Factor xi activation inhibitors

A compound of the formula:

• wherein
• R1 is N(C3-6 cycloalkyl)(R8) or a nitrogen-containing ring system, which may be monocyclic, bicyclic or tricyclic, wherein said nitrogen-containing ring system is optionally substituted with one to three substituents independently selected from the group consisting of halo, oxo, cyano, R6, OR6, R7, (C1-3 alkyl)R7 and (C3-6 cycloalkyl)R7;
• R2 is hydrogen, halo, cyano, C1-6 alkyl or C3-6 cycloalkyl, wherein said alkyl group is optionally substituted with one to three halo;
• R3 is hydrogen or C1-6 alkyl, wherein said alkyl group is optionally substituted with one to three halo;
• R4 is hydrogen, halo, cyano, phenyl or C1-6 alkyl, wherein said alkyl group is optionally substituted with one to three halo;
• R5 is hydrogen, halo, cyano, phenyl or C1-6 alkyl, wherein said alkyl group is optionally substituted with one to three halo;
• R6 is hydrogen or C1-6 alkyl, which is optionally substituted with one to three halo;
• R7 is phenyl, C3-6 cycloalkyl, heterocyclyl or heteroaryl, wherein said phenyl and heterocyclyl groups are optionally substituted with one to three substituents independently selected from the group consisting of C1-6 alkyl and halo;
• R8 is C1-6 alkyl, which is optionally substituted with one or two substituents independently selected from the group consisting of halo, hydroxyl and C3-6 cycloalkyl;
• or a pharmaceutically acceptable salt thereof.