Ewa Krawczyk

Studies on the interaction of phosphine selenides and their structural analogues wth dihalogens and sulfuryl chloride

The phosphine selenides, tris(dimethylamino)phosphine selenide, esters of selenophosphoric acid, and esters of selenophosphonic acid react with dihalogens and sulfuryl chloride to form halogenoselenophosphonium salts (P–SeX)+X−. The latter undergo deselenization via ligand exchange to form phosphonium salts (P–X)+X− and elemental selenium. The stability of these salts depends on the substituents at the phosphorus atom and the type of counter ion. It is likely that the phosphonium salts are in equilibrium with the corresponding phosphoranes, and this is demonstrated for esters containing an o-phenylene ligand. The structures of phosphonium salts, phosphoranes and other phosphorus compounds are supported by 31P NMR spectroscopy data and electrical conductivity. Additional evidence comes from addition reactions of halogenoselenophosphonium salts to cyclohexene.

Stereospecific [2,3] sigmatropic rearrangement of allylic sulfoxides and selenoxides. Synthesis of novel polycyclic allylic alcohols and α-hydroxy ketones

Abstract A stereospecific [2,3] sigmatropic rearrangement of functionalized bi- or tricyclic allylic sulfoxides and selenoxides as a route to new allylic alcohols and their transformation into the corresponding α-hydroxy ketones having a defined stereochemistry is described. It has been demonstrated that cycloadducts, derived from [4+2] cycloaddition of (Z)-1-alkylthio-2-diethoxyphosphoryloxy-1,3-dienes to a various dienophiles, are versatile synthons carrying much structural and stereochemical information.

Reaction of Tricoordinate Phosphorus Compounds with Pseudohalogens. Scope and Mechanism

Abstract The selectivity of sulphur, selenium and oxygen removal from pseudohalogens: phosphorus disulphides 1 and 2, diselenides 3 and oxophosphoranesulphenyl chlorides 4 has been investigated. A mechanistic rationalization is proposed to account for sulphur (selenium)/oxygen extrusion variation as a function of substrates structure and reaction conditions.

The Diels-Alder Reactions of (Z)-1,2-Diheterosubstituted-1,3-Dienes. Sulfur as a Regiochemical Control

Abstract Thermal and Lewis acid catalysed cycloadditions of dienes 1 to dienophiles proceed with complete regio-and stereo-selectivity and provide a route to the cyclic enones.

Synthesis of (z)-1,2-diheterosubstituted-1,3-dienes. novel annelating agents

Abstract Readily available thiophosphates containing an α,β-unsaturated moiety have been efficiently converted into the novel (Z)-1,2-diheterosubstituted-1,3-dienes by treatment with sodium hydride followed by the corresponding electrophile

An expedient, stereoselective synthesis of highly functionalized cyclic compounds

New thiophosphates containing functionalized cyclic ketone derivatives as ligands have been stereoselectively prepared from readily available starting materials. Full axial stereoselectivity of the NaBH4 reduction of the carbonyl group in thiophosphates providing the corresponding thiols or sulfides has been demonstrated. The sulfides have been transformed into new functionalized cyclic Baylis–Hillman type adducts of defined configuration. The prospects for the useful synthetic application of these adducts appear to be very promising.

The Reactions of Phosphorus Selenonoesters, > P(Se)OR, with Halogens. New Five-Co-Ordinate and Phosphonium Intermediates Containing P-Se Bond

Abstract As a continuation of our investigation on the chemistry of thiono- and selenonophosphorus acid esters, the reactions of phosphoroselenoates with various halogens were studied (1). Depending on the structure of selenonophosphoryl compound and on the nature of halogen these reactions involve the formation of different type of intermediates like:

Reaction of diphosphoryl diselenides with dialkyltrimethylsilyl phosphites: a new route to symmetrical monoselenopyrophosphates

Abstract A novel efficient synthesis of sym-monoselenopyrophosphates 3 based on the reaction of diphosphoryl diselenides 1 with dialkyltrimethylsilyl phosphites 2 is described.

Reaction of three-coordinate phosphorus compounds with organophosphorus pseudohalogens 3. Phosphonium and phosphorane intermediates in the desulfurization and deoxygenation of bis(phosphinoyl) disulfides. Influence of Lewis acids on the reaction chemoselectivity

The reactions of bis(phosphinoyl) disulfides RR1P(O)S–S–P(O)RR11 with PIII compounds have been investigated and various mechanistic features have been elucidated by variable-temperature 31P NMR spectroscopy. These studies show that in most cases phosphonium intermediates [[graphic omitted]P(O)–S–[graphic omitted]–O–P(S)[graphic omitted]]5 and [[graphic omitted]P(S)–O–[graphic omitted] –O–P(S)[graphic omitted]]6 are involved. In cases where ligands on PIII increase the stability of the five-coordinate structures phosphorane intermediates are observed. In the isomerization 5→6, the mode of decomposition (desulfurization, deoxygenation or dealkylation) to give stable end products is influenced by electronic and steric factors. The presence of the Lewis acid BF3 influences considerably the stability of the transient species 5 and 6 and the chemoselectivity of the reaction.

A NEW SYNTHESIS OF BIS-PHOSPHORYL DISULFIDES[(RO)2 P(O)S]2

Abstract Bis-phosphoryl disulfides 2 are synthesized in excellent yields from the phosphorothiorates 5 by means of half equimolar amounts of sulfuryl chloride. In the case of cyclic diastereoisomeric phosphorothioates derivatives of 4-methyl-1,3,2-dioxaphosphorinan, the pronounced kinetic preference of exocyclic axial sulfur atoms towards disulfides bond formation have been demonstrated.