Colorless poly(ether-imide)s deriving from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA) and aromatic bis(ether amine)s bearing pendent trifluoromethyl groups

A series of poly(ether-imide)s (III) characterized by colorless, highly solubility was synthesized from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride(BPADA) and various fluorinated aromatic diamines (I_a-h) in DMAc via polycondensation to form poly(amic acid) (II), followed by chemical (C) and thermal (H) imidization. These polymers had inherent viscosities ranging from 0.60 to 1.3 dL/g. These polyimides were highly soluble in a variety of organic solvent such as amide-type, ether-type and chlorinated solvents. Moreover, these poly(ether-imide) films were almost colorless, with an ultraviolet-visible absorption cutoff wavelength below 390 nm and low b* value (a yellowness index) of 4.6-18.0. The III series showed strength tensile of 72-101 MPa, elongation at break of 11-25%, initial modulus of 1.5-2.0 GPa. The glass transition temperature (T_g) of III_a-h were in the range of 202-267 °C, and the decomposition temperature above 493 °C and left 40-65% char yield at 800 °C in nitrogen. They had the lower dielectric constants of 3.39-3.72 (1 MHz) and moisture absorptions in the range of 0.11-0.40%.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

Novel organosoluble and colorless poly(ether imide)s based on 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride and trifluoromethyl-substituted aromatic bis(ether amine)s

A series of novel fluorinated poly(ether imide)s (IV) having inherent viscosities of 0.70-1.08 dL/g were prepared from 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride (I) and various trifluoromethyl (CF₃)-substituted aromatic bis(ether amine)s II_a-g by a standard two-step process with thermal and chemical imidization of poly(amic acid) precursors. These poly(ether imide)s showed excellent solubility in many organic solvents and could be solution-cast into transparent, flexible, and tough films. These films were essentially colorless, with an ultraviolet-visible absorption edge of 375-380 nm and a very low b^∗ value (a yellowness index) of 5.5-7.3. They also showed good thermal stability with glass-transition temperatures of 207-269 °C, 10% weight loss temperatures in excess of 474 °C, and char yields at 800 °C in nitrogen more than 62%. In comparison with analogous V series poly(ether imide)s without the -CF₃ substituents, the IV series polymers showed better solubility, lower color intensity, and lower dielectric constants.     

A highly stereoselective preparation of CF3-substituted 1-aryl-1,2-diphenylethenes: application to the synthesis of panomifene

β-CF₃-α,β-diphenylvinyl sulfide 3a was prepared stereoselectively in 77% yield from the reaction of 2 with phenyllithium at room temperature for 5 h. Oxidation of 3a with MCPBA afforded the corresponding vinyl sulfone 4a, in which (E)-4a can be crystallized in a mixture of CH₂Cl₂ and hexane. The addition-elimination reaction of (E)-4a with phenyllithium having substituents on the benzene ring provided 5a-j in 51-82% yields stereospecifically. Similarly, the treatment of (E)-4a with p-chloroethoxyphenyllithium in the presence of 12-crown-4 (20 mol %) at −10 °C, followed by slowly warming to room temperature, resulted in the formation of the corresponding panomifene precursor 6 in 82% yield.     

Synthesis, characterization, and ethylene polymerization behavior of [(RR′-admpzp)2Ti(OPr)2] complexes (RR′-admpzp = 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-olate)

[(RR′-admpzp)₂Ti(OPrⁱ)₂] complexes (2a-c), synthesized from reaction of Ti(OPrⁱ)₃Cl (0.5 equiv) with 1-dialkylamino-3-(3,5-dimethyl-pyrazol-1-yl)-propan-2-ol compounds in the presence of triethylamine (0.5 equiv), are pseudo-octahedral with each RR′-admpzp ligand κ²-O,N(pyrazolyl) coordinated to the titanium center. In solution, 2a-c adopt isomeric structures that are in dynamic equilibrium. At 23 °C, 2a-c/1000 MAO catalyst systems furnished high molecular weight polymers with narrow molecular weight distributions (M_w/M_n = 2.7-2.8). At 100 °C, 2a-c/MAO catalyst systems exhibited increased polymerization activity and 2c/1000 MAO system furnished high molecular weight polyethylene with a molecular weight distribution (M_w/M_n = 2.1) that is close to that found for single-site catalysts.     

The cyclopalladation reaction of 2-phenylaniline revisited

2-Phenylaniline reacted with Pd(OAc)₂ in toluene at room temperature for 24 h in a one-to-one molar ratio and with the system PdCl₂, NaCl and NaOAc in a 1 (2-phenylaniline):1 (PdCl₂):2 (NaCl):1 (NaOAc) molar ratio in methanol at room temperature for one week to give the dinuclear cyclopalladated compounds (μ-X)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ [1a (X = OAc) and 1b (X = Cl)] in high yield. Moreover, the reaction between 2-phenylaniline and Pd(OAc)₂ in one-to-one molar ratio in acid acetic at 60 °C for 4 h, followed by a metathesis reaction with LiBr, allowed isolation of the dinuclear cyclopalladated compound (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}]₂ (1c) in moderate yield. A parallel treatment, but using monodeuterated acetic acid (DOAc) as solvent in the cyclopalladation reaction, allowed isolation of a mixture of compounds 1c, 1c_d1 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄](μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃] and 1c_d2 (μ-Br)₂[Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)-3-d-C₆H₃}]₂ in moderate yield and with a deuterium content of ca. 60%. 1a and 1b reacted with pyridine and PPh₃ affording the mononuclear cyclopalladated compounds [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(X)(L)] [2a (X = OAc, L = py), 2b (X = Cl, L = py), 3a (X = OAc, L = PPh₃) and 3b (X = Cl, L = PPh₃)] in a yield from moderate to high. Furthermore, 1a reacted with Na(acac) · H₂O to give the mononuclear cyclopalladated compound 4 [Pd{κ²-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(acac)] in moderate yield. ¹H NMR studies in CDCl₃ solution of 2a, 2b, 3a, 3b and 4 showed that 2a and 3a presented an intramolecular hydrogen bond between the acetato ligand and the amino group, and were involved in a dynamic equilibrium with water present in the CDCl₃ solvent; and that the enantiomeric molecules of 2b and 4 were in a fast exchange at room temperature, while they were in a slow exchange for 2a, 3a and 3b. The X-ray crystal structures of 3b and 4 were determined. 3b crystallized in the triclinic space group with a = 9.9170(10), b = 10.4750(10), c = 12.0890(10) Å, α = 98.610(10)°, β = 94.034(10)° and γ = 99.000(10)° and 4 in the monoclinic space group P2₁/a with a = 11.5900(10), b = 11.2730(10), c = 12.2150(10) Å, α = 90°, β = 107.6560(10)° and γ = 90°.     

Preparation and nonlinear optical properties of novel Y-type polyesters with highly enhanced thermal stability of second harmonic generation

3,4-Di-(2′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with terephthaloyl chloride and adipoyl chloride to yield novel Y-type polyesters (4-5) containing 3,4-dioxybenzylidenemalononitrile groups as NLO-chromophores, which constituted parts of the polymer main-chains. The resulting polymers 4-5 are soluble in common organic solvents such as acetone and N,N-dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis with glass-transition temperatures obtained from differential scanning calorimetry in the range 89-91 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength were around 2.47 pm/V. The dipole alignment exhibited high thermal stability even at 10 °C higher than T_g, and there is no SHG decay below 100 °C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.     

A flow chemistry route to 2-phenyl-3-(1H-pyrrol-2-yl)propan-1-amines

The Knoevenagel condensation of pyrrole-2-carboxaldehyde (1) with a range of substituted benzyl nitriles (2a-e) afforded rapid access to a family of α,β-unsaturated nitriles (3a-e) in good yields (67-78%). Flow hydrogenation (ThalesNano H-cube™) at 60 °C, 50 bar H₂ pressure, 1.0 mL/min through a 10% Pd-C catalyst selectively, and quantitatively, hydrogenated the olefin double bond (4a-e). Use of a Raney Nickel catalyst at 70 °C, 70 bar H₂ pressure and flow rates of 0.5-1.0 mL/min afforded quantitative conversion into the corresponding saturated amines with the reduction of both the olefin and nitrile bonds (5a-e). The versatility of this approach was further exemplified by reaction of 5a and 5c with norcantharidin to afford acid amide norcantharidin analogues 7 and 8 as novel protein phosphatase 1 and 2A inhibitors.     

Synthesis of 2,3-disubstituted benzofurans and indoles by π-Lewis acidic transition metal-catalyzed cyclization of ortho-alkynylphenyl O,O- and N,O-acetals

The PtCl₂-catalyzed cyclization reaction of ortho-alkynylphenyl acetals 1 in the presence of COD (1,5-cyclooctadiene) produces 3-(α-alkoxyalkyl)benzofurans 2 in good to high yields. For example, the reaction of acetaldehyde ethyl 2-(1-octynyl)phenyl acetal (1a), acetaldehyde ethyl 2-(cyclohexylethynyl)phenyl acetal (1c), and acetaldehyde ethyl 2-(phenylethynyl)phenyl acetal (1f) in the presence of 2 mol % of platinum(II) chloride and 8 mol % of 1,5-cycloocatadiene in toluene at 30 °C gave the corresponding 2,3-disubstituted benzofurans 2a, 2c, and 2f in 91, 94, and 88% yields, respectively. Moreover, the reaction of N-methoxymethyl-2-alkynylanilines 3 was catalyzed by PdBr₂, affording the corresponding 2,3-disubstituted indoles 4 in moderate yields. For example, the reaction of N-methoxymethyl-2-(1-pentynyl)-N-tosylaniline (3a) and N-methoxymethyl-2-(phenylethynyl)-N-tosylaniline (3b) in the presence of 10 mol % of PdBr₂ in toluene at 80 °C gave 3-methoxymethyl-2-propyl-1-tosylindole (4a) and 3-methoxymethyl-2-phenyl-1-tosylindole (4b) in 33 and 33% yields, respectively.     

New synthetic route to polyphosphine ligands bearing 1,2,4,5-tetrakis(phosphino)benzene framework: structural characterizations of 1,4-(PPh2)2-2,5-(PR2)2-C6F2 (R = Ph, Pr, Et)

Reactions of 1,4-dibromo-2,5-difluorobenzene with two equivalents of lithium diisopropylamide at low temperature (T < −90 °C) followed by a quench with a slight excess of ClPPh₂ afford 1,4-dibromo-2,5-bis(diphenylphosphino)-3,6-difluorobenzene (1) in good yields. Reacting 1 with two equivalents of BuLi followed by a quench with a slight excess of ClPR₂ yield novel 1,2,4,5-tetrakis(phosphino)-3,6-difluorobenzenes 1,4-(PPh₂)₂-2,5-(PR₂)₂-C₆F₂ (R = Ph (2a); R = ⁱPr (2b); R = Et (2c)) in moderate yields. Compounds 1 and 2a-c were characterized by multinuclear NMR spectroscopy and elemental analyses. In addition, molecular structures of 2a-c have been determined by single crystal X-ray crystallography. Phosphorus atoms of PPh₂/PR₂ substituents in 2a-c are displaced from the plane of the central phenyl ring due to steric interactions with neighboring groups.     

Synthesis and properties of soluble and light-colored poly(amide-imide-imide)s based on tetraimide-dicarboxylic acid (TIDA) and various aromatic diamines: TIDA from 4,4′-oxydiphthalic anhydride, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, and 3-aminobenzoic acid

A new tetraimide-dicarboxylic acid (TIDA) I was synthesized starting from 3-aminobenzoic acid (m-ABA), 4,4′-oxydiphthalic anhydride (ODPA), and 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (BAFPB) at a 2:2:1 molar ratio in N-methyl-2-pyrrolidone (NMP). A series of organosoluble, light-colored poly(amide-imide-imide)s (PAII, III_a-j) was prepared by triphenyl phosphite-activated polycondensation from the tetraimide-diacid I with various aromatic diamines (II_a-j). All the polymers were readily soluble in a variety of organic solvents such as NMP, N,N-dimethyl acetamide (DMAc), dimethyl sulfoxide, and even in less polar m-cresol and pyridine. Polymer films cast from DMAc had the cutoff wavelengths between 374 and 384 nm and had the b^∗ values in the range of 14.8-30.2. Polymers III_a-j afforded tough, transparent, and flexible films, which had tensile strengths ranging from 87 to 103 MPa, elongations at break from 11% to 37%, and initial moduli from 1.9 to 2.3 GPa. The glass transition temperatures of these polymers were in the range of 242-274 °C. They had 10% weight loss temperature above 526 °C and showed the char yield more than 55% residue at 800 °C in nitrogen.     

Synthesis, characterization, and derivatization of some novel types of fluorinated mono- and bis-imidazolidineiminothiones with antitumor, antiviral, antibacterial, and antifungal activities

A series of thirty eight novel imidazolidineiminothiones (6a-g, 10a-h, 13a,b, 15a-d, and 16a), 5-thioxoimidazolidine-2,4-diones (7a-d, 11a-e, 14a,b, and 16b), and bis-imidazolidineiminothiones (17-20) with various fluorinated aromatic substituents at N-(1) and N-(3) were prepared in 75-85% yields. The imidazolidineiminothiones were synthesized from fluorinated N-arylcyanothioformanilides and substituted aromatic isocyanates, and by the reactions of fluorinated aromatic isocyanates with fluorinated and non-fluorinated aromatic N-arylcyanothioformanilides. Subsequent hydrolysis of selected products produced the corresponding 5-thioxoimidazolidine-2,4-diones. Preliminary screening of several compounds against Ehrlich ascites carcinoma (EAC) cells indicated that 6f and 16a were the most active (90% and 80% inhibition, respectively). Further evaluation for cytotoxicity against other tumor cell lines gave IC₅₀ values ranging from 0.67 to 3.83 μg/mL, where compounds 15a and 16a were markedly active against all cell lines. This highlights the synergistic effect of the suitably positioned fluorinated substituents on N-(1) and N-(3) of the imidazolidineiminothiones. Compounds 6a,e-g, 10a-c, 13b, 15a-d, and 17-20 were tested against microbial organisms (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Salmonella typhi, and Sarcina lutea), and fungal strains (Candida albicans, Aspergillus niger, and Aspergillus flavus). Whereas compound 6a exhibited the highest antibacterial activity against Gram positive and Gram negative bacteria, 13b displayed the strongest antifungal activity against all fungal strains, reaching as high as 30 mm. Finally, 15a,b,d were subjected to in vitro testing of antiviral activity against hepatitis A virus (HAV), human herpes simplex virus 1 (HSV1), and Coxsackie B4 (COxB4) viral strain, where 15b was the most effective, reducing virus plaque count of HSV1 and COxB4 by 50% and 60%, respectively.     

Ring-opening metathesis polymerization (ROMP) of N-cycloalkyl-7-oxanorbornene dicarboximides by well-defined ruthenium initiators

Ring-opening metathesis polymerization (ROMP) of exo-N-(1-adamantyl)-7-oxanorbornene-5,6-dicarboximide (AdONDI) (3a), exo-N-cyclohexyl-7-oxanorbornene-5,6-dicarboximide (ChONDI) (3b) and exo-N-phenyl-7-oxanorbornene-5,6-dicarboximide (PhONDI) (3c) using well-defined alkylidene ruthenium catalysts (PCy₃)₂(CI)₂RuCHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy₃)CI₂RuCHPh (II) was studied. The catalysts I and II gave polymers with around 70% and 50% trans vinylene content, respectively. The homopolymer of 3a had a T_g of 198 °C, while poly-3b showed a T_g of 122 °C. Copolymers of 3a, 3b and 3c with norbornene (NB) showed significant T_g increases over poly-NB.     

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH₂CH₂CH₂P(OR′)₂]₂ (I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO)₂ (1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1-8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer,trans-(13a-20a) and mer,cis-[M(Me)(triphos)(CO)₂]I (13b-20b) (M = Ru, Fe; triphos = I-IV). The structures of 13a and 20a (as the tetraphenylborate salt (21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1-8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer,cis-[M(I)(triphos)(CO)₂]I (22-29) (M = Ru, Fe; triphos = I-IV) were produced. Complexes 22-29 could also be obtained by the addition of a stoichiometric amount of I₂ to 1-8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/b-20a/b with CO afforded the acetyl complexes mer,trans-[M(COMe)(triphos)(CO)₂]I, 30-37, respectively (M = Ru, Fe; triphos = I-IV). The ruthenium acetyl complexes 30-33 reacted slowly with 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34-37 were completed within 24-40 h to afford the corresponding zero valent complexes 5-8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer,trans-[Fe(COCD₃)(triphos)(CO)₂]I (38) and mer,trans-[Fe(¹³COMe)(triphos)(CO)₂]I (39).     

Synthesis and characterization of phosphorous-bridged bisphenoxy titanium complexes and their application to ethylene polymerization

Phosphorous-bridged bisphenoxy titanium complexes were synthesized and their ethylene polymerization behavior was investigated. Bis[3-tert-butyl-5-methyl-2-phenoxy](phenyl)phosphine tetrahydrofuran titanium dichloride (4a) was obtained by treatment of 3 equiv of n-BuLi with bis[3-tert-butyl-2-hydroxy-5-methylphenyl](phenyl)phosphine hydrochloride salt (3a) followed by TiCl₄(THF)₂ in THF. THF-free complexes 5a-5d were synthesized more conveniently by the direct reaction of MOM-protected ligands (2a-2d) with TiCl₄ in toluene. X-ray analysis of 4a revealed that the ligand is bonded to the octahedral titanium (IV) center in a facial fashion and two chlorine atoms possess cis-geometry. Complexes 4a and 5a-5d were utilized as catalyst precursors for ethylene polymerization. Complex 5c gave high molecular weight polyethylene (M_w = 1,170,000, M_w/M_n = 2.0) upon activation with Al(ⁱBu)₃/[Ph₃C][B(C₆F₅)₄] (TB). Ethylene polymerization activity of 5d activated with Al(ⁱBu)₃/TB reached 49.0 × 10⁶ g mol (cat) ⁻¹ h⁻¹.     

Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR’(OSiMe3)

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting from the conversion of the corresponding trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at −110 °C was investigated.The trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a: R = Et, 1b: R = ⁱPr, 1c: R = Mes) react with lithium to give initially the trimethylsiloxysilyllithium compounds (Me₃SiO)RPhSiLi (2a-c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlorosilanes 1 to produce the siloxydisilanes (Me₃SiO)RPhSi-SiPhR(OSiMe₃) (Ia-c), and they undergo bimolecular self-condensation affording the trimethylsiloxydisilanyllithium compounds (Me₃SiO)RPhSi-RPhSiLi (3a-c). The siloxydisilanes I are cleaved by excess of lithium to give the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a: R = Et, 3b: R = ⁱPr) a reaction with more trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a, 1b) takes place under formation of siloxytrisilanes (Me₃SiO)RPhSi-RPhSi-SiPhR(OSiMe₃) (IIa: R = Et, IIb: R = ⁱPr) which are cleaved by lithium to yield the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me₃SiO)Mes₂SiLi (2d) was obtained directly by reaction of the trimethylsiloxychlorosilane (Me₃SiO)Mes₂SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium compounds 2 and 3 were trapped with HMe₂SiCl giving the products (Me₃SiO)RR′Si-SiMe₂H and (Me₃SiO)RPhSi-RPhSi-SiMe₂H.     

Reactivity of cyclopalladated compounds derived from biphenyl-2-ylamine towards carbon monoxide, butyl isocyanide and alkynes

The reactivity of the dimeric cyclopalladated compounds derived from biphenyl-2-ylamine (μ-X)₂[κ²-N2′,C1-1-Pd-2-{(2′-NH₂C₆H₄)C₆H₄}]₂ [X = OAc (1), X = Cl (2)] towards unsaturated organic molecules is reported. Compound 1 reacted with carbon monoxide and ^tbutyl isocyanide producing phenanthridin-6(5H)-one and N-tert-butylphenanthridin-6-amine in 63% and 88% yield, respectively. Compound 2 reacted separately with diphenylacetylene and 3-hexyne, affording the mononuclear organopalladium compounds [κ²-N2″,C1-η²-C2,C3- 1-Pd{(R-CC-R)₂-2′-(2″-NH₂C₆H₄)C₆H₄}Cl] [R = Ph (5), R = Et (6)] in 50-60% yield, which derived from the insertion of two alkyne molecules into the C-Pd σ bonds of 2. The crystal structure of compounds 5 and 6 has been determined. Compound 5 crystallized in the monoclinic space group P2₁/n with a = 13.3290(10) Å, b = 10.6610(10) Å and c = 22.3930(10) Å and β = 100.2690(10)°. Compound 6 crystallized in the triclinic space group with a = 7.271(7) Å, b = 10.038(3) Å and c = 16.012(5) Å, and α = 106.79(3)°, β = 96.25(4)° and γ = 99.62(4)°. The crystal structures of 5 and 6 have short intermolecular Pd-Cl?H-N-Pd non-conventional hydrogen bonds, which associated the molecules in chains in the first case and in dimers in the second.     

Synthesis of sulfur containing analogues of the soluble guanylate cyclase inhibitor 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazin-1-one NS2028

Sulfur analogues of the soluble guanylate cyclase (sGC) inhibitor NS2028 1a are synthesized. Treating 8-bromo-2H-benzo[b][1,4]oxazin-3(4H)-one oxime (6) with 1,1′-thiocarbonyldiimidazole (1.1 equiv) gave the carbamothioate 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazine-1-thione (3a) in 83% yield. Alternatively reacting NS2028 1a with P₂S₅ (0.5 equiv) affords the carbamothioate 3a in 80% yield. Similar treatment of 8-aryl substituted NS2028 analogues 1b-d with P₂S₅ gave the carbamothioates 3b-d in 64-91% yields. Although quite stable, the carbamothioates 3a-d could be thermally isomerized in the presence of Cu (10 mol %) to afford the thiocarbamates 4a-d in high yields. Interestingly, in the case of carbamothioate 3a Pd and In metals also facilitated the isomerization. Furthermore, treatment of the thiocarbamates 4a-d with P₂S₅ (0.5 equiv) affords the carbamodithioates 5a-d in 72-89% yields. All new compounds are fully characterized including single crystal X-ray data for carbamothioate 3a and thiocarbamate 4a. Finally, a mechanism is proposed for the carbamothioate to thiocarbamate isomerization.     

Molecular design, synthesis and electro-optic properties of novel Y-type polyurethanes with high thermal stability of second harmonic generation

2,4-Di-2^′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with 2,4-toluenediisocyanate and 3,3^′-dimethoxy-4,4^′-biphenylenediisocyanate to yield unprecedented novel Y-type polyurethanes (4-5) containing 2,4-dioxybenzylidenemalononitrile group as a nonlinear optical (NLO) chromophore, which constitutes a part of the polymer backbone. The resulting polyurethanes 4-5 were soluble in common organic solvents such as acetone and DMF. Polymers 4-5 showed a thermal stability up to 260 °C from thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) giving T_g values around 143-156 °C. The approximate lengths of aligned NLO-chromophores estimated from AFM images of poled polymer films were about 10 nm. The SHG coefficients (d₃₃) of poled polymer films were around 7.4 × 10⁻⁹ esu. These Poled polymers exhibited a greater thermal stability of dipole alignment even at 10 °C higher than T_g, and no SHG decay was observed below 155 °C due to the partial main chain character of the polymer structure and extensive hydrogen bonds between urethane linkage, which is acceptable for NLO device applications.     

Nitrile ligands activation in dinuclear aminocarbyne complexes

The diiron complexes [Fe(Cp)(CO){μ-η²:η²-C[N(Me)(R)]NC(C₆H₃R′)CCH(Tol)}Fe(Cp)(CO)] (R = Xyl, R′ = H, 3a; R = Xyl, R′ = Br, 3b; R = Xyl, R′ = OMe, 3c; R = Xyl, R′ = CO₂Me, 3d; R = Xyl, R′ = CF₃, 3e; R = Me, R′ = H, 3f; R = Me, R′ = CF₃, 3g) are obtained in good yields from the reaction of [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)(p-NCC₆H₄R′)(Cp)₂]⁺ (R = Xyl, R′ = H, 2a; R = Xyl, R′ = Br, 2b; R = Xyl, R′ = OMe, 2c; R = Xyl, R′ = CO₂Me, 2d; R = Xyl, R′ = CF₃, 2e; R = Me, R′ = H, 2f; R = Me, R′ = CF₃, 2g) with TolCCLi. The formation of 3 involves addition of the acetylide at the coordinated nitrile and C-N coupling with the bridging aminocarbyne together with orthometallation of the p-substituted aromatic ring and breaking of the Fe-Fe bond. Complexes 3a-e which contain the N(Me)(Xyl) group exist in solution as mixtures of the E-trans and Z-trans isomers, whereas the compounds 3f,g, which posses an exocyclic NMe₂ group, exist only in the Z-cis form. The crystal structures of Z-trans-3b, E-trans-3c, Z-trans-3e and Z-cis-3g have been determined by X-ray diffraction experiments.