Resolution of P-Sterogenic 1-Phenylphosphin-2-en-4-one 1-Oxide into Two Enantiomers by (,)-TADDOL and Conformational Diversity of the Phosphinenone Ring and TADDOL in the Crystal State.

The resolution of racemic 1-phenylphosphin-2-en-4-one 1-oxide (), was achieved through the fractional crystallization of its diastereomeric complexes with (4,5)-(-)-2,2-dimethyl -α,α,α',α'-tetraphenyl-dioxolan-4,5-dimethanol (-TADDOL) followed by the liberation of the individual enantiomers of by flash chromatography on silica gel columns. The resolution process furnished the two enantiomers of of 99.1 and 99.

Reduction of functionalized tertiary phosphine oxides with BH3.

A direct stereoselective conversion of tertiary hydroxyalkylphosphine oxides to the corresponding tertiary hydroxyalkylphosphine-boranes involving facile reduction of the P═O bond by BH3 under mild conditions has been developed. The unprecedented facility of reduction of the strong P═O bond by BH3, a mild reducing agent, has been achieved through an intramolecular P═O···B complexation directed by proximal α- or β-hydroxy groups present in the phosphine oxide structures. As established by two chemical correlations, the developed transformation of hydroxyalkylphosphine oxides into hydroxyalkylphosphine-boranes takes place with complete inversion of configuration at P.

Structures and phase transitions in a new ferroelectric -- pyridinium chlorochromate -- studied by X-ray diffraction, DSC and dielectric methods.

Pyridinium chlorochromate, [C(5)H(5)NH](+)[ClCrO(3)](-) (hereafter referred to as PyClCrO(3)), was studied by X-ray diffraction, differential scanning calorimetry (DSC) and dielectric methods. Studies reveal three reversible phase transitions at 346, 316 and 170 K with the following phase sequence: R ̅3m (I) → R3m (II) → Cm (III) → Cc (IV), c' = 2c. PyClCrO(3) is the first pyridinium salt in which all four phases have been successfully characterized by a single-crystal X-ray diffraction method.

The neutron diffraction study, calorimetry and spontaneous polarization of pyridinium perrhenate at 350, 300 and 100 K.

The crystal and molecular structure of pyridinium perrhenate [H(5)C(5)NH](+) [ReO(4)](-) (hereafter referred to as PyReO(4)) was determined by single-crystal neutron diffraction at 350, 300 and 100 K. The neutron study confirmed the x-ray diffraction results in all three phases. The three temperature-dependent polymorphs are orthorhombic, with the following sequence of phases: Cmcm − → Cmc2(1) − → Pbca, with the a lattice parameter doubled.

Structural and dynamical aspects of the phase transition in the new thiourea thiazolium bromide inclusion compound.

A new thiourea thiazolium bromide inclusion compound is presented here. Detailed investigations of its phase transition were performed by differential scanning calorimetry, x-ray diffraction, and dielectric and nuclear magnetic resonance spectroscopy methods, completed by calculation of the steric hindrances for molecular reorientations and simulations of the second moment of the nuclear magnetic resonance line by the Monte Carlo method. A second order ferrielectric structural phase transition has been detected at 190.