The Structural Determination of the Ozonides and Their Reaction with Stabilizel Phosphorus Ylides

The ozonides reacted with stabilized phosphorus ylides to give the α,β-unsaturated carbonylcompounds in high yield. The Z/E ratio is dependent on the substituent of the ozonide. Their possiblemechanism was described.     

Copolymers from α-Pinene. 2. Cationic Copolymerization of Styrene and α-Pinene

A study of the copolymerization of α-pinene and styrene has been carried out at 10°C using anhydrous AlCl₃ as the initiator. It is found that styrene forms copolymer with α-pinene at all mono-meric ratios. A copolymer of 2320–3080 molecular weight is obtained. The softening range of the copolymer is 82 to 85°C. The copolymers are of commercial value.     

Umpolung of α-Allenic Ketones and Esters by Phosphorus Groups

Abstract

Change in the regioselectivity of the addition of nucleophilic compounds YH (ROH, RSH, RNH₂) on α -allenic ketones and esters can be achieved by using the triphenylphosphonio group as an umpolung agent¹⁾. In this way α, β-unsaturated ketones and esters 4 are obtained with heteroatomic substituents in the γ position. The Umpolung scheme of the activated allene 1 is charaterized by a functional vinylphosphonium salt 2 as a synthetic equivalent of the a⁴-synthon 3.     

An Improved Synthesis of α-Phenylseleno Arsonium Ylides

The first a-seleno arsonium ylides have been synthesized by Typical procedure for the synthesis of compound sa. To a stirred suspension ofmethoxycarbonylmethylene triphenylarsorane (4a) (0.378 g, I mmol) and triethylamine(0. I I g, 1. 1 mmol) in MeOH-Et,O (0.6 mml, v/v=l f I ) was added dropwise the solutionof phenylselenenyl iodide 2 (0.85 mmol) in MeOH-Et,O (2.8 mml, v/v=l f l) at 0 "C for14 hrs. The mixture was stirred again for 6 hrs. After the solvent in the mixture wasevaporated un…     

Cationic Copolymerization with Depropagation. The Copolymerization of α-Methylstyrene and Styrene

ABSTRACT

To evaluate the existence of the depropagation reaction in the copolymerization of vinyl monomers, the cationic copolymerization of α-methylstyrene with styrene was studied. The copolymer composition exhibited an extensive dependency on the temperature of polymerization and the monomer concentration, this fact not being explained by the Mayo-Lewis equation. Treatment of the copolymerization in terms of the depropagation reaction led to an estimate of the monomer reactivity ratio and the equilibrium constant between the polymer and the monomer of α-methylstyrene. A comparison of the equilibrium constants thus obtained with those reported in the literature indicates that the magnitude of the equilibrium constants depends on the sequence length of α-methylstyrene units. By extrapolation to long sequence length, the equilibrium constants approach the values which are reported for high molecular weight poly(α-methylstyrene).     

Enantioselective S−H Insertion Reactions of α-Carbonyl Sulfoxonium Ylides

The first example of enantioselective S−H insertion reactions of sulfoxonium ylides is reported. Under the influence of thiourea catalysis, excellent levels of enantiocontrol (up to 95 % ee) and yields (up to 97 %) are achieved for 31 examples in S−H insertion reactions of aryl thiols and α-carbonyl sulfoxonium ylides.     

Spacial Structure of Cationic Phosphorus Ligand-Ru （Ⅱ） Halide Complexes-by DFT Study

The full-parameter geometry optimization of cationic （ S ） - BINAP - Ru （ Ⅱ ） halide complex was performed by DFT method using B3LYP, PW91 and PBE potentials with several basis sets. PW91 with 3-21G / SDD basis sets is found to be the most suitable method with consideration of both precision and efficiency. The dihedral angles （ θ ） of the binaphthyl or biphenyl with different phosphorus ligand - Ru （ Ⅱ ） halide complexes were found changing from 59.9 to 79.3 degree, while the natural bite angle （ βn ） of those complexes only changes from 87.4 to 90.3 degree. It is different from the common view of asymmetric organic chemists＇ that θ directly influences βn.     

Preliminary Study of Cationic Copolymerization of α-Methylstyrene and Isobutyl Vinyl Ether. II

α-Methylstyrene (α-MS) and isobutyl vinyl ether (IBVE) were copolymerized by using the H₂O/EtAlCl₂ initiator system and CH₂Cl₂ and CH₃Cl solvent in the temperature range from -30 to -90°C. As compared to homopolymerization of α-MS, both yields and molecular weights are reduced upon addition of small amounts of IBVE to the feed. The reactivity ratios were calculated by the method of Kelen and Tödös as well as the Fineman and Ross method, and the combined effect of change of solvent and temperature on reactivity ratios was determined. Effects of feed composition and temperature on the copolymer yield, composition, and number-average molecular weight M _n were studied in detail. M _n showed a novel exponential dependence on the IBVE concentration in the feed. The overall activation energies of molecular weight were determined from the Arrhenius plots for both homo-and copolymerization systems. Based on these and the yield data, a speculation is made regarding reaction mechanism for molecular weight control. NMR and DTA data are reported, which establish the random nature of the copolymers.     

One-Pot Chlorine-Free Synthesis of Chiral Organophosphorus Compounds from Elemental Phosphorus and α-Methylstyrene Dimer

Direct phosphorylation of α-methylstyrene dimer with red phosphorus in KOH/DMSO superbasic system has provided the preparation of 4-methyl-2,4-diphenylpentylphosphonous acid (heating at 105°C for 3 h) or tris(4-methyl-2,4-diphenylpentyl)phosphine oxide (microwave irradiation, 15 min) in 21 and 38% yield, respectively.     

New α-Functionalized Phosphorus Acid Surfactants: Synthesis,Dissociation Constants and Molecular Aggregation

Abstract

Pursuing our investigation into h e reactivity of red phosphorus. its hydrolysis derivatives (PH₃, and H₃,PO₂).^1,2 and P-H labile compounds? we report here a convenient method for the direct synthesis of free a-hydroxyalkyl phosphinic acid surfactants from aqueous hypophosphorous acid and the long-chain aldehydes or imincs under sonication.     

Studies on the Aromatic Dihalocarbonyl Ylides and Their Deoxygenation

The deoxygenation reaction of heptanones, cycloheptanone, cycloheptatrienone or substituted cycloheptatrienone with dihalo-carbene results in carbon monoxide and corresponding halides. The yield of CO produced by 2 , 4 , 6-triphenylcycloheptatrienone is 2.6-3.5 times as high as that produced by the saturated heptanones. The structures, energies, charge distributions, bond orders, and other relative parameters of the dihalocarbonyl glides were calculated by using the SCF-MNDO method. The obtained data reveal that the ylides from cycloheptatrienone have aromatic structure and are different from those produced from saturated cycloheptanone. The reactivities of the dihalocarbonyl ylides are discussed. It is proposed that this aromatic structure should be responsible for the high yield of CO from the reaction of cycloheptatrienone with dihalocarbene.     

Silica-Gel–Catalyzed Conversion of Stabilized Phosphorus Ylides to Benzo[e][1,3]Thiazocin Derivatives

The reaction between triphenylphosphine, dialkylacetylenedicarboxylates, and N-benzoyl thiourea derivatives leads to intermediates such as vinyltriphenylphosphonium salts, which undergo Michael addition to produce the highly functionalized phosphorus ylides containing alkyl groups in excellent yields. Using silica gel as a catalyst, the conversion of the stabilized phosphorus ylides to benzo[e][1,3]thiazocin derivatives in solvent free conditions at 90°C in fairly high yields is achieved.     

Synergistic Cu/Pd-Catalyzed Asymmetric Allenylic Alkylation of Azomethine Ylides for the Construction of α-Allene-Substituted Nonproteinogenic α-Amino Acids

An unprecedented asymmetric allenylic alkylation of readily available imine esters, which was enabled by a synergistic Cu/Pd catalysis, has been developed. This dual catalytic system possesses good substrate compatibility, delivering a diverse array of nonproteinogenic α-allenylic α-mono- or α,α-disubstituted α-amino acids (α-AAs) with high yields and generally excellent enantioselectivities. Furthermore, the scalability and practicability of the current synthetic protocol were proven by performing gram-scale reactions and by the first catalytic asymmetric synthesis of naturally occurring (S)-γ-allenic α-amino acid, respectively.     

A Protocol for Accessing the β-Azidation of α,β-Unsaturated Carboxylic Acids

This contribution reports the preparation and use of a new immobilized catalyst, PS-DABCOF (9), which has been specifically designed to access for the first time the efficient β-azidation of α,β-unsaturated carboxylic acids.     

Spacial Structure of Cationic Phosphorus Ligand–Ru (II) Halide Complexes—by DFT Study

The increasing demand to produce enantio-pure pharmaceuticals, flavors, and other fine chemicals has advanced the field of asymmetry catalytic technologies. Among all asymmetry catalytic methods, catalytic enantioselective hydrogenation of unsaturated bonds such as olefins, ketones, and imines, which employs dihydrogen and small amounts of transition-metal complexes modified intrinsically by chiral ligands, is now recognized as being the most promising strategy for the synthesis of large amount…     

Synthesis and Characterization of Photosensitive Phosphorus Based Polymers Containing α,β‐Unsaturated Ketones in the Main Chain

1,3‐Bis(4‐hydroxyphenyl)propenone (BHPP) and 3‐(4‐hydroxy‐3‐methoxy phenyl)‐1‐(4‐hydroxyphenyl)propenone (HMPHPP) were used as monomers for preparing photosensitive phosphorus containing polyesters. The photosensitive monomers BHPP and HMPHPP were prepared respectively by refluxing 4‐hydroxybenzaldehyde and 3‐methoxy‐4‐hydroxybenzaldehyde with 4‐hydroxy acetophenone. The polyesters were synthesized by interfacial polycondensation of photosensitive diols with N‐phenylphosphoramidic dichloride using hexadecyltrimethyl ammonium bromide (HDTMAB) as phase‐transfer catalyst. Copolymers were also prepared by incorporating terephthaloyl chloride in the polymer backbone. The synthesized monomers and polymers were characterized by UV, FT‐IR and ¹H, ¹³C and ³¹P‐NMR spectroscopic techniques. The resulting polymers had inherent viscosities in the range of 0.15–0.51 dL/g and showed good solubility in polar organic solvents. The thermal properties of the polymers were studied by thermogravimetric analysis and differential scanning calorimetry under nitrogen atmosphere. The TGA data revealed that the 10% weight loss occurs at 275–320°C and all the synthesized polymers showed high char residues. DSC studies indicate that these polymers possess T_g in the range of 48 to 64°C. The photosensitive property of the polymers in film and solution state was investigated by ultraviolet spectroscopy. The effect of incorporation of terephthaloyl unit on photocrosslinking and thermal properties of the polymers was also studied.     

γ-Silylated α,β-unsaturated amides. Formation by [1,5] silicon migration from O-silylated vinyl ketene aminals and fluoride- and Lewis acid-mediated aldol condensations

O-Silylated vinyl ketene aminal 2, obtained from lithiated unsaturated amide 1, undergoes a thermal [1,5] silicon migration to give γ-silylated product 3b which participates in fluoride- and titanium tetrachloride-mediated aldol condensations to give adducts 5 in poor and excellent syn diastereoselectivity respectively.     

Effects of Phosphorus Substituents on Reactions of α-Alkoxyphosphonium Salts with Nucleophiles

The effects of phosphorus substituents on the reactivity of α-alkoxyphosphonium salts with nucleophiles has been explored. Reactions of α-alkoxyphosphonium salts, prepared from various acetals and tris(o-tolyl)phosphine, with a variety of nucleophiles proceeded efficiently. These processes represent the first examples of high-yielding nucleophilic substitution reactions of α-alkoxyphosphonium salts. The reactivity of these salts was determined by a balance between steric and electronic factors, respectively, represented by cone angles θ and CO stretching frequencies ν (steric and electronic parameters, respectively). In addition, a novel reaction of α-alkoxyphosphonium salts derived from Ph₃P with Grignard reagents was observed to take place in the presence of O₂ to afford alcohols in good yields. A radical mechanism is proposed for this process that has gained support from isotope-labeling and radical-inhibition experiments.     

Cationic β-Scission of C−H and C−C Bonds for Selective Dimerization and Subsequent Sulfur-Free RAFT Polymerization of α-Methylstyrene and Isobutylene

A series of exo-olefin compounds ((CH₃)₂C(PhY)−CH₂C(=CH₂)PhY) were prepared by selective cationic dimerization of α-methylstyrene (αMS) derivatives (CH₂=C(CH₃)PhY) with p-toluenesulfonic acid (TsOH) via β-C−H scission. They were subsequently used as reversible chain transfer agents for sulfur-free cationic RAFT polymerization of αMS via β-C−C scission in the presence of Lewis acid catalysts such as SnCl₄. In particular, exo-olefin compounds with electron-donating substituents, such as a 4-MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo-olefin terminals. Other exo-olefin compounds (R−CH₂C(=CH₂)(4-MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur-free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo-olefin αMS dimer ((CH₃)₂C(Ph)−CH₂C(=CH₂)Ph). Furthermore, telechelic poly(IB) with exo-olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo-olefins. Finally, block copolymers of αMS and methyl methacrylate (MMA) were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo-olefin terminals containing 4-MeOPh groups as common sulfur-free RAFT groups for both cationic and radical polymerizations.