Larock indole synthesis using palladium complexes immobilized onto mesoporous silica

Batail, Nelly Bendjeriou, Anissa Djakoyitch, Laurent Dufaud, VeroniqueInternational audienceHeterogeneous palladium catalysts were prepared by covalent immobilization of palladium (II) complexes of the general formula PdCl2L2 (L = P, CN) onto SBA-15 silica using a post-synthetic method. The state of the hybrid materials was characterized using a wide variety of molecular and solid-state techniques. In general, all the palladium modified solids exhibited highly ordered mesostructures while keeping the integrity of the parent molecular precursors. The catalytic performances of the materials were evaluated in the heteroannulation of 2-iodoaniline and 2-bromoaniline with triethyl(phenylethynyl)silane which showed high activities and selectivities with isolated yields in the range of 80-85%. Despite a decrease in the initial activity, quantitative conversion of iodoaniline to the expected product was observed over multiple recyclings, making these materials particularly efficient for such applications. The catalytic process was shown to be homogeneous in nature, the solid apparently serving as a "reservoir" for the metal between cycles. (C) 2010 Elsevier B.V. All rights reserved

Optimised procedures for the one-pot selective syntheses of indoxyls and 4-quinolones by a carbonylative Sonogashira/cyclisation sequence

Genelot, Marie Bendjeriou, Anissa Dufaud, Veronique Djakovitch, LaurentA selective one-pot synthesis of carbonyl-containing N-heterocyclic compounds has been developed using a carbortylative Sonogashira/cyclisation sequence. Various catalytic protocols were studied (CO pressure, temperature, catalyst identity, base and substrate/catalyst ratio) with the objective of obtaining selectively either indoxyl or 4-quinolone products. The origin of the selectivity toward the 5-or 6-membered ring compounds was explained through the respective role of the various catalytic species involved, whether they are organic or metallic. The non-cyclic common intermediate was selectively prepared using [PdCl2(dppp)] as catalyst. By using a two-step multi-catalysis, i.e. {[Pd]+HNEt2}, 4-quinolones were obtained whereas with a tandem catalysis, i.e. {[Pd]/PR3), indoxyls were synthesised. (C) 2009 Elsevier B.V. All rights reserved

Efficient access to functionalised indoles via improved heterogeneous Larock synthesis or "on water" C-H arylation.

internationa

Palladium complexes grafted onto mesoporous silica catalysed the double carbonylation of aryl iodides with amines to give alpha-ketoamides

BIOVERT+MGE:NVI:ABN:PJA:LDJA promising route for the double carbonylation of aryl iodide derivatives with secondary and primary amines to produce alpha-ketoamides is described using covalently immobilized palladium complexes on SBA-15 silica. Adequate adjustments of the different reaction parameters (temperature, CO pressure, nature of base, solvent, substrate...) to achieve optimal catalyst performance were made using PdCl2(PPh2)(2)@SBA-15 as catalytic system. High conversions (up to 80%) and excellent selectivities (up to 96%) for the double carbonylated alpha-ketoamide products were obtained using K2CO3 as base, MEK or DMF as solvent and a 1 mol% [Pd] catalyst. We also demonstrated that two other palladium hybrid mesoporous materials can be alternatively used, namelyPdCl(2)(PCy2)(2)@SBA-15 and PdCl2(PNP)@SBA-15, without loss of activity and selectivity. Finally, catalyst recycling of PdCl2(PPh2)(2)@SBA-15 showed that the catalyst could be reused for up to 3 cycles without affecting catalyst performance

A well-defined mesoporous amine silica surface via a selective treatment of SBA-15 with ammonia

2D double-quantum H-1-H-1 NMR unambiguously shows that the ``isolated'' Si-OH surface silanols of dehydroxylated SBA-15 are converted upon treatment with ammonia into single silylamine surface site Si-NH2. The ``gem'' di-silanols (= Si(OH)(2)) remain intact. Treatment using HMDS produces (= Si(OSiMe3)(2)) but leaves Si-NH2 untouched. The resulting surface is hydrophobic and stable

Transmission and fluorescence X-ray absorption spectroscopy cell/flow reactor for powder samples under vacuum or in reactive atmospheres.

X-ray absorption spectroscopy is an element-specific technique for probing the local atomic-scale environment around an absorber atom. It is widely used to investigate the structures of liquids and solids, being especially valuable for characterization of solid-supported catalysts. Reported cell designs are limited in capabilities-to fluorescence or transmission and to static or flowing atmospheres, or to vacuum. Our goal was to design a robust and widely applicable cell for catalyst characterizations under all these conditions-to allow tracking of changes during genesis and during operation, both under vacuum and in reactive atmospheres. Herein, we report the design of such a cell and a demonstration of its operation both with a sample under dynamic vacuum and in the presence of gases flowing at temperatures up to 300 °C, showing data obtained with both fluorescence and transmission detection. The cell allows more flexibility in catalyst characterization than any reported

Transmission and fluorescence X-ray absorption spectroscopy cell/flow reactor for powder samples under vacuum or in reactive atmospheres.

X-ray absorption spectroscopy is an element-specific technique for probing the local atomic-scale environment around an absorber atom. It is widely used to investigate the structures of liquids and solids, being especially valuable for characterization of solid-supported catalysts. Reported cell designs are limited in capabilities-to fluorescence or transmission and to static or flowing atmospheres, or to vacuum. Our goal was to design a robust and widely applicable cell for catalyst characterizations under all these conditions-to allow tracking of changes during genesis and during operation, both under vacuum and in reactive atmospheres. Herein, we report the design of such a cell and a demonstration of its operation both with a sample under dynamic vacuum and in the presence of gases flowing at temperatures up to 300 °C, showing data obtained with both fluorescence and transmission detection. The cell allows more flexibility in catalyst characterization than any reported

Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n-butane

International audienceWe present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [( Si-NH2)( Si-OH)] (1) and [( Si-NH2)(2)] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [( Si-NH-)( Si-O-)]Zr-(CH(2)tBu)(2) (3) and [( Si-NH-)(2)]Zr(CH(2)tBu)(2) (4) have been obtained by reaction with Zr(CH(2)tBu)(4). The surfaces were characterized with 2D multiple-quantum H-1-H-1 NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH(2)tBu)(4) reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 degrees C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [( Si-NH-)(2)]Zr(H)(2) (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [( Si-NH-)(2)(Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an H-1 NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [( Si-N=)( Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [( Si-NH-) ( Si-O-)]Zr(H)(2) (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [( Si-NH-)( Si-O-)(2)]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C-H and C-C Bonds in n-Butane

We present a new generation of ``true vicinal'' functions well-distributed on the inner surface of SBA15: [( Si-NH2)( Si-OH)] (1) and [( Si-NH2)(2)] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [( Si-NH-)( Si-O-)]Zr-(CH(2)tBu)(2) (3) and [( Si-NH-)(2)]Zr(CH(2)tBu)(2) (4) have been obtained by reaction with Zr(CH(2)tBu)(4). The surfaces were characterized with 2D multiple-quantum H-1-H-1 NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH(2)tBu)(4) reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 degrees C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [( Si-NH-)(2)]Zr(H)(2) (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [( Si-NH-)(2)(Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an H-1 NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [( Si-N=)( Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [( Si-NH-) ( Si-O-)]Zr(H)(2) (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [( Si-NH-)( Si-O-)(2)]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]