Heterogeneous Palladium Catalysts Applied to the Synthesis of 2- and 2,3-Functionalised Indoles

Abstract

Abstract:Heterogeneous palladium catalysts ([Pd(NH 3 ) 4 ] 2 þ /NaY and [Pd]/SBA-15) were applied to the synthesis of 2-functionalised indoles, giving generally high conversions and selectivities ( > 89% yield) using only 1 mol % [Pd]-catalyst under standard reaction conditions (polar solvent, 80 8C). For the synthesis of 2,3-functionalised indoles by crosscoupling arylation, the [Pd]/SBA-15 catalyst was found to be particularly interesting, producing the expected compound with ¼ 35% yield after 12 days of reaction, which is comparable to the homogeneous catalyst, Pd(OAc) 2 ( ¼ 48% yield). In the course of the study, the dual reactivity of the indole nucleus was demonstrated: aryl bromides gave clean C À C coupling while aryl iodides led to a clean C À N coupling.

Übergangsmetallkatalysierte direkte Arylierungen von (Hetero)Arenen durch C‐H‐Bindungsbruch

“…[133] Des weiteren zeigten Bellina et al, dass palladiumkatalysierte direkte Arylierungen an der C3-Position von Indolen bei Zusatz von PCy 3 oder Bn(nBu) 3 NCl möglich sind (Schema 65). [134] Das letztere der beiden Verfahren sowie eine [135,136] zeigte ein bemerkenswerte Anwendungsbreite, einschließlich der effizienten Funktionalisierung von C-H-Bindungen sterisch anspruchsvoller 2-substituierter Indole.…”

Aerosol‐Spraying Synthesis of Periodic Mesoporous Organometalsilica Spheres with Chamber Cavities as Active and Reusable Catalysts in Aqueous Organic Reactions

“…Meanwhile, the Pd-PPh 2 -MOC-G with Pd(II) organometals terminally bonded to the pore surface was prepared by coordinating metallic ions with the PPh 2 -ligands Pd-PPh 2 -PMO(H) to that of PdCl 2 (PPh 3 ) 2 suggests the chemical environment of Pd(II) active sites remained almost unchanged after incorporation into the silica network. [ 28 ] Meanwhile, the TG/DTA curves in Figure 4 reveal that, besides a weak endothermic peak around 80 ° C with weight loss of about 4% due to the desorption of water and/or ethanol remaining from solvent extraction processes, the Pd-PPh 2 -PMO(H) displayed two peaks around 372 ° C and 440 ° C resulting from the successive breakage of two PPh 2 -Pd-PPh 2 bonds, [ 29 ] corresponding to total weight loss around 14%, in good accordance with the total amount of PPh 2 -CH 2 -CH 2 -groups added in the mother solution for aerosol-spraying. Furthermore, the Pd(II) loading detected by inductively coupled plasma optical emission spectrometer (ICP) was consistent with the total amount of Pd(II) added in the initial solution before aerosol-spraying.…”

One‐Pot Suzuki/Heck Sequence for the Synthesis of (E)‐Stilbenes Featuring a Recyclable Silica‐Supported Palladium Catalyst via a Multi‐Component Reaction in 1,3‐Propanediol

“…Pursuing our efforts devoted to the application of heterogeneous Pd catalysts [14][15][16][17][18][19][20][21] in one-pot procedures, [7,[22][23][24][25] we have recently disclosed the vinylation of aryl halides through the use of commercially available Pd/C. [26,27] Such compounds are useful intermediates for the synthesis of stilbenes, an important class of biologically relevant molecules including the wellknown resveratrol and combretastatin A-4.…”