The effect of nitrobenzene and aminobenzoic acids on the hydration of tricalcium silicate: a conduction calorimetric study

The hydration of tricalcium silicate (C₃S) in the presence of 0.004, 0.008 and 0.016 mol.% (with respect to 100 g of the silicate) of benzole acid, o-, m- and p-nitrobenzoic and aminobenzoic acids, was followed by conduction calorimetry. Benzoic acid at 0.004 and 0.008 moles behaved as a delayed accelerator of hydration, whereas at a dosage of 0.016 moles it performed as an accelerator by decreasing the onset of the induction period and promoting the earlier appearance of the main exothermic peak. The m- and p-nitrobenzoic acids accelerated the hydration of C₃S, whereas o-nitrobenzoic acid acted as a retarder. Both m-and p-aminobenzoic acids retarded the hydration by delaying the appearance of the main exothermal peak. o-Aminobenzoic acid showed a similar effect to that of the reference at early times by not affecting the induction period and the maximum rate-of-heat peak. However, it increased slightly the amplitude of the main exothermic peak. The compounds that promoted the appearance of a heat peak at periods of 1 h or earlier exhibited an acceleration effect. In the presence of retarders this peak did not appear.     

Synthesis and characterization of dinuclear p-, m- and o-xylyl bridged complexes of molybdenum and tungsten. The crystal structures of μ-p-xylyl- bis(η-pentamethyl-cyclopentadienyltri- carbonylmolybdenum) and μ-m-xylyl-bis(η- pentamethylcyclopentadienyltricarbonyltungsten)

The reactions of η⁵-Cp^*M(CO)₃Na (M = Mo, W) with ,′-p-, m- and o-dichloro-xylenes yielded p-, m- and o-xylyl bridged dinuclear complexes of η⁵-Cp^*M(CO)₃ in high yields. All of such new complexes are stable to air and water, even stable in dilute acids and bases.     

Addition of a Reformatsky reagent to N-anthracene-9-sulfonyl and related imines: Synthesis of protected β-amino acids

The Reformatsky reagent tert-butoxycarbonylmethylzinc bromide adds in high yields to N-sulfonylimines, e.g. 1a–1d, derived by condensation of benzaldehyde dimethyl acetal with methanesulfonamide, toluene-4-sulfonamide, 4-(methoxycarbonyl)benzenesulfonamide and sulfamide: the products are protected β-amino acids 2a–2d. N-Deprotection occurs reductively (Na-naphthalene; low yields) for 2b and 2c or hydrolytically (refluxing aq. pyridine; 76% yield of amino acid 3a after acid hydrolysis of the t-butyl ester) for the sulfamide derivatives 2d. Anthracene-9-sulfonamide (6) is readily available by sulfonation and chlorination of anthracene, and condenses with aldehydes [RCHO; R = Ph, 4-FC₆H₄, 4-MeOC₆H₄, 4-NCC₆H₄, 2-furyl, (E)-styryl], e.g. in the presence of TiCl₄/Et₃N, to yield imines 7a–7f, which after addition of tert-butoxycarbonylmethylzinc bromide give protected amino acids 8a–8f; however, 8f cyclizes to the sultam 9 via a spontaneous intramolecular Diels-Alder reaction. Reductive cleavage of the N-anthracene-9-sulfonyl group is much easier than for traditional N-sulfonyl protecting groups, as demonstrated by the deprotection of 8a and 8c using aluminium amalgam.     

Substituent effects on the frontier molecular orbitais of aryl isonitriles

An investigation of the frontier molecular orbitais ofo- and p-RC₆H₄NC (R=H, CH₃, NO₂, F, Cl, CF₃, OCH₃) was carried out so that a thorough understanding of the intricacies of σ donation and π acceptance could be developed and used to modify subtly the electron density on metal centers. The results of this study-Indicate that the substituent position (ortho vs. para ) does alter the electron density in the ligand appreciably and that substitution of the phenyl ring with the groups indicated has a smaller effect on the σ-donating ability than it does on the π-accepting ability of the isonitrile ligand.

The π-accepting abilities of the isonitrile ligands increase in the order o-, p-CH₃OC₆H₄NC, o-, p-CH₃C₆H₄NC, o-, p-C₆H₅NC, o-, p-FC₆H₄NC, o-, p-CF₃C₆NC, o-, p-ClC₆H₄NC, o-, p-NO₂C₆H₄NC while the σ-donating ability decreases in this order. The energies of the σ-donor and π-acceptor orbitais are shown to correlate well with observed E values of Cr(RC₆H₄NC)₆ and Mn(RC₆H₄NC)₆⁺¹ complexes. This demonstrates how the theoretical results can be useful in understanding the observed physical properties of isonitrile-metal complexes.     

七水合三氯化铈-碘化钠催化氨基苯硫酚与高位阻α, β-不饱和酮的迈克尔加成反应

对七水合三氯化铈-碘化钠(CeCl₃·7H₂O-NaI)化邻氨基苯硫酚、 对氯邻氨基苯硫酚、 间氨基苯硫酚、 对氨基苯硫酚和对甲基苯硫酚与α,β-不饱和酮(1a~1o)的迈克尔加成反应进行了系统研究. 结果表明, CeCl₃·7H₂O-NaI-SiO₂复合催化剂能有效催化邻氨基苯硫酚及对氯邻氨基苯硫酚与α,β-不饱和酮(1a~1o)的迈克尔加成反应. 在优化的反应条件下, 即n(CeCl₃·7H₂O):n(NaI):n(α,β-不饱和酮)=1:2:2, m(CeCl₃·7H₂O):m(SiO₂)=1:1.6, 三氯甲烷作溶剂, 反应温度为回流温度, 反应时间为2 h, 反应可达到中等产率(43.1%~58.8%). 催化剂重复使用4次基本稳定. 此外, 提出了可能的催化机理.     

Synthesis and properties of halogen- or methyl-containing poly(diphenylacetylene) membranes

Novel diphenylacetylenes with both trimethylsilyl groups and other substituents (R₂C₆H₃CCC₆H₄-p-SiMe₃, R = m,p-Cl,Cl, m,m-Cl,Cl, m,p-Br,Br, m,m-Br,Br, m,p-Me,Me, m,m-Me,Me, 1a–f, respectively) were polymerized with TaCl₅–n-Bu₄Sn to produce solvent-soluble polymers (2a–f). Most polymers (2a–e) had high molecular weight over 1 × 10⁶, and gave free-standing membranes by the solution casting method. Desilylation of these Si-containing polymer membranes was carried out with trifluoroacetic acid (TFA), which afforded solvent-insoluble desilylated polymer membranes (3a–e). According to thermogravimetric analysis (TGA), both Si-containing and desilylated polymers showed high thermal stability (T₀ ≥ 420 °C). The fractional free volume (FFV) of both Si-containing and desilylated polymer membranes (2a–d, 3a–d) were fairly large (ca. 0.27–0.32), while the FFVs of membranes (2e, 3e) were rather small (0.28 and 0.24). The oxygen permeability coefficients (P_O2) of 2a was as high as 5400 barrers, which is the largest among all the poly(diphenylacetylene) derivatives. Polymers 2b–d also exhibited high oxygen permeability, and their desilylated ones 3b–d retained similar high oxygen permeability. On the other hand, the P_O2 values of 2e and 3e were 1200 and 530 barrers, respectively, which are smaller than those of the halogen-containing polymers (2a–d and 3a–d).     

Laser-induced fluorescence, dispersed fluorescence and lifetime measurements of jet-cooled chloro-substituted benzyl radicals

We measured the laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of jet-cooled -, o- and m-chlorobenzyl radicals after they were generated by the 193 nm photolysis of the corresponding parent molecules. The vibronically resolved spectra were obtained to analyze their D₁–D₀ transitions. The fluorescence lifetimes of -, o-, m- and p-chlorobenzyls in the zeroth vibrational levels of the D₁ states were measured to estimate the oscillator strengths of a series of benzyl derivatives. It was found that the -substitution is inefficient to break the ‘accidental forbiddenness' of the D₁–D₀ transition of benzyl, while the ring-substitution enhances the oscillator strength by 50%.     

Dienon-phenol-umlagerung von Chinolen—II Beitrag zur klärung des reaktionsmechanismus

Rearrangements of o- and p-quinol-acetates and of p-quinols under conditions of the Thiele-reaction are described. To investigate the mechanism of these reactions rearrangements have also been carried out in diacetyl-sulphide.

The differences between the reactions of p-quinols and p-quinol-acetates are being discussed in some detail.

The results of action of acids upon p-toluquinol and its acetate are in accordance with our conceptions on the course of other reactions mentioned in this paper.     

Reactions of boroxazolidones with aromatic aldehydes : An easy route to derivatives of isoquinoline and iso-indolinone

Boroxazolidones 1 derived from glycine and phenylalanine react with aromatic aldehydes to form the corresponding imines. The product 3 from 1a with o-carboxybenzaldehyde is converted into 4-hydroxyisoquinoline-3-carboxylic acid 6 by dimethyl sulfate, followed by t-BuOK, and aqueous acid.

With o-phthalaldehyde and 1a,b the isoindolinones 11a,b are obtained. These reactions proceed via carboxylic acids 9. Compound 9a was also prepared from 3 by catalytic, hydrogenation. Salicylaldehyde and 1a gave polymeric material, but the preformed Schiff's base 13 can be transformed into the p-nitrobenzyl ester 15 by treatment successively with dicyclohexylamine, triethylborane and p-nitrobenzyl bromide.     

New enantiopure C2 symmetric bis(2-oxazolinyl)cage (Cage-Box) ligands from 4,5-dicyanopyridazine

7,8-Dicyanotetracyclo[7.3.0.0^2,60^5,10]dodec-7-ene 3, obtained from 4,5-dicyanopyridazine 1 and cycloocta-1,5-diene 2 through a three-step pericyclic homodomino process, was found to react with optically active β-amino alcohols 4a–d, under zinc chloride catalysis, to afford a new class of enantiopure C₂ symmetric bis(oxazolinyl)cage (Cage-Box) ligands 6a–d, along with the corresponding mono(oxazolinyl) derivatives 5a–d.     

Systematische untersuchungen über das verhalten von organozinnverbindungen gegenüber flüssigem schwefeldioxid II. Reaktionen von arylstannanen mit flüssigem SO2

The behaviour of tetraarylstannanes, R₄Sn (R = C₆H₅CH₂, C₆H₅, o-, m-, p-CH₃C₆H₄), towards SO₂ under various conditions has now been studied in detail. Compared to aliphatic tetraorganostannanes, the variability of the reaction products is much less, so that in nearly all cases only disulfinates, R₂Sn(O₂SR)₂, are formed. The aromatic tin(IV) mono-, di- and tri-sulfinates are also obtained by metathetical reaction between the corresponding organotin halides and sodium sulfinates. A unique feature of triaryltin chlorides, R₃SnCl (R = C₆H₅, o-, m-, p-CH₃C₆H₄), is their disproportionation in liquid SO₂ leading to disulfinates, R₂Sn(O₂SR)₂, and dichlorides, R₂SnCl₂. (p-CH₃C₆H₄)₂SnCl₂, under more efficient conditions, also accepts SO₂ forming (p-CH₃C₆H₄SO₂)₂SnCl₂. The structural investigations of the newly prepared compounds are carried out on the basis of their IR and ¹H NMR spectra.     

Photochemical addition of amino acids and peptides to homopolyribonucleotides of the major DNA bases

Abstract— The photochemical quantum yields for addition of glycine and the L-amino acids commonly occurring in proteins (excluding proline) to polyadenylic acid, polycytidylic acid, polyguanylic acid and polyribothymidylic acid have been determined in deoxygenated phosphate buffer at Λ 254 nm and pH 7, using a fluorescamine assay technique. Polyadenylic acid was reactive with eleven of the twenty amino acids tested, with phenylalanine, tyrosine, glutamine, lysine and asparagine having the highest quantum yields. Polyguanylic acid reacted with sixteen amino acids; phenylalanine, arginine, cysteine, tyrosine, and lysine displayed the largest quantum yields. Polycytidylic acid showed reactivity with fifteen amino acids with lysine, phenylalanine, cysteine, tyrosine and arginine having the greatest quantum yields. Polyribothymidylic acid, reactive with fifteen of nineteen amino acids surveyed, showed the highest quantum yields for cysteine, phenylalanine, tyrosine, lysine and asparagine. None of the polynucleotides were reactive with aspartic acid or glutamic acid.
The quantum yields for photoaddition of eighteen dipeptides of the form glycyl X (X being one of the amino acids commonly occurring in proteins, including proline), and of L-alanyl-L-tryptophan, L-seryl-L-seryl-L-serine, L-threonyl-L-threonyl-L-threonine, L-cystine- bis -glycine, and N_α-acetyllysine to polyadenylic acid, polycytidylic acid and polyguanylic acid were measured. All of these were found to add photochemically to each of these polymers. Polyribothymidylic acid, tested with eleven of these peptides and with N_α-acetyllysine, was found to be reactive with all.     

Synthetic studies towards cyclic peptides. Concise synthesis of thiazoline and thiazole containing amino acids

Concise and efficient syntheses of optically pure thiazoline and thiazole containing amino acids of the constitution (26) and (27), based on simple condensation reactions between cysteine esters and N-protected imino ethers (22) and (25) derived from chiral amino acids, are described. The synthetic procedures are compatible with a range of amino acid side chains and protecting groups, and allow the preparation of a variety of small optically pure peptides i.e. (32) and (34) suitable for elaboration to naturally occurring cyclic peptides e.g. the lissoclinamides (3) and (4).     

Chemistry and reactivity of dinuclear manganese oxamate complexes: Aerobic catechol oxidation catalyzed by high-valent bis(oxo)-bridged dimanganese(IV) complexes with a homologous series of binucleating 4,5-disubstituted-o-phenylenedioxamate ligands

The high-valent bis(oxo)-bridged dimanganese(IV) complexes with the series of binucleating 4,5-X₂-o-phenylenebis(oxamate) ligands (opbaX₂; X = H, Cl, Me) (1a–c) have been synthesized and characterized structurally, spectroscopically and magnetically. Complexes 1a–c possess unique Mn₂(μ-O)₂ core structures with two o-phenylenediamidate type additional bridges which lead to exceptionally short Mn–Mn distances (2.63–2.65 Å) and fairly bent Mn–O–Mn angles (94.1°–94.6°). The cyclovoltammograms of 1a–c in acetonitrile (25 °C, 0.1 M Bu₄NPF₆) show an irreversible one-electron oxidation peak at moderately high anodic potentials (E_ap = 0.50–0.85 V versus SCE), while no reductions are observed in the potential range studied (down to −2.0 V versus SCE). These dinuclear manganese oxamate complexes are excellent catalysts for the aerobic oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone in acetonitrile at 25 °C. The order of increasing catecholase activity (k_obs) with the electron donor character of the ligand substituents as 1b (X = Cl) < 1a (X = H) < 1c (X = Me) correlates with Hammett σ⁺ values (ρ = −0.95). A mechanism involving initial activation of the catechol substrate by coordination to the dimetal center and subsequent oxidation to quinone by O₂ is proposed, which is consistent with the observed saturation kinetics.     

Preparation, properties, and reactions of metal-containing heterocycles: Part CV. Synthesis and structure of polyoxadiphosphaplatinaferrocenophanes

A series of novel heterobimetallic crown ether-like polyoxadiphosphaplatinaferrocenophanes cis-[1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂]PtCl₂ (n=1–3) (4a–c) was synthesized in good yield by cyclization of the bis(phosphine) ligands 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂PPh₂)₂ (n=1–3) (3a–c) and (PhCN)₂PtCl₂ under high dilution conditions in CH₂Cl₂. The bisphosphines 3a–c are obtained by reaction of the corresponding diols 1,1′-Fc(CH₂O(CH₂CH₂O)_nCH₂CH₂OH)₂ (n=1–3) (1a–c) with: (i) CH₃SO₂Cl in CH₂Cl₂ and (ii) LiPPh₂ in THF. Although the X-ray crystal structure of 4a shows that the cavity is large enough for the encapsulation of small metal cations, inclusion experiments of 4a–c with Group 1 cations, and Mg²⁺, or NH₄⁺ in solution applying NMR titration and cyclovoltammetric methods reveal no evidence for the formation of host–guest complexes for 4a,b. In the case of 4c only the addition of Na⁺ or K⁺ leads to an insignificant effect.     

Preparation, properties, and reactions of metal-containing heterocycles: Part CVI. Three-dimensional water-soluble platinacyclophanes

Trifunctional primary phosphines of the type 1,3,5-[PH₂(CH₂)_n]₃C₆H₃ (3b–d) were obtained via an Arbusov reaction between the 1,3,5-tris(bromoalkyl)benzenes 1b–d and P(OEt)₃ followed by a reaction of the trisphosphonates 1,3,5-[(EtO)₂P(O)(CH₂)_n]₃C₆H₃ (2b–d) with LiAlH₄. A straightforward conversion of these sensitive key phosphines 3b–d to the corresponding water-soluble ligands 1,3,5-tris[bis(hydroxymethyl)phosphinylalkyl]benzenes 4b–d and 1,3,5-tris[bis(2′-diethylphosphonatoethyl)phophinylalkyl]benzenes 5b–d was achieved by formylation with formaldehyde and hydrophosphonation with diethyl vinylphosphonate, respectively. A five component self-assembly consisting of three equivalents of the platinum(II) complex Cl₂Pt(NCPh)₂ and two equivalents of the ligands 5b–d under high dilution conditions resulted in the formation of the nanoscaled, water-soluble triplatinacyclophanes 6b–d in high yields. However, comparable reactions with the ligands 4b–d led only to polymeric materials, which are insoluble in all organic solvents and water. The structures of the metallacyclophanes 6b–d were elucidated by ³¹P{¹H}-, ¹³C{¹H}-, and ¹⁹⁵Pt{¹H}-NMR spectroscopic investigations.     

Synthesis of bicyclic dioxetanes bearing a 2-hydroxy-1,1′-binaphthyl-5-yl moiety active toward intramolecular charge-transfer-induced chemiluminescent decomposition

Five pairs of diastereoisomeric dioxetanes, cis- and trans-2a–2e, were synthesized. These dioxetanes underwent intramolecular charge-transfer-induced decomposition with accompanying emission of orange light in TBAF in DMSO (system A) as a complete homogeneous system and in [K(18C6)]⁺t-BuO⁻ in PhH–THF (system B) as a sterically anisotropic environment. Maximum wavelength (λ_max^CTICL) of chemiluminescence did not vary practically with the triggering system. The λ_max^CTICL was little affected also by substituents on the upper-Nap of dioxetanes 2, nor by the difference in their stereochemistry, namely, cis- or trans-isomer. On the other hand, chemiluminescent efficiency was found to split up depending on stereochemistry of 2. Dioxetane 2b bearing a methoxycarbonyl group on the upper-Nap gave significantly weak light, while its free carboxylic acid analog 2c afforded light effectively.     

The effect of temperature on the solubility of benzoic acid derivatives in water

Using a laser monitoring observation technique, solubilities of o-nitro-benzoic acid, p-hydro-benzoic acid, p-methyl-benzoic acid and m-methyl-benzoic acid in water have been measured in the temperature range 290.15–323.15 K. The experimental data are regressed with the Wilson equation and the λH equation. The experimental results show that solubilities of these compounds in the range of 10⁻⁴–10⁻⁵ mole fraction in water, increase significantly with temperature. Except for o-nitro-benzoic acid, the solubility data are described adequately with the Wilson equation. The λH equation gives good agreement with all experimental data. The results indicate that the molecular structure and interactions affect the solubilities significantly.     

Synthesis, characterization, and X-ray crystal structures of W(VI) alkyl complexes with chelating diamide and imido co-ligands

The complex W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄] 3 was synthesized from PhN = WCl₄ · OEt₂ and N,N′-(Li₂[o-(NSiMe₃)₂C₆H₄] and reacts with Lewis bases to form the adducts W(NPh)Cl₂[o-(NSiMe₃)₂C₆H₄](L) (L = PMe₃, THF, 3-picoline, ^tBuNC, MeCN) 4a–e. Crystals of 4a are triclinic, space group P1¯, with a = 9.562(1), b = 10.277(1), c = 14.920(2) Å, = 82.15(1), β = 80.18(1), γ = 80.41(1)°, and Z = 2. The structure was solved by the heavy atom method and refined to R = 0.0408 for 4224 observed (I > 2σ(I)) reflections. The dialkyl complexes W(NPh)R₂[o-(NSiMe₃)₂C₆H₄] (R = Me, Et, CH₂Ph, CH₂CMe₃, CH₂CMe₂Ph) 5–9 are formed through subsequent reactions of 3 with the corresponding Grignard reagent. Crystals of complex 5 are monoclinic, space group P2(1)/n, with a = 10.3545(2), b = 17.9669(1), c = 13.3168(1) Å, β = 103.826(1)°, and Z = 4. The structure of complex 5 was solved by direct methods in SHELXTL5 and refined to R = 0.0247 for 4572 observed reflections. Compound 5 has a square pyramidal geometry in which the imido ligand occupies the apical position and reacts with PMe₃ to form the adduct W(NPh)Me₂[o-(NSiMe₃)₂C₆H₄](PMe₃) 5a. Crystals of complex 5a are monoclinic, space group C2/m, with a = 13.5336(1), b = 14.4291(1), c = 15.3785(1) Å, β = 110.365(1)°, and Z = 4. The structure of compound 5a was solved by direct methods in shelxtl5 and refined to R = 0.0272 for 3057 observed reflections. Crystals of the bis-neopentyl complex 8 are monoclinic, space group P2(1)/n, with a = 10.6992(4), b = 18.3144(7), c = 16.0726(6) Å, β = 92.042(1)°, and Z = 4. The structure of 8 was solved by direct methods in shelxtl5 and refined to R = 0.0261 for 5881 observed reflections. Complex 8 has a trigonal bipyramidal geometry with both neopentyl groups and one amido nitrogen in the equatorial plane.     

A study of ortho- and para-siloxyanilines for the synthesis of mono-, bi-, and tetra-nuclear early transition metal–imido complexes

The siloxyanilines o-Me₃SiOC₆H₄NH₂ (1) and p-RMe₂SiOC₆H₄NH₂ (R=H (2); R=Me (3)), and their N-silylated derivatives p-Me₃SiOC₆H₄NHSiMe₃ (4) and p-Me₃SiOC₆H₄N(SiMe₃)₂ (5) have been prepared from ortho- or para-aminophenol and used in the synthesis of imido complexes. Thus, binuclear [{Ti(η⁵-C₅H₅)Cl}{μ-NC₆H₄(p-OSiMe₃)}]₂ (6) and mononuclear [TiCl₂{NC₆H₄(p-OSiMe₃)}(py)₃] (7) imido complexes have been obtained from the reaction of 3 and [Ti(η⁵-C₅H₅)Cl₃] or [TiCl₂(N^tBu)(py)₃], respectively. In contrast, the reaction of 1 with TiCl₄ and ^tBupy affords the titanocycle [TiCl₂{OC₆H₄(o-NH)---N,O}(^tBupy)₂] (8). Compound 5 has also been used to prepare the niobium imide complex [NbCl₃{NC₆H₄(p-OSiMe₃)}(MeCN)₂] (9), by its reaction with NbCl₅ in CH₃CN. These findings have been applied to the synthesis of polynuclear systems. Thus, chlorocarbosilane Si[CH₂CH₂CH₂Si(Me)₂Cl]₄ (CS–Cl) has been functionalized with the ortho- and para-aminophenoxy groups to give 10 and 11, respectively. The use of 11 has allowed the formation of the tetranuclear compound 12. Attempts to synthesize terminal imido titanium complexes from 10 and TiCl₄ in the presence of ^tBupy and Et₃N, give complex 8 and carbosilane CS–Cl.