Organocatalytic Enantioselective Continuous-Flow Cyclopropanation

Abstract

A set of six solid-supported diarylprolinol catalysts (varying on the anchoring strategy and the type of polymeric support) has been prepared and applied to the enantioselective cyclopropanation reaction. The selected candidate allows implementation of a long flow experiment (48 h) and generates a library of 12 cyclopropanes by sequential flow experiments. The mildness and utility of the method have enabled a telescoped process in which the outstream is directly used in a Wittig flow reaction.

Silica gel-immobilized multidisciplinary materials applicable in stereoselective organocatalysis and HPLC separation

“…More efficient and already veried supports such as organic polymers [29][30][31][32][33][34][35] or nanoparticles 36,37 have, however, not been considered in this study. The obvious reason is that we aimed for simultaneous use of the new materials as continuous ow organocatalysts and stationary phases for HPLC.…”

“…The current approach to address this problem involves immobilization of the catalyst to a solid support. 28 Several types of solid matrices, such as polystyrene, [29][30][31][32][33][34][35] metal nanoparticles, 36,37 metalorganic frameworks, 38 ion-modied resins for non-covalent binding, [39][40][41] or mesoporous silica [42][43][44][45] have been introduced as solid supports for various types of organocatalysts.…”

Recent Advances in Continuous‐Flow Enantioselective Catalysis

“…Enantioselective cyclization reactions : One study on enantioselective cyclopropanation was reported by Pericàs and co‐workers . Six solid‐supported diarylprolinol catalysts were prepared to analyze which immobilization method gave the best enantioselectivity in the cyclopropanation of enals 79 with dimethyl bromomalonate 80 (Scheme ).…”

Catalytic Enantioselective Flow Processes with Solid‐Supported Chiral Catalysts

“…In order to dig into this issue, we selected the diarylprolinol‐catalyzed cyclopropanation of α,β‐unsaturated aldehydes as a touchstone. Thus, a library of supported catalysts ( 8 – 10 ) was prepared with two points of diversity: the type of resin and the immobilization strategy . For the resin, we chose a microporous polystyrene resin (low cross‐linking) or a macroporous monolith; the three immobilization strategies to be compared were (a) a hydroxyproline with a benzylic linker ( 8 ), (b) a triazole‐based 9 and (c) a co‐polymerization approach analogous to the one followed for 10 (Figure ).…”

“…Thus, a library of supported catalysts (8-10) was prepared with two points of diversity: the type of resin and the immobilization strategy. [49] For the resin, we chose a microporous polystyrene resin (low cross-linking) or a macroporous monolith; the three immobilization strategies to be compared were (a) a hydroxyproline with a benzylic linker (8), (b) a triazole-based 9 and (c) a co-polymerization approach analogous to the one followed for 10 [47] (Figure 9). Catalysts 8-10 were thus tested in batch in the abovementioned cyclopropanation reaction; the results show that the parameters under study significantly affect the performance of the resin.…”