Electronic Ligand Effect

Cyclometallation reactions form only a part of the broad class of C-H bond metallations or C-H activation. Such reactions facilitate the synthesis of organic compounds, including pharmaceuticals, the activation of small molecules, and industrial processes. Better control of ligand electronic effects and ligand sphere geometry will enhance the development and versatility of this class of metallation reactions. 

Keywords Asymmetric hydrocyanation. Hydrogen cyanide, Vinylarenes, 2-Arylpropanoic acids, Naproxen, Arylphosphinites, Carbohydrate ligands. Electronic effects. Electronic asymmetry... 

In the case of supported metal catalysts, promoters alter the three basic features, activity, selectivity and stability through ensemble / dilution / geometric effect and/or ligand/electronic effect. Besides, a number of other characteristics like, acidity, metal-support and metal- promoter interactions also play a crucial role. The myraid of changes in the characteristics of the catalyst, brought in and the resultant effects in the course of the raection are described in Scheme 1. 

Table 9.1 Ligand electronic effects in oxidative indole annulations.

Zou, G., Huang, W., Xiao, Y. and Tang, J. (2006) Heckreaction catalysed by palladium supported with an electron-rich benzimidazoly lidene generated in situ remarkable ligand electronic effects and controllable mono- and di-arylation. New J. Chem., 30, 803-9. 

Table 8.1.. The effect of ancillary ligand electronic effects on the rate of reductive elimination of benzene from Cp RhtPRjKPhKH).

Gambs, C. Chaloupka, S. Consigho, G Togni, A. Ligand electronic effect in enantioselective palladium-catalyzed copolymerization of carbon monoxide and propene. Angew. Chem., Int. Ed. 2000, 39, 2486-2488. 

A.L. Casalnuovo et al. - Ligand Electronic Effects in Asymmetric Catalysis Enhanced Enantioselectivity in the Asymmetric Hydrocyanation of Vinylarenes,... 

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