10.1002/ejoc.201901706
The research aims to develop a new class of bifunctional hydrogen-bond donor organocatalysts using oxoporphyrinogens (OxPs), which are highly non-planar rigid macrocycles containing multiple hydrogen bond forming binding sites. The study focuses on the synthesis and application of these catalysts for various chemical transformations, demonstrating their ability to catalyze 1,4-conjugate additions, sulfa-Michael additions, and Henry and aza-Henry reactions at low catalyst loadings (≤ 1 mol%) under mild conditions. The introduction of β-substituents was found to be key to the catalytic activity, and preliminary mechanistic studies suggest that these catalysts interact with substrates through hydrogen-bonding interactions, similar to other reported catalysts. The chemicals used in the process include 2,4-pentanedione, β-nitrostyrene, malononitrile, chalcone, and a range of other substrates for the various reactions, as well as the catalysts themselves, which are derivatives of oxoporphyrinogens with different β-substituents. The conclusions highlight the potential of these OxP systems as an adaptable scaffold for the development of H-bond catalysts due to their concave 3-dimensional structure at the binding sites, which can be modified to optimize catalytic processes.
10.3998/ark.5550190.p008.801
The research aims to develop a simple and efficient method for synthesizing 2-aryl-3-nitro-2H-chromenes and 2,3,4-trisubstituted chromanes, which are important building blocks in organic synthesis and pharmaceuticals. The study employs salicylaldehydes and β-nitrostyrenes as starting materials, using a combination of pyrrolidine and benzoic acid as catalysts to achieve tandem oxa-Michael-Henry reactions in refluxing ethanol, yielding 2-aryl-3-nitro-2H-chromenes with up to 83% yield. These chromenes are then reacted with acetone under the same catalytic combination in brine to produce 2,3,4-trisubstituted chromanes with yields up to 86% and excellent stereoselectivities. The structures of the synthesized compounds are confirmed by X-ray single crystal diffraction analysis. Additionally, the reductive amination of a suitable 2,3,4-trisubstituted chromane with Zn/HOAc yields a fused tricyclic amine in 92% yield. The research concludes that this catalytic strategy is practical and efficient, offering a reliable synthesis method under mild conditions, and ongoing work is focused on exploring enantioselective synthesis using various organocatalysts.
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