Molecular design and synthesis of coumarin by indexing

1)（1）芳基炔丙基醚在CsF存在下经Claisen重排得到芳基呋喃，再经OsO_4、NaIO_4和aq. NaHCO_3的产率较高。2）与Wittig试剂反应合成香豆素（2）1与Ph_3P =CHCOOEt在二乙基苯胺中回流反应得到香豆素（2），产率较高。1上C_4位的甲氧基取代基比其它位置的甲氧基更有利于香豆素环的形成。3）天然香豆素化合物的合成与结构鉴定在Reisch香豆素化合物的合成研究中，利用上述新方法合成了香豆素化合物（3和4）。此外，Dopke从菊科植物中分离的香豆素经人工合成证实为7，8-二甲氧基香豆素，而不是5，8-二甲氧基香豆素。

1)Development of a novel synthetic method of salicylaldehyde(1)Claisen rearrangement of aryl propargyl ether in the presence of CsF afforded exclusively an arylfuran, which was converted to salicylaldehyde(1)by successive treatment with OsO_4 NaIO_4 and aq. NaHCO_3 in good yield. oxidation oy the furan ring with ozone was more convenient and effective.2)Convenient synthesis of coumarin(2)by reaction of with wittig reagent Reaction of 1 with Ph_3 P=CHCOOEt in diethylaniline under reflux gave coumarin(2)in a high yield. Tae methoxy substituent at C_4 on 1 facilitated the formation of coumarin ring in comparison with the methoxy group at other positions.3)Structural elucidation of naturally occurring coumarins by syntheses In connection with synthetic studies on Reisch's coumarin, coumarins(3 and 4)were synthesized by utilizing novel methods mentioned above. Moreover, the coumarin isolated from a Compositae plant by Dopke was synthetically proven to be 7, 8-dimethoxycoumarin, not 5, 8-dimethoxycoumarin.