Solvent effect tuning reactivity

Concluding Remarks. New uses for TBAF, a highly soluble source of nucleophilic and basic fluoride ion, continue to be developed. The ability to tune the reactivity of TBAF using solvent effects is a key to its exploitation in organic S3mthesis. The recent synthesis of anhydrous variants of this reagent should further expand the synthetic utility of this reagent. 

The role of the ligands is both to stabilize the Pd(0) state and to tune the reactivity of the palladium. The outline mechanism above does not specify many detailed aspects of the reaction that are important to understanding the effect of ligands, added salts, and solvents. Moreover, it does not address the stereochemistry, either in terms of the Pd center (tetracoordinate pentacoordinate , cisl, transl) or of the reacting carbon groups (inversion , retention ). Some of these issues are addressed by a more detailed mechanism.190... 

Equation 6 indicates that the solvent strength, 6, is pressure-dependent, providing a potential route to improved selectivity and rate by "pressure-tuning the solvent. A number of attempts to demonstrate reactivity control in su rcritical CO2 for Diels-Alder (75-77) and organic photoreactions (78,79) have exhibited very small effects. Andrew and coworkers have recently demonstrated dramatic solvent cage effects on selectivity of a photo-Fries reaction close to the critical density.(80) More polar SCF s have shown more promising results control of esterification rates and polyester molecular weight distribution via enzymatic catalysis in fluoroform has been demonstrated. (81,82)... 

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