Dendrons and dendritic catalysts immobilized on solid support: Synthesis and dendritic effects in catalysis

Abstract

Dendrimers, the aesthetically beautiful macromolecules displaying a variety of potentially useful architecture-induced properties, are traditionally assembled in solution. However, since 1988, a number of dendritic structures have been assembled on insoluble organic and inorganic polymers, and thus dendronized supports have been formed. One of the major applications of these new materials is in the field of heterogeneous catalysis. Supported dendritic catalytic systems, bearing the catalytic units on the dendron periphery, have been examined in the last 5 years in such reactions as hydroformylation, Heck and other Pd-catalyzed COC bond formations, oxidation, and enantioselective addition to aldehydes. In the majority of these studies, substantial dendritic effects on the reactivity, selectivity, or recyclability of the catalysts were observed. Although a number of factors have been suggested as sources of the effects, it is most likely that the phenomenon has a multicomponent origin. Additional research, including a full determination of the effects and their causes, is likely to lead to markedly better heterogeneous catalytic systems.

Dendronized polystyrene supports for new catalytic systems

“…Still, the preparation of dendrimers having regular structure and high molecular weight is not easy. Branched groups immobilized on polymeric supports are thus a compromise since they can provide the polymeric system with so called dendritic effect [10]. Dendronization of a polymer gives a swelling-like effect, due to the separation of polymer chains and weakening of interchain interactions.…”

Decorating step-by-step and independently the surface and the core of dendrons

“…Amongst the various areas of researches about dendritic molecules, one of the most active concerns organometallic chemistry [10,11], often carried out with the aim of using the resulting complexes as catalysts [10][11][12][13][14][15][16]. We reasoned that dendrons possessing organometallic derivatives as end groups and one reactive functional group at the core would be valuable targets.…”

“…8H, CH ArCymene ), 6.00-6.75 (m, 3H, CH 2 @CH), 6.95-8.10 (m, 76H, H Ar , CH@N) ppm 13. C { 1 H} NMR (CDCl 3 ): d 17.4 (s, CH 3 ), 21.4 (s, CH(CH 3 ) 2 ), 29.9 (s, CH(CH 3 ) 2 ), 33.1 (d, 2 J CP = 12.7 Hz, P 1 -N-CH 3 ), 38.6 (s, CH 3 NCH 2 ), 54.9 (d, 1 J CP = 22.9 Hz, CH 2 P), 85.6 (s, CH ArCymene ), 89.9 (d, 2 J CP = 5.5 Hz, CH ArCymene ), 94.1 (s, CH 3 C ArCymene ), 108.0 (s, (CH 3 ) 2 CHC ArCymene ), 121.48.…”

Dendrimers Clicked Together Divergently

“…The ability to tune the properties of dendrimers [1][2][3][4][5] has allowed their development for use in diverse applications, including drug delivery, [6][7][8][9][10][11][12][13][14][15] biomimicry, 8,9,[16][17][18][19] catalysis, 15,[20][21][22][23][24][25][26] organic light emitting diodes, 15,21,[27][28][29] molecular wires, 30,31 sensors, [32][33][34][35] imaging agents, 7,9 and various other utilities. 15,[36][37][38][39][40][41][42] Coincident with these developments is the increasing nee...…”