Disclosed are compounds of Formula (I) to (IV): or a stereoisomer, tautomer, pharmaceutically acceptable salt, solvate or prodrug thereof. Also disclosed are methods of using such compounds as PAR4 inhibitors, and pharmaceutical compositions comprising such compounds. These compounds are useful in inhibiting or preventing platelet aggregation, and are useful for the treatment of a thromboembolic disorder or the primary prophylaxis of a thromboembolic disorder.