The Indium-Mediated Acyloxyallyation – A Tool for the Elongation of Aldoses Towards Non-Natural Sugar Alcohols as Potential Phase Change Materials

Abstract

The synthesis of defined higher-carbon sugars and derivatives is a difficult synthetic task. However, with the indium-mediated acyloxyallylation (IMA) a method was developed in the past years, that allows the direct elongation of unprotected aldoses by three carbons with high control of diastereoselectivity.[1,2] In a recent study [3], non-natural higher sugar alcohols were investigated as potential phase change materials (PCM) for thermal energy storage applications. The authors predicted extraordinarily high thermal storage densities of up to 450-500 kJ/kg for sugar alcohols with manno-configuration that fulfil three structural criteria: a linear carbon backbone, an even number of carbon atoms and 1,3-anti-configuration of all hydroxyl groups. Prompted by the computational prediction, we set out to confirm these predicted values and extend the pool of promising PCM candidates, relying on a synthetic strategy based on the IMA as it gives rise to extended sugar alcohols that fulfil the required rules. We synthesized several of the investigated sugar alcohols with manno-configuration presented in the computational study [3] and the calculated values could in fact be confirmed with our experimental data. Since the natural occurring galactitol has an even higher latent heat of fusion than D-mannitol, we studied additionally the synthesis of higher sugar alcohols derived from galactitol ("galacto-series"). [1] Palmelund A., Madsen R., Eur. J. Org. Chem., 2005, 70(20), 8248-8251. [2] Draskovits M., Stanetty C., Baxendale I.R., Mihovilovic M.D., J. Org. Chem., 2018, 83(5), 2647-2659. [3] Inagaki T., Ishida T., J. Am. Chem. Soc., 2016, 138, 11810-11819.