Compounds

1 . A compound of formula (I), or a pharmaceutically acceptable salt thereof:

wherein:

R 1 , R 2 , R 3 and R 4 are independently selected from the group consisting of:

(i) H;

(ii) C 1-3 alkyl, optionally substituted by:

hydroxy,

C 1-2 alkoxy, optionally substituted by one or more fluoro groups,

NH 2 ,

phenyl,

C 5-6 heteroaryl,

C 1-4 alkyl carbamoyl,

acylamido, or

one or more fluoro groups;

(iii) C 1-3 alkoxy, optionally substituted by C 3-6 cycloalkyl or by one or more fluoro groups;

(iv) C 3-6 cycloalkyl;

(v) halo;

(vi) COR C , where R C is selected from NR N1 R N2 , where R N1 and R N2 are independently selected from H and methyl;

(vii) cyano, NH 2 , or NO 2 ; and

(viii) phenyl or C 5-6 heteroaryl, optionally substituted by methyl, cyano, hydroxy or methoxy;

Ar is selected from the group consisting of:

(a) 5-ethyl-2-methoxyphenyl;

(b) 5-CF 3 -2-methoxyphenyl; and

(c) 2,6-dimethoxyphenyl.

2 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 1-3 alkyl, optionally substituted by:

hydroxy,

C 1-2 alkoxy, optionally substituted by one or more fluoro groups,

NH 2 ,

phenyl,

C 5-6 heteroaryl,

C 1-4 alkyl carbamoyl,

acylamido, or

one or more fluoro groups.

3 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 1-3 alkoxy, optionally substituted by C 3-6 cycloalkyl or one of more fluoro groups.

4 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 3-6 cycloalkyl.

5 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is halo.

6 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is COR C , where R C is selected from NR N1 R N2 , where R N1 and R N2 are independently selected from H and methyl.

7 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is cyano, NH 2 or NO 2 .

8 . The compound or salt according to claim 1 , wherein at least one of R 1 , R 2 , R 3 and R 4 is phenyl or C 5-6 heteroaryl, optionally substituted by methyl, cyano, hydroxy or methoxy.

9 . The compound or salt according to claim 1 , wherein:

(a) R 4 is methoxy, R 2 is CH 2 OCH 3 or CH 2 OCH 2 CH 3 , and R 1 and R 3 are H;

(b) R 4 is methoxy, R 2 is phenyl, optionally substituted by methyl or methoxy, and R 1 and R 3 are H;

(c) R 4 is methoxy, R 2 is C 5-6 heteroaryl, optionally substituted by methyl;

(d) R 4 is methoxy and R 1 , R 2 and R 3 are H;

(e) R 4 is chloro, R 2 is C 1-3 alkyl or bromo, and R 1 and R 3 are H;

(f) R 4 is chloro and R 1 , R 2 and R 4 are H; or

(g) R 3 is C 1-3 alkyl and R 1 , R 2 and R 4 are H.

10 . The compound or salt according to claim 1 , wherein Ar is 2,6-dimethoxyphenyl.

11 . A method of treating cancer comprising administering to a patient in need of treatment a compound of formula (I), or a pharmaceutically acceptable salt thereof:

wherein:

R 1 , R 2 , R 3 and R 4 are independently selected from the group consisting of:

(i) H;

(ii) C 1-3 alkyl, optionally substituted by:

hydroxy,

C 1-2 alkoxy, optionally substituted by one or more fluoro groups,

NH 2 ,

phenyl,

C 5-6 heteroaryl,

C 1-4 alkyl carbamoyl,

acylamido, or

one or more fluoro groups;

(iii) C 1-3 alkoxy, optionally substituted by C 3-6 cycloalkyl or by one or more fluoro groups;

(iv) C 3-6 cycloalkyl;

(v) halo;

(vi) COR C , where R C is selected from NR N1 R N2 , where R N1 and R N2 are independently selected from H and methyl;

(vii) cyano, NH 2 , or NO 2 ; and

(viii) phenyl or C 5-6 heteroaryl, optionally substituted by methyl, cyano, hydroxy or methoxy;

Ar is selected from the group consisting of:

(a) 5-ethyl-2-methoxyphenyl;

(b) 5-CF 3 -2-methoxyphenyl; and

(c) 2,6-dimethoxyphenyl.

12 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 1-3 alkyl, optionally substituted by:

hydroxy,

C 1-2 alkoxy, optionally substituted by one or more fluoro groups,

NH 2 ,

phenyl,

C 5-6 heteroaryl,

C 1-4 alkyl carbamoyl,

acylamido, or

one or more fluoro groups.

13 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 1-3 alkoxy, optionally substituted by C 3-6 cycloalkyl or one of more fluoro groups.

14 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is C 3-6 cycloalkyl.

15 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is halo.

16 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is COR C , where R C is selected from NR N1 R N2 , where R N1 and R N2 are independently selected from H and methyl.

17 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is cyano, NH 2 or NO 2 .

18 . The method according to claim 11 , wherein at least one of R 1 , R 2 , R 3 and R 4 is phenyl or C 5-6 heteroaryl, optionally substituted by methyl, cyano, hydroxy or methoxy.

19 . The method according to claim 11 , wherein:

(a) R 4 is methoxy, R 2 is CH 2 OCH 3 or CH 2 OCH 2 CH 3 , and R 1 and R 3 are H;

(b) R 4 is methoxy, R 2 is phenyl, optionally substituted by methyl or methoxy, and R 1 and R 3 are H;

(c) R 4 is methoxy, R 2 is C 5-6 heteroaryl, optionally substituted by methyl;

(d) R 4 is methoxy and R 1 , R 2 and R 3 are H;

(e) R 4 is chloro, R 2 is C 1-3 alkyl or bromo, and R 1 and R 3 are H;

(f) R 4 is chloro and R 1 , R 2 and R 4 are H; or

(g) R 3 is C 1-3 alkyl and R 1 , R 2 and R 4 are H.

20 . The method according to claim 11 , wherein Ar is 2,6-dimethoxyphenyl.