Sequential Multi-step Transformations

Other reagent systems have been created that function as multi-purpose species in order to mimic classical solution phase reactions, an example of this is shown 

Nevertheless chromatography was still necessary in order to guarantee high purities of the products. 

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During the last decade, molecular ruthenium catalysts have attracted increasing interest for organic synthesis due to their ability to perform specific new reactions with a large panel of applications. Beside individual catalytic transformations, a variety of multi-step catalytic transformations in one pot have appeared. These transformations present practical and economic advantages as far as they are efficient, selective and proceed with atom economy. Ruthenium catalysis has entered this field with a variety of cascade and sequential catalytic transformations. 

Tandem catalysis refers to the use of a single catalyst which promotes the sequential transformation of a substrate via two or more mechanistically distinct processes in a single reaction vessel. Applied to carbohydrates, this should make multi-step routes, such as chemical oligosaccharide syntheses, faster. We explain how iron(iii) chloride hexahydrate, acting as a Lewis acid, is appropriate to catalyze one-pot regioselective protection of carbohydrates. 

Enzymatic reactions, despite the obvious energy preference of certain concerted mechanisms, may be inefficient because of a too low synchronization factor. In such cases, the sequential transformation of the system through a number of steps is favorable. Here, the role of a multi-functional catalyst, in reaching a pretransition state is to provide favorable energy and synchronization factors through the optical use of the corresponding functional groups at each step of the process. 

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