(348a) Chiral and Achiral Dendrimers Supported on Mcm-41 as Organocatalysts

Organocatalysis has attracted substantial interest in the last ten years as an intriguing alternative to organometallic-based catalysts for enantioselective catalysis. Our lab has recently found that melamine-based dendrimers supported on MCM-41 and SBA-15 possess significant catalytic activity for the nitroaldol reaction between nitrobenzaldehyde and nitromethane. Here we will present our initial results attempting to extend this to organocatalysts with chiral centers. Our initial work investigated dendrimers wherein piperazine groups were the amine center catalyzing the reaction, thus leading to no ee enhancement. In these materials we found high (> 80%) conversion and selectivity (> 95%) after 2 hours of reaction at 313 K.

The talk will highlight our initial efforts investigating chiral primary (e.g. lysine) and secondary (e.g amino-proline) amines attached to the dendrimer periphery. We will report results illustrating how dendrimer generation, OMS pore topology and OMS surface chemistry impact both the activity and enantioselectivity of these materials. These materials will be compared to simple control samples where the chiral centers are covalently attached to OMS in the absence of the dendrimer scaffold.