Guoxiong Hua

Synthesis and Structure of Eight‐, Nine‐, and Ten‐Membered Rings with P‐Se‐Se‐P Linkages

Organoselenium compounds are studied because of their interesting reactivities and potential biological or pharmaceutical significance. Organic diselenides, as useful synthetic reagents and intermediates, have played an important role in organoselenium chemistry, as they are stable, easily handled, and reactive enough to generate electrophilic, nucleophilic, and radiophilic species. There are only a few examples of macrocycles containing diselenide linkages, and many of the known routes to diselenides in general suffer from the use of highly toxic H2Se, harsh reaction conditions, low yields, or complicated manipulations. We are developing the chemistry of 2,4bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide [PhP(Se)(m-Se)]2 (known as Woollins) reagent, WR). Herein, we report the synthesis of five novel P Se diselenides with eight-, nineand ten-membered rings; this is the first reported synthesis of such large-ring diselenides bearing the P-Se-Se-P linkage. Cleavage of the four-membered P2Se2 ring in WR by alkyl diols affords the corresponding bis(diselenophosphonic) acids quantitatively as yellow oils. These acids were converted into the corresponding amine salts by treatment with butylamine and were oxidized using I2/KI to give eight-, nineand tenmembered-ring diselenides 1–3 (70–90% yields, Scheme 1). Compounds 1–3 are soluble in common polar organic solvents and were crystallized from dichloromethane solutions with slow diffusion of hexane to give transparent, colorless, cubic crystals. The compounds are stable to air and moisture for several months. The P NMR spectra of 1–3 exhibit sharp singlets at d 67 ppm, which are accompanied by two sets of satellites for the endocyclic and exocyclic selenium atoms (J(P,Seendo) and J(P,Seexo): 444 and 822 Hz for 1, 465 and 812 Hz for 2, and 460 and 808 Hz for 3), thus indicating the presence of single and double P Se bonds in each compound. Detailed NMR spectroscopic analysis reveals the relatively small coupling constant between phosphorus atoms (J(P,P)= 3.0–4.7 Hz), supporting the presence of the P-Se-Se-P group (cf. J(P,P)= 4 Hz for the analogous P-S-S-P system). The Se NMR spectra for 1–3 contain signals arising from exocyclic (d = 75, 61, and 80 ppm; J(P,Seexo)= 822, 810, and 806 Hz, respectively) and endocyclic selenium atoms (d = 491, 441, and 441 ppm). The X-ray structures of 1–3 (Figure 1) confirm the presence of the eight-, nine-, and ten-membered rings. Both R,R and S,S enantiomers are present in all the structures, and no R,S/S,R diastereomers are observed. The macrocyclic framework is highly puckered with the two phenyl rings on opposite sides of the heterocycle. The Se Se bond (2.3393(12), 2.3518(7), and 2.3475(6) A in 1–3, respectively) is slightly shorter than that in acyclic structures containing the P-Se-Se-P linkage (2.384(1) A). The geometry around P(1) and P(2) is distorted tetrahedral (Se(1)-P(1)-Se(2) and Se(3)-P(2)Se(4): 103.94(9) and 105.25(9), 105.49(6) and 105.76(6), 103.94(9) and 106.04(5)8 for 1–3, respectively). Heating equimolar amounts of aromatic diol and WR at reflux in toluene for 15 h affords, after workup in air, diselenides 4 and 5 as white crystals in 61% and 65% yields (Scheme 2). 4 and 5 are soluble in organic solvents, are airstable, and display the expected NMR spectra. The X-ray structures of 4 and 5 (Figure 2) are similar to the structures of 1–3, although the P(1)-Se-Se angles (106.83(4), 107.27(4)8 for 4 and 106.22(5), 108.18(5)8 for 5) are larger than in 1–3. Since the Se Se bond is labile and can be broken easily, studies to use these P Se heterocyclic diselenides as multidonor ligands and as synthetic precursors are now underway.

The X-Ray Crystal Structures of Primary Aryl Substituted Selenoamides

The X-ray structures of 12 primary selenoamides are reported. Metric parameters are provided, together with an illustration of the range of hydrogen bonding motifs.

Novel non-aqueous Fe(III)/Fe(II) redox couple for the catalytic oxidation of hydrogen sulfide to sulfur by air

A series of Fe(III) salts and organic solvents have been screened to develop novel non-aqueous catalysts for the conversion of H2S to sulfur. FeCl3/95% N-methylpyrrolidinone/5% H2O was found to be a most efficient non-aqueous system. The process chemistry, the proposed mechanism of catalytic oxidation of H2S, and the electrochemistry are discussed.

One-Pot Three-Component Condensation Synthesis and Structural Features of Organophosphorus–Sulfur Macrocycles

A new preparative route was developed to synthesize new phosphorus-sulfur [SP(═S)S moiety]-containing macrocycles via a one-pot and three-component domino reaction of four-membered ring thionation reagents such as 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide (LR, Lawessons reagent) and 2,4-diferrocenyl-1,3,2,4-diathiadiphosphetane 2,4-disulfide (FcLR, a ferrocene analogue of Lawessons reagent) and alkyldithiols(aryldithols) and dihaloalkanes in the presence of sodium hydride. Therefore, a series of 12- to 18-membered macrocycles incorporating two phosphorus and six sulfur atoms were synthesized. The synthesis features a novel application of the multicomponent reaction, providing an efficient route to the preparation of the new phosphorus-sulfur-containing macrocycles. Seven representative X-ray structures confirm the formation of these macrocycles and show the presence of a number of the intramolecular C-H···S hydrogen bonding, intermolecular C-H···S, C-H···Cl, and Cl···Cl short contacts and π-stacking interactions in their 3D network structures.

5-Benzyl-idene-2,3-diphenyl-1,2-selenaphosphole-2-selenide.

The title compound, C(23)H(19)PSe(2), has a central five-membered twist C(3)PSe ring conformation. One phenyl ring substituent, attached to an sp(2) carbon, is approximately coplanar with the C(3)PSe ring whilst the other organic substituents, attached to an sp(3)-carbon and a P(V) atom, lie on the same side of the ring.

1,5,6-Triphenyl-8-oxa-7-selena-6-phos­phabicyclo­[3.2.1]octane-6-selone

The structure of the title compound, C23H21OPSe2, consists of fused puckered five- and six-membered rings, PSeC2O and C5O, respectively, with a C2O bridgehead. The C5O ring adopts a chair conformation, whilst the C2PSeO ring has an envelope conformation.

Improvement of the Fe-NTA Sulfur Recovery System by the Addition of a Hydroxyl Radical Scavenger

The degradation of Nitrilotriacetic Acid (NTA), which results from the oxidation of hydroxyl radicals formed in the process, is a major deficiency in the present Fe-NTA system for the oxidation of hydrogen sulfide to sulfur by air. The degradation of NTA can be slowed down considerably by the addition of a hydroxyl radical scavenger. In this study, a series of inorganic and organic materials was tested as scavengers/inhibitors of hydroxyl radicals in attempts to improve the Fe-NTA system. The results showed that N-methylpyrrolidinone and ethylene glycol could be used as potentially powerful scavengers of hydroxyl radicals to improve the Fe-NTA system.

Novel aqueous chelating agents for catalytic oxidation of hydrogen sulfide to sulfur by air

Six phosphorus-containing analogues of nitrilotriacetic acid (NTA) or ethylenedinitrilotetraacetic acid (EDTA) form stable Fe(III) complexes which have been tested as catalysts for the oxidation of hydrogen sulfide. Ligand 4, phosphonomethyliminodiacetic acid (NTAP), was found to be comparable with NTA in efficiency of catalytic activity such as the conversion of hydrogen sulfide to sulfur, half-life of ligand, consumption of ligand per kg of sulfur product. A quantitative analytical method of phosphorus-containing ligand in the absorbed solution has been successfully established by applying 31P-{1H} NMR.

Synthesis and coordination chemistry of aminophosphine derivatives of adenineElectronic supplementary information (ESI) available: Preparation of all compounds apart from L1 and complex 11; Tables S1?S8: NMR spectral data of all the compounds. See http://www.rsc.org/suppdata/dt/b3/b303715k

Two aminophosphine derivatives of adenine N9-(N2′-diphenylphosphinoaminoethyl)adenine L1 and N9-(N2′-diphenylphosphino-N2′-n-propylaminoethyl)adenine L2 were synthesized. Oxidation of L1 and L2 with H2O2, elemental sulfur or elemental selenium led to the corresponding oxidized products 5–10. Both L1 and L2 behave as monodentate ligands towards late transition metals. Reaction of compound L1 or L2 with [AuCl(tht)], [{RhCl(μ-Cl)(η5-C5Me5)}2], [{IrCl(μ-Cl)(η5-C5Me5)}2], [{Rh(μ-Cl)(cod)}2], [{RuCl(μ-Cl)(η3:η3-C10H16)}2] and [{RuCl(μ-Cl)(p-MeC6H4iPr)}2] gave the corresponding “dangling” monodentate complexes 11–20, leaving the adenine ring free for complementary hydrogen bonding. Interaction of L1 and L2 with [MX2(cod)] (M = Pt; X = Cl, Me) in 2 : 1 molar ratio also gave monodentate complexes 21 and 22. All compounds have been fully characterized by microanalysis, IR, 31P-{1H} NMR, 1H NMR and EI/CI/FAB MS spectroscopies. 1H-{31P} NMR, 1H–1H-COSY or 1H–13C correlation experiments were used to confirm the spectral assignments. Four compounds were structurally characterized by crystallographic X-ray analysis.

Synthesis and characterization of novel organic heteroatom compounds from reaction of Woollins’ Reagent with various organic substrates

GRAPHICAL ABSTRACT ABSTRACT A series of new selenium-containing heteroatom compounds were synthesized in good yields by the reaction of Woollins’ reagent with various organic substrates such as cyclohexylamine, N-benzoylbenzamide, benzoic anhydride, 4-fluoro-N-(2-oxo-2-phenylethyl)benzamide, N-benzoylbenzamide, benzoic anhydride, 3-(bromomethyl)benzonitrile, 1,2-diphenylethane-1,2-diol, and sodium alcoholate. Three representative X-ray structures are described.