Heterocyclic compounds as inhibitors of platelet aggregation

A compound of Formula I:

• or a stereoisomer, tautomer, pharmaceutically acceptable salt, solvate or prodrug thereof, wherein:
• the dashed lines represent double-bonds with the proviso that only one of the two dashed line double bonds exists at the same time;
• X1 is O and X2 is ═N— or CR1a;
• or
• X2 is S and X1 is ═N— or CR1a;
• or
• X1 is ═N— and X2 is O or NR1b;
• or
• X1 is NR1b and X2 is CR1a;
• or
• X1 is CR1a and X2 is NR1b;
• X3, X4, and X5 are independently selected from CR1d and ═N—;
• R1a is selected from the group consisting of H, halo, cyano, C1-C3 alkyl, C3-C5 cycloalkyl, halo-C1-C2alkyl, and C1-C3 alkoxy;
• R1b is selected from the group consisting of H, C1-C3 alkyl, C3-C5 cycloalkyl, and halo-C1-C2alkyl;
• R1d is selected from the group consisting of H, C1-C4 alkyl, C2-C4 alkenyl, C2-C4 alkynyl, C1-C4 alkoxy, C1-C4 alkylthio, halo, OH, CN, OCF3, OCHF2, OCH2F, C1-C2-alkoxy-C1-C2-alkoxy, halo-C1-C3-alkyl, halo-C1-2-alkoxy, halo-C1-2-alkylthio, benzyloxy substituted (on the phenyl of said benzyl) by 0 to 3 groups independently selected from the group consisting of halo, C1-C4 alkoxy, C1-C4 alkyl, cyclopropyl, CF3, OCF3, 5- or 6-membered heteroaryl, OH, OCHF2, di-C1-C4-alkylamino, and cyano, and —(CH2)n-phenyl substituted by 0 to 3 groups independently selected from the group consisting of halo, C1-C4 alkoxy, C1-C4 alkyl, cyclopropyl, CF3, OCF3, 5- or 6-membered heteroaryl, OH, OCHF2, di-C1-C4-alkylamino, and cyano;
• n is 1 or 2;
• Y is S, O or —CR1e═CR1f—;
• R1e is independently at each occurrence selected from the group consisting of H, halo, cyano, C1-C3 alkyl, C3-C5 cycloalkyl, halo-C1-C2 alkyl, C1-C3 alkoxy, and halo-C1-C3 alkoxy;
• R1f is independently at each occurrence selected from the group consisting of H, halo, cyano, C1-C3 alkyl, C3-C5 cycloalkyl, halo-C1-C2 alkyl, C1-C3 alkoxy, and halo-C1-C3 alkoxy;
• R2 is H, halo, C1-C3 alkyl, halo-C1-C2 alkyl, C1-C3 alkoxy, halo-C1-C3 alkoxy, CN or C3-C5 cycloalkyl;
• R3 is selected from the group consisting of C1-4 alkyl, C1-4 alkoxy, C1-4 alkylthio, C1-2 haloalkyl, C1-2 haloalkoxy, C1-2 haloalkylthio, C3-4 cycloalkyl, halo-C3-4 cycloalkyl, C1-4 alkylamino, di-C1-4 alkylamino, (C1-2 alkoxy) C1-2 alkyl, halo(C1-2 alkoxy) C1-2 alkyl, C2-3 alkenyl, C2-3 alkynyl, tetrahydrofuran-2-yl, and halo;
• W is O or S;
• R4 and R5 are independently selected from H, C1-C6 alkyl, C1-C4 fluoroalkyl, and C1-C4 hydroxyalkyl, or R4 and R5 can be taken together with the carbon to which they are attached to form a C3-C7 cycloalkyl ring;
• is selected from the group consisting of:
• a piperidine ring which may be unsubstituted or substituted with 0-1 R6 and 0-4 R7 substituents;
• a piperazine ring which may be unsubstituted or substituted with 0-1 R6 and 0-4 R7 substituents;
• a morpholine ring which may be unsubstituted or substituted with 0-1 R6 and 0-4 R7 substituents;
• and an azetidine ring which may be unsubstituted or substituted with 0-1 R6 and 0-4 R7 substituents;
• R6 is selected from the group consisting of C6-C10 aryl, 5-10 membered heteroaryl, 4-8 membered saturated heterocyclic ring, or C3-C8 cycloalkyl ring, wherein each of said C6-C10 aryl, 5-10 membered heteroaryl, 4-8 membered saturated heterocyclic ring, or C3-C8 cycloalkyl ring, can be substituted with 0-4 R7a substituents;
• R7 is independently selected at each occurrence from the group consisting of halo, C1-C4 alkyl, C1-C4 alkoxy, halo C1-C4 alkyl, halo C1-C4 alkoxy, C1-C4 alkylthio, halo C1-C4 alkylthio, hydroxy, hydroxy C1-C4 alkyl, hydroxy C1-C4 alkoxy, (C1-C6 alkyl)carboxy-, carboxy, —C(O)Oalkyl, —C(O)NH2, —C(O)NHalkyl, —C(O)N-dialkyl, —NH2, (alkyl)amino-, (dialkyl)amino-, —NH-carboxy-C1-C6 alkyl, nitro, cyano, oxo, (haloaryl)alkyl-, C3-C6 cycloalkyl, —S(O)-alkyl, —S(O)-aryl, —S(O)-heteroaryl, —S(O2)alkyl, —S(O2)aryl, —S(O2)heteroaryl, —S(O2)NH2, —S(O2)NHalkyl, —S(O2)N-dialkyl, or if two R7 substituents are attached to the same carbon atom, they may be taken together with the carbon atom to which they are attached to form a C3-C6 cycloalkyl group or a 3-6 membered heterocyclic ring, or if two R7 substituents are attached to adjacent carbon atoms, they may be taken together with the carbon atoms to which they are attached to form a C3-C6 cycloalkyl group or a 3-6 membered heterocyclic ring;
• and
• R7a is independently selected at each occurrence from the group consisting of halo, C1-C4 alkyl, C1-C4 alkoxy, halo C1-C4 alkyl, halo C1-C4 alkoxy, C1-C4 alkylthio, halo C1-C4 alkylthio, hydroxy, hydroxy C1-C4 alkyl, hydroxy C1-C4 alkoxy, (C1-C6 alkyl)carboxy-, carboxy, —C(O)Oalkyl, —C(O)NH2, —C(O)NHalkyl, —C(O)N-dialkyl, —NH2, (alkyl)amino-, (dialkyl)amino-, —NHC(O)O—C1-C6 alkyl, —NHC(O)-halo C1-C6 alkyl, nitro, cyano, oxo, C3-C6 cycloalkyl, —S(O)— alkyl, —S(O)-aryl, —S(O)-heteroaryl, —S(O2)alkyl, —S(O2)aryl, —S(O2)heteroaryl, —S(O2)NH2, —S(O2)NHalkyl, —S(O2)N-dialkyl, aryl C1-C4 alkoxy, —C(O)aryl, —C(O)—C1-C6 alkyl, or if two R7a substituents are attached to the same carbon atom, they may be taken together with the carbon atom to which they are attached to form a C3-C6 cycloalkyl group or a 3-6 membered heterocyclic ring, or if two R7a substituents are attached to adjacent carbon atoms, they may be taken together with the carbon atoms to which they are attached to form a C3-C6 cycloalkyl group or a 3-6 membered heterocyclic ring.