Direct Utilization of Waste Glycerol from Biodiesel Production for the Synthesis of Perimidines

The production and consumption of biodiesel in Brazil and worldwide have considerably increased in the last decades. As a consequence, the waste glycerol (glycerin) as a byproduct from this synthetic process has also increased since approximately 10-30% of glycerol is generated in the biodiesel synthesis process. Therefore, the reuse of glycerol after the biodiesel synthesis is highly desired. However, waste glycerol purification is still a costly process. In this context, herein, we propose a synthetic alternative for the use of waste glycerol as a solvent and promoting medium for condensation reactions of 1,8-diaminonaphthalene and different aldehydes. The reactions were carried out using the waste glycerol without prior purification at room temperature for 30 min, affording the synthesis of a series of perimidines in excellent yields. Furthermore, a comparative study was performed between the use of commercial glycerol or waste glycerol in the reactions, and the results showed that the waste glycerol is more efficient considering the product yields. The use of waste glycerol as a green solvent and a promotion medium for organic processes is a robust, sustainable, and economically viable option for the application of this undesired byproduct of biodiesel synthesis.