Spick-and-span protocol for designing of silica-supported enantioselective organocatalyst for the asymmetric aldol reaction

In the present work, we report a ground-breaking strategy in the development of spick-and-span protocol for the synthesis of L-proline chiral scaffold tethered onto the silica matrix i.e., L-proline-(3 degrees amine)-f-SiO2 via the reaction between L- proline methyl ester and N-methyl aminopropyl silica with absolutely no use of protecting/deprotecting groups. The as-synthesized catalyst was well corroborated through various physicochemical techniques such as C-13 CP MAS NMR, X-ray diffraction (XRD), HRTEM, N-2 adsorption-desorption isotherms, elemental analysis and FT-IR spectral studies. Emphatically, L-proline-(3 degrees amine)-f-SiO2 significantly promoted an asymmetric aldol reaction under ambient conditions with no use of redundant organic solvent, bestowing unprecedented activity with 100% conversion and (ee) > 99% enantioselectivity of S-isomer. Moreover, the as-synthesized catalyst was effortlessly recycled seven consecutive times with absolutely zero loss of activity as well.

Automated summary

In this work, a groundbreaking strategy for the synthesis of L-proline chiral scaffold tethered onto the silica matrix was reported. The synthesized catalyst showed excellent activity in an asymmetric aldol reaction with high enantioselectivity. Moreover, the catalyst could be recycled multiple times without any loss of activity.