Efficient Construction of Quinoxaline Derivatives by Cesium Hydroxide-Catalyzed Mild Aerobic Annulation Reaction

氢氧化铯催化温和有氧环化反应高效构建喹喔啉杂环衍生物

Simple inorganic base cesium hydroxide is found to be the best catalyst for aerobic annulation reaction of o-phenylenediamine andα-hydroxy-2-phenylacetophenone in constructing the quinoxaline skeleton,i.e.,catalytic amount of cesium hydroxide can catalyze the reaction efficiently under mild conditions of room temperature in air atmosphere.This method is extendable to a series of vicinal diamines andα-hydroxyl ketones,thus having a relatively broad substrate scope.As no transition metal catalyst is required and cesium hydroxide highly water-soluble,cesiume can be effectively removed by washing with water,the prodcuts can be obtained without cesium and transition metal residue contamination.This reaction requires no other stoichiometric oxidants but the readily available and convenient air as the oxidant,and the only byproduct is water,hence a transition metal-free,mild and efficient,green and practical approach for efficient construction of the quinoxaline derivatives is provided.

研究发现简单无机碱氢氧化铯是邻苯二胺与2-羟基-2-苯基苯乙酮有氧环化反应构建喹喔啉骨架的最佳催化剂,即催化量氢氧化铯可在室温、空气的温和条件下催化反应高效进行.本方法适用于一系列邻二胺和α-羟基酮类化合物,底物范围较广.由于不使用过渡金属催化剂,且催化剂氢氧化铯具有很好的水溶性,简单水洗即可将其从产物中除去,因此产物没有铯及过渡金属残留.此方法采用方便易得的空气为氧化剂、无需使用其它化学计量的氧化剂,唯一副产物为水,因而可为喹喔啉杂环衍生物的高效构建提供一种无过渡金属参与、温和高效、绿色实用的方法.