N,N-dihydroxypyromellitimide: a new and efficient organocatalyst for the Biginelli reaction under solvent-free conditions

Solvent free condition is an area in modern organic synthesis. Biginelli reaction is one of the useful multi-component reactions due to it is an acid catalyzed condensation of bketoester with an aldehyde and urea/thiourea to yield 3,4-dihydropyrimidin- 2(1H)-ones (DHPMs) and their sulfuranalogs. These pyrimidinones have found to possess pharmacological activities such as antibacterial, antiviral, antioxidative as well as antiinflammatory [1-2]. In this work, N,N-dihydroxypyromellitimide (DHPHI) was directly synthesized via reaction of phthalic dianhidride with hydroy amine hydrochloride in pyridine. Synthesis of 3,4-dihydropyrimidin-2(1H)-thiones using DHPHI under solvent free conditions leads to excellent yield. In the present methodology, the catalyst is inexpensive, readily available, efficient, recyclable and green. The three-component reaction of aryl aldehydes derived thiourea, and ethyl acetoacetate or acetylacetone occurs by means of 15 mol % of (DHPHI) insolvent-free reaction conditions. (Figure 1).