abstract |
Compounds having the structural formula <CHEM> wherein R and R<1> are hydrogen, C1-C4 alkyl, R<a>OC(O)-, where R<a> is C1-C4 alkyl; R<2> is chlorine, bromine, iodine or C1-C4 alkoxy; and R<3>, R<4> and R<5> independently are hydrogen or an aliphatic group. |