Studies on highly regio- and stereoselective selenohydroxylation reaction of 1,2-allenyl phosphine oxides with PhSeCl

The selenohydroxylation of readily available 1,2-allenyl phosphine oxides with PhSeCl in MeCN/H₂O afforded 3-hydroxy-2-phenylselanyl-1(E)-alkenyl diphenyl phosphine oxides in good yields with very high regio- and stereoselectivities including the high efficiency of the axial chirality transfer. The E-stereoselectivity is believed to be determined by the neighboring group participation effect of the diphenyl phosphine oxide functionality.     

Selective reduction of allenyl(diphenyl)phosphine oxides to allyl(diphenyl)phosphine oxides

The reduction of allenyl(diphenyl)phosphine oxides with HSiCl₃ or LiAlH₄ selectively afforded the corresponding allyl(diphenyl)phosphine oxides. 3-Methylbut-2-en-1-yl(diphenyl)phosphine oxide reacted with AlCl₃ to give a mixture of 4,4-dimethyl-1-phenyl-1,2,3,4-tetrahydro-λ⁵-phosphinoline 1-oxide and 4,4-dimethyl-1-phenyl-1,4-dihydro-λ⁵-phosphinoline 1-oxide.     

Studies on highly regio- and stereoselective fluorohydroxylation reaction of 3-aryl-1,2-allenyl phosphine oxides with Selectfluor

The fluorohydroxylation of allenyl phosphine oxides with Selectfluor in commercial MeCN without prior treatment or a mixed solvent of anhydrous MeCN (refluxed over CaH₂ and distilled before use) and 7.0 equiv of H₂O or MeNO₂/H₂O=10/1 afforded 2-fluoro-3-hydroxy-1(E)-alkenyl diphenyl phosphine oxides in moderate yields with very high regio- and stereoselectivities. The E-stereoselectivity is believed to be controlled by the phosphine oxide functionality. In the reaction of 3-(4-methoxyphenyl)-1,2-propadienyl diphenyl phosphine oxide, further fluorination on the electron-rich phenyl ring was also observed.     

Synthesis and electrophilic cyclization reactions of diphenyl 3‐methylhexa‐ 1,3,4‐trien‐3‐yl phosphine oxide

Diphenyl 3‐methylhexa‐1,3,4‐trien‐3‐yl phosphine oxide can be readily prepared via an atom‐economical 2,3‐sigmatropic rearrangement of the mediated alkenynyl phosphinite formed in situ by a reaction of 2‐methylhex‐5‐en‐3‐yn‐2‐ol with diphenylchlorophosphine. Electrophilic cyclization reactions of prepared 1‐vinylallenyl phosphine oxide were investigated as it was established that the reactions proceeded with formation of heterocyclic compounds with participation of the allenic and/or 1,3‐dienic part of the vinylallenic system with neighboring group participation of the phosphoryl and/or vinylic group. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:345–351, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21023     

Reaction of Pentafluorophenyl(diphenyl)phosphine with Nitrilimines

Reaction of pentafluorophenyl(diphenyl)phosphine with nitrilimines is a multistep process leading to formation of unstable fused heterocycles with a fluorophosphorane moiety as primary products. Their hydrolysis involves opening of the heteroring and subsequent cleavage of the N-N bond in intermediate phosphorylated hydrazones. The final products are diphenyl(6-arylamino-2,3,4,5-tetrafluorophenyl)phosphine oxides.     

Diastereoselective and intramolecular cycloadditions of asymmetric p-nitroso phosphine oxides

Benzyl phenyl P-nitroso phosphine oxide (5) reacts as an N-O heterodienophile with 1,3-cyclopentadiene to give the diastereomeric cycloadducts 6a,b in a ratio of 1.5:1 (6a:6b). The same reaction in the presence of tin tetrachloride produces 6a,b in a ratio of 2.9:1 (6a:6b). Cycloaddition of the structurally modified P-nitroso phosphine oxide (18) with 1,3-cyclopentadiene forms the diastereomeric cycloadducts 16a,b in a ratio of 3.1:1 (16a:16b). These results suggest the reactions of these P-nitroso phosphine oxides and 1,3-cyclopentadiene occur through a transition state where the heterodienophile adopts an s-cis conformation and approaches the diene in an exo fashion syn to the phenyl group. This model resembles those proposed for the cycloadditions of the structurally similar asymmetric vinyl phosphine oxides. Reaction of 18 with 1,3-cyclopentadiene in the presence of a Lewis acid produces cycloadducts 16a,b in a ratio of 7:1 (16a:16b), which approaches synthetic utility. Similar experiments show that 1,3-cyclohexadiene likely reacts with P-nitroso phosphine oxides through a different transition state, limiting current predictions regarding the diastereoselectivity of these reactions. The intramolecular cycloaddition of an asymmetric P-nitroso phosphine oxide (19) for the first time produces a unique phosphorus-containing heterocyclic compound (20).     

The synthesis of a [2.2]paracyclophane-derived secondary phosphine oxide and a study of its reactivity

A planar chiral secondary phosphine oxide based on [2.2]paracyclophane was synthesized and its chemistry investigated; it was shown to be a competent pre-ligand in palladium(0)-mediated reactions, and displayed promising activity in gold(I)-catalysed cyclisations. The secondary phosphine oxide could be transformed into a collection of P-stereogenic tertiary phosphine oxides. These are rare examples of the planar chirality of [2.2]paracyclophane being combined with a P-stereogenic centre. Unfortunately, epimerisation of the phosphorus stereocentre during reduction limits the use of this chemistry.     

Extraction and coordination behavior of diphenyl hydrogen phosphine oxide towards actinides

Extraction behavior of some selected actinides like U(VI), Th(IV), and Am(III) was investigated with three different H-phosphine oxides, viz. diphenyl hydrogen phosphine oxide (DPhPO), dihexyl hydrogen phosphine oxide (DHePO) and diphenyl phosphite (DPP). The H-phosphine oxides exhibited a dual nature towards the extraction of actinides where the ligand not only extracts the metals by cation exchange but also by coordination with the phosphoryl group at lower and higher acidic concentrations, respectively. Among all ligands employed, DPhPO showed highest extraction with actinides with a substituent dependent trend as follows: DPhPO > DHePO > DPP. This trend emphasizes the importance of substituents around the phosphine oxide towards their extraction of actinides. The coordination behavior of DPhPO was studied by investigating its corresponding complexes with Th(NO₃)₄ and UO₂(NO₃)₂. The metal complexes of these actinides were characterized using FT-IR, ¹H and ³¹P NMR spectroscopic techniques. Density Functional Theory (DFT) calculations were also performed to understand the electronic and geometric structure of the ligand and the corresponding metal complexes.     

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.     

Conformational analysis of 2-aminophenyl-, 2-aminobenzyl-, and 2-nitrobenzyl(diphenyl)phosphine oxides

The polarity and conformations of 2-aminophenyl-, 2-aminobenzyl-, and 2-nitrobenzyl(diphenyl)-phosphine oxides were studied by the dipole moment method, IR spectroscopy, and quantum chemical calculations. 2-Aminophenyl- and 2-aminobenzyl(diphenyl)phosphine oxides were found to exist preferentially as conformers with intramolecular hydrogen bond. 2-Nitrobenzyl(diphenyl)phosphine oxide is likely to be represented by equilibrium mixture of three conformers in which the phosphoryl and nitro groups are oriented syn or anti with respect to the \(PC_{sp^3 } C_{sp^2 } \) fragment.     

MECHANISM OF THE REACTION OF DIPHENYL N-BROMOSULFILIMINE WITH SULFIDES,PHOSPHINES AND TERTIARY AMINES

Abstract

The mechanism of the reactions of diphenyl N-bromosulfilimine (I) with such nucleophiles as sulfides, phosphines and tertiary amines was investigated. In the presence of water, (I) reacts with sulfides or phosphines to afford the corresponding sulfoxides or the phosphine oxides in moderate yields; however, the reaction with tertiary amine gave only the N-t-aminosulfilimine derivative. The effect of ring size in the reaction with cyclic sulfides suggests that the reaction proceeds via initial bromine transfer from the nitrogen atom to the sulfur atom of the cyclic sulfides followed by S_N2 type substitution of bromide on the sulfur atom of the cyclic sulfide with the sulfilimino group. The phosphine oxide obtained in the reaction of (I) with optically active methyl n-propyl phenyl phosphine was racemized but retained a small portion of the optical activity. In the case of tertiary amines, even 1,4-diazabicyclo-(2,2,2)-octane (DABCO), in which the back side of the nitrogen atom is blocked, reacted smoothly to afford the corresponding ammonium salts, suggesting the reaction to be of S_N2 type on the nitrogen atom of the sulfilimine.     

Reaction of diphenyl[2-(triethoxysilyl)ethyl]phosphine oxide with boron trifluoride etherate

Diphenyl[2-(trifluorosilyl)ethyl]phosphine oxide was synthesized by the reaction of diphenyl[2-(triethoxysilyl)ethyl]phosphine oxide with boron trifluoride etherate. As shown by the ¹H, ¹³C, ¹⁹F, ³¹P, ²⁹Si multinuclear NMR spectroscopy data, the silicon atom in the molecule is tetracoordinate. The absence of P=O→Si interaction in diphenyl[2-(trifluorosilyl)ethyl]phosphine oxide, as follows from the comparison of the calculated [GIAO B3LYP/6-311++G(2d,p)] and experimental δ(²⁹Si) and δ(³¹P) values, is due to the formation of complex with BF₃ by the phosphoryl oxygen.     

Alpha-monodeuterated benzyl alcohols and phosphobetaines from reactions of aromatic aldehydes with a water/D2O-soluble phosphine

With the aim of learning more about the bleaching action of pulps by (hydroxymethyl)phosphines, we reacted several benzaldehydes, containing MeO, Me, OH, or halogen substituents, with tris(3-hydroxypropyl)phosphine, [HO(CH2)3]3P, in aqueous solution at 90 degrees C under argon. Effective reduction of the aldehydes to the corresponding benzyl alcohols with concomitant oxidation of the phosphine to the phosphine oxide takes place, the reaction proceeding via an initially formed phosphonium species. When the reactions are carried out in D2O, the benzyl alcohol product from 3,4-dimethoxybenzaldehyde contains one deuterium atom at the benzyl-carbon atom, consistent with the last step of the mechanism involving a carbanion intermediate. With syringaldehyde (3,5-dimethoxy-4-hydroxy-benzaldehyde), the reduction product (syringyl alcohol) is more reactive toward the phosphine than is the starting aldehyde, and a zwitterionic, phosphobetaine product is formed. In D2O, the zwitterion benzyl protons and protons of the hydroxypropyl-CH2 adjacent to the P atom undergo H/D exchange via presumed phosphorus ylide intermediates. Under the same aqueous reaction conditions, tris(3-hydroxypropyl)phosphine, [HO(CH2)3]3P (THPP), does not undergo redox reactions with aliphatic aldehydes but simply promotes a base-catalyzed self-condensation (aldol) reaction. THPP reduction of an aromatic ketone is sluggish, presumably because the carbonyl C-atom is less electrophilic than that present in an aromatic aldehyde.     

Study of thermochemical properties of diphenyl[dialkyl(alkyl)carbamoylmethyl]phosphine oxides

The synthesis and the studies of properties of diphenyl[dialkyl(alkyl)carbamoylmethyl]phosphine oxides by differential scanning calorimetry, mass spectrometry and Knudsen effusion method were performed. The thermodynamic parameters of melting and vaporization were calculated.     

Diastereoselective cobalt-mediated [2 + 2 + 2] cycloadditions of substituted linear enediynes phosphine oxides: scope and limitations

Variously substituted linear enediynes phosphines oxides possessing the double bond at either the terminal or internal position and with the phosphine oxide appended onto the alkyne or the alkene terminus have been prepared. Their cobalt(I)-mediated cyclizations produce the eta(4)-complexed tricyclic compounds in high yields. The endo/exo selectivity depends on both the position of the phosphine oxide on the enediyne and the position of the double bond in the tether. With chiral phosphine oxides, a certain degree of induction was observed, and depending on the substituents on the phosphorus atom, the diastereoselectivity can reach 74%. Up to now, it is the highest level reported for such a cyclization in which a stereogenic center is created. Regarding all of our results, two reaction pathways involving an initial coordination of the cobalt moiety on the chelating site of the substituent have been suggested to explain the observed selectivities.     

Stereospecific nucleophilic substitution of optically pure H-phosphinates: a general way for the preparation of chiral P-stereogenic phosphine oxides

Contrary to the generally held view, it is found that the rapid epimerization of (-)-menthyl (RP)-phenylphosphinate under basic conditions is not due to the so far believed inherent stereolability of its corresponding anion but due to a reaction of the hydrogen phosphinate ester with a metal alkoxide. This finding successfully leads to a discovery that, by adding an H-phosphinate to organolithiums or Grignard reagents at a low temperature, the nucleophilic substitution of the alkoxy group of the H-phosphinate with organolithiums or Grignard reagents proceeds stereospecifically with inversion of configurations at phosphorus to give a wide range of P-stereogenic secondary phosphine oxides and tertiary phosphine oxides, by quenching the reaction mixture with water and alkyl halides, respectively. This finding establishes a general protocol for the preparation of optically active secondary phosphine oxides and tertiary phosphine oxides from the easily accessible optically pure H-phosphinates. Mechanistic studies show that the substitution reactions of H-phosphinates with organolithiums and Grignard reagents proceed via two competing reaction paths, that is, a two-step reaction path involving first a deprotonation of H-phosphinates followed by a substitution of the corresponding anion with inversion of configuration at phosphorus and a direct substitution of RM with H-phosphinates generating the SPO directly.     

Metal-free reduction of tertiary phosphine oxides with Hantzsch ester简

The （COCl）2/Hantzsch ester is found to be an effective system for the metal-free reduction of tertiary phosphine oxides. The reaction proceeds under mild conditions, and is applicable to triarylphosphine oxides and alkyldiarylphosphine oxides to produce the corresponding tertiary phosphines in good to excellent yields. This new finding provides a practical, convenient and metal-free method for the reduction of tertiary phosphine oxides to tertiary phosphines, and shows potential application in organic synthesis.     

Synthesis of polymers containing tertiary phosphine oxides using complex bases

Tertiary phosphine oxides have been prepared in excellent yield from primary alkyl halides or aromatic halides and activated sodium phosphinates obtained by reaction of dialkyl phosphine oxides with complex bases (NaNH₂/tBuONa). This reaction has been successfully applied to soluble and cross-linked bromopolystyrenes and to macroporous polystyrenes with bromooctyl substituents giving polymers which contain pendant phosphine oxide groups.     

Simple unprecedented conversion of phosphine oxides and sulfides to phosphine boranes using sodium borohydride

A variety of phosphine oxides and sulfides can be efficiently converted directly to the corresponding phosphine boranes using oxalyl chloride followed by sodium borohydride. Optically active P-stereogenic phosphine oxides can be converted stereospecifically to phosphine boranes with inversion of configuration by treatment with Meerwein's salt followed by sodium borohydride.     

Mechanism of noncatalytic synthesis of tris(hydroxymethyl)phosphine. Nonempirical quantum-chemical approach

The gas-phase reaction of the synthesis of tris(hydroxymethyl)phosphine from phosphine and formaldehyde was studied using a calculation scheme based on the density functional theory with hybrid exchange-correlation functional B3LYP in the 6–311++G** basis. The reaction was shown to proceed with the participation of unstable intermediates containing three-membered ring. The transformation into final products includes opening of the three-membered ring and intramolecular proton transfer. The results can be useful at selecting catalysts and for explaining the mechanism of the catalytic reaction of tris(hydroxymethyl)phosphine synthesis.