铜催化异噁唑还原开环清洁高效合成1-氨基-2-乙酰基蒽醌(英文)

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

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.

A clean and highly efficient synthesis of 1-amino-2-acetylanthraquinone via reductive isoxazole ring cleavage of 3-methylanthra[1,2-c]isoxazole-6,11-dione catalyzed by trace copper using hy-drazine hydrate as a clean reducing agent and water as a green reaction medium under mild reac-tion conditions was investigated. Various transition-metal catalysts were screened for the reduc-tive 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 spectros-copy and mass spectrometry; the main byproduct was hydroxyl-substituted 1-amino-2- acetylan-thraquinone. A possible reaction mechanism for the copper-catalyzed ring cleavage of 3-methylanthra[1,2-c]isoxazole-6,11-dione with hydrazine hydrate was proposed.