Structurally sound: The synthesis of AlPO4‐LTA zeolite in ionic liquids employs 1‐benzyl‐3‐methylimidazolium, tetramethylammonium, and fluoride ions for structuring α cages, sodalite cages, and cubes (see picture; C gray, N blue, O red, Al and P purple, F green). Selective removal of 1‐benzyl‐3‐methylimidazolium ions results in a stable AlPO4‐LTA molecular sieve. The α cages of AlPO4‐LTA framework can be evacuated while maintaining structural integrity.
Preparation and characterization of the first examples of copper(I) ferrocenylpolyphosphine complexes are reported. The molecular structure of complex {P,P′,P′′-[1,1′,2,2′-tetrakis(diphenylphosphino)-4,4′di-tert-butylferrocene]iodocopper(I)} (1) was solved by X-ray diffraction studies, and its fluxional behavior in solution was investigated by VT-31 P NMR; both revealed a net triligated coordination preference of the ferrocenyl tetraphosphine Fc(P) 4t Bu with copper. The tetradentate ligand is an active auxiliary in Sonogashira alkynylation; therefore the general question of copper as a competitive coordination partner in the Pd/Cu-catalyzed Sonogashira reaction was raised and discussed. Electronically neutral, activated, and deactivated aryl bromides were employed for coupling with phenylacetylene with various [(Pd)/ (Cu)/(tetraphosphine)] systems. The catalytic investigations shown that 1 mol % of complex 1 in combination with palladium is far more effective and selective for Sonogashira coupling than 5 mol % of CuI and palladium in the coupling to phenylacetylene of the deactivated aryl bromide 4-bromoanisole. This system efficiently avoids the concurrent and deleterious consumption of phenylacetylene by formation of diyne or enynes. To our knowledge, this is the first time that this kind of high selectivity is induced in Sonogashira alkynylation by initial ligand complexation to copper instead of palladium. These results demonstrate that coordination of Cu halide cocatalyst is a factor that should no longer be neglected in mechanistic and applied studies of the Sonogashira reaction.
Abstract:The straightforward synthesis of a new donor-stabilized phosphenium ligand 3d by addition of bromodifurylphosphine to 1,3-dimethylimidazolium-2-carboxylate 1 is described. The obtained ligand exhibits a very strong p-acceptor character, comparable to that of triphenyl phosphite [PA C H T U N G T R E N N U N G (OPh) 3 ] or of tris-halogenophosphines, with a n CO (A 1 ) at 2087 cm
À1for its nickel tricarbonyl complex. This ligand, as well as the related 3a which was obtained from chloroA C H T U N G T R E N N U N G diphenylphosphine, were tested in palladiumcatalyzed aryl alkynylation and in the platinum-catalyzed selective hydrogenation of chloronitrobenzenes, both in an ionic liquid phase. In C À C bond cross-coupling we observed that the increase of the p-acceptor character in ligand 3d, due to the introduction of an additional electron-withdrawing group, provides a very efficient catalyst in the alkynylation reaction of aryl bromides with phenylacetylene, including the deactivated 4-bromoanisole or the sterically hindered 2-bromonaphthalene. The catalytic activity decreases with recycling due to the sensitiveness of ligands to protonation in the ionic phase.Conversely, a multiple recycling of the metal/ligand system in non-acidic media was achieved from platinum-catalyzed hydrogenation of m-chloronitrobenzene. The catalytic results obtained by employing the complex of platiA C H T U N G T R E N N U N G num(II) chloride with 3a [transPtCl 2 (3a) 2 ] in comparison with the non-ionic related trans-tris(triphenylphosphine)platinum dichloride [trans-PtCl 2 A C H T U N G T R E N N U N G (PPh 3 ) 2 ] complex clearly indicate that the simultaneous existence of a strong p-acceptor character and a positive charge within the ligand 3a significantly increases the life-time of the platinum catalyst. The selectivity of the reaction is also improved by decreasing the undesirable formation of dehalogenation products. This cationic platinum complex trans-PtCl 2 (3a) 2 is the first example of a highly selective catalyst for hydrogenation of chloronitroarenes immobilized in an ionic liquid phase. The system was recycled six times without noticeable metal leaching in the organic phase, and no loss of activity.
Ordered mesoporous silica (OMS) has been recognized as promising adsorbent material for drug molecules with low aqueous solubility. The release of drug molecules from OMS upon contact with aqueous environment enhances their oral bioavailability. The release is governed by a complex interplay of adsorption, diffusion, and intermolecular interaction inside OMS pores. The presence of water hampers in situ FT-IR investigation of the behavior of the drug molecules upon release. The poorly water-soluble etravirine molecule having two nitrile functions was selected for an in situ FT-IR spectroscopic investigation of the release process. The stretching vibration of the nitrile organic function (υ(CN)) is a spectral feature that is accessible to FT-IR even in the presence of water. Etravirine depending on the loading was found to be present in SBA-15 pores as isolated adsorbed molecules, solvated molecules, and aggregates with intermolecular interaction similar to the crystalline state, each with a different spectroscopic fingerprint. Etravirine evacuation from the SBA-15 pores was shown to proceed in the solvated state. Surprisingly, the etravirine clusters inside pores were converted more readily into solvated molecules compared to individually adsorbed molecules.
Pore mouth hydrogenation of vegetable oil with Pt/ZSM-5 is confirmed by the similar intermediately melting product selectivity for various crystal sizes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.