Benzoxazinone derivatives as selective cytotoxic agents

A compound of Formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is halo or —C1-8alkyl unsubstituted or substituted with 1 to 7 of —F;
• R2 is —H, halo, —CN, —C1-8alkyl, —C2-8alkenyl, —C(O)OC1-8alkyl, —C(O)C1-8alkyl or —NR6R7;
• R3 is —H or halo;
• R4 is —H or halo;
• R5 is a 5 or 6-membered ring selected from phenyl, pyrimidinyl, pyrimidinone, pyrazinone, pyrazolyl and pyridinyl, wherein each ring is unsubstituted or substituted with one or more substituents up to the maximum number allowed by valence, independently selected at each occurrence from:
• (i) halo,
• (ii) —CN,
• (iii) —NR6R7,
• (iv) —SO2—NR6R7,
• (v) —C1-8alkyl unsubstituted or substituted with 1 to 8 substituents independently selected at each occurrence from —OH and halo,
• (vi) —C1-4alkyl-O—C1-4alkyl unsubstituted or substituted with 1 to 8 substituents independently selected at each occurrence from —OH or halo, and
• (vii) —OC1-8alkyl unsubstituted or substituted with 1 to 8 substituents independently selected at each occurrence from —OH and halo;
• R6 is —H or —C1-8alkyl unsubstituted or substituted with 1 to 8 substituents independently selected at each occurrence from —OH and halo;
• and
• R7 is —H or —C1-8alkyl unsubstituted or substituted with 1 to 8 substituents independently selected at each occurrence from —OH and halo.