Half-esters are very versatile building blocks applied to synthesis of polymers and dendrimers.  Among the most typical methods for synthesis of half-esters are selective monosaponification reactions of symmetric diesters with the use of a solid NaOH or KOH and alcoholic solvents, but the statistically expected yield of half-esters would be a maximum of only 50%, typically yielding complex mixtures.  Earlier, we reported highly efficient selective monohydrolysis of symmetric diesters without relying on enzymes.  In this reaction, an aqueous base such as NaOH or KOH is added to a symmetric diester suspended in water that may contain a co-solvent at 0 <sup>o</sup>C.  This reaction produces pure half-esters in high to near-quantitative yields without producing dirty waste.  While the reason for this high selectivity is not understood yet, one possibility is the formation of micelle-like aggregates in which the hydrophobic carboalkoxy group is pointed inside and the hydrophilic COO<sup>-</sup> is pointed outside after monohydrolysis occurs, which would prohibit further hydrolysis by the aqueous base.  Here we attempted to detect such aggregates as the key intermediate for this selective monohydrolysis reaction by dynamic light scattering experiments.  We believe these results support our mechanistic hypothesis for the high selectivity described above.

Mechanistic studies on selective monohydrolysis of symmetric diesters with the use of dynamic light scattering

249th National Meeting (2015)

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