Diastereoselective synthesis of C2-symmetric hexacoordinated phosphate anions (HYPHATs) with predetermined chirality from 1,2-diaryl-ethane-1,2-diols

Structure-reactivity studies on hypervalent square-pyramidal dithieno[3,2-b:2',3'-d]phospholes

A series of neutral pentacoordinate dithieno[3,2-b:2',3'-d]phosphole compounds were synthesized by [4 + 1] cycloaddition with o-quinones. Counter to the expected trigonal bipyramidal geometry, the luminescent hypervalent dithienophospholes exhibit square pyramidal geometry with inherently Lewis acidic phosphorus center that is stabilized via supramolecular π-stacking interactions in the solid state and in solution. Due to their Lewis-acid character, the compounds react with nucleophiles, suggesting their potential as mediator in organic transformations. The new species thus present an intriguing structural plaform for the design of neutral P(v) Lewis acids with useful reactivities.

2-Aminophenolate ligands for phosphorus(v): a lithium salt featuring the chiral [P(OC6H4NR)3]- anion

Phosphoranes P(OC6H4NR)2(OC6H4NHR) [R = Me (2a), Ph (2b), C6F5 (2c)] were synthesized by treating PCl5 with the respective 2-aminophenol derivative (1a-c, 3.1 equiv.). In one instance, an intermediate species, P(OC6H4NR)2Cl [R = Me (3a)], was isolated and structurally characterized. Deprotonation of the amine moieties (-NH[combining low line]R) in phosphoranes 2a and 2b with a strong alkali-metal base (e.g. n-BuLi) in the presence of a strong-donor solvent (e.g. THF) afforded salts composed of the hexacoordinate P(v)-anions [P(OC6H4NR)3]- (R = Me, [4a]-; Ph, [4b]-). Employing precursor 2a, the salt Li(THF)3fac-[4a]- was isolated. The X-ray crystal of each enantiomer of [4a]- was determined and, to our knowledge, represents the first structurally characterized example of a salt containing a hexacoordinate P(v)N3O3 anion featuring P(v)-N bonds.

Hydrogenations without hydrogen: titania photocatalyzed reductions of maleimides and aldehydes

A mild procedure for the reduction of electron-deficient alkenes and carbonyl compounds is described. UVA irradiations of substituted maleimides with dispersions of titania (Aeroxide P25) in methanol/acetonitrile (1:9) solvent under dry anoxic conditions led to hydrogenation and production of the corresponding succinimides. Aromatic and heteroaromatic aldehydes were reduced to primary alcohols in similar titania photocatalyzed reactions. A mechanism is proposed which involves two proton-coupled electron transfers to the substrates at the titania surface.

Atropisomeric Discrimination in New RuII Complexes Containing theC2-Symmetric Didentate Chiral Phenyl-1,2-bisoxazolinic Ligand

A new family of Ru(II) complexes containing the tridentate meridional 2,2':6',2''-terpyridine (trpy) ligand, a C(2)-symmetric didentate chiral oxazolinic ligand 1,2-bis[4'-alkyl-4',5'-dihydro-2'-oxazolyl]benzene (Phbox-R, R = Et or iPr), and a monodentate ligand, of general formula [Ru(Y)(trpy)(Phbox-R)](n+) (Y = Cl, H(2)O, py, MeCN, or 2-OH-py (2-hydroxypyridine)) have been prepared and thoroughly characterized. In the solid state the complexes have been characterized by IR spectroscopy and by X-ray diffraction analysis in two cases. In solution, UV/Vis, cyclic voltammetry (CV), and one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy techniques have been used. We have also performed density functional theory (DFT) calculations with these complexes to interpret and complement experimental results. The oxazolinic ligand Phbox-R exhibits free rotation along the phenyloxazoline axes. Upon coordination this rotation is restricted by an energy barrier of 26.0 kcal mol(-1) for the case of [Ru(trpy)(Phbox-iPr)(MeCN)](2+) thus preventing its potential interconversion. Furthermore due to steric effects the two atropisomers differ in energy by 5.7 kcal mol(-1) and as a consequence only one of them is obtained in the synthesis. Subtle but important structural effects occur upon changing the monodentate ligands that are detected by NMR spectroscopy in solution and interpreted by using their calculated DFT structures.