Reaction of secondary phosphine chalcogenides with diallylamine

Diphenyl- or bis(2-phenylethyl)phosphine sulfides and -phosphine selenides react with diallylamine under radical initiation (UV or AIBN) to afford the corresponding diadducts and tetrahydropyrrolylmethyl phosphine chalcogenides. The yield and the ratio of the products depend on the structure of the starting secondary phosphine chalcogenides.     

Reaction of divinyl selenide with secondary phosphine chalcogenides

Under the conditions of free-radical initiation (AIBN, UV irradiation), divinyl selenide regioselectively reacts with secondary phosphine sulfides and phosphine selenides to afford, depending on the ratio of the reagents, mono- or diadducts mainly of the anti-Markownikoff structure. The conditions which allow obtaining the diadducts in up to 97% yield are found. By the example of 2-{[2-(diphenethylphosphoroselenoyl) ethyl]selanyl}ethyl(diphenethyl)phosphine selenide the diadducts were shown to react with aqueous hydrogen peroxide at 53–56°C to give vinyl(diphenethyl)phosphine oxide in 76% yield.     

Reaction of secondary phosphine chalcogenides with 2,2,2-trichloroacetaldehyde

The nucleophilic addition of secondary phosphine chalcogenides to 2,2,2-trichloroacetaldehyde proceeds under mild noncatalytic conditions (12–25dgC, 15–90 min) with the formation of functional tertiary phosphine chalcogenides, containing hydroxy groups in up to 98% yield. Using the method of concurrent reactions the reactivity of secondary phosphine chalcogenides in this reaction was shown to decrease in the order: (PhCH₂CH₂)₂P(O)H ≫ (PhCH₂CH₂)₂P(S)H > (PhCH₂CH₂)₂P(Se)H, and the secondary bis[2-(2-pyridyl) ethyl]-phosphine oxide was more reactive than bis(2-phenethyl)phosphine oxide.     

Reaction of divinyl telluride with secondary phosphine chalcogenides

Divinyl telluride reacted with 2 equiv of diphenylphosphine sulfide in the presence of AIBN as radical initiator (63–68°C) to give the corresponding anti-Markovnikov adduct in 68% yield with high regioselectivity. Treatment of the addition product with aqueous hydrogen peroxide at room temperature afforded 71% of vinyldiphenylphosphine oxide. Radical addition of diphenylphosphine selenide to divinyl telluride (AIBN, 63–68°C) led to the formation of 1,1,3,3-tetraphenyldiphosphoxane 1,3-diselenide in 82% yield.     

Michael-type addition of secondary phosphine oxides to (1,4-cyclohexadien-3-yl)phosphine oxides

Base-induced reaction between (1,4-cyclohexadien-3-yl)phosphine oxides and secondary phosphine oxides gives 3,4-bis(phosphinoyl)cyclohexenes and 2,3-bis(phosphinoyl)cyclohexenes through an in situ isomerization of one of the cyclohexadienyl double bonds and a subsequent Michael-type addition of the secondary phosphine oxide.     

Microemulsions with alkyldimethyl phosphine oxides and alkyldiethyl phosphine oxides

Alkyldimethyl phosphine oxides (C n DMPO) as well as alkyldiethyl phosphine oxides (C n DEPO) with chain lengths of n = 10 (decyl), 12 (dodecyl), and 14 (tetradecyl) were synthesized and purified to study how the formation of microemulsions depends on the size of the headgroup and on the length of the alkyl chain. For that purpose, equal amounts of water and n-octane were taken and surfactant was added to solubilize the two solvents. The resulting fish-shaped phase diagrams for C 10DEPO, C 12DEPO, and C 14DEPO show that the longer the hydrophobic chain the more efficient the surfactant. Simultaneously, the extension of the lamellar phase (L alpha) shifts toward lower total mass fractions gamma of the surfactant, i.e., the tendency to form lyotropic liquid crystals (LCs) increases. These trends are well-known for nonionic alkyl ethylene oxides and can thus be interpreted accordingly. What is astonishing, however, is the significant influence the size of the short side chains has. Replacing two methyl groups by two ethyl groups leads to a drastic drop of the three-phase region toward lower temperatures, while the efficiency remains nearly unchanged. Moreover, the tendency to form LCs decreases significantly.     

Room temperature, palladium-mediated p-arylation of secondary phosphine oxides

We show that a broad range of aryl iodides are efficiently coupled with secondary phosphine oxides using 1 mol % of a catalyst formed in situ from tris(dibenzylideneacetone)dipalladium and Xantphos (1). Scalemic (S)-methylphenylphosphine oxide [(S)-2e] is shown to undergo arylation without detectable stereoerosion. The application of this method to the synthesis of novel P-chiral phosphines and PCP ligands is demonstrated.     

A superior method for the reduction of secondary phosphine oxides

[reaction: see text] Diisobutylaluminum hydride (DIBAL-H) and triisobutylaluminum have been found to be outstanding reductants for secondary phosphine oxides (SPOs). All classes of SPOs can be readily reduced, including diaryl, arylalkyl, and dialkyl members. Many SPOs can now be reduced at cryogenic temperatures, and conditions for preservation of reducible functional groups have been found. Even the most electron-rich and sterically hindered phosphine oxides can be reduced in a few hours at 50-70 degrees C. This new reduction has distinct advantages over existing technologies.     

Catalyst-free regio- and chemoselective addition of secondary phosphine oxides to isoquinolines

Russian Chemical Bulletin - Isoquinolines react with secondary phosphine oxides without catalyst (70–75 °C, 10–15 h, without solvent or in MeCN) to chemo- and regioselectively form...     

Air-induced anti-Markovnikov addition of secondary phosphine oxides and H-phosphinates to alkenes

[reaction: see text] Air (oxygen) induces the addition of secondary phosphine oxides and H-phosphinates to alkenes to selectively produce the corresponding anti-Markovnikov adducts in good to high yields. Mechanistic studies show that the addition probably proceeds via a radical chain mechanism.     

Reduction of tertiary phosphine oxides with DIBAL-H

The reduction of tertiary phosphine oxides (TPOs) and sulfides with diisobutylaluminum hydride (DIBAL-H) has been studied in detail. An extensive solvent screen has revealed that hindered aliphatic ethers, such as MTBE, are optimum for this reaction at ambient temperature. Many TPOs undergo considerable reduction at ambient temperature and then stall due to inhibition. 31P and 13C NMR studies using isotopically labeled substrates as well as competition studies have revealed that the source of this inhibition is tetraisobutyldialuminoxane (TIBAO), which builds up as the reaction proceeds. TIBAO selectively coordinates the TPO starting material, preventing further reduction. Several strategies have been found to circumvent this inhibition and obtain full conversion with this extremely inexpensive reducing agent for the first time. Practical reduction protocols for these critical targets have been developed.     

Optically active phosphine oxides. 5. P-chiral 2-aminoethyl phosphine oxides

Homochiral 2-aminoethyl phosphine oxides are expeditiously prepared by thermal addition of primary and secondary amines to (−)-(S)-methylphenylvinylphosphine oxide. Their transformation into optically active 2-aminoethyl phosphines and 2-aminoethyl phosphine sulphides is exemplified.     

Rapid synthesis of an electron-deficient t-BuPHOX ligand: cross-coupling of aryl bromides with secondary phosphine oxides

Herein an efficient and direct copper-catalyzed coupling of oxazoline-containing aryl bromides with electron-deficient secondary phosphine oxides is reported. The resulting tertiary phosphine oxides can be reduced to prepare a range of PHOX ligands. The presented strategy is a useful alternative to known methods for constructing PHOX derivatives.