A range of heterogeneous ‐SO₃H functionalized catalysts including carbon and halloysite nanotubes, commercial K10 clay, Amberlyst‐15 etc. was investigated for the first time using as a model the Prins‐Ritter reaction of (−)‐isopulegol with benzaldehyde and acetonitrile producing 4‐amido derivatives of octahydro‐2H‐chromenes (as (S)‐ and (R)‐diastereomers). A strong effect of water addition prior the reaction on the overall selectivity and the ratio of isomers in the case of heterogeneous and homogeneous (p‐toluenesulfonic acid) catalysis was found for the first time. The yield of the (R)‐diastereomer sharply increased with increasing amount of added water, while the S‐isomer prevailed with a minimum amount of added water. Experimental results and DFT calculations clearly indicate a kinetic control for R‐amide formation. Typically synthesis of 4‐amidooctahydro‐2H‐chromenes requires subzero temperatures and toxic catalysts, which were avoided in the current work. Nevertheless, the yield of the desired products (up to 83 %) at 30 °C after water addition exceeded the values reported previously. Thus, adding water is a simple and a very effective method for controlling both the yield and stereoselectivity of the Prins‐Ritter reaction products under mild conditions.

中文翻译：

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在−SO3H催化的串联Prins-Ritter反应中加水进行立体选择性转化，合成4-酰胺基四氢吡喃衍生物

首次以（-）-异薄荷醇与苯甲醛和乙腈的Prins-Ritter反应为模型，研究了一系列多相-SO ₃ H官能化催化剂，包括碳和埃洛石纳米管，商业K10粘土，Amberlyst-15等。产生八氢-2 H-色酮的4-酰胺基衍生物（作为（S）-和（R）-非对映异构体）。在非均相和均相（对甲苯磺酸）催化的情况下，首次发现在反应前加水对整体选择性和异构体比例有强烈影响。（R）-非对映异构体的产率随着添加水量的增加而急剧增加，而S异构体占主导地位，加水量最少。实验结果和DFT计算清楚地表明了R酰胺形成的动力学控制。通常，合成4-酰胺基八氢-2 H-色酮需要低于零温度和有毒催化剂，这在当前工作中已避免。然而，加水后在30°C下所需产品的产率（最高83％）超过了先前报道的值。因此，加水是在温和条件下控制Prins-Ritter反应产物收率和立体选择性的一种简单有效的方法。