A clean and simple method for deprotection of phosphines from borane complexes

Simple, efficient, clean, and stereospecific protocols of protection of phosphorus atom with borane and deprotection from the borane complexes of the tertiary phosphines in mild conditions are reported. The proposed protection/deprotection reactions tolerate a range of functional groups and lead to pure products with excellent yield with no need for application of chromatographic or crystallisation purification procedures. For the first time mechanisms of the reactions of phosphine protection and deprotection have been studied based on experimental kinetic data as well as quantumchemical calculations, which allows designing reaction conditions suitable for a given substrate.

Enantioselective Synthesis and Photoreactivity of a Diazirinyl-substituted (R)-β-Phenylalanine

The first enantioselective synthesis of a photoreactive (R)-β-phenylalanine is described. In the key step, m-diazirinyl-substituted benzaldehyde is converted to a chiral sulfinimine in a Ti(OEt)4- mediated reaction, followed by diastereoselective enolate addition. The absolute configuration of photo (R)-β-phenylalanine was confirmed by Mosher analysis. The photo amino acid proved to be thermally stable under standard laboratory conditions. Irradiation in toluene afforded cycloheptatriene=norcaradiene valence tautomers, together with carbene benzylation. Quantumchemical calculations indicate a small triplet-singlet gap.

Synthesis, Structure, and Spectral Properties of Pvrylium Salts and Their Derivatives. II.5-(Benzyliden)- and 5-(Cinnamvliden)-5,6,7,8-Tetrahydro-1,3-Diphenyl-2-Benzopyrylium Salts

The synthesis, structure and spectral properties of a group of dyes with a pyrylium ring are described. Quantumchemical calculations indicate that the chromophore system has a structure corresponding to that of the polymethine dyes.

Synthesis, Structure and Spectral Properties of Pyrylium Salts and Their Derivatives. I. 5,6-Dihydro-benzo(c)xanthylium Salts

The synthesis and spectral properties of a group of xanthylium salts are described. The longest wavelength absorption maximum in organic solvents (ethanol, 1,4-dioxane, acetonitrile) is the region 17 000-20 000 cm-1, the molar absorptivity exceeding 30 000 1 • mol-1 cm-1. The fluorescence Frank Condon transition is in the region 16 000-19 000 cm-1, the fluorescence quantum yield of some of the compounds is greater than 0.9. The relation between the structure and the spectral properties of the molecules is interpreted by means of PPP-quantumchemical calculations.