Substituted imidazo[1,2-a]pyrazines as Syk inhibitors

At least one chemical entity of Formula I:

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is pyridinyl;
• R2 is a 5- to 6-membered aromatic carbocyclic ring fused to (i) a 5- to 7-membered heterocycloalkyl ring or to (ii) a 5- to 7-membered heteroaryl ring;
• wherein R1 and R2 are each independently and optionally substituted with one or more substituent groups independently chosen from —Ra, —ORb, —O(C1-C2 alkyl)O—, —SRb, guanidine, guanidine wherein one or more of the guanidine hydrogens are replaced with C1-C6 alkyl, —NRbRc, halo, cyano, oxo (as a substituent for heterocycloalkyl), nitro, —CORb, —CO2Rb, —CONRbRc, —OCORb, —OCO2Ra, —OCONRbRc, —NRcCORb, —NRcCO2Ra, —NRcCONRbRc, —SORa, —SO2Ra, —SO2NRbRc, and —NRcSO2Ra;
• wherein Ra is chosen from C1-C6 alkyl, C3-C6 cycloalkyl, aryl, heterocycloalkyl, and heteroaryl;
• wherein Rb is chosen from hydrogen, C1-C6 alkyl, aryl, and heteroaryl;
• and
• wherein Rc is chosen from hydrogen and C1-C4 alkyl;
• or
• wherein Rb and Rc, and the nitrogen to which they are attached, form a heterocycloalkyl group;
• wherein Ra, Rb, and Rc are each independently and optionally substituted with one or more substituent groups independently chosen from C1-C4 alkyl, C3-C6 cycloalkyl, aryl, heteroaryl, aryl-C1-C4 alkyl-, heteroaryl-C1-C4 alkyl-, C1-C4 haloalkyl-, —OC1-C4 alkyl, —OC1-C4 alkylphenyl, —C1-C4 alkyl-OH, —C1-C4 alkyl-O—C1-C4 alkyl, —OC1-C4 haloalkyl, halo, —OH, —NH2, —C1-C4 alkyl-NH2, —N(C1-C4 alkyl)(C1-C4 alkyl), —NH(C1-C4 alkyl), —N(C1-C4 alkyl)(C1-C4 alkylphenyl), —NH(C1-C4 alkylphenyl), cyano, nitro, oxo (as a substituent for heteroaryl), —CO2H, —C(O)OC1-C4 alkyl, —CON(C1-C4 alkyl)(C1-C4 alkyl), —CONH(C1-C4 alkyl), —CONH2, —NHC(O)(C1-C4 alkyl), —NHC(O)(phenyl), —N(C1-C4 alkyl)C(O)(C1-C4 alkyl), —N(C1-C4 alkyl)C(O)(phenyl), —C(O)C1-C4 alkyl, —C(O)C1-C4 phenyl, —C(O)C1-C4 haloalkyl, —OC(O)C1-C4 alkyl, —SO2(C1-C4 alkyl), —SO2(phenyl), —SO2(C1-C4 haloalkyl), —SO2NH2, —SO2NH(C1-C4 alkyl), —SO2NH(phenyl), —NHSO2(C1-C4 alkyl), —NHSO2(phenyl), and —NHSO2(C1-C4 haloalkyl);
• R3 is hydrogen;
• R4 is hydrogen;
• and
• R5 is hydrogen.