Brock University , 1812 Sir Isaac Brock Way , St. Catharines , Ontario L2S 3A1 , Canada.
J Org Chem. 2018 Nov 16;83(22):13973-13980. doi: 10.1021/acs.joc.8b02321. Epub 2018 Oct 30.
An integral part of modern organocatalysis is the development and application of thiourea catalysts. Here, as part of our program aimed at developing cyclopropenium catalysts, the synthesis of a thiourea-cyclopropenium organocatalyst with both cationic hydrogen-bond donor and electrostatic character is reported. The utility of the this thiourea organocatalyst is showcased in pyranylation reactions employing phenols, primary, secondary, and tertiary alcohols under operationally simple and mild reaction conditions for a broad substrate scope. The addition of benzoic acid as a co-catalyst facilitating cooperative Brønsted acid catalysis was found to be valuable for reactions involving phenols and higher substituted alcohols. Mechanistic investigations, including kinetic and H NMR binding studies in conjunction with density function theory calculations, are described that collectively support a Brønsted acid mode of catalysis.
脲催化剂的开发和应用是现代有机催化不可或缺的一部分。在这里，作为我们旨在开发环丙烯鎓催化剂计划的一部分，报告了具有阳离子氢键供体和静电特性的硫脲-环丙烯鎓有机催化剂的合成。该硫脲有机催化剂在使用苯酚、伯醇、仲醇和叔醇进行的吡喃酯化反应中的用途，在操作简单和温和的反应条件下，展示了广泛的底物范围。发现添加苯甲酸作为共催化剂有利于涉及苯酚和高取代醇的协同布朗斯特酸催化，这是有价值的。描述了包括动力学和 H NMR 结合研究以及密度泛函理论计算在内的机理研究，这些研究共同支持布朗斯特酸催化模式。
