Sharma Dhruv, Pequeno Madureira Leticia Maria, Kowalewski Tomasz, Noonan Kevin J T
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, Pennsylvania 15213, United States.
J Org Chem. 2025 Jul 18;90(28):9733-9742. doi: 10.1021/acs.joc.5c00526. Epub 2025 Jul 7.
Shape-persistent conjugated macrocycles have attracted interest for their unique optoelectronic and self-assembly properties, but the syntheses to obtain these structures can be laborious. In this work, we describe the straightforward synthesis of a recently discovered class of macrocycle, the cyclo[]furan, using Suzuki-Miyaura cross-coupling of a simple aromatic monomer. We demonstrate that the combination of hexyl 2-bromo-5-(boronic acid pinacol ester)furan-3-carboxylate with tris(dibenzylideneacetone)dipalladium(0), tri--butylphosphonium tetrafluoroborate and cesium fluoride leads to cyclo[6]- and cyclo[7]furan esters in 45% yield (28% and 17%, respectively). Crude H NMR spectroscopy revealed that total conversion to macrocycles was 52 ± 6% over 3 runs, highlighting the robustness of this protocol for cyclofuran synthesis. The oligomerizations are rapid, and model compound studies suggest that a chain-growth mechanism may be operative. The hexyl-substituted cyclo[]furan esters ( = 6 and 7) are separable via column chromatography. The unique optical and electronic features for each cycle can be partially explained by the size difference for the two systems, as well as the increased conformational flexibility for the larger, ester-functionalized cyclo[7]furan.
形状持久的共轭大环因其独特的光电和自组装特性而备受关注,但其合成过程可能很繁琐。在这项工作中,我们描述了一种简单的芳香族单体通过铃木-宫浦交叉偶联直接合成最近发现的一类大环化合物——环[]呋喃。我们证明,己基2-溴-5-(硼酸频哪醇酯)呋喃-3-羧酸酯与三(二亚苄基丙酮)二钯(0)、三丁基膦四氟硼酸盐和氟化铯反应,以45%的产率得到环[6]-和环[7]呋喃酯(分别为28%和17%)。粗产物的核磁共振氢谱显示,在3次反应中,大环化合物的总转化率为52±6%,突出了该环呋喃合成方法的稳健性。低聚反应迅速,模型化合物研究表明可能存在链增长机制。己基取代的环[]呋喃酯( = 6和7)可通过柱色谱分离。两个体系的尺寸差异以及较大的酯官能化环[7]呋喃增加的构象灵活性可以部分解释每个环独特的光学和电子特性。