铜催化异噁唑还原环清洁高效合成1-氨基-2-乙酰基蒽醌简

以水为反应介质，水合肼为还原剂，研究了痕量铜催化3-甲基蒽醌-1，2-c]-异噁唑还原开环反应以清洁高效合成1-氨基-2-乙酰基蒽醌，考察了不同种类过渡金属硝酸盐的催化性能，发现Cu（NO₃）₂性能最好. 加入 2.6% 的催化剂和1.3倍的水合肼，在室温反应 2 h，底物转化率和目标产物选择性分别可达到 97.2%和 95%，TON达到38. 产品结构经氢核磁谱和质谱得以确证，主要副产为羟基取代的1-氨基-2-乙酰基蒽醌. 此外，提出了铜催化 3-甲基蒽醌-1，2-c]-异噁唑还原开环反应合成 1-氨基-2-乙酰基蒽醌的可能反应机理.

Highly efficient and clean synthesis of 1-amino-2-acetylanthraquinone by copper-catalyzed reductive cleavage of isoxazole motif

A clean and highly efficient synthesis of 1-amino-2-acetylanthraquinone via reductive isoxazole ring cleavage of 3-methylanthra1,2-c]isoxazole-6,11-dione catalyzed by trace copper using hydrazine hydrate as a clean reducing agent and water as a green reaction medium under mild reaction conditions was investigated. Various transition-metal catalysts were screened for the reductive ring-opening reaction, and Cu(NO₃)₂ was shown to be an excellent catalyst. A conversion of 97.2% and 1-amino-2-acetylanthraquinone selectivity greater than 95% were obtained in the presence of 2.6 mol% Cu(NO₃)₂ (turnover number 38) with 1.3 equiv. of hydrazine hydrate for 2 h in water. The structure of the product was confirmed by ¹H nuclear magnetic resonance spectroscopy and mass spectrometry; the main byproduct was hydroxyl-substituted 1-amino-2-acetylanthraquinone. A possible reaction mechanism for the copper-catalyzed ring cleavage of 3-methylanthra1,2-c]isoxazole-6,11-dione with hydrazine hydrate was proposed.