Synthesis of New 1,3-Oxaphosphorinanium Salts. Stereochemistry of Hydroxide-Induced Displacement of Methoxide Ion

Abstract

[reaction: see text] The synthesis of pure cis- and trans-3-methoxy-2,2,6-trimethyl-3-phenyl-1,3-oxaphosphorinanium tetrafluoroborate salts 3a and 3b, respectively, molecules designed to evaluate the effect of oxygen on the steric course of base-induced nucleophilic displacement of the methoxy group at phosphorus, was accomplished. It was found that these isomeric salts react with aqueous sodium hydroxide to produce the corresponding phosphine oxides 7a and 7b with complete retention of configuration at phosphorus.

A computational study of axial vs. equatorial preferences of phenyl-substituted phosphorinane oxides

“…Although there is precedent for a parallel equatorial orientation of phenyl rings on P-substituted heterocycles [2], we have never before observed a parallel axial orientation.…”

“…In this work, we present theoretical calculations on conformers of cis and trans 3-oxo-2,2,6-and 3-oxo-2,2,5-trimethyl-3-phenyl-1,3-oxaphosphorinanes. These compounds have previously been synthesized and used as precursors of 1,3-oxaphosphorinanium salts in nucleophilic substitution studies by Lopez-Cortina et al [2].…”

Chiral Hypervalent, Pentacoordinated Phosphoranes

“…The detailed NMR and stereochemical studies allow rationalization of the stereochemical outcome of this reaction in terms of the addition-elimination mechanism, A-E, involving two hydroxyphosphorane intermediates 10a and 10b (that are able to undergo pseudorotation) in which at least one oxygen is apical as shown in Scheme 6 [49]. Similarly, the participation of the chiral hydridophosphorane 12 as an intermediate in the intramolecular transesterification of the 2-hydroxyphenyl phosphite 11 to the 3-hydroxypropyl phosphite 13 (Scheme 7) was supported by low temperature 31 P-NMR measurements [50].…”

“…As another example of such a transformation, hydrolysis of quasiphosphonium salts, cis-and trans-3-methoxy-2,2,6-trimethyl-3-phenyl-1,3-oxaphosphorinanium tetrafluoroborate salts 8a and 8b can be presented, by which the corresponding phosphine oxides 9a and 9b were formed with complete retention of configuration at phosphorus. The detailed NMR and stereochemical studies allow rationalization of the stereochemical outcome of this reaction in terms of the addition-elimination mechanism, A-E, involving two hydroxyphosphorane intermediates 10a and 10b (that are able to undergo pseudorotation) in which at least one oxygen is apical as shown in Scheme 6 [49]. reaction of the diastereomerically pure dioxaphospholane borane 4 with organolithium reagents which afforded phosphinite boranes 7a,b (Scheme 5) [48].…”

Cover Picture: Catalytic Molecular Logic Devices by DNAzyme Displacement (ChemBioChem 7/2014)

“…This procedure was improved to give better yields by Marsi, who obtained products 62 in 70 % yield from reactions with acetone 47. Both 1,3‐oxaphospholanes 63 48 and oxaphosphorinanes49 have recently been synthesized by this method (Scheme ).…”