Functionalized hollow double-shelled polymeric nano-bowls as effective heterogeneous organocatalysts for enhanced catalytic activity in asymmetric Michael addition

摘要

A facile and robust strategy to fabricate organocatalyst-functionalized hollow double-shelled nano -bowl was developed for the first time by hard-templating synthesis. After the core was etched by DMF, the outer shell thicknesses below 50 nm and above 50 nm deformed into hollow nano-bowl and hollow nanosphere, respectively. Furthermore, the outer shell with the average thickness of 20-50 nm deformed into hollow double-shelled nano-bowl with a void between two semi-shells. However, the shell with the thicknesses below 20 nm severely deformed into hollow nano -bowl with no void owing to the overlapping of two semi-shells. Compared with hollow nanosphere and nano -bowl with no void, hollow double shelled nano -bowl displayed superior catalytic performances owing to the thin shell thickness and a void between two semi-shells. In heterogeneous asymmetric Michael addition, the double-shelled nano-bowl exhibited good to excellent yields (86-98%), stereoselectivities (syn/anti = 81-93/19-7 and 93-99%ee syn) and good reusability. (C) 2017 Elsevier Inc. All rights reserved.