Environmentally green syntheses of Biginelli compounds, some fused and spiro-fused analogues and bis(indolyl)methanes

One-pot synthesis of various known and new 3,4-dihydropyrimidin-2(1H)-ones/thiones, 5-oxooctahydroquinazolin-2-ones/thiones and spiro-fused heterocycles are reported using Aliquat (R) 336 as a phase-transfer catalyst under microwave irradiation in water. This new method provides comparatively better catalyst for both Biginelli and Biginelli-like cyclocondensation, greener and milder reaction conditions, quicker reaction, simpler isolation of products and better yields. Catalysing efficiency of Aliquat (R) 336 in conjunction with (NH4)(2)SO4 was also tested for one pot two-component condensation of aldehydes and indole yielding various bis(indolyl)methanes in excellent yield under conventional heating.