Physicochemical properties of a urea/zinc chloride eutectic mixture and its improved effect on the fast and high yield synthesis of indeno[2,1-c]quinolines

In this contribution, a low melting mixture of urea-zinc chloride was prepared and characterized using FTIR, RAMAN and TGA. In addition, the physicochemical properties, such as electrical conductivity, density, pH and refractive index were measured and analysed as a function of temperature. To further expand the use of this DES as a valuable reaction medium, the three-component Povarov reactions between aromatic aldehydes, anilines and indene were studied obtaining a series of pharmacologically important indeno[2,1-c]quinolines in high yields with short reaction times. All the reactions proceeded efficiently using the eutectic mixture as an environmentally friendly solvent, which was reused up to three cycles. Moreover, green metrics analysis showed that this protocol offers a green and very efficient alternative to the traditionally reported methods for constructing the same heterocyclic system.