Synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and 2,3-dihydroquinazolin-4(1H)-ones under metal-free and solvent-free conditions for minimizing waste generation.

Brønsted acidic ionic liquid was found to be an efficient and recyclable catalyst for the synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and 2,3-dihydroquinazolin-4(1H)-ones. The reactions proceeded smoothly with a broad scope of substrates providing the expected products in good to excellent yields under an atom-economical pathway. The low-cost recyclable catalyst, metal- and solvent-free conditions, and the ease of product isolation are the highlighted advantages in solving the issue of trace metal contamination in synthesized pharmaceuticals.