Synthesis of 4-(alkoxyamino)chroman-2-ones via 6-exo-trig cyclization of carbon-centered radicals into oxime ethers
作者:Carlos A. Bejarano、John E. Díaz、Alix E. Loaiza
DOI:10.1007/s10593-016-1857-z
日期:2016.3
synthesized via a 6-exo-trig cyclization of alkyl radicals obtained from α-bromoesters containing an oxime ether group. In the case of secondary bromides, the best results were achieved using tris(trimethylsilyl)silane as the chain transfer agent and Et3B as the initiator in dichloromethane at room temperature; the corresponding chromanones were produced in 58–70% yield. Low yields of the cyclized compounds
Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers
作者:Nicola Otto、Till Opatz
DOI:10.3762/bjoc.8.122
日期:——
In the search for new ligands for the Ullmanndiaryl ether synthesis, permitting the coupling of electron-rich aryl bromides at relatively low temperatures, 56 structurally diverse multidentate ligands were screened in a model system that uses copper iodide in acetonitrile with potassium phosphate as the base. The ligands differed largely in their performance, but no privileged structural class could
Hydroxyl‐substituted benzaldimines underwent a RhIII‐catalyzed C−Hactivation and annulation with alkynes to provide novel mesoionicisoquinoline derivatives in moderate to excellent yields using oxygen as an internal anion source. This simple and efficient approach has a broad substrate scope.
Tuning the exchange dynamics of boronic acid hydrazones and oximes with pH and redox control
作者:Gun Su Han、Dylan W. Domaille
DOI:10.1039/d1ob00191d
日期:——
equilibrium. Carbonyl compounds with proximal boronic acids, including 2-formylphenylboronic acid (2-FPBA), have been reported to form highly dynamic covalent hydrazone and oxime bonds in physiological conditions, but strategies to tune the dynamics have not yet been reported. Here, we characterize the dynamics of 2-FPBA-derived hydrazones and oximes and account for both the rapid rate of formation (∼102–103
动态键在平衡状态下不断形成和解离。据报道,具有近端硼酸的羰基化合物,包括2-甲酰基苯基硼酸(2-FPBA),可以在生理条件下形成高度动态的共价腙和肟键,但尚未报道调节动力学的策略。在这里,我们描述了2-FPBA衍生的腙和肟的动力学,并解释了快速的形成速率(∼10 2 –10 3 M -1 s -1 )和相对较快的水解速率(∼10 -4 s -1 ) 在生理pH值下。我们进一步表明,这些底物与 α-亲核试剂发生交换,可以通过 pH 控制可逆地暂停和重新启动。最后,我们发现芳基硼酸的氧化有效地消除了快速动力学,从而使正向反应减慢了 30 000 倍以上,并将生理 pH 下的水解半衰期从 50 分钟延长至 6 个月。这些结果为探索动态组合库、可逆生物共轭和自修复材料中的这些联系奠定了基础。