One-pot three-component condensation of aromatic ketones (1-tetralones, acetophenones, indane-1,3-dione), substituted aromatic aldehydes and thiourea in the presence of N-methylpyridinium tosylate under solvent free conditions at 100–110 °C for 2–4 h afforded tetrahydrobenzo[ h]quinazoline-2-thiones, pyridimidine-2-thiones and indeno-pyrimidine-2-thiones in excellent yields. All synthesised thiones were screened for their antimicrobial activities.