1,3-Disulfonic acid imidazolium hydrogen sulfate: a reusable and efficient ionic liquid for the one-pot multi-component synthesis of pyrimido[4,5-b]-quinoline derivatives

A green, simple and convenient method for the synthesis of pyrimido-[4,5-b]quinoline derivatives has been developed through a three-component one-pot condensation of 6-amino-1,3-dimethyluracil, aldehydes, and cyclic 1,3-diketones in the presence of 1,3-disulfonic acid imidazolium hydrogen sulfate [dsim]HSO4 as an efficient catalyst. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times, high yields of the products and easy work-up procedures. Also, the catalyst was readily recovered and could be reused several times without a noticeably decrease in its activity.