PhCH CH Research Articles

Synthesis and ligand substitution reactions of κ4-B,S,S',S''-ruthenaboratranes.

A range of ruthenaboratranes of the form [Ru(CO)L{κ4-B,S,S',S''-B(mt)3}] (mt = N-methylmercaptoimidazolyl) have been prepared either by substitution of the PPh3 ligand in [Ru(CO)(PPh3){κ4-B,S,S',S''-B(mt)3}] by L (L = PMe2Ph, PMe3, P(OMe)3, P(OEt)3, P(OPh)3) or reactions of [RuCl(R)(CO)Ln] (R = Ph, CH[double bond, length as m-dash]CHPh; n = 2, L = PCy3; n = 3, L = P(OMe)3, PMe2Ph) with Na[HB(mt)3].

Methimazolyl based diptych bicyclo-[3.3.0]-ruthenaboratranes.

The reactions of [RuCl(R)(CO)(PPh3)2] (R = CH[double bond, length as m-dash]CHPh, Ph) with Na[H2B(mt)2] (mt = N-methyl-2-mercaptoimidazolyl) transiently provide [Ru(R)(CO)(PPh3){κ3-H,S,S'-H2B(mt)2}] which each evolve to the ruthenaboratrane [Ru(CO)(PPh3)2{κ3-B,S,S'-BH(mt)2}](Ru→B)8. The phosphine ligands may be selectively replaced to provide the complexes [Ru(CO)(L)(PPh3){κ3-B,S,S'-BH(mt)2}] (L = CO, PMe2Ph) and [Ru(CO)L2{κ3-B,S,S'-BH(mt)2}] (L = PMe2Ph, P(OMe)3, L2 = Z-Ph2PCH[double bond, length as m-dash]CHPPh2) with, in each case, retention of the ruthenium-boron dative bond.

Exploring the activities of vanadium, niobium, and tantalum PNP pincer complexes in the hydrogenation of phenyl-substituted CN, CN, CC, CC, and CO functional groups

The structures and stability of the designed PNP pincer amido M(NO) 2 (PNP) and amino H M(NO) 2 (PN H P) complexes [M = V, Nb, and Ta, PNP = N(CH 2 CH 2 P(isopropyl) 2 ) 2 , PN H P = HN(CH 2 CH 2 P(isopropyl) 2 ) 2 ] and their hydrogenation mechanisms for phenyl-substituted unsaturated functional groups have been explored at the B3PW91 level of density functional theory. Under H 2 environment, these conjugated complexes can form equilibrium and fulfill the criteria of metal–ligand cooperated bifunctional hydrogenation catalysts. For the hydrogenation of Ph-C N, Ph-CH NH, Ph-CH NH-Ph, Ph-CH N CH 2 Ph, Ph-C CH, Ph-CH CH 2 , Ph-CHO, and Ph-CO CH 3 , the reaction prefers either a two-step or one-step mechanism for the hydridic M H and protonic N H transfer. These results clearly show that the V, Nb, and Ta complexes are promising catalysts for the hydrogenation reactions, and these provide experimental challenges.

Reaction of an N-heterocyclic carbene-stabilized silicon(II) monohydride with alkynes: [2+2+1] cycloaddition versus hydrogen abstraction.

An in depth study of the reactivity of an N-heterocyclic carbene (NHC)-stabilized silylene monohydride with alkynes is reported. The reaction of silylene monohydride 1, tBu3 Si(H)Si←NHC, with diphenylacetylene afforded silole 2, tBu3 Si(H)Si(C4 Ph4 ). The density functional theory (DFT) calculations for the reaction mechanism of the [2+2+1] cycloaddition revealed that the NHC played a major part stabilizing zwitterionic transition states and intermediates to assist the cyclization pathway. A significantly different outcome was observed, when silylene monohydride 1 was treated with phenylacetylene, which gave rise to supersilyl substituted 1-alkenyl-1-alkynylsilane 3, tBu3 Si(H)Si(CHCHPh)(CCPh). Mechanistic investigations using an isotope labelling technique and DFT calculations suggest that this reaction occurs through a similar zwitterionic intermediate and subsequent hydrogen abstraction from a second molecule of phenylacetylene.

Reactivity of TpMe2‐Supported Yttrium Alkyl Complexes toward Aromatic N‐Heterocycles: Ring‐Opening or CC Bond Formation Directed by CH Activation

Unusual chemical transformations such as three-component combination and ring-opening of N-heterocycles or formation of a carbon-carbon double bond through multiple C-H activation were observed in the reactions of Tp(Me2) -supported yttrium alkyl complexes with aromatic N-heterocycles. The scorpionate-anchored yttrium dialkyl complex [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with 1-methylimidazole in 1:2 molar ratio to give a rare hexanuclear 24-membered rare-earth metallomacrocyclic compound [Tp(Me2) Y(μ-N,C-Im)(η(2) -N,C-Im)]6 (1; Im=1-methylimidazolyl) through two kinds of C-H activations at the C2- and C5-positions of the imidazole ring. However, [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with two equivalents of 1-methylbenzimidazole to afford a C-C coupling/ring-opening/C-C coupling product [Tp(Me2) Y{η(3) -(N,N,N)-N(CH3 )C6 H4 NHCHC(Ph)CN(CH3 )C6 H4 NH}] (2). Further investigations indicated that [Tp(Me2) Y(CH2 Ph)2 (THF)] reacted with benzothiazole in 1:1 or 1:2 molar ratio to produce a C-C coupling/ring-opening product {(Tp(Me2) )Y[μ-η(2) :η(1) -SC6 H4 N(CHCHPh)](THF)}2 (3). Moreover, the mixed Tp(Me2) /Cp yttrium monoalkyl complex [(Tp(Me2) )CpYCH2 Ph(THF)] reacted with two equivalents of 1-methylimidazole in THF at room temperature to afford a trinuclear yttrium complex [Tp(Me2) CpY(μ-N,C-Im)]3 (5), whereas when the above reaction was carried out at 55 °C for two days, two structurally characterized metal complexes [Tp(Me2) Y(Im-Tp(Me2) )] (7; Im-Tp(Me2) =1-methyl-imidazolyl-Tp(Me2) ) and [Cp3 Y(HIm)] (8; HIm=1-methylimidazole) were obtained in 26 and 17 % isolated yields, respectively, accompanied by some unidentified materials. The formation of 7 reveals an uncommon example of construction of a CC bond through multiple C-H activations.

Elevated atherogenic index following oral administration of quaternized polyamine nanogels

Quaternized polyamine nanogels possessing poly(ethylene glycol) (PEG)-tethered chains as the surface layer were prepared by redox-initiated emulsion polymerization of 2-(N,N-diethylamino)ethyl methacrylate (EAMA) in the presence of vinylbenzyl-ended poly(ethylene glycol) (PEG-CH2PhCHCH2), followed by quaternization with methyl iodide (QNG-I). QNG-I absorbed taurocholic acid regardless of environmental pH, because of the fixed positive charge of QNG-I. Oral administration of polyamine nanogels into mice tended to cause intestinal retention, with accumulation of up to 70% of the initial dose. Levels of low-density lipoprotein cholesterol (LDL-C) in hyperlipidemic mice effectively decreased following oral administration of QNG-I. Interestingly, oral administration of QNG-I increased the levels of high-density lipoprotein cholesterol (HDL-C), resulting in an extremely high atherogenic index. Iodide counter-anions in QNG-I played an important role in the increase in HDL-C levels.

Study of the Lithiated Phenylacetonitrile Monoanions and Dianions Formed According to the Lithiated Base Used (LHMDS, LDA, or n-BuLi). 2. Alkylation and Deuteriation Mechanism Study by Vibrational and NMR Spectroscopy and Quantum Chemistry Calculations

Mechanisms of alkylation by PhCH(2)Cl or CH(3)I in THF and of deuteriation by DCl (4 N in D(2)O) in THF or THF-toluene of lithiated phenylacetonitrile monoanions and dianions obtained with LHMDS, LDA, or n-BuLi are studied by vibrational and NMR spectroscopy and quantum chemistry calculations. Dialkylation of the three dilithio dianions generated with n-BuLi (2.0-2.7 equiv, THF-hexane) depends on their structure: N-lithio (PhCCNLi)(-)Li(+) and (C,N)-dilithio PhCLiCNLi dianions afford PhCR(2)CN (R = PhCH(2), CH(3)) from the intermediate N-lithio monoalkylated monoanion PhCRCNLi 10; C-lithio dianion (PhCLiCN)(-)Li(+) leads to a carbenoid species, the C-lithio monoalkylated nitrile PhCLiRCN 11, which either eliminates carbene Ph-C-R and different LiCN species or isomerizes to PhCRCNLi in the presence of LiX (X = Cl, I). Dialkylation or dideuteriation of monoanions (monomers, dimers, and heterodimers [PhCHCNLi·LiR'], R' = (SiMe(3))(2)N, (i-Pr)(2)N) obtained with LHMDS or LDA (2.4 equiv, THF) proceeds via a sequential mechanism involving monometalation-monoalkylation (or monodeuteriation) reactions. Some carbene and (LiCNLi)(+) are also observed, and explained by another mechanism implying the C-lithio monoalkylated monoanion PhCLiRCN 9 in the presence of LiX. These results show the ambiphilic behavior of PhCLiRCN as a carbenoid (11) or a carbanion (9) and the importance of LiX formed in situ in the first alkylation step.

Enantioselective Multicomponent Synthesis of Fused 6–5 Bicyclic 2‐Butenolides by a Cascade Heterobicyclisation Process

The successive coupling of an alkoxy(aryl/heteroaryl)carbene complex of chromium with either a ketone or an imide lithium enolate and then a 3-substituted (H, TMS, PhCH(2), PhCH(2)CH(2), Me) propargylic organomagnesium reagent has afforded novel hydroxy-substituted bicyclic [4.3.0]-γ-alkylidene-2-butenolides with three modular points that has allowed the efficient introduction of molecular complexity, including a homopropargylic alcohol core. The selective formation of these five- or six-component heterobicyclisation products is the result of the regioselective integration of the Grignard reagent as a propargyl fragment followed by a cascade CO/alkyne/CO insertion, ketene trapping and elimination sequence. By using lithium enolates of chiral N-acetyl-2-oxazolidinones and the corresponding propargylic organocerium reagents, both enantiomers of these bicyclic heterocycles were efficiently prepared with very high enantiomeric purity. Architecturally, these fused bicyclic butenolides are characterised by a highly unsaturated and oxygenated core and they exhibit strong blue fluorescence in solution.

Enantiomerically Pure Phosphaalkene–Oxazolines (PhAk‐Ox): Synthesis, Scope and Copolymerization with Styrene

The design of a synthetic route to a class of enantiomerically pure phosphaalkene-oxazolines (PhAk-Ox) is presented. The condensation of a lithium silylphosphide and a ketone (the phospha-Peterson reaction) was used as the P=C bond-forming step. Attempted condensation of PhC(=O)Ox (Ox = CNOCH(iPr)CH(2)) and MesP(SiMe(3))Li gave the unusual heterocycle (MesP)(2)C(Ph)=CN-(S)-CH(iPr)CH(2)O (3). However, PhAk-Ox (S,E)-MesP=C(Ph)CMe(2)Ox (1 a) was successfully prepared by treating MesP(SiMe(3))Li with PhC(=O)CMe(2)Ox (52 %). To demonstrate the modularity and tunability of the phospha-Peterson synthesis several other phosphaalkene-oxazolines were prepared in an analogous manner to 1 a: TripP=C(Ph)CMe(2)Ox (1 b; Trip = 2,4,6-triisopropylphenyl), 2-iPrC(6)H(4)P=C(Ph)CMe(2)Ox (1 c), 2-tBuC(6)H(4)P=C(Ph)CMe(2)Ox (1 d), MesP=C(4-MeOC(6)H(4))CMe(2)Ox (1 e), MesP=C(Ph)C(CH(2))(4)Ox (1 f), and MesP=C(3,5-(CF(3))(2)C(6)H(3))C(CH(2))(4)Ox (1 g). To evaluate the PhAk-Ox compounds as prospective precursors to chiral phosphine polymers, monomer 1 a and styrene were subjected to radical-initiated copolymerization conditions to afford [{MesPC(Ph)(CMe(2)Ox)}(x){CH(2)CHPh}(y)](n) (9 a: x = 0.13n, y = 0.87n; GPC: M(w) = 7400 g mol(-1) , PDI = 1.15).

Substituent effects on Ni–S bond dissociation energies and kinetic stability of nickel arylthiolate complexes supported by a bis(phosphinite)-based pincer ligand

Pincer complexes of the type [2,6-(R(2)PO)(2)C(6)H(3)]NiSC(6)H(4)Z (R = Ph and i-Pr; Z = p-OCH(3), p-CH(3), H, p-Cl, and p-CF(3)) have been synthesized from [2,6-(R(2)PO)(2)C(6)H(3)]NiCl and sodium arylthiolate. X-ray structure determinations of these thiolate complexes have shown a somewhat constant Ni-S bond length (approx. 2.20 Å) but an almost unpredictable orientation of the thiolate ligand. Equilibrium constants for various thiolate exchange (between a nickel thiolate complex and a free thiol, or between two different nickel thiolate complexes) reactions have been measured. Evidently, the thiolate ligand with an electron-withdrawing substituent prefers to bond with "[2,6-(Ph(2)PO)(2)C(6)H(3)]Ni" rather than "[2,6-(i-Pr(2)PO)(2)C(6)H(3)]Ni", and bonds least favourably with hydrogen. The reactions of the thiolate complexes with halogenated compounds such as PhCH(2)Br, CH(3)I, CCl(4), and Ph(3)CCl have been examined and several mechanistic pathways have been explored.

Ferrocene- and ruthenocene-containing chalcones: A spectroscopic and electrochemical study

Chalcones of the type Mc-CO–CH CH-Ph, Ph-CO–CH CH-Mc and Mc-CO–CH CH-Mc with Mc = Fc = ferrocenyl or Rc = ruthenocenyl, and Ph = phenyl were synthesized. Synthesis was achieved by base catalyzed Claisen–Schmidt condensation of the appropriated acetyl and aldehyde in ethanol. Cyclic voltammetry in CH 3CN in the presence of 0.1 mol dm −3 [N(Bu) 4][PF 6] revealed chemical and electrochemical reversible behaviour for the Fc/Fc + couple and irreversible electrochemistry for the two electron Rc/Rc 2+ couple. The potential ranges for the Fc/Fc + couple varied in the range 138 ⩽ E°′ ⩽ 302 mV while E pa for Rc/Rc 2+ couple was between 358 and 510 mV vs. FcH/FcH +, the internal standard. Chalcones with the carbonyl group adjacent to the metallocene, are more difficult to oxidize.

Pyrolysis of Phenethyl Phenyl Ether Tethered in Mesoporous Silica. Effects of Confinement and Surface Spacer Molecules on Product Selectivity

There has been expanding interest in exploring porous metal oxides as a confining environment for organic molecules resulting in altered chemical and physical properties including chemical transformations. In this paper, we examine the pyrolysis behavior of phenethyl phenyl ether (PPE) confined in mesoporous silica by covalent tethers to the pore walls as a function of tether density and the presence of cotethered surface spacer molecules of varying structure (biphenyl, naphthyl, octyl, and hexadecyl). The PPE pyrolysis product selectivity, which is determined by two competitive free-radical pathways cycling through the two aliphatic radical intermediates (PhCH·CH(2)OPh and PhCH(2)CH·OPh), is shown to be significantly different from that measured in the liquid phase as well as for PPE tethered to the exterior surface of nonporous silica nanoparticles. Tailoring the pore surface with spacer molecules further alters the selectivity such that the PPE reaction channel involving a molecular rearrangement (O-C phenyl shift in PhCH(2)CH·OPh), which accounts for 25% of the products in the liquid phase, can be virtually eliminated under pore confinement conditions. The origin of this change in selectivity is discussed in the context of steric constraints on the rearrangement path inside the pores, surface and pore confinement effects, pore surface curvature, and hydrogen bonding of PPE with residual surface silanols supplemented by nitrogen physisorption data and molecular dynamics simulations.

Lewis acid-activated oxidation of alcohols by permanganate

The oxidation of alcohols by KMnO(4) is greatly accelerated by various Lewis acids. Notably the rate is increased by 4 orders of magnitude in the presence of Ca(2+). The mechanisms of the oxidation of CH(3)OH and PhCH(OH)CH(3) by MnO(4)(-) and BF(3)·MnO(4)(-) have also been studied computationally by the DFT method.

Substituent effect on the UV spectra of p‐disubstituted compounds XPh(CHCHPh)nY (n = 0, 1, 2)

AbstractThree parameters, ${\rm \sigma }_{\rm CC}^{\rm ex} $, ${\rm \sigma }_{\rm CC}^{\rm ex} ({\rm XY)}$ and $\upsilon_{{\rm max,}\,{\rm parent}} $, are developed to express the substituent effect and the effect of the parent molecular structure of p‐disubstituted compounds XPh(CHCHPh)nY (n = 0, 1, 2). The investigated result shows a good correlation between the UV absorption wavenumbers (υmax) and the three parameters for a diverse set of title compounds, and the correlation equation can be used to predict the UV absorption energy of compounds with the mentioned structure. This approach provides a new insight for the quantitative structure‐property relationship (QSPR) correlation of the UV absorption energy of p‐disubstituted homologues. Copyright © 2010 John Wiley & Sons, Ltd.

1-(3-Phenylpropyl)urea

In the crystal of the title compound, C10H14N2O, double supra­molecular layers of PhCH2CH2CH2NHC(O)NH2 are formed parallel to the bc plane by inter­molecular N—H⋯O hydrogen bonding, with R 2 2(8) and R 2 1(6) motifs in the b- and c-axis directions, respectively. The mean plane of the Car—C—C group makes a dihedral angle of 84.8 (2)° with the benzene ring.

Ancillary Ligand and Ketone Substituent Effects on the Rate of Ketone Insertion into Zr−C Bonds of Zirconocene−1-Aza-1,3-diene Complexes

Zirconocene−1-aza-1,3-diene complexes, [Me2Si(C5H4)2]Zr[N(Ar)CH═CHCH(Ph)] (Ar = Ph, 2a; Ar = p-MeOC6H4, 2b) and Cp2Zr[N(Ar)CH═CHCH(Ph)] (Ar = Ph, 3a; Ar = p-MeOC6H4, 3b), have been synthesized and characterized by NMR spectroscopy. X-ray crystal structure determinations of compounds 2a and 3a,b reveal folded five-membered-ring moieties for the zirconacycles. DFT calculations and variable-temperature NMR experiments for complex 2a establish a rapid ring-flipping process at room temperature, with the conformation bearing a pseudoequatorial Ph group more stable by 5.6 kcal/mol. Kinetic studies on ketone insertion into these zirconocene complexes show second-order reactions, and the insertion is more favorable in the presence of a [Me2Si] ansa bridge, a less electron-rich substituent on the nitrogen, and a more basic ketone. One of the insertion products, namely Cp2Zr[N(Ph)CH═CHCH(Ph)CPh2O] (5a), has also been characterized by X-ray crystallography.

Reversible decomposition of mono(α-hydroxy)phosphines and their reaction with α,β-unsaturated aldehydes

The mono(α-hydroxy)phosphines R2PCH(OH)R′ (R = Ph, R′ = H, Et, CH2Ph, Ph, p-X-C6H4; R = cyclohexyl, R′ = Ph) are prepared under solvent-free conditions by a 1:1 reaction of Ph2PH with the appropriate aldehyde, and their stabilities (with respect to reversible dissociation into reactants), studied in DMSO, Et2O, and MeOH, increase with decreased basicity of the hydroxyphosphine; for example, for the Ph2PCH(OH)C6H4-p-X phosphines, stability decreases in the order: X = CN > Cl > F > H > Me > OMe. A 1:1 room-temperature reaction of the (α-hydroxy)phosphines (except for R′ = H) with cinnamaldehyde in DMSO slowly yields the known mono- and di-phosphines Ph2PCH(Ph)CH2CHO (4a) and Ph2PCH(Ph)CH2CH(PPh2)OH (10a), and the corresponding R′CHO aldehyde. In MeOH, the sequentially formed intermediates, PhCH=CHCH(OH)PPh2, PhCH(OH)CH=CHPPh2, and Ph2PCH(Ph)CH=CHOH, were detected en route to 4a and 10a. Reaction of cinnamaldehyde with Ph2PCH2OH gives 4a and the hemiacetal Ph2PCH2OCH2OH formed from the reactant hydroxyphosphine with the co-product formaldehyde. Reactions carried out in MeOH are faster because of the formation of hemiacetals from the phosphine-containing aldehyde products; thus, 4a is seen as Ph2PCH(Ph)CH2CH(OMe)(OH), which on dissolution in Et2O, reverts to the aldehyde. The reaction rates and equilibrium concentrations of the various species depend on the R′ group of the reactant phosphine; the rates of consumption of the hydroxyphosphines in the reactions with cinnamaldehyde decrease in the order: Ph2PCH(OH)Ph > Ph2PCH(OH)Et > Ph2PCH(OH)CH2Ph >> Ph2PCH2OH. The reactivity pattern of Ph2PCH(OH)Ph with sinapaldehyde [3,5-(OMe)2-4-OH-cinnamaldehyde] in DMSO follows that seen for cinnamaldehyde. Reaction of Ph2PH with cinnamaldehyde in DMSO affords 4a and 10a via the same intermediates seen with the Ph2PCH(OH)R′ reagents, but these latter reactions are thought to occur via direct attack on cinnamaldehyde by the hydroxyphosphine rather than via Ph2PH.

Reaction of secondary phosphine selenides with the system Se/MOH (M = Li, Na, K, Rb, Cs): A novel three-component synthesis of diorganodiselenophosphinates

Secondary phosphine selenides, R 2P(Se)H (R = PhCH 2CH 2, PhCH(Me)CH 2, 4- t-BuC 6H 4CH 2CH 2, NaphthylCH 2CH 2, Ph), react with the system Se/MOH (M = Li, Na, K, Rb, Cs) in the system THF/EtOH at ambient temperature unusually fast (20–30 s) to give cleanly and almost quantitatively (in 94–100% yield) earlier unknown diorganodiselenophosphinates of alkali metals.

2D IR photon echo spectroscopy reveals hydrogen bond dynamics of aromatic nitriles

The CN vibrations of two aromatic nitriles, cinnamonitrile, PhCH CH–CN and benzonitrile, PhCN, representative of components of common enzyme inhibitors, are examined by two-dimensional infrared spectroscopy. In methanol, these spectra display cross peaks between the two CN components whose evolution exposes the few picosecond (4.5 ps for CIN and 5.3 ps for BN) equilibrium dynamics of hydrogen bond making and breaking. The main features of the 2D IR spectra are reproduced by simulations only when exchange is incorporated. The lowest free energy state is the non-hydrogen bonded form. Both alkyl and aryl nitriles have now shown this picosecond exchange process.

Reactivity of the N-heterocyclic carbene complexes [Ru(IMes) 2(CO)HX] (X = OH, Cl) with alkynes

Treatment of the 16-electron hydroxy hydride complex [Ru(IMes) 2(CO)H(OH)] ( 1, IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene) with HC CR affords the alkynyl species [Ru(IMes) 2(CO)H(C CR)] (R = Ph 3, SiMe 3, 4) and [Ru(IMes) 2(CO)(C CR) 2] (R = Ph, 5). Deuterium labelling studies show that the mono-alkynyl complexes are formed via hydrogen transfer from a coordinated alkyne ligand to Ru–OH, while bis-alkynyl formation is proposed to take place through hydrogen transfer to Ru–H. Both 3 and 5 readily coordinate CO to give the corresponding dicarbonyl species 6 and 7. Addition of HC CPh to the hydride chloride precursor [Ru(IMes) 2(CO)HCl] ( 2) results in a different reaction pathway involving alkyne insertion into the Ru–H bond to yield the alkenyl chloride complex [Ru(IMes) 2(CO)(CH CHPh)Cl] 8. Complexes 3– 8 have been structurally characterised by X-ray crystallography.