| 摘要 |
A compound of the formula: (I): wherein R<SUB>1</SUB>, R<SUB>2 </SUB>and R<SUB>3 </SUB>are independently selected from the group consisting of H, C<SUB>1</SUB>-C<SUB>8 </SUB>alkyl, (CH<SUB>2</SUB>)<SUB>n</SUB>-aryl (wherein n is 0-6, phenyl or benzyl), NO<SUB>2 </SUB>or CN, F, Cl, Br and I; and n is 0 or 1. The present invention also relates to a compound of the formula (II): wherein R<SUB>1</SUB>, R<SUB>2 </SUB>and R<SUB>3 </SUB>are independently selected from the group consisting of H, C<SUB>1</SUB>-C<SUB>8 </SUB>alkyl, (CH<SUB>2</SUB>)<SUB>n</SUB>-aryl (wherein n is 0-6, phenyl or benzyl), NO<SUB>2 </SUB>or CN, F, Cl, Br and I; and n is 0 or 1.
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