Benzthiazole-3 oxides useful for the treatment of proliferative disorders

A method of treating a proliferative disorder, wherein said method comprises administering to a subject in need thereof a compound of formula I, or a pharmaceutically acceptable salt thereof:

• wherein
• R1, R2, R3, and R4 are each independently H, NO2, CF3, SCF3, CN, halo, OH, OR6, NH2, NHR6, NR6R7, N+R6R7R8, COOH, COOR6, CONH2, CONHR6, CONR6R7, COH, COR6, SR6, SOR6, SO2R6, SO2OH, SO2OR6, SO2NH2, SO2NHR6, SO2NR6R7, alkyl, cycloalkyl, cycloheteroalkyl, aryl, or heteroaryl, with the proviso that at least one of R1, R2, R3, and R4 is other than H;
• or R1 and R2, R2 and R3, or R3 and R4, may together form part of a fused or unfused saturated or unsaturated ring system, optionally containing up to two heteroatoms selected from N, O, and S;
• R5 is OH, OR9, CN, CONH2, CONHNH2, CONHOH, CONHR9, CONR9R10, NH2, NHR9, or NR9R10;
• each R6, R7 and R8 is independently hydrocarbyl, or two of R6, R7 and R8 together form part of a saturated or unsaturated ring system, optionally containing up to two heteroatoms selected from N, O, and S;
• each R9 and R10 is independently hydrocarbyl, or R9 and R10 together form part of a saturated or unsaturated ring system, optionally containing up to two heteroatoms selected from N, O, and S, such that the proliferative disorder in the subject is treated.