Kinetics of Electrophilic Fluorinations of Enamines and Carbanions: Comparison of the Fluorinating Power of N–F Reagents
作者:Daria S. Timofeeva、Armin R. Ofial、Herbert Mayr
DOI:10.1021/jacs.8b07147
日期:2018.9.12
leaving groups and the calculated fluorine plus detachment energies are discussed. The rate constants for the reactions with deoxybenzoin-derived enamines follow the linear free energy relationship log k2(20 °C) = sN( N + E) which allows the empirical electrophilicity parameters E for these fluorinating agents to be derived from the measured rate constants and the tabulated N and sN parameters for the nucleophiles
在乙腈中研究了烯胺和碳负离子与常用氟化试剂、N-氟苯磺酰亚胺 (NFSI)、N-氟吡啶盐、Selectfluor 和 N-氟化金鸡纳生物碱的反应动力学。反应遵循二级动力学,从测得的速率常数可以推导出氟化是通过亲核试剂在氟处的直接攻击进行的,而不是通过 SET 过程进行的。讨论了氟化速率与离核离去基团的 p KaH 值和计算的氟加脱离能的相关性。与脱氧安息香衍生的烯胺反应的速率常数遵循线性自由能关系 log k2(20 °C) = sN( N + E),这使得这些氟化剂的经验亲电性参数 E 可以从测量的速率常数中得出以及亲核试剂的列表 N 和 sN 参数。尽管测得的速率常数与通过这种关系计算的速率常数的偏差大于以 Csp2 为中心的亲电试剂与亲核试剂的反应,但表明这项工作中报道的亲电参数 E 能够合理化已知的氟化反应,因此,推荐作为设计新的亲电子氟化的指南。
<i>ortho</i>
‐Alkylation of Pyridine
<i>N</i>
‐Oxides with Alkynes by Photocatalysis: Pyridine
<i>N</i>
‐Oxide as a Redox Auxiliary
作者:Jonathan P. Markham、Ban Wang、Edwin D. Stevens、Stuart C. Burris、Yongming Deng
DOI:10.1002/chem.201901065
日期:2019.5.7
A photocatalyzed ortho‐alkylation of pyridine N‐oxide with ynamides and arylacetylenes has been developed, which yields a series of α‐(2‐pyridinyl) benzyl amides/ketones. Mechanistic studies, including electrochemical studies, radical‐trapping experiments, and Stern–Volmer fluorescence quenching studies demonstrate that pyridine N‐oxide serves as both a redox auxiliary and radical acceptor to achieve
Solvatochromism, acidochromism and aggregation-induced emission of propeller-shaped spiroborates
作者:Kang Li、Jichun Cui、Zeren Yang、Yanmin Huo、Wenzeng Duan、Shuwen Gong、Zhipeng Liu
DOI:10.1039/c8dt03374a
日期:——
Propeller-shaped pyridyl-enolato-catecholate/-salicyl spiroborates (Sborepy1–6) were synthesized. The complexes Sborepy3–6 show weak emission in fluid solution and aggregation-induced emission enhancement in the aggregation state with large Stokes shifts of 4025–5237 cm−1. Moreover, intense solid-state emissions with high Φf ranging from 25% to 37% were observed for Sborepy3–6 owing to the weak intermolecular
合成了螺旋形的吡啶基-烯醇-邻苯二酚/水杨基螺硼酸酯(Sborepy1-6)。Sborepy3-6配合物在流体溶液中显示出微弱的发射,并且在聚集状态下发生聚集诱导的发射增强,斯托克斯位移为4025-5237 cm -1时有很大的变化。此外,具有高激烈固态排放Φ ˚F观察用于测距从25%到37%Sborepy3-6由于在其固态弱的分子间相互作用。通过以下方式揭示了AIE和强烈的固态发射X射线衍射分析和理论计算。此外,还证明了溶液状态下的溶剂变色作用以及在Sborepy3和Sborepy6固态下作为荧光酸性蒸气传感器的潜在应用。
α-Functionalization of Ketones via a Nitrogen Directed Oxidative Umpolung
作者:Gabriel M. Kiefl、Tanja Gulder
DOI:10.1021/jacs.0c10700
日期:2020.12.9
methods available today, overcoming the inherent reactivity still remains a constant challenge in organic chemistry. The oxidative α-functionalization of ketones by external nucleophiles constitute such an example. Herein, we present a hypervalent F-iodane mediated umpolung of pyridyl ketones triggered by Lewis base/Lewis acid noncovalent interactions. A wide variety of external nucleophiles are introduced
A synthesis of 2,3-diaryl-substituted pyrazolo[1,5-a]pyridines in moderate to good yields under metal-free and mild conditions is described. The intramolecular cyclization of the oxime substrates is mediated by PPh3/I2, which leads directly to pyrazolo[1,5-a]pyridines without the formation of a 2H-azirine intermediate. Various substituents on the aryl rings are compatible with the method.