phosphorinane ring is retained during the first stage of hydrolysis. Five-, seven-, and eight-membered rings were preferentially hydrolysed (Equation 4) <1998POL3643>. 

Addition of triethylamine to 146 results in loss of HC1 and formation of 147 which slowly dimerizes to give bis-spirophosphorane 32 (Scheme 9) <1996PS493>. Substitution of the chloride in spirophosphorane 53 (R = C1) with pyrazole or imidazole has been reported <2006NJC717>. 

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