Multilayer graphene functionalized through thermal 1,3-dipolar cycloadditions with imino esters: a versatile platform for supported ligands in catalysis

Abstract

Multilayer graphene (MLG), obtained by mild sonication of graphite, was functionalized via 1,3-dipolar cycloaddition with azomethine ylides and used as a heterogeneous N,O-chelating ligand to coordinate iridium atomic centers.

The Crucial Role of S‐oxidation State on the Selectivity and Reaction Rate of the 1,3‐Dipolar Cycloaddition of Azomethine Ylides and Homochiral Thiazolines

“…Although thermic activation is a known methodology for the 1,3-dipolar cycloaddition of azomethine ylides since several years ago [59][60][61] this methodology has been scarcely applied in the last years. [62][63][64] Surprisingly, the outcome of the reaction by thermic activation between thiazoline 1 b and α-imino ester 2 was better than expected. Thermic activation gave higher yields than metal activation in a highly diastereo-enantio-and regioselective way, giving solely the endo isomer from a 2,3-addition by the opposite face of the bulky tert-butyl group and syn to the oxygen attached to the sulfur atom starting from thiazoline 1 b (Table 2, entry 1).…”

Microwave-Assisted Functionalization of Single-Walled Carbon Nanotubes as a Platform for a Supported Iridium Catalyst

“…As occurred in previous work with multilayer graphene, the presence in the sample of traces of NaCl interfered with the signals of iridium, preventing the characterization of the iridium by XPS. 16 The incorporation of 1.21% of iridium was confirmed by quantitative ICP–mass analysis. The robustness of the newly prepared iridium catalyst was analyzed by TG, and a weak mass loss was detected at 110–150 °C (assigned to a loss of water).…”

“…Additionally, a total atom economy is achieved in this work, unlike other chemical methods for generating azomethine ylides. The new modified material acted as a solid support for an iridium catalyst that promoted the MPV reduction of benzophenone with an efficiency that is comparable to that of iridium supported on multilayer graphene, 16 and more efficient than [Cp*IrCl 2 ] 2 itself or an iridium complex anchored to a fullerene, 25 although reaction times were longer than those for other homogeneous iridium-catalyzed transformations. 22 23 The new SWCNT-supported Ir catalyst was robust in heterogeneous catalysis of the MPV reduction of acetophenone (no metal leaching was observed).…”

Shedding Light on the Chemistry and the Properties of Münchnone Functionalized Graphene

“…During the last decade, several groups have pioneered cycloaddition chemistry for the chemical modification of a wide array of carbon-based nanomaterials, including fullerene, carbon nanotubes, graphene, and carbon quantum dots, either in their pristine or functionalized forms [ 1 , 2 , 3 , 4 , 5 ]. The different cycloaddition strategies are an important tool to increase the processability, solubility, and colloid stability of nanostructures, to achieve better control over composition, and to target specific applications [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Among the different types of cycloaddition reactions employed for the covalent functionalization of the graphene sp 2 network, it is arguable that the 1,3-dipolar cycloaddition (1,3-DC) and, in particular, the cycloaddition of azomethine ylides, is the most heavily used.…”