R1 and R2 may be identical or different and must be chosen from substituted or unsubstituted alkyl or aryl groups. They may also form part of a ring system. R3 must be chosen from hydrogen, substituted or unsubstituted alkyl, aryl, alkoxy groups or halogens. R3 is typically a methyl or chloro group. R4 must be chosen from substituted or unsubstituted monoarylamino groups. If R3 is hydrogen then R4 must be a substituted monoarylamino group. R1, R2 and R4 may not be hydrogen. R5 is hydrogen or halogen, typically hydrogen.
