We report an update of the Competing Enantioselective Conversion (CEC) method for determining the absolute configuration of secondary alcohols. This method, first disclosed from our group in 2011,1 utilizes parallel reactions where the enantioenriched secondary alcohol of interest is esterified in the presence of the R- and S-HBTM catalysts respectively. The parallel reactions are both quenched at a specific time and the fast reaction, therefore producing a higher conversion to the ester product during that period of time, is discovered. We report here that the fast reaction can be determined qualitatively using thin-layer chromatography (TLC), which significantly reduces the quantity of material necessary to determine the absolute configuration. The reaction conversions of the parallel reactions were also determined using 1H NMR spectroscopy to provide a quantitative assessment that confirmed the qualitative TLC analysis of the fast reaction in all cases tested. A mnemonic then provided guidance for the absolute configuration to be assigned based on the fast reaction. The parallel reactions use micromolar quantities of the substrate alcohol and the qualitative assessment with thin-layer chromatography displays nanomolar sensitivity.1 Wagner, A. J.; David, J. G.; Rychnovsky, S. D. Org. Lett. 2011  , 13, 4470�4473.

Competing enantioselective conversion (CEC) method to determine absolute configuration of secondary alcohols

246th National Meeting (2013)

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