Abstract
Hypervalent iodine compounds, in particular aryl-λ3-iodanes, have been used extensively as electrophilic group-transfer reagents. Even though these compounds are superior substrates in terms of reactivity and stability, their utilization is accompanied by stoichiometric amounts of an aryl iodide as waste. This highly nonpolar side product can be tedious to separate from the desired target molecules and significantly reduces the overall atom efficiency of these transformations. In this short review, we want to give a brief summary of recently developed methods, in which this arising former waste is used as an additional reagent in cascade transformations to generate multiple substituted products in one step and with high atom efficiency.
Highlights
Atom economy (AE) is an important parameter which helps to evaluate the overall efficiency of a chemical reaction or a chemical process [1,2]
It is defined as the quotient between the molecular mass of the desired reaction product(s) and the molecular mass of all reactants (Equation 1): In an ideal reaction with 100% atom economy, every atom of the reactants is becoming part of the desired product
If benziodoxolones or benziodoxoles are used as group-transfer reagents, nearly 100% AE is possible since the counterion is covalently attached to the aryl iodide and does not get lost during the reaction cascade (Scheme 1, reaction (d))
Summary
Atom economy (AE) is an important parameter which helps to evaluate the overall efficiency of a chemical reaction or a chemical process [1,2]. If benziodoxolones or benziodoxoles are used as group-transfer reagents, nearly 100% AE is possible since the counterion (the carboxylate or alcoholate) is covalently attached to the aryl iodide and does not get lost during the reaction cascade (Scheme 1, reaction (d)) This is very effective, if this ortho-functionality is a desired part of the final reaction product or if it can be readily transformed into synthetically useful functional groups. Scheme 1: Overview of different types of iodane-based group-transfer reactions and their atom economy based on the molecular mass of the corresponding λ3-iodane In this short review, we will give a brief summary of very recent efforts toward the atom-economical use of aryl-λ3iodanes, in particular aryliodonium salts in group-transfer reactions. Other additives, such as additional bases, acids or catalysts were neglected
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