nanotubes) has been studied as catalysts in the cascade Prins-Ritter reaction of (-)-isopulegol with benzaldehyde and acetonitrile for synthesis of octahydro-2H-chromene amides (as 4R- and 4S-isomers). A high selectivity to these products at 30 °C in the presence of H2O was observed on catalysts modified with chlorosulfonic acid (CSA) reaching 84% (4R/4S of 5.7) in the case of biochar, while a relatively
许多 SO 3 H 功能化固体(生物炭、蒙脱石、碳和埃洛石纳米管)已被研究作为催化剂在 (-)-异胡薄荷醇与苯甲醛和乙腈的级联 Prins-Ritter 反应中用于合成八氢-2 H-色烯酰胺(作为 4 R - 和 4 S - 异构体)。在生物炭的情况下,在氯磺酸 (CSA) 改性的催化剂上观察到在 30 °C 下在 H 2 O 存在下对这些产物的高选择性达到 84%(4 R /4 S为 5.7),而相对较大的octahydro-2 H的量-色烯醇(高达 31%)是 Prins 缩合的产物,在 2-(4-氯磺酰基苯基)乙基三甲氧基硅烷 (CSP) 功能化的材料上形成。尽管 Prins 缩合在弱酸位点上有效进行,但 Prins-Ritter 反应需要具有强 (0.33 – 5.8 mmol/g) Brønsted 酸度的硫酸化材料。CSP 功能化的催化剂是稳定的,而对于氯磺酸改性的材料,观察到
Sc(OTf)3-catalyzed one-pot ene-Prins cyclization: a novel synthesis of octahydro-2H-chromen-4-ols
(R)-Citronellal undergoes initial ene reaction followed by Prins cyclization with aldehydes in the presence of 5 mol % of scandium triflate at ambient temperature to furnish octahydro-2H-chromen-4-ols in good yields and with high cis-selectivity. The use of scandium triflate makes this procedure simple, more convenient, and practical. (C) 2010 Elsevier Ltd. All rights reserved.
An Environmentally Benign Synthesis of Octahydro-2H-chromen-4-ols via Modified Montmorillonite K10 Catalyzed Prins Cyclization Reaction
(-)-Isopulegol undergoes Prins cyclization reaction in the presence of 20 wt% of acid-treated montmorillonite K10 to produce octahydro-2H-chromen-4-ols in good yields and with high cis selectivities under solvent-free conditions. The solid-acid catalyst can be reused without loss of its activity.