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多甲氧基菲-9-甲酸及酯是合成娃儿藤生物碱及其类似物的关键中间体.以4-(3,4-二甲氧基苯亚甲基)-6,7-二甲氧基-3-异色酮(6)为底物,2,3-二氯-5,6-二氰基苯醌(DDQ)/CH3SO3H作为氧化体系,没有得到预期的多甲氧基菲-9-甲酸内酯(1),意外产物经核磁共振等确定为两个新的3-取代苯基香豆素2,3.进一步的实验研究显示:底物发生分子内脱氢偶联为香豆素2而非菲环化合物1,是因为异色酮6苯环A上2位取代基的存在所致,其内酯环开环化合物10以及2,3-二苯基丙烯酸(12)的对比实验印证了该取代基对脱氢偶联反应选择性的影响;异色酮6氧化偶联为香豆素2的反应机理可能为酸解开环以及途经自由基正离子的脱氢偶联,香豆素3为DDQ氧化2的前体化合物8所得.
Methoxyphenanthroline-9-carboxylic acid and ester are the key intermediates for the synthesis of vines alkaloids and their analogues. 4- (3,4-dimethoxybenzylidene) -6,7-bis Methoxy-3-isochromanone (6) as substrate and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) / CH3SO3H as oxidation system, -9-formate lactone (1). The unexpected product was identified as two new 3-substituted phenylcoumarins 2,3 by NMR, etc. Further experimental studies have shown that intramolecular dehydrogenation of the substrate to Coumarin 2, but not phenanthrene ring 1, is due to the lactone ring ring-opening compound 10 and 2,3-diphenylacrylic acid (12) due to the presence of the 2-position substituent on the benzene ring A of the isochromanone 6, The experimental results confirm that the substituent has an effect on the selectivity of dehydrogenation coupling reaction. The reaction mechanism of the oxidation of isochromanone 6 to coumarin 2 may be the acid-cleavage ring and dehydrogenation coupling via free radical cations, Coumarin 3 was obtained as precursor compound 8 of DDQ oxidation 2.