4737-21-7Relevant articles and documents
A series of uranium (IV, V, VI) tritylimido complexes, their molecular and electronic structures and reactivity with CO2
Schmidt, Anna-Corina,Heinemann, Frank W.,Maron, Laurent,Meyer, Karsten
, p. 13142 - 13153 (2014)
A series of uranium tritylimido complexes with structural continuity across complexes in different oxidation states, namely UIV, UV, and UVI, is reported. This series was successfully synthesized by employing the trivalent uranium precursor, [((nP,MeArO)3tacn)UIII] (1) (where (nP,MeArO)3tacn3- = trianion of 1,4,7-tris(2-hydroxy-5-methyl-3-neopentylbenzyl)-1,4,7-triazacyclononane), with the organic azides Me3SiN3, Me3SnN3, and Ph3CN3 (tritylazide). While the reaction with Me3SiN3 yields an inseparable mixture of both the azido and imido uranium complexes, applying the heavier Sn homologue yields the bis-μ-azido complex [{((nP,MeArO)3tacn)UIV}2(μ-N3)2] (2) exclusively. In contrast to this one-electron redox chemistry, the reaction of precursor 1 with tritylazide solely leads to the two-electron oxidized UV imido [((nP,MeArO)3tacn)UV(N-CPh3)] (3). Oxidation and reduction of 3 yield the corresponding UVI and UIV complexes [((nP,MeArO)3tacn)UVI(N-CPh3)][B(C6F5)4] (4) and K[((nP,MeArO)3tacn)UIV(N-CPh3)] (5), respectively. In addition, the UV imido 3 engages in a H atom abstraction reaction with toluene to yield the closely related amido complex [((nP,MeArO)3tacn)UIV(N(H)-CPh3)] (6). Complex 6 and the three tritylimido complexes 3, 4, and 5, with oxidation states ranging from +IV to +VI and homologous core structures, were investigated by X-ray diffraction analyses and magnetochemical and spectroscopic studies as well as density functional theory (DFT) computational analysis. The series of structurally very similar imido complexes provides a unique opportunity to study electronic properties and to probe the uranium imido reactivity solely as a function of electron count of the metal-imido entity. Evidence for the U-N bond covalency and f-orbital participation in complexes 3-6 was drawn from the in-depth and comparative DFT study. The reactivity of the imido and amido complexes with CO2 was probed, and conclusions about the influence of the formal oxidation state are reported.
Cholecystokinin Peptidomimetics as Selective CCK-B Antagonists: Design, Synthesis, and in Vitro and in Vivo Biochemical Properties
Blommaert, Armand G.S.,Weng Jian-Hui,Dorville, Agnes,McCort, Isabelle,Ducos, Bertrand,et al.
, p. 2868 - 2877 (2007/10/02)
Antagonists of cholecystokinin-B (CCK-B) receptors have been shown to alleviate CCK4-induced panic attacks in humans and to potentiate opioid effects in animals.The clinical use of these compounds is critically dependent on their ability to cross the blood-brain barrier.In order to improve this property, new, peptoid-derived CCK-B antagonists, endowed with high affinity, selectivity, and increased lipophilicity have been developed.The affinity and selectivity of these compounds have been cheracterized in vitro and in vivo using guinea pig, rat, and mouse.Most of these compounds proved to be selective for the CCK-B receptor, the most potent analog, N--D-α-methyltryptophanyl>-N-i value of 6.1 nM for guinea pig cortex membranes in vitro and a good selectivity ratio (Ki CCK-A/Ki CCK-B = 174).Furthermore, the in vivo affinity of 26A for mouse brain CCK-B receptors, following intracerebroventricular injection at different concentrations, was found to be 10 nmol.Using competition experiments with the specific CCK-B ligand pBC 264, compound 26A was shown to cross the blood-brain barrier (0.2percent) after intraperitoneal administration in mice.This compound is therefore an interesting pharmacological tool to further elucidate the physicopathological role of endogenous CCK.
Alkylation of Nitrocyanamide. A New Synthesis of Isocyanates
Boyer, Joseph H.,Manimaran, Thanikavelu,Wolford, Lionel T.
, p. 2137 - 2140 (2007/10/02)
Thirteen alkyl halides (primary, secondary, and tertiary aliphatic including alicyclic, aralkyl, and heteroalkyl systems) and certain non-vicinal dihalides on treatment with silver nitrocyanamide are converted into the corresponding isocyanates (63-95percent).Intermediate alkylnitrocyanamides, spectroscopically detected, thermolysed (-20-80 deg C) to the expected isocyanates.In certain examples silver nitrocyanamide is generated in situ from sodium nitrocyanamide and silver nitrate.Silver nitrocyanamide does not react with cyclopropyl bromide, acetyl chloride, toluene-p-sulphonyl chloride, phenacyl bromide and 2-bromomethyldioxolane (27), and the ethylene acetal (28) of 1-bromo-4-iodopentacyclo-nonan-9-one.Silver nitrocyanamide reacts with 4,6-bis(bromomethyl)-3,7-dimethyl-1,5-diazabicyclo3.3.0)octane-2,8-dione (26), to give an intractable mixture.Vicinal dihalides give erratic results without detectable formation of vicinal di-isocyanates: unisolated 2-bromoethyl isocyanate (tentative assignment) has been detected in a product mixture from ethylene dibromide; an expected rearrangement during the reaction with 1,2-dibromocyclobutane, brought about the formation of 4-bromobut-3-enyl isocyanate isolated as ethyl 4-bromobut-3-enylcarbamate in low yield; and 1,2-dibromocyclohexane gives 2-bromocyclohexyl isocyanate isolated as ethyl N-(2-bromocyclohexyl)-carbamate in low yield.
