In recent years, sugar alcohols have gained significant attention as organic phase change materials (PCMs) for thermal energy storage due to their comparably high thermal storage densities up to 350 J/g. In a computational study, outstandingly high values of up to ~ 450–500 J/g have been postulated for specific higher-carbon sugar alcohols. These optimized structures feature an even number of carbon atoms in the backbone and a stereochemical configuration in which all hydroxyl groups are in an 1,3-anti-relationship, as found in the natural hexitol d-mannitol. However, these manno-configured higher-carbon sugar alcohols have not been experimentally investigated as PCMs yet and described synthetic routes are elaborate multiple steps syntheses. Therefore, we aimed to synthesize sugar alcohols of the manno-series with a concise synthetic protocol based on the indium-mediated acyloxyallylation (IMA) of aldoses. En route the C2-epimers were easily accessible, namely gluco-configured sugar alcohols, bearing one set of hydroxyl groups in a suboptimal 1,3-syn-realtionship. The synthesized compounds were found to possess thermal properties consistent with the predicted values, and the “perfect” higher-carbon sugar alcohol with eight carbon atoms was found to have indeed an outstanding high latent heat of fusion of ~ 380 J/g with a melting point of 260 °C.

Graphical abstract

中文翻译：

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通过铟介导的酰氧基烯丙基化合成高碳糖醇作为潜在相变材料

近年来，糖醇作为用于热能存储的有机相变材料（PCM）因其相对较高的热存储密度（高达350 J/g）而受到广泛关注。在一项计算研究中，对于特定的高碳糖醇，假设其值高达约 450-500 J/g。这些优化的结构具有偶数个主链碳原子和立体化学构型，其中所有羟基均呈 1,3-反关系，如天然己糖醇 d-甘露醇中所见。然而，这些甘露糖配置的高碳糖醇尚未作为相变材料进行实验研究，并且描述的合成路线是复杂的多步骤合成。因此，我们的目标是通过基于铟介导的醛糖酰氧基烯丙基化（IMA）的简洁合成方案来合成甘露糖系列糖醇。在途中，C2-差向异构体很容易获得，即葡萄糖配置的糖醇，带有一组处于次优 1,3-syn 关系的羟基。发现合成的化合物具有与预测值一致的热性能，并且发现具有八个碳原子的“完美”高碳糖醇确实具有约 380 J/g 的出色高熔化潜热，并且熔化点260℃。

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