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Aspects of the chemistry of phosphoranes.

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posted on 19.11.2015, 08:48 by Robin Egerton Lowry. Waddling
A review of the structure, bonding and pseudorotations of spirophosphoranes is presented. The use of N-chlorodiisopropylamine as a reagent for preparing spirophosphoranes was developed to include the use of amine and thiol groupings. Pseudorotations of the resulting unsymmetrical spirophosphoranes were examined and ?G* values obtained. This reaction is thought to proceed via a concerted process. Phosphoranes were also prepared by the enolisation of ?-hydroxyketones and benzhydrazide. The oxidising properties of N-chlorodlisopropylamine were used in a low temperature generation of diimide from hydrazine. A review of the chemistry of hydroxyphosphoranes is presented. The isomerie phosphates derived from o-phenylene phosphorochloridate and styrene glycol was reinvestigated and their interconversion interpreted in terms of pseudorotations of the tautomeric hydroxyphosphorane oxyanions. Other ester-hydroxyphosphorane equilibria were examined. The eclipsing action of the methyl groups in the pinacol ester displaces the equilibrium in favour of the ester. Azoxaphospholans derived from N-(2-hydroxyethyl) ethanamide were prepared and ?G* for rotation about the N-ethanoyl bond determined. Pseudorotations of corresponding hexafluoroacetone adducts in which the N-ethanoyl group is placed equatorially have unusually low ?G* values. This is interpreted in terms of a lowering of electron density on the nitrogen atom by the carbonyl group. The hydrolysis of o-phenylene phosphorochloridte, bis-o-phenylene pyrophosphate and biscatecholhydridophosphorane are thought to involve the highly reactive o-phenylene phosphite. The synthesis of phospholans and spirophosphoranes derived from meso-butane-2,3-diol is described. These compounds could not be obtained by hydrogenation of biacetyl adducts as hydrogenolysis occurred. Substitution of the chlorine atom in the o-chloranil adduct of the chlorophospholan was followed by low temperature 31P.F.T nmr. Reaction with lithim dimethylamide and dimethylamine proceeds with a predominance of inversion of configuration about phosphorus. Sodium with a predominance of inversion of configuration about phosphorus. Sodium phenoxide and phenol/triethylamine give a near equimolar set of isomers that are able to equilibrate via hexacoordinate species. With sodium 2,6-dimethylphenoxide this equilibration is much slower due to the steric compression required in the hexacoordinate species.


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University of Leicester

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