A STUDY ON THE PHOTOCHEMICAL DIMERIZATION OF COUMARINS IN THE SOLID-STATE
A STUDY ON THE PHOTOCHEMICAL DIMERIZATION OF COUMARINS IN THE SOLID-STATE
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DOI：
10.1021/jo00213a027
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发表时间：
1985-01-01
影响因子：
3.6
通讯作者：
RAMAMURTHY, V
中科院分区：
文献类型：
--
作者：
GNANAGURU, K;RAMASUBBU, N;RAMAMURTHY, V
结果表I显示了在固态下研究的28种香豆素的光行为。其中，12个经历了光二聚化。相应的二聚体是在这些情况下分离的唯一产物。虽然质谱证实产物是二聚体，但NMR有助于确定构型。二聚体的光谱数据见表IV。通过X-射线晶体结构分析证实了7-甲氧基香豆素二聚体的结构。照射方法包括在玻璃板之间压碎晶体，并用450-W中压汞弧灯作为外部光源照射它们。如果需要，通过冷却浴将样品的温度保持在0 ℃。二聚化之后是微量TLC和1H NMR。辐射时间对通过1H NMR测量的二聚体产率的曲线示于图1中。在所有情况下，二聚体产率达到平台，表I中所示的产率对应于该数值。进一步的照射没有带来任何变化。用7-甲氧基-、7-乙酰氧基-、6-氯-和4-甲基-6-氯香豆素进行的粉末衍射实验表明，反应从一个晶相进行到另一个晶相，在任何情况下反应物都不会变成无定形的。
ResultsTable I shows the 28 coumarins investigated in the solid state for their photobehavior. Of these, 12 underwent photodimerization. Corresponding dimers are the only products isolated in these cases. While mass spectra confirmed the products to be the dimer, NMR was helpful in assigning the configuration. Spectral dataof dimers are provided in Table IV. The structure of the dimer of 7-methoxycoumarin was confirmed by X-ray crystal structure analysis. The method of irradiation consisted of crushing the crystals between glass plates and irradiating them with a 450-W medium-pressure mercury arc lamp as the external light source. The temperature of the sample was maintained at 0 C, if needed, by a cooling bath. Dimerization was followed by micro TLC and XH NMR. Plots of time of irradiation vs. the yield of the dimer as measured by: H NMR are shown in Figure 1. In all cases the dimer yield reached a plateau and the yields represented in Table I correspond to this number. Further irradiation did not bring about any change. Powder diffraction experiments carried out with 7-methoxy-, 7-acetoxy-, 6-chloro-, and 4-methyl-6-chlorocoumarins indicated that the reaction proceeded from one crystalline phase to another crystalline phase and in no case did the reactants become amorphous.