[Cp*RhCl2]2, catalyzes efficiently the transferhydrogenation of various quaternary pyridinium salts under mild conditions, affording not only piperidines but also 1,2,3,6‐tetrahydropyridines in a highly chemoselective fashion, depending on the substitution pattern at the pyridinium ring. The reduction is conducted in azeotropic formic acid/triethylamine (HCOOH‐Et3N) mixture at 40 °C, with catalyst loadings
of various nitrogenheterocycles, including but not limited to quinolines, isoquinolines, indoles and pyridinium salts, in an aqueous solution of HCO2H/HCO2Na under mild conditions. The catalyst shows excellent functional‐group compatibility and high turnover number (up to 7500), with catalyst loadings as low as 0.01 mol % being feasible. Mechanistic investigation of the quinolinereduction suggests
在温和条件下,显示出环金属化的铱络合物在HCO 2 H / HCO 2 Na的水溶液中催化各种氮杂环的转移加氢反应,包括但不限于喹啉,异喹啉,吲哚和吡啶鎓盐。该催化剂表现出出色的官能团相容性和高周转率(最高7500),催化剂用量低至0.01 mol%是可行的。对喹啉还原反应的机理研究表明,转移氢化反应是通过1,2和1,4加成途径进行的,催化转化受氢化物转移步骤的限制。
Copper-Catalyzed Oxidative [3 + 2] Cycloaddition of <i>N</i>-Alkyl Pyridinium Salts to Imidazo[1,2-<i>a</i>]pyridines
作者:Yuan Zhang、Weibin Fan、Yinghua Li、Deguang Huang
DOI:10.1021/acs.joc.3c00728
日期:2023.9.1
A copper-catalyzed reaction of pyridiniumsalts and trimethylsilyl cyanide (TMSCN) in the presence of diethyl phosphite is developed. This reaction, which allows the single-step construction of biologically important 2-cyanoimidazo[1,2-a]pyridine from readily available starting materials, is realized for the first time and is feasible at the gram scale. The scope of the protocol is demonstrated with
开发了在亚磷酸二乙酯存在下吡啶鎓盐和三甲基硅烷基氰化物 (TMSCN) 的铜催化反应。该反应首次实现了从容易获得的起始材料一步构建生物学上重要的2-氰基咪唑并[1,2- a ]吡啶的反应,并且在克级是可行的。该协议的范围通过 27 个示例进行了演示。在这一一锅法中可以实现连续的双氰化和环化。TMSCN 发挥双重作用,不仅作为“CN”源,而且作为咪唑并[1,2- a ]吡啶环化的偶联伙伴。