Department of Chemistry, Princeton University, Princeton, NJ 08544, USA.
Science. 2015 Aug 28;349(6251):960-3. doi: 10.1126/science.aac7440.
Cycloadditions, such as the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely used methods in synthetic chemistry. The analogous [2+2] alkene cycloaddition to synthesize cyclobutanes is kinetically accessible by photochemical methods, but the substrate scope and functional group tolerance are limited. Here, we report iron-catalyzed intermolecular [2+2] cycloaddition of unactivated alkenes and cross cycloaddition of alkenes and dienes as regio- and stereoselective routes to cyclobutanes. Through rational ligand design, development of this base metal-catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks.
环加成反应，如[4+2]Diels-Alder 反应形成六元环，是合成化学中最强大和最广泛使用的方法之一。类似的[2+2]烯烃环加成反应通过光化学方法可以动力学上可得到，但底物范围和官能团容忍度有限。在这里，我们报告了铁催化的未活化烯烃的分子间[2+2]环加成和烯烃与二烯的交叉环加成，作为区域和立体选择性合成环丁烷的途径。通过合理的配体设计，这种基础金属催化方法的发展扩展了从丰富的碳氢化合物原料中获得的化学空间。
