Sergey E. Pipko

Peculiarities of structure and properties of phosphorus-containing cations with two intramolecular donor-acceptor bonds N→P. Synthesis of the first 5-coordinated P-cation with PN bond

cations 1a,b display dual reactivity, and they interact both with electrophilic and nucleophilic reagents. Reaction with chloramine B or benzenesulphonylazide leads to the formation of first representative of 5-coordinated P-cations with PN bond.

Phosphorus halides complexes with 4-dimethylaminopyridine and N-methylimidazole

Formation of complexes between phosphorus halides and 4-dimethylaminopyridine or N-methylimidazole was studied. The following phosphorus halides: trichloride, oxychloride, and sulfochloride, were found to form equilibrium mixtures of the complexes containing different numbers of the ligand molecules. Among the studied phosphorus halides only pentachloride and tribromide form stable complexes with a constant composition.

Dichlorothiophosphoric acid and dichlorothiophosphate anion as thionating agents in the synthesis of thioamides

A method for the thionation of carboxylic acid amides with dichlorothiophosphoric acid and dichlorothiophosphate anion, providing thioamides in high yields, was developed. The facility of the thionation and the yields of the final products were shown to depend on the nature of the starting amide. The optimal reaction conditions are reported.

Complexes of silicon and phosphorus chlorides with nitrogen-containing bases as the condensing agents in the synthesis of amides

High effectiveness of new condensing agents on the basis of complexes of silicon and phosphorus chlorides with nitrogen-containing bases in the synthesis of amides from carboxylic acids and amines and also in heterocyclization is shown. Factors affecting the readiness of formation of the amide bond and the yields of the final products are established.

Complexes of phosphorus halides with two or more coordination bonds

The review considers complexes of phosphorus as central atom with the variously dentate ligands of different topology and type of donor groups. The most stable complexes form the N-donor ligands, which are strong nucleophiles. The P-donor ligands stabilize the lower oxidation state of phosphorus. Only a few examples of complexes is known of the neutral O- and S-donor ligands. The most stable are the chelates with the ligands forming with the phosphorus atom alongside a donor-acceptor bond also a common covalent bond.

FORMATION OF PHOSPHORUS-CONTAINING SPIRO CATIONS, STABILIZED BY THREE-CENTERED N → P ← N BOND, IN THE SERIES OF PHOSPHORYLATED α-AMINOKETONES

Abstract Spiro cation stabilized by three-centered bond N → P ← N, is formed in the reaction of phosphorus trichloride with two molecules of t-BuCOCH2NMe2. According to X-ray analysis data, the structure of the compound obtained is close to a trigonal bipyramid with nitrogen atoms in axial positions (P-N 2.05 A), and two oxygen atoms and lone electron pair of phosphorus in equatorial positions.

Exocyclic P--Hlg Bond Ionization in 1,3,2-Oxazaphospholines

The x-ray and spectral data allow us to suppose the existence of equilibrium between 1,3,2-oxazaphospholines with highly polarized P Hlg bonds and their ionization products in solvents with high dielectric constant. In CDCl3 solution compounds I a–d virtually don’t display ionization signs, but iodide I d dissociates in (Me2N)3PO solution up to 80–90%. The addition of Lewis acids to the solutions of halogenides I a,b in CDCl3 leads to the shift of equilibrium toward the ionized form. Salts II a,b were isolated as pure crystals after evaporation of reaction solutions.

Frozen Friedel-Krafts Type Reaction of Phosphorus Halides with Tetraphenylborate Anion

Abstract The Friedel-Krafts type reaction of phosphorus halides are well known and widely used in organic synthesis. Usually it requires catalyst and elevated temperature and spreads on the most electrophilic phosphorus halides.