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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 13, Number 6
BKCSDE 13(6)
June 20, 1992 

Photodimerization of 5,7-Dimethoxycoumarin
Sang Chul Shim*, Bong Mo Jeong, Young Hee Paik
Three photocyclodimers of 5,7-dimethoxycoumarin (DMC) were isolated and characterized from the photolysis of DMC in acetonitrile. The configuration of the dimers was found to be anti head-to-head, syn head-to-head and syn head-to-tail, respectively. The number and the ratio of the products are solvent dependent. The anti head-to-head dimer is favored in nonpolar solvents and the preference decreases as the solvent polarity increases giving almost 100% syn dimers and less than 1% anti dimer from methanol solution. The overall yields of dimers also increase with the solvent polarity. From sensitization and quenching experiments, anti dimer was found to be formed via excited singlet state while syn dimers were formed via both excited singlet and triplet states.
684 - 688
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