Continuous Flow Solvent-Free and Catalyst-Free Mechanochemical Production of Rhodamine-B Dyes and its Derivatives

In this communication, we have described a simple and efficient, catalyst free and solvent-free protocol for continuous flow synthesis of Rhodamine-b dyes developed from the 3-diethyl amino phenol and phthalic anhydride. Nearly complete conversion was achieved within 12 minutes using a jacketed single screw reactor. This method is further used for the synthesis of six derivatives with 70 - 84% yield, when compared to 85% yield from a 1-hour long batch synthesis involving a catalyst.