4-甲基-7，10-二氢苯并[h]香豆素的合成研究

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Na_2SO_3为最佳反应条件，化学选 择性约为70：30(4：5)，收率49．1％．

Study on the Synthesis of 4-Methyl-7,10-cUhydrobenzo[/j]coumarin

4-Methyl-7,10-dihydrobenzoh]coumarin (4) was prepared by condensation of ethyl acetoacetate with 5,8-dihydro-l-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 CH_3SO_3H as catalyst in the presence of antioxidant Na_2S0_3), 4 and 5 could be obtained in 49.1% yield with chemical selectivity of 70 = 30 (4:5)