4-甲基-7,10-二氢苯并[h]香豆素的合成研究

Study on the Synthesis of 4-Methyl-7,10-dihydrobenzo[h]coumarin

以 1 萘酚 ( 6)为起始原料 ,经过Birch还原得到 5 ,8 二氢 1 萘酚 ( 7) ;7与乙酰乙酸乙酯在不同条件下缩合合成了 4 甲基 7,10 二氢苯并 [h]香豆素 ( 4 ) .研究结果表明 ,无氧和酸催化的反应条件对缩合反应是至关重要的 .在没有酸催化的条件下 ,反应生成 3 乙酰基 2 羟基 6 甲基 -吡喃 4 酮 ( 8) ,并通过单晶X射线衍射分析确定了产物的结构 ;在酸催化的条件下 ,除了生成产物 4外 ,还伴随生成脱氢芳构化产物 4 甲基苯并 [h]香豆素 ( 5 ) ,而且在不同条件下二者的比例不同 ,其中以甲磺酸为催化剂、在氮气保护下并加入抗氧化剂无水Na2 SO3 为最佳反应条件 ,化学选择性约为 70∶3 0 ( 4∶5 ) ,收率49 1%.

4-Methyl-7,10-dihydroxybenzo[h]coumarin (4) was prepared by condensation of ethyl acetoacetate with 5, 8-dihydro-1-naphthol (7), which was obtained by Birch reduction of 1-naphthol (6). It was found that the reaction conditions, particularly the presence of acid and the absence of oxygen, were critical for the condensation reaction. Under the acid-free condition, 3-acetyl-2-hydroxy-6-methyl-pyran-4-one (8) was obtained and its structure was confirmed by X-ray diffraction analysis. In the presence of acid, the condensation of 7 with ethyl acetoacetate proceeded to give a mixture of the expected product 4 and an aromatized derivative 4-methyl-benzo[h]coumarin (5). Under the optimized conditions (under Ar atmophere with CH3SO3H as catalyst in the presence of antioxidant Na2SO3), 4 and 5 could be obtained in 49.1% yield with chemical selectivity of 70:30 (4:5).