A Colorimetric Method for Quantifying Cis‐ and Trans‐Alkenes Using an Indicator Displacement Assay

A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis- and trans-alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis- or trans-alkenes depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis- and trans-alkenes. Further, blind mixtures of cis- and trans-alkenes were made resulting in an average error of ± 2% in the percentage of cis- or trans-alkenes, and implementing E2 and Wittig reactions gave errors of ± 3%. Furthermore, we developed variants of the IDA that alter the color changes to optimize the response to the human eye.