Boric Acid-Functionalized Fe۳O۴@SiO۲ 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 ((۱-methoxy-۲-methylprop-۱-enyloxy) trimethylsilane), and various aldehydes (aromatic, aliphatic, α,β-unsaturated), in acetonitrile and the yields were in the range of ۴۵-۹۸%. Magnetic Fe۳O۴-boric acid was multi-functional. The Fe۳O۴ 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 BF۳. Boric acid functionality had the advantage of being moisture insensitive, economically reasonable and environmentally friendly. Furthermore Fe۳O۴@ SiO۲@Boric acid was magnetically recovered via an external permanent magnet and was reused at least ۶ times with a negligible change in its activity.

Keywords:

Mukaiyama , Boric acid , Magnetic catalyst