Tönjes Jan, Medvarić Viktorija, Werner Thomas
Leibniz Institute for Catalysis at the University of Rostock (LIKAT Rostock), Albert Einstein Str. 29a, Rostock D-18059, Germany.
Department of Chemistry and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Str. 100, Paderborn D-33098, Germany.
J Org Chem. 2024 Aug 2;89(15):10729-10735. doi: 10.1021/acs.joc.4c00985. Epub 2024 Jul 15.
The organocatalytic formation of an underrepresented family of trisubstituted and tetrasubstituted furans from activated alkenes and acyl chlorides is reported. In a reaction sequence based on P(III)/P(V) redox cycling catalysis, the cyclic phosphine catalysts react with diacylethenes or acyl acrylates in Michael addition, followed by acylation and either an intramolecular Wittig reaction or a ring closure reaction, liberating the furans. The formed phosphine oxides are reduced in situ by phenylsilane as a terminal reductant. In the first step, 12 diacylethenes were converted to the respective trisubstituted furans. The reaction of acyl acrylates showed a surprising, catalyst-dependent alternate reaction forming tetrasubstituted furans. Two additional methods were developed, giving 14 trisubstituted furans using a phospholene catalyst and an additional 6 tetrasubstituted furans using a phosphetane catalyst. This encompassed 19 newly described compounds.
报道了通过有机催化从活性烯烃和酰氯形成一个研究较少的三取代和四取代呋喃家族。在基于P(III)/P(V)氧化还原循环催化的反应序列中，环状膦催化剂与二酰基乙烯或酰基丙烯酸酯进行迈克尔加成反应，随后进行酰化反应以及分子内维蒂希反应或闭环反应，从而生成呋喃。生成的氧化膦通过苯基硅烷作为终端还原剂进行原位还原。第一步中，12种二酰基乙烯被转化为相应的三取代呋喃。酰基丙烯酸酯的反应显示出一种令人惊讶的、依赖于催化剂的交替反应，生成四取代呋喃。还开发了另外两种方法，使用磷杂环戊烯催化剂得到14种三取代呋喃，使用磷杂环丁烷催化剂得到另外6种四取代呋喃。这涵盖了19种新描述的化合物。
