Boric Acid-Functionalized Fe3O4@SiO2 as a Novel Superparamagnetically Recoverable Nano Catalyst for Mukaiyama-Aldol Reaction

We have reported the fabrication of boric acid incorporated into surface of magnetite nanoparticles. The catalyst was characterized using spectroscopic, magnetic and thermal techniques (FT-IR, SEM, XRD, ICP, VSM and TGA). It catalyzed Mukaiyama aldol reaction of a ketene silyl acetal type nucleophile ((1-methoxy-2-methylprop-1-enyloxy) trimethylsilane), and various aldehydes (aromatic, aliphatic, α,β-unsaturated), in acetonitrile and the yields were in the range of 45-98%. Magnetic Fe3O4-boric acid was multi-functional. The Fe3O4 core of the catalyst made easy separation and recycling while its boric acid portion catalyzed Mukaiyama aldol reaction. Nano size nature of the catalyst increased its activity in a way that boric acid, which is a weak Lewis acid, functioned similar to a more strong one like BF3. Boric acid functionality had the advantage of being moisture insensitive, economically reasonable and environmentally friendly. Furthermore Fe3O4@ SiO2@Boric acid was magnetically recovered via an external permanent magnet and was reused at least 6 times with a negligible change in its activity.