p-Menthane-3,8-diol (PMD) is gradually dethroning the synthetic golden standard mosquito repellent, N,N-diethyl-m-toluamide (DEET), as PMD is natural and considered safer while displaying an excellent repellent activity. In this study, we revisited the synthetic route of PMD from citronellal in greener conditions, while maintaining the highest yield, and developed a sustainable post-reaction process. Biosourced ammonium salts were tested to catalyze the carbonyl-ene reaction-hydration transforming citronellal and essential oils rich in citronellal into PMD. Ammonium salts led to excellent conversions and selectivities toward PMD, better than previously reported, even at low catalytic loading and rapidly. Catalytic solution of ammonium salts could be directly reused, up to six times without any loss of activity. The sustainability of the methodology was evaluated using a holistic approach which gave excellent green metrics, such as the PMI (6), TON (708), TOF (17), and E-factor (0.68) in comparison to other processes. The repellent activities of PMD synthesized from citronellal and from essential oils were evaluated against Aedes albopictus, the most invasive mosquito in the world, and were as much or even more repellent than pure PMD.

中文翻译：

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使用生物来源的铵盐作为催化剂生产对薄荷烷-3,8-二醇的高效和绿色工艺

p -Menthane-3,8-diol (PMD) 正在逐渐取代合成黄金标准驱蚊剂N , N -diethyl- m- 甲苯酰胺 (DEET)，因为 PMD 是天然的并且被认为更安全，同时显示出出色的驱虫活性。在这项研究中，我们重新审视了在更环保的条件下从香茅醛合成 PMD 的路线，同时保持最高产率，并开发了可持续的后反应工艺。测试了生物来源的铵盐以催化羰基-烯反应-水合作用，将香茅醛和富含香茅醛的精油转化为 PMD。铵盐导致对 PMD 的优异转化率和选择性，比以前报道的要好，即使在低催化负载和快速的情况下也是如此。铵盐催化溶液可以直接重复使用，最多可重复使用六次而不损失任何活性。该方法的可持续性使用整体方法进行了评估，该方法提供了出色的绿色指标，例如 PMI (6)、TON (708)、与其他过程相比，E因子 (0.68)。对从香茅醛和精油合成的 PMD 的驱避活性进行了评估，以对抗世界上最具侵略性的蚊子白纹伊蚊，其驱避力与纯 PMD 一样甚至更强。