Photochemistry of Pesticides, 13.1some Photoreactions Ofo,o-Diethyl-O-(4-Methyl-2-Oxo-2h-1-Benzopyran-7-Yl)-Phosphorothioate (Potasan®)

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UV-irradiation (δ > 313nm) of O,O-diethyl-O-(4-methyl-2-oxo-2H-1-benzopyran-7-yl)-phosphoro-thioate (Potasan®) la in chloroform and/or methanol with and without singlet oxygen results in the formation of the 2-oxo-2H-1-benzopyran-phosphate 2 the 3,3′-bipotasan dehydrodimer 3, and 7-ethoxy-4-methyl-2-oxo-2H-1-benzopyran 4: the mechanisms of formation, especially for 4 are discussed.