Acceleration of the pseudorotation rates in pentacoordinated phosphorus compounds. Conformational transmission versus hexacoordinated zwitterionic intermediates

Abstract

A variable-temperature 13C NMR study, accompanied by a high-resolution NMR conformational analysis study, on a series of monocyclic oxyphosphoranes is reported. The selected compounds enabled us to study the acceleration of the rates of intramolecular ligand reorganization on pentacoordinated phosphorus. It allowed us to determine whether the enhancement of the reorganization rates was brought about by accelerated pseudorotation due to the conformational transmission effect or by the involvement of hexacoordinated zwitterionic phosphorus intermediates. The results of the study further substantiate the findings that the involvement of such hexacoordinated intermediates is of no importance in the type of oxyphosphoranes studied.

Synthesis of Heterocyclic Pentavalent Phosphorus Compounds from Phosphite Derivatives and Indane-1,2,3-Trione

“…8 However, application of indane-1,2,3-trione 2 in the synthesis of heterocyclic pentavalent phosphorus compounds has not been reported. As part of our ongoing program to develop efficient and robust methods for the preparation of heterocyclic compounds, 31-60 we sought to develop a convenient preparation of heterocyclic pentavalent phosphorus compounds 4 from trialkylphosphite derivatives 1 and indane-1,2,3-trione 2 in fairly good yields under neutral conditions (Scheme 1).…”

“…However, a possible explanation is it is reasonable to assume that nucleophilic addition of 1 to indane-1,2,3-trione 2 followed by a cyclization reaction can generate the corresponding heterocyclic pentavalent phosphorus compounds 4 (Scheme 1). 8 The structures of the products 4a-c were deduced from their IR, 1 H NMR, and 13 C NMR spectra. The mass spectra of these compounds displayed molecular ion peaks at the appropriate m/z values.…”

“…4 During last few decades, a dramatic increase in research activity of the chemistry of pentavalent [P(V)] phosphorus compounds (phosphorans) has taken place. 8 This has led to a more thorough understanding of the features that determine the stability and the ligand reorganization within such molecules. Nucleophilic attack on one of the alkoxy ligands followed by ring opening leads to the formation of the products.…”

“…However, ring opening might precede the alkyl transfer, generating the isomeric phosphonium ion. 8 In general, several methods are available for the synthesis of oxyphosphoranes. The reaction of dialkyl peroxides with phosphites in aprotic media at room temperature affords a general synthesis of oxyphosphoranes.…”

“…4 From both the theoretical and X-ray crystallographic analyses of several P(V) structures, it could be established that the trigonal bipyramid (TBP) is the most stable configuration for acyclic and monocyclic P(V) compounds. 8 These days, phosphorus chemistry forms an important discipline in element chemistry. 5 Heterocyclic phosphorus chemistry is a dynamically developing field 5 including, among other aspects, the chemistry of P-ligands 2-5 and fragmentation-related phosphorylations.…”