Despite its importance and wide use as oxidizing agent, aqueous H2O2 has many disadvantages. It is difficult to ship and easily decomposes, which necessitates the determination of its oxidizing power prior to each reaction. Furthermore, it requires biphasic reaction mixtures in case the substrates are not water-soluble. Therefore, stable adducts of H2O2 which are also soluble in organic solvents are desired. This quest for molecular oxidizing agents with known and reproducible composition led to the synthesis of H2O2 (Hilliard) and di(hydroperoxy)alkane (Ahn) adducts of phosphine oxides. These hydrogen-bonded adducts are safe with shelf lives of months, they crystallize in large habits and, most importantly, they are highly soluble in organic solvents. The direct oxidative esterification of aldehydes in the presence of an alcohol receives increasing attention. It is a conceptually and economically attractive approach as compared to traditional methods that are based on acid activation followed by nucleophilic substitution. We have developed a method for the esterification of aldehydes using Ahn adducts as oxidizers and AlCl3 as a catalyst. It is an attractive alternative to the current methods because it does not require a transition metal, works at room temperature, and uses an inexpensive, non-toxic catalyst. Our method is compatible with both alkyl and aryl aldehydes and optimized conditions afford 99% conversion of aldehydes to yield the esters selectively. Furthermore, the synthesis and characterization of the novel di(hydroperoxy)adamantane adducts of phosphine oxides will be discussed in this presentation.

Di(hydroperoxy)alkane adducts of phosphine oxides (Ahn adducts): Safe, stoichiometric, solid and soluble oxidizing agents

ACS Spring 2022

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