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The long-sought pathway by which selenocysteyl-tRNA[Ser]Sec is synthesized in eukaryotes has been revealed. Seryl-tRNA[Ser]Sec is O-phosphorylated and SecS, a pyridoxal phosphate-dependent protein, catalyzes the reaction of O-phosphoseryl-tRNA[Ser]Sec with monoselenophosphate to give selenocysteyl-tRNA[Ser]Sec . 1 H- 77 Se HMQC-TOCSY NMR spectroscopy has been developed to detect the selenium-containing amino acids present in selenized yeast after protease XIV digestion. An archived selenized yeast sample is found to contain the novel amino acid S-(methylseleno)cysteine in addition to selenomethionine. Arsenite and selenite react with GSH to form (GS) 2 AsSe−. The structure of this compound has been determined by EXAFS, 77 Se NMR and Raman spectroscopic and chromatographic studies. Its formation under biological conditions has been demonstrated.

Thermal and Lewis acid catalyzed cycloadditions of (Z)-1,2-diheterosubstituted-1,3-dienes to a variety of dienophiles are described. Both endo/exo and regioselectivity have been investigated. In all cases cycloaddition reactions exhibited full regio- and endo-stereoselectivity. The obtained cycloadducts are new polycyclic allylic sulfides carrying much structural and stereochemical informations. Work on transformation of the adducts, mainly to the corresponding new 1,3-dienes and aromatic compounds, is also presented.

New important organic compounds multifunctionalized cyclic 6-membered and 7-membered allylic amines, azide and phosphonates have been obtained via regio- and diastereoselective reactions of cyclic Baylis–Hillman type adducts 1 with N-nucleophiles and P-nucleophile. We have found that the reactions proceed by SN2 or SN2′ processes exclusively, or by both processes simultaneously. The SN2′ process occurs with anti stereochemistry.

The reaction of chlorophosphanes with azazirconacyclopentenes provides an unique way to cyclic P-metalated trans-iminodiphosphanes, which rearrange to give unprecedented N-metalated cis-iminodiphosphanes. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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.

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.

A new way of M−Cl bond activation (M = Si, P, Au fragments) is reported. It consists on the 1,2-addition of M−Cl containing species on the Zr−N bond of azazirconaindene complexes. Unprecedented imino gold complexes incorporating two electron-deficient metallic centers (Au, Zr) have been prepared.

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.

The azazirconacyclopentene-substituted phosphines 3 and 4 have been found to activate the C-H bonds of acetylenic systems, such as methylpropiolate, diphenylphosphinoacetylene and phenylacetylene, or of methylene compounds, such as malonitrile and diethylmalonate, to give complexes 5a-c, 6a and 6b. C-H bond activation also takes place with vinylacetate. Similar reactions with amines, alcohols, enolisable ketones, phenols, phosphonates, thiols and a second-generation SH-terminated dendrimer lead through X-H bond activation (X = N, O, P, S) to new complexes 8a-c, 9, 12 a,b, 13, 14a-c, 15, 16a and 16b. The azazirconacyclopentene-substituted amine 20 reacts to form analogous complexes. Zr-X bonds of these complexes (X = C, N, O, S) can be cleaved with diphenylchlorophosphine to give P-X phosphorus derivatives in high yield.

Polycyclic zwitterionic complexes that incorporate one or two phosphonium unit(s) as cationic center(s) and zirconocene-ate moiety(ies) as the anionic counterpart(s) can be easily prepared by either [1+3] or [1+3] and [2+3] cycloadditions which involve bi- or tricyclic alpha-zirconated phosphanes 3 or 4 and various azides. Some of these species exhibit unprecedented phosphazide chelation with bonding between the zirconium and a nitrogen atom in the alpha position relative to phosphorus. When heated, the phosphazide complexes lose dinitrogen to form stable polycyclic zwitterionic phosphonium mono- or dinuclear complexes. The solid-state structure of the two zwitterionic complexes 5 and 8 was determined by X-ray crystallography.

The reaction of bis(phosphinoyl) diselenides R1R2P(O)Se–SeP(O)R1R21 with P(III) compounds has been investigated and its mechanistic features have been elucidated by variable temperature 31P NMR spectroscopy. These studies show that in most cases phosphonium intermediates 7, 13 and 10, 16 are involved. In the case when ligands on P(III) increase the stability of the five-coordinate structure, a phosphorane intermediate is observed. In the isomerization 7→10 and 13→16 the pathway of decomposition (deselenization, deoxygenation or dealkylation) to give stable end products is influenced by electronic and steric factors.

A series of new unstable tris(bidentate) hexacoordinated phosphorus compounds 1 with 1,3,2-dioxaphosphorinane rings was prepared and studied by NMR and X-ray crystallography. The X-ray crystal structures showed that the 1,3,2-dioxaphosphorinane ring adopts different conformations depending on the number and size of substituents at the carbon atom C14. Substituents are deployed around the phosphorus atom in a slightly deformed octahedral structure. Deviations in bond lengths around the phosphorus atom depend on the character of the bonds and the distribution of the negative charge. (1)H and (13)C NMR measurements showed that in solution the flexibility of 1,3,2-dioxaphosphorinane ring depends on the size of substituents at the carbon C14.

Phosphinozirconocene complexes react with isocyanides to give unprecedented bi- or tricyclic β-phosphino imines through three successive and controlled steps. Spectroscopic and chemical evidence for the formation of the first neutral η1-imine zirconocene complexes in the reductive elimination reaction sequence is presented.

The reaction of α-zirconated phosphorus compounds 6 and 10 with methyl propiolate or dimethylacetylene dicarboxylate gives rise to stable zwitterionic zirconocene-ate complexes 7, 8 , 11 and 12 in which the zirconium atom is linked exclusively to carbon atoms.

Bis[6-O,6′-O-(1,2∶3,4-diisopropylidene-α-D-galactopyranosyl)thiophosphoryl] disulfide 1 (C48H76O24P2S4) crystallized from polar and/or nonpolar solvents forms different inclusion complexes and solvates. The X-ray data for complexes of 1 with propan-2-ol (1a) and acetone (1b) are reported. From DSC measurements it is apparent that with loss of the solvent, crystals undergo complex rearrangements below the melting point forming the 1c modification. Each form is characterized by 31P CP/MAS experiment. The analysis of the 31P δii principal elements of the chemical shift tensor suggests that distinction of δ33 for different modifications is related to O–H· · ·SP and C–H· · ·SP intermolecular contacts. 2H NMR spectroscopy is employed to investigate the mechanism of phase reorientation and molecular dynamics of methyls of the isopropylidene blocking groups. At ambient temperature, the C3v jump of the methyl group and additional small-amplitude motion of the five membered ring is deduced from line-shape analysis of a 2H QUADECHO experiment. During the change of sample composition at 370 K, fast molecular motion of the methyl groups is observed while the SP–S–S–PS backbone remains rigid. From variable temperature 2H T1 inversion–recovery measurements it is concluded that the Ea of the C3v jump strongly depends on molecular packing.

Interactions between zirconocene or benzyne zirconocene and unsaturated species incorporating main group elements lead to a variety of new metallaheterocycles. Efficient new methodologies of regiospecific syntheses of mono-, bi-, or tricyclic systems incorporating phosphorus, nitrogen, selenium, antimony, germanium or tin are reported.

Selective reductions of PO, PS, >CC

Hydrozirconation by means of [Cp2ZrHCl]n (2) of phospholene PhPCH2CHCHCH2 (1) leads to the β-zirconated phospholane 3 which reacts with phosphenium salts R2P+OSO2CF3- (4, R = NiPr2; 5, R = NCy2) to give unsaturated acyclic 1,1-diphosphines 6 or 7. Compound 3 also reacts with other electrophiles like [CH2NMe2]Cl, tBuCOCl, or HOSO2CF3 leading to unsaturated phosphines PhP(R)(CH2)2CHCH2, 8 (R = CH2NMe2), 9 (R = C(O)tBu), or 10 (R = H), respectively. Hydrozirconation of 2,5-dihydrofuran (12) or 2,3-dihydrofuran (13) affords the acyclic zirconated species Cp2Zr(Cl)O(CH2)2CHCH2 (15), which reacts with 4, Ph2PCl, [CH2NMe2]Cl, PhCOCl, or HOSO2CF3 to give, via exchange reactions, the corresponding substituted olefines 16−20. Treatment of 12 or 13 with 2 equiv of 2 leads to dizirconated compound Cp2Zr(Cl)O(CH2)4Zr(Cl)Cp2 (21) which reacts with Ph2PCl (2 equiv) to give the phosphino−phosphinite Ph2PO(CH2)4PPh2 (22) isolated as its disulfide 23. 2-Methyl-4,5-dihydrofuran (24) treated first with 2 equiv of 2 and then ...

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

The structural investigation of the phosphoroorganic selenium-containing title compound C10H20O6P2Se (1) was carried out. The structure of 1 has been determined by X-ray analysis and correlated with the solid state NMR studies, its purity and identity was confirmed by elemental analysis. The following crystal data were found: triclinic, P1, a = 5.6557(6) A, b = 10.2717(8) A, c = 13.761(1) A, α = 105.580(7)β, p = 90.992(7)°, γ = 101.745(8)°, and Z = 2. Two six-membered rings in the molecule of 1 are in the chair conformation. The selenium atom which bridges the rings is situated axially with respect to both rings. The exocyclic oxygens are, consequently, in equatorial positions.

31 P principal elements of chemical shift tensors δii for a series of hexacoordinate organophosphorus compounds have been obtained from spinning sideband intensities employing the MASNMR program based on a graphical method of Berger and Herzfeld. It was found that anisotropy parameters Δδ and span Ω reflect the distortion of the molecular structure from the ideal octahedral geometry. The asymmetry parameter η and skew κ suggest that the phosphorus shielding depends not only on the local bonding, but also on the octahedral structure as a whole. Comparison of isotropic chemical shifts in solution and in solids revealed that in both phases the molecular structures are not changed. Moreover, this work shows that for PVI moieties with unknown X-ray structure, crucial information regarding the geometry can be obtained from solid-state NMR data and a molecular modelling approach.

The reaction of readily available dialkyltrimethylsilyl phosphites (RO)2POSiMe3 5 with sulfur dichloride leads to tetra-alkyl sym-monothio-pyrophosphates (RO)2P(O)SP(O)(OR)2 1 in high yield. The method is suitable for the synthesis of tetra t-butyl thiopyrophosphate 1d.

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 convenient synthesis of dieneynes 1 is described. Our strategy involves reaction of readily available thiophosphates with sodium acetylides, in which new single and double carbon–carbon bonds are formed.

Stereoselective synthesis of a number of various olefins including functionalized unsaturated compounds based on the S-(β-oxoalkyl) thiophosphates and Se-(β-oxoalkyl) selenophosphates is described.

Reaction between oxophosphoranesulfenyl chloride 1(R = R′= EtO) and o-phenylene neopentyl phosphite 4 takes predominantly the deoxygenation course, yielding the phosphorochloridothioate 7 and the phosphate 8. Formation of minor products 5 and 6 corresponding to the desulfurization pathway, and low-temperature 31P NMR observations, are rationalized by proposing phosphoranephosphonium equilibria which are shifted towards phosphorane structures 9, 13, 11. These results supplement our earlier studies on desulfurization and deoxygenation of compound 1 with tricoordinate phosphorus compounds and add new evidence for phosphonium–phosphorane equilibria.

Stereoselective synthesis of a number of various olefins including functionalized unsaturated compounds based on the S-(β-oxoalkyl) thiophosphates and Se-(β-oxoalkyl) selenophosphates is described.

A general synthesis of a new class of compounds Se-(β-oxoalkyl) O,O-dialkyl selenophosphates based on selenophosphorylation of silyl enol ethers with a chloroselenotrialkoxyphosphonium chlorosulfide is described

Thioxaphosphoranesulfenyl bromide 1 reacts with various aliphatic alkenes to give the corresponding adducts 3. These species can be reacted with tetrabutylammonium fluoride trihydrate (TBAF·3H2O) at room temperature to give the episulfides 4 in satisfactory yield. The great affinity of fluoride to phosphorus is claimed to be the driving force in the formation of the s-bromo thiolate ion 6 which gives ring closure.

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

A one-pot regioselective synthesis of tricyclic 1,1-diphosphines involving, first, insertion reaction of 2,3-dihydrophosphole (3) into the zirconium−carbon bond of a generated in situ zirconocene benzyne and, then, an exchange reaction between the resulting tricyclic metalated phosphine 4 and various dichlorophosphines is reported. One of these 1,1-diphosphines, 15a (bis(sulfide) adduct), is characterized by single-crystal X-ray diffraction studies.

Selective reductions of PO, PS, >CC

Interactions between zirconocene or benzyne zirconocene and unsaturated species incorporating main group elements lead to a variety of new metallaheterocycles. Efficient new methodologies of regiospecific syntheses of mono-, bi-, or tricyclic systems incorporating phosphorus, nitrogen, selenium, antimony, germanium or tin are reported.