Organometallic and related imidotitanium compounds containing a pendant arm functionalised benzamidinate ligand

Chloride ligand substitution reactions of tert-butyl- and arylimido-titanium complexes supported by the pendant arm functionalised N-trimethylsilyl benzamidinate ligand Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂ are described. Reaction of previously-described [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}Cl] (1) with PhLi afforded thermally sensitive [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}Ph] (2). The corresponding reaction of 1 with MeLi afforded [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}Me] (3) detected by ¹H-NMR spectroscopy but this compound could not be isolated. Reaction of 1 with LiCH₂SiMe₃ gave a complex mixture, but with LiN(SiMe₃)₂ and LiO-2,6-C₆H₃Me₂ the compounds [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}X] (X=N(SiMe₃)₂ (4) or O-2,6-C₆H₃Me₂ (5)) were isolated. The X-ray structure of 5 was determined. Reaction of the homologous compound [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂NMe₂}Cl] (6) (containing a 2-carbon atom chain in the pendant arm) with MeLi or PhLi were unsuccessful although the aryloxide compound [Ti(N^tBu){Me₃SiNC(Ph)NCH₂CH₂NMe₂}(O-2,6-C₆H₃Me₂)] (7) could be isolated from the reaction of 6 with LiO-2,6-C₆H₃Me₂. Reaction of the 3-carbon pendant arm arylimido compound [Ti(N-2,6-C₆H₃Me₂){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}Cl] (8) with MeLi afforded thermally sensitive [Ti(N-2,6-C₆H₃Me₂){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}Me] (9), and although the analogous phenyl homologue was elusive, the aryloxide derivative [Ti(N-2,6-C₆H₃Me₂){Me₃SiNC(Ph)NCH₂CH₂CH₂NMe₂}(O-2,6-C₆H₃Me₂)] (10) was successfully isolated and structurally characterised. Comparison of the X-ray structures of 5 and 10 show unexpectedly large differences between the TiNR and TiOAr bond lengths in the two compounds.     

ZrIV‐ und TaV‐Komplexe mit methanoverbrückten Bis(aryloxy)‐Liganden

Zr^IV and Ta^V Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe₃) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (L^Br–SiMe₃) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for L^Br–SiMe₃: space group P2₁/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) ų, Z = 4. L–SiMe₃ and L^Br–SiMe₃ react with Zr^IV and Ta^V chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl₃ with L^Br–SiMe₃ in the ratio of 3 : 2 a Zr₃ complex ( 7 ) is obtained, with one L^Br ligand only, which Zr atoms are bridged by a μ₃‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) ų, Z = 18) additionally reveals that one phenolato oxygen atom of the L^Br ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the L^Br ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe₃ and L^Br–SiMe₃ with CpTaCl₄ and TaCl₅ yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr₃‐complex with one terminal and one bridging phenolato oxygen atom. The Zr₃ and the Ta complexes L^BrTa₂Cp₂Cl₆ and LTa₂Cl₈ were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO.     

Regioselective synthesis of pyrano[3,2-c]pyrimidine derivatives via a palladium-catalyzed unusual [1,3] aryloxy shift and cycloisomerization: first report of a [1,3] shift of an aryloxy group

Uracil-annulated pyrano heterocycles are regioselectively synthesized in excellent yields (92-100%) via a palladium-catalyzed unusual [1,3] aryloxy shift followed by 6-endo dig cyclization and [1,3] prototropic shift.     

Microwave Irradiation Promoted Synthesis of Aryloxy Acetic Acids

Several aryloxy acetic acids were synthesized under microwave irradiation. The factors, which affect the reaction, were investigated and optimized. It was revealed that the best yields(92. 7%--97.4%) were obtained when the molar ratio of the reactants was n(ArOH) : n(NaOH) : n(CICH2CO2H) = 1：2.5： 1.2 with microwave irradiation power of 640 W for 65--85 s.     

A new approach for the synthesis of N-sulfonyl hydantoins

Two methods are described for the synthesis of a new series of hydantoins using the same reagents. The best process is based on the addition of N-aryloxy(alkoxy)sulfonyl isocyanates to an equimolar mixture of bromoamides and triethylamine dissolved in anhydrous acetone. This reaction is violent and provides the urea salts in situ which are transformed into the corresponding substituted hydantoins.     

Alkyloxy- and aryloxy-titanocenes: Synthesis, solid-state structure and cyclic voltammetric studies

Alkyloxy- and aryloxy-functionalized titanocenes of type [Ti](Cl)(OR) (R = Me (2), CH₂PPh₂ (3), CH₂Fc (4), C₆H₅ (5), C₆H₄-4-CN (6), C₆H₄-4-NO₂ (7), C₆H₄-4-Me (8), C₆H₄-4-OMe (9), C₆H₄-4-C(O)Me (10), C₆H₄-4-CO₂Me (11), C₆H₄-3-NO₂ (12); [Ti] = (η⁵-C₅H₄SiMe₃)₂Ti; Fc = (η⁵-C₅H₄)(η⁵-C₅H₅)Fe) were synthesized by the reaction of [Ti]Cl₂ (1) with ROH in a 1:1 molar ratio and in presence of Et₂NH. Diaryloxy-titanocenes (e.g., [Ti](OC₆H₄-4-NO₂)₂ (13)) are accessible, when the ratio of 1 and ROH is changed to 1:2. This synthesis methodology also allowed the preparation of dinuclear complexes of composition ([Ti](Cl))₂(μ-OC₆H₄O) (14) and ([Ti](Cl)(μ-OC₆H₄-4))₂ (15) by the reaction of 1 with hydroquinone or 1,1′-dihydroxybiphenyl in a 2:1 stoichiometry.Cyclic voltammetric studies show the characteristic [Ti(IV)/Ti(III)] reductions. It was found that the potentials of the alkyloxy titanocenes 2–4 do not differ, while for the aryloxy-titanocenes 5–15 the reduction potentials correlate linearly with the σ_p/m Hammett substituent constants showing a strong influence of the substituents on the electron density at titanium.The structures of titanocenes 4, 5, 9, and 11–13 in the solid state are reported. Typical for these organometallic sandwich compounds is a distorted tetrahedral coordination geometry around titanium with D1–Ti–D2 angles (D1, D2 = centroids of the cyclopentadienyl ligands) of ca. 130 °. In comparison to FcCH₂O-functionalized 4, for the aryloxy-titanocenes 5, 9, and 11–13 a significant larger Ti–O–C angle was found confirming electronic interactions between the titanium atom and the appropriate aryl group.     

Synthese und Struktur von Tetrachloro[4-tert-butyl-2(diphenylphosphanyl-κP-methyl)phenolato-κO]tantal(V), ein neuartiger TaV-Komplex mit einem chelatisierenden Aryloxyphosphanliganden

Synthesis and Structure of Tetrachloro[4- tert -butyl-2(diphenylphosphanyl-κP-methyl)phenolato-κO]tantalum(V), a Novel Ta^V Complex with a Chelating Aryloxy Phosphane Ligand 4-tert-Butyl-2-(diphenylphosphanylmethyl)anisol ( 1 ) is prepared from 2-chlormethyl-4-tert-butylanisol and potassium diphenylphosphide in very good yields as a novel oxygen-phosphorus compound with potentially hemilabile ligand properties. Compound 1 reacts with tantalum pentachloride under cleavage of methylchloride revealing the complex tetrachloro[4-tert-butyl-2-(diphenylphosphanyl-κP-methyl)phenolato-κO]tantalum(V) ( 2 ) with a distorted octahedrally coordinated tantalum atom and a chelating aryloxy phosphane ligand. Complex 2 crystallizes in the tetragonal, chiral space group P4₁2₁2 with a = 11.719(5), c = 37.95(5) Å, V = 5171(7) ų, Z = 8. ³¹P NMR spectroscopic studies of 2 establish the coordination of the phosphane unit to the Ta^V center in solution.     

Synthesis of Novel Aryloxy Propanoyl Thiadiazoles as Potential Antihypertensive Agents

2‐Amino‐5‐aryl/alkyl‐1,3,4‐thiadiazoles 3a‐e were synthesized from aliphatic and aromatic acids and thiosemicarbazide. These 2‐amino‐5‐aryl/alkyl‐1,3,4‐thiadiazoles 3a‐e were condensed with 2‐(naphthalenyloxymethyl) oxirane 4a‐b to prepare some naphthalenyloxy‐propanol amine derivatives 5a‐j . These compounds were synthesized as potential antihypertensive agents.     

Synthesis of Potentially Bioactive Heterocycles: Thermal [3,3]Sigmatropic Rearrangement of 4‐(4′‐Aryloxybut‐2′‐ynyloxy)‐6‐methyl‐2‐pyridone

Synthesis of a number of hitherto unreported 4‐aryloxymethylene‐7‐methyl‐2,3‐dihydropyrano[3,2‐c]pyridine‐5‐ones 4a–h have been achieved in moderate yields by the thermal [3,3]sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐6‐methyl‐2‐pyridone.